TECHNICAL FIELD
[0001] The present invention relates to a radiation imaging
system, a communication method of the radiation imaging system,
and a radiographic image detecting device.
BACKGROUND ART
[0002] In a medical field, an X-ray imaging system using X-rays,
as a kind of radiation, is known. The X-ray imaging system is
constituted of an X-ray generating apparatus for generating the
X-rays and an X-ray imaging apparatus, which receives the X-rays
and takes an X-ray image. The X-ray generating apparatus includes
an X-ray source for emitting the X-rays to an object, a source
control device for controlling the operation of the X-ray source,
and an emission switch for inputting an emission start command
of the X-rays. The X-ray imaging apparatus includes an X-ray
image detecting device and a console. The X-ray image detecting
device detects the X-ray image upon receiving the X-rays passed
through the object. The console controls the operation of the
X-ray image detecting device and applies various image processes
to the X-ray image.
[0003] Recently, in a field of the X-ray imaging system, an X-ray
image detecting device that uses a flat panel detector (FPD) as
a detection panel, instead of an X-ray film or an imaging plate
(IP), becomes widespread. The FPD has a matrix of pixels each
for accumulating signal charge in accordance with the amount of
X-rays incident thereon. The FPD accumulates the signal charge
on a pixel-by-pixel basis. The FPD converts the accumulated
signal charge into a voltage signal at its signal processing
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circuit, and thereby detects the X-ray image representing image
information of the object and outputs the X-ray image as digital
image data.
[0004] The X-ray image detecting device and the console are
connected in a communicatable manner through wired or wireless
communication I/Fs. The image data of the X-ray image detected
by the X-ray image detecting device is transmitted to the console
through the communication I/F. The console transmits
information including an imaging condition, various setting
commands, and the like to the X-ray image detecting device. The
console applies the image processes to the received X-ray image.
Then, the console displays the X-ray image on a monitor and stores
the X-ray image to an image server.
[0005] An electronic cassette (portable X-ray image detecting
device) that is composed of the FPD contained in a rectangular
parallelepiped housing is in practical use. The electronic
cassette is used while being loaded detachably into an existing
imaging stand sharable with a film cassette and an IP cassette
or a specific imaging stand designed for the electronic cassette,
in contrast to a non-detachable type. Furthermore, the
electronic cassette is used while being put on a bed or held by
the object himself/herself, to take an image of a body part that
is hard to take with the non-detachable type. The electronic
cassette is sometimes brought out from a hospital to a place having
no imaging stand, for use in bedside radiography of an elder
patient or in urgent radiography of an injured patient, natural
disaster victims, or the like.
[0006] Also, the X-ray imaging system performs an automatic
exposure control (AEC) of the X-ray image in which the X-ray
emission from the X-ray source is stopped as soon as an applied
X-ray dose has reached a predetermined threshold value. In the
AEC, an AEC-specific dose detection sensor (AEC sensor) for
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detecting a radiation dose during irradiation with the X-rays,
such as an ion chamber is used together with the X-ray image
detecting device.
[0007] Also, there is a proposed technology for containing such
an AEC sensor in the X-ray image detecting device, to eliminate
the need for providing the AEC sensor independently of the X-ray
image detecting device (patent document 1). According to the
patent document 1, the X-ray image detecting device has an output
terminal for outputting an AEC signal for stopping the X-ray
emission. The X-ray image detecting device is communicatably
connected to the source control device through the output
terminal. The AEC signal includes a timing signal such as an
emission stop signal (interception signal) for stopping the X-ray
emission and a dose detection signal representing the radiation
dose detected by the AEC sensor. In the case of sending the
emission stop signal (timing signal) as the AEC signal from the
X-ray image detecting device, the X-ray image detecting device
integrates the dose detection signal outputted from the AEC
sensor, and compares an integrated value with the threshold value
to judge whether or not the integrated value has reached the
threshold value. Upon judging that the integrated value has
reached the threshold value, the emission stop signal is sent from
the X-ray image detecting device to the source control device.
[0008] On the other hand, in the case of sending the dose
detection signal from the X-ray image detecting device as the AEC
signal, the X-ray image detecting device sequentially sends the
dose detection signal to the source control device. The source
control device performs a series of processes related to the AEC,
including integration of the dose detection signal sent from the
X-ray image detecting device, comparison between the dose
detection signal and the threshold value, and judgment whether
or not the integrated value has reached the threshold value.
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PRIOR ART DOCUMENTS
Patent Documents
[0009] Patent Document 1: Japanese Patent No. 4006255
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0010] In performing the AEC, as described above, the X-ray image
detecting device communicates the AEC signal with the source
control device, in addition to communication of the image data
and the like with the console. The communication of the AEC signal
requires rapidity, as compared with the communication of the image
data and the like. This is because a delay in a process of stopping
the X-ray emission reduces the quality of the X-ray image and
causes unnecessary radiation exposure of the patient, owing to
an excessive radiation dose beyond an appropriate value. For
example, in chest radiography, time from the start of X-ray
emission to the stop thereof is extremely short on the order of
50 ms. In such short time, the X-ray image detecting device or
the source control device has to perform a series of processes
related to the AEC based on the dose detection signal outputted
from the AEC sensor, and the source control device has to perform
a process for actually stopping the X-ray emission from the X-ray
source. Therefore, the communication of the AEC signal between
the source control device and the X-ray image detecting device
requires rapidity.
[0011] On the contrary, the communication of the other
information such as the image data between the X-ray image
detecting device and the console does not require as much rapidity
as the communication of the AEC signal. Instead, since the
console is often installed in an operators room partitioned from
an examination room, it is required to reduce complicated routing
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of a communication cable between the X-ray image detecting device
and the console. This is a matter of concern especially in the
case of using the electronic cassette as the X-ray image detecting
device. As described above, the electronic cassette is sometimes
used while being detached from the imaging stand. The electronic
cassette and the console are sometimes carried about to be shared
in a plurality of examination rooms having the X-ray source. In
the case of using the electronic cassette in a detached state from
the imaging stand or carrying about the electronic cassette, the
complicated routing of the communication cable adversely affects
the handleability and the portability of the electronic cassette
and the console. Therefore, it is required to ease the routing.
[0012] The patent document 1 describes no measure against the
above requests regarding the communication between the source
control device and the X-ray image detecting device and the
communication between the X-ray image detecting device and the
console.
[0013] The present invention aims to provide a radiation imaging
system, a communication method of the radiation imaging system,
and a radiographic image detecting device that can meet the
requests regarding the communication between the source control
device and the radiographic image detecting device and the
communication between the radiographic image detecting device and
the console to establish communication in an optimal operating
environment.
Means for Solving the Problems
[0014] A radiation imaging system according to the present
invention includes a radiation source, a source control device,
a radiographic image detecting device, a console, a high speed
communication unit, and a low speed wireless communication unit.
The radiation source emits radiation to an object. The source
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control device controls an operation of the radiation source. The
radiographic image detecting device detects a radiographic image
by receiving the radiation passed through the object.
Furthermore, the radiographic image detecting device has an AEC
sensor for performing automatic exposure control that detects a
radiation dose passed through the object and stops a radiation
emission from the radiation source as soon as an integrated value
of the radiation dose has reached a predetermined emission stop
threshold value. The console receives the radiographic image
detected by the radiographic image detecting device. The high
speed communication unit has a relatively high communication
speed, and communicates an AEC signal related to the automatic
exposure control between the source control device and the
radiographic image detecting device. The low speed wireless
communication unit has a communication speed lower than the
communication speed of the high speed communication unit, and
wirelessly communicates a signal other than the AEC signal between
the radiographic image detecting device and the console.
[0015] The high speed communication unit has small average delay
time of data communication, for example. The low speed wireless
communication unit has delay time larger than the delay time of
the high speed communication unit, for example.
[0016] The high speed communication unit performs wireless
communication of the AEC signal, for example. The high speed
communication unit preferably performs communication of the AEC
signal by ad-hoc communications. The low speed wireless
communication unit preferably performs communication of the
signal other than the AEC signal by infrastructure
communications. It is preferable that the radiographic image
detecting device directly communicates the AEC signal with the
source control device by the ad-hoc communications.
[0017] The high speed communication unit may perform wired
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communication of the AEC signal. The high speed communication
unit may also perform wired communication of the signal other than
the AEC signal. The radiation imaging system may include a
judging section for judging whether or not to perform the
automatic exposure control in radiography in accordance with an
imaging condition inputted through the console, and a
communication switching section for making the high speed
communication unit, instead of the low speed wireless
communication unit, communicate the signal other than the AEC
signal, in a case where the judging section judges that the
automatic exposure control is not performed.
[0018] The high speed communication unit and the low speed
wireless communication unit may be made of different hardware
resources. The radiographic image detecting device may include
a first control section for performing control of a process and
communication of the AEC signal, and a second control section for
performing control of a process and communication of the signal
other than the AEC signal.
[0019] The radiation imaging system may include a low speed wired
communication unit for performing wired communication of the
signal other than the AEC signal at a communication speed lower
than the communication speed of the high speed communication unit.
[0020] The AEC signal is preferably one of a dose detection signal
of the AEC sensor and an emission stop signal that is outputted
as soon as an integrated value of the dose detection signal of
the AEC sensor has reached a predetermined emission stop threshold
value. The radiographic image detecting device preferably has
two modes, including a first AEC mode for transmitting the dose
detection signal of the AEC sensor and a second AEC mode for
transmitting the emission stop signal to the source control device
through the high speed communication unit.
[0021] The source control device and the radiographic image
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detecting device preferably have, as the high speed communication
unit, a detection signal I/F for communicating the dose detection
signal and an emission signal I/F for communicating the emission
stop signal.
[0022] The radiographic image detecting device may have a main
body and a supplemental device. The main body has an image
detector for detecting the radiographic image and the AEC sensor.
The supplemental device has the detection signal I/F and the
emission signal I/F. In this case, communication between the
supplemental device and the main body adopts a same communication
method as a communication method of the high speed communication
unit.
[0023] The radiographic image detecting device is preferably an
electronic cassette having a portable housing. It is preferable
that the electronic cassette can be driven by a battery contained
in the housing.
[0024] The radiation imaging system preferably includes a
noncontact power feeding device for supplying electric power to
recharge the battery. The battery is rechargeable in a state of
being contained in the electronic cassette with the electric power
from the noncontact power feeding device. It is preferable that
the noncontact power feeding device is embedded in a holder of
an imaging stand into which the electronic cassette is detachably
loaded.
[0025] It is preferable that the radiographic image detecting
device includes an image detector that has an imaging surface and
detects the radiographic image, and the AEC sensor is disposed
in the imaging surface.
[0026] According to a communication method of a radiation imaging
system according to the present invention, the radiation imaging
system includes a radiation source for emitting radiation to an
object; a source control device for controlling an operation of
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the radiation source; a radiographic image detecting device for
detecting a radiographic image by receiving the radiation passed
through the object, the radiographic image detecting device
having an AEC sensor for performing automatic exposure control
that detects a radiation dose passed through the object and stops
a radiation emission from the radiation source as soon as an
integrated value of the radiation dose has reached a predetermined
emission stop threshold value; and a console for receiving the
radiographic image detected by the radiographic image detecting
device. The communication method includes a high speed
communication step and a low speed wireless communication step.
In the high speed communication step, an AEC signal related to
the automatic exposure control is communicated at relatively high
speed between the source control device and the radiographic image
detecting device. In the low speed wireless communication step,
a signal other than the AEC signal is wirelessly communicated
between the radiographic image detecting device and the console
at a communication speed lower than the communication speed of
the AEC signal.
[0027] A radiographic image detecting device according to the
present invention is to be used in combination with a radiation
source for emitting radiation to an object and a source control
device for controlling an operation of the radiation source, to
detect a radiographic image by receiving the radiation passed
through the object. The radiographic image detecting device
includes an AEC sensor, a high speed communication unit, and a
low speed wireless communication unit. The AEC sensor performs
automatic exposure control that detects a radiation dose passed
through the object and stops a radiation emission from the
radiation source as soon as an integrated value of the radiation
dose has reached a predetermined emission stop threshold value.
The high speed communication unit communicates an AEC signal
11
related to the automatic exposure control with the source control
device at a relatively high communication speed. The low speed
wireless communication unit wirelessly communicates a signal
other than the AEC signal with a console for receiving the
radiographic image at a communication speed lower than the
communication speed of the AEC signal.
Effect of the Invention
[0028] According to the present invention, the AEC signal is
communicated at the relatively high communication speed, and the
signal other than the AEC signal is communicated wirelessly at
the communication speed lower than the communication speed of the
AEC signal. Therefore, it is possible to provide the
communication method of the radiation imaging system and the
radiographic image detecting device that can make communication
in an optimal operating environment.
BRIEF DESCRIPTION OF DRAWINGS
[0029] Fig. 1 is a schematic view showing the structure of an
X-ray imaging system;
Fig. 2 is a diagram showing the internal structure of a
source control device and the connection relation between the
source control device and other devices;
Fig. 3 is a block diagram showing the internal structure
of an electronic cassette;
Fig. 4 is a diagram for explaining the disposition of
detection pixels in an FPD of the electronic cassette;
Fig. 5 is a block diagram showing the internal structure
of an AEC unit and a communication unit of the electronic cassette;
Fig. 6 is a diagram showing imaging conditions set in a
console;
Fig. 7 is a block diagram showing the internal structure
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of the console;
Fig. 8 is a block diagram showing the functions of the
console and the flow of information;
Fig. 9 is a table of radiation source information;
Fig. 10 is a comparison table between an easy installation
priority type (first AEC mode) and an easy installation
non-priority type (second AEC mode);
Fig. 11 is a flowchart of an initial setting process;
Fig. 12 is a flowchart of an AEC execution process in
radiography;
Fig. 13 is a diagram showing an operation state of the
communication unit and the AEC unit in the first AEC mode in a
case where the source control device has no integrator;
Fig. 14 is a diagram showing an operation state of the
communication unit and the AEC unit in the first AEC mode in a
case where the source control device has an integrator;
Fig. 15 is a diagram showing an operation state of the
communication unit and the AEC unit in the second AEC mode;
Fig. 16 is a flowchart of a communication method choosing
process;
Fig. 17 is a block diagram in a state where hardware
resources of a controller and a communicator related to AEC are
operated independently of hardware resources of the other
controller and communicator;
Fig. 18 is a diagram showing an example of the structure
of a power feeding electrode and a power receiving part of the
electronic cassette;
Fig. 19 is a block diagram showing an example of the
electronic cassette that is constituted of a cassette main body
and a supplemental device;
Fig. 20 is a diagram showing an example of a type selection
window to which the type differing from area to area is inputted
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manually;
Fig. 21 is a diagram for explaining imaging conditions
settable in the source control device and a measure against a case
where emission stop threshold values of the source control device
are less than those of the electronic cassette; and
Fig. 22 is a block diagram showing an example where signals
other than an emission stop signal are transmitted and received
through a communication I/F, while the emission stop signal is
received through an I/F dedicated to the emission stop signal.
DESCRIPTION OF INVENTION
[0030] First Embodiment
In Fig. 1, an X-ray imaging system (radiation imaging system) 2
includes an X-ray source (radiation source) 10 containing an X-ray
tube for radiating X-rays, a source control device 11 for
controlling the operation of the X-ray source 10, an emission
switch 12 for commanding a start of X-ray emission, an electronic
cassette (radiographic image detecting device) 13 for detecting
the X-rays passed through an object and outputting an X-ray image,
a console 14 for performing operation control of the electronic
cassette 13, an image process of the X-ray image, and display of
the X-ray image, an imaging stand 15 for imaging the object in
a standing position, and an imaging table 16 for imaging the object
in a lying position. The X-ray source 10, the source control
device 11, and the emission switch 12 compose an X-ray generating
apparatus 2a. The electronic cassette 13 and the console 14
compose an X-ray imaging apparatus 2b. In addition to above, the
X-ray imaging system 2 is provided with a cradle 17 for recharging
a battery 38 (see Fig. 3 too) to be contained in the electronic
cassette 13, a source moving device (not shown) for setting the
X-ray source 10 in a desired orientation and position, and the
like. Note that, the source control device 11 and the console
14
14 may be integrated into one unit.
[0031] The X-ray source 10 has the X-ray tube for radiating the
X-rays and an irradiation field limiting device (collimator) for
limiting an irradiation field of the X-rays radiating from the
X-ray tube. The X-ray tube has a cathode composed of a filament
for emitting thermoelectrons, and an anode (target) that radiates
the X-rays by collision of the thermoelectrons emitted from the
cathode. The irradiation field limiting device is composed of,
for example, four lead plates for blocking the X-rays. The four
lead plates are disposed in each side of a rectangle so as to form
a rectangular irradiation opening in a middle to pass the X-rays
therethrough. Shifting the position of the lead plates varies
the size of the irradiation opening to limit the irradiation
field.
[0032] As shown in Fig. 2, the source control device 11 is
provided with a high voltage generator 20, a controller 21, and
a communication I/F 22. The high voltage generator 20 generates
a high tube voltage by multiplying an input voltage using a
transformer, and supplies the tube voltage to the X-ray source
10 through a high voltage cable. The controller 21 controls the
tube voltage that determines an energy spectrum of the X-rays
radiating from the X-ray source 10, a tube current that determines
an X-ray emission amount per unit of time, and an X-ray emission
time. The communication I/F 22 mediates transmission and
reception of principal information and signals to and from the
console 14.
[0033] To the controller 21, the emission switch 12, a memory
23, and a touch panel 24 are connected. The emission switch 12
is, for example, a two-step press switch to be operated by an
operator such as a radiological technician. Upon a first-step
press of the emission switch 12, a warm-up start signal is issued
to start warming up the X-ray source 10. Upon a second-step press,
15
an emission start signal is issued to make the X-ray source 10
start emitting the X-rays. These signals are inputted to the
source control device 11 through a signal cable. Upon receiving
the emission start signal from the emission switch 12, the
controller 21 starts electric power supply from the high voltage
generator 20 to the X-ray source 10.
[0034] A radiation dose necessary for obtaining the X-ray image
of favorable image quality approximately depends on a body part
to be imaged of the object. However, since X-ray transmittance
depends on a physique of the object, even if the same radiation
dose is applied, a radiation dose received by the electronic
cassette 13 varies in accordance with the physique of the object.
For this reason, the X-ray imaging system 2 adopts AEC so that
the electronic cassette 13 can obtain the necessary radiation dose
irrespective of variations in the physique of the object.
[0035] To the source control device 11, an AEC sensor 25 is
connectable. The AEC sensor 25 is composed of, for example, a
well-known ion chamber and the like. The AEC sensor 25 has been
used together with a film cassette or an IP cassette to perform
the AEC in radiography, since before introducing the X-ray imaging
apparatus 2b having the electronic cassette 13. The AEC sensor
25 is a device independent of the electronic cassette 13, and
outputs a dose detection signal representing an incident
radiation dose as the AEC signal.
[0036] As described later on, the electronic cassette 13 has
another integral AEC sensor, and the AEC sensor 25 is not used
in the case of using the electronic cassette 13. To distinguish
between the AEC sensor 25 and the integral AEC sensor embedded
in the electronic cassette 13, the AEC sensor 25 is hereafter
called a previous AEC sensor. To distinguish between a dose
detection signal outputted from the previous AEC sensor 25 and
a dose detection signal outputted from the AEC sensor embedded
16
in the electronic cassette 13, the dose detection signal outputted
from the previous AEC sensor 25 is called a previous AEC detection
signal, while the dose detection signal outputted from the AEC
sensor embedded in the electronic cassette 13 is called a new AEC
detection signal.
[0037] The previous AEC sensor 25 detects the incident radiation
dose as a voltage value, and outputs the detected voltage value
as the previous AEC detection signal. The previous AEC sensor
25 repeats detecting the radiation dose in a predetermined
sampling cycle. The previous AEC detection signal outputted from
the previous AEC sensor 25 may be a voltage value (instantaneous
value) obtained by one-time detection of the radiation dose, or
an integrated value of the voltage value obtained by plural-time
detection of the radiation dose. The integrated value represents
an accumulative dose of the incident radiation dose. In the case
of outputting the integrated value, the previous AEC sensor 25
is provided with an integrator. The previous AEC sensor 25
updates the integrated value whenever detecting the radiation
dose, and outputs the updated integrated value as the previous
AEC detection signal.
[0038] The previous AEC sensor 25 is of approximately the same
size in plane as the size the cassette usable in the X-ray imaging
system 2, and is used in a state of being disposed in front of
an imaging surface of the cassette. The previous AEC sensor 25
has, for example, three dose measurement areas A, B, and C at upper
left and upper right corresponding to lungs in chest radiography
and at lower middle, respectively. The previous AEC sensor 25
can output the previous AEC detection signal of each dose
measurement area, or a sum value or an average value of the previous
AEC detection signals of the plurality of dose measurement areas,
depending on its setting.
[0039] A detection signal I/F 26 is a connection I/F for
17
connecting the previous AEC sensor 25, and receives the previous
AEC detection signal (dose detection signal). The detection
signal I/F 26 can receive a signal that is in the same format as
the format of the previous AEC detection signal. In the case of
using the electronic cassette 13, the detection signal I/F 26 can
receive the new AEC detection signal (dose detection signal)
outputted from the AEC sensor embedded in the electronic cassette
13.
[0040] The detection signal I/F 26 inputs the received previous
AEC detection signal to the controller 21. Upon receiving the
emission start signal from the emission switch 12, the controller
21 starts monitoring the previous AEC detection signal. The
controller 21 compares the integrated value of the previous AEC
detection signal with an emission stop threshold value set in an
imaging condition at appropriate timing. To be more specific,
the controller 21 repeats the comparison between the previous AEC
detection signal and the emission stop threshold value whenever
receiving the previous AEC detection signal from the previous AEC
sensor 25.
[0041] The controller 21 continues the X-ray emission from the
X-ray source 10, until the previous AEC detection signal reaches
the emission stop threshold value. As soon as the previous AEC
detection signal has reached the emission stop threshold value,
the controller 21 sends an emission stop command to the high
voltage generator 20 to stop the X-ray emission. The high voltage
generator 20 stops supplying the electric power to the X-ray
source 10 in response to the emission stop command, and stops the
X-ray emission.
[0042] The controller 21 performs the same process as the process
of the previous AEC detection signal also in a case where the
detection signal I/F 26 receives the new AEC detection signal
outputted from the AEC sensor embedded in the electronic cassette
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13.
[0043] The memory 23 stores in advance a plurality of types of
imaging conditions, each including a tube voltage and a tube
current-time product (mAs value) preset in the source control
device 11. In this embodiment, the tube current-time product,
the dose measurement areas of the previous AEC sensor 25, the
emission stop threshold value to judge the stop of X-ray emission
by comparison with the previous AEC detection signal outputted
from the previous AEC sensor 25, and the like are stored as the
imaging condition corresponding to each number (No.) and tube
voltage (each of four types of 120 kV of No. 1, 90 kV of No. 2,
70 kV of No. 3, and 50 kV of No. 4) of the imaging condition. As
the emission stop threshold value, default values TH1 to TH4 are
set in advance in shipping the X-ray source 10. As shown in No.
1 having a tube voltage of 120 kV and No. 3 having a tube voltage
of 70 kV, if the operator adjusts the default value (TH1 and TH3)
during use, both an adjusted value (TH1’ and TH3’) and the default
value (TH1 and TH3) are stored. The imaging condition is set
manually by the operator by designating the number (No.) of the
imaging condition through the touch panel 24. The item of the
dose measurement area includes dose measurement area designating
information, which represents which of the three dose measurement
areas A to C provided in the previous AEC sensor 25 to use.
[0044] The source control device 11 starts the X-ray emission
with the tube voltage and the tube current-time product
corresponding to the designated number (No.) of the imaging
condition. As soon as the AEC detects that the incident radiation
dose has reached a sufficient target dose, the AEC stops the X-ray
emission even if the tube current-time product has not yet reached
the value designated in the imaging condition. Note that, in
order to prevent a shortage of the incident radiation dose caused
by completion of the X-ray emission before the AEC judges the stop
19
of X-ray emission using the target dose, a value having a margin
adequate for the target dose is set as the imaging condition of
the X-ray source 10. The value having the margin is, for example,
a maximum value allowable under safety restrictions. Note that,
the tube current-time product is preferably set at a value in
accordance with the body part to be imaged. Instead of the tube
current-time product, the tube current and the X-ray emission time
may be set separately.
[0045] The memory 23 also stores an ID (source ID) to identify
a model of the X-ray generating apparatus 2a. The source ID is
used for establishing a setting of the X-ray imaging apparatus
2b, which is used together with the X-ray generating apparatus
2a, in accordance with the model of the X-ray generating apparatus
2a. In installing the X-ray imaging apparatus 2b, the console
14 and the source control device 11 are connected communicatably.
Upon establishing the communication with the console 14, the
controller 21 sends the source ID read from the memory 23, together
with information of the emission stop threshold value being the
imaging condition, to the console 14 through the communication
I/F 22.
[0046] An emission signal I/F 27 is used when using the electronic
cassette 13, for sending and receiving a start synchronization
signal for synchronization between a time of starting the X-ray
emission from the X-ray source 10 and a time of starting the
operation of the electronic cassette 13. The controller 21 sends
and receives the start synchronization signal to and from the
electronic cassette 13, upon receiving the warm-up start signal
from the emission switch 12.
[0047] More specifically, the controller 21 sends to the
electronic cassette 13 through the emission signal I/F 27 an
emission start request signal, which inquires whether or not the
electronic cassette 13 is ready for a start of the X-ray emission.
20
Upon receiving the emission start request signal, the electronic
cassette 13 completes a reset process described later on, and
performs a preparation process including an accumulation start
process and the like. Then, upon receiving through the emission
signal I/F 27 an emission permission signal being a response of
the emission start request signal from the electronic cassette
13 and further receiving the emission start signal from the
emission switch 12, the controller 21 starts supplying the
electric power from the high voltage generator 20 to the X-ray
source 10. Upon stopping the X-ray emission, the controller 21
sends an emission stop signal to the electronic cassette 13
through the emission signal I/F 27.
[0048] The electronic cassette 13 has two AEC modes to perform
the AEC, i.e. a first AEC mode and a second AEC mode. An output
format and an output I/F of the AEC signal from the electronic
cassette 13 to the source control device 11 differ from mode to
mode. In the first AEC mode, the new AEC detection signal (dose
detection signal) similar to the previous AEC detection signal
(dose detection signal) outputted from the previous AEC sensor
25 is outputted. In the first AEC mode, the new AEC detection
signal outputted from the electronic cassette 13 is sent to the
detection signal I/F 26 of the source control device 11, just as
with the previous AEC detection signal outputted from the previous
AEC sensor 25. The source control device 11 performs the
comparison with the emission stop threshold value based on the
received new AEC detection signal.
[0049] In the second AEC mode, the emission stop signal (timing
signal) for regulating emission stop timing is outputted as the
AEC signal. The emission stop signal is received not by the
detection signal I/F 26 but by the emission signal I/F 27. In
the second AEC mode, the electronic cassette 13 compares the
integrated value of the new AEC detection signal with the emission
21
stop threshold value and sends the emission stop signal to the
source control device 11 when the integrated value has reached
the emission stop threshold value, instead of sending the new AEC
detection signal outputted from the integral AEC sensor to the
source control device 11. In other words, in the second AEC mode,
the electronic cassette 13 performs a process that is performed
by the source control device 11 in the first AEC mode based on
the previous AEC detection signal or the new AEC detection signal.
[0050] Upon receiving by the emission signal I/F 27 the emission
stop signal from the electronic cassette 13, the controller 21
of the source control device 11 stops supplying the electric power
from the high voltage generator 20 to the X-ray source 10 to stop
the X-ray emission. As shown in Fig. 2, in a case where the
electronic cassette 13 performs the AEC in the first AEC mode,
both the emission signal I/F 27 and the detection signal I/F 26
are connected to the electronic cassette 13. The electronic
cassette 13 outputs the new AEC detection signal in the first AEC
mode, so the emission signal I/F 27 is used only for transmitting
and receiving the synchronization signal for synchronization of
an emission start timing. The detection signal I/F 26 is used
for receiving the new AEC detection signal from the electronic
cassette 13.
[0051] On the other hand, in the second AEC mode, the electronic
cassette 13 outputs the emission stop signal as the AEC signal.
The emission stop signal is received by the emission signal I/F
27, which is used for transmitting and receiving the
synchronization signal. Accordingly, only the emission signal
I/F 27 is used, and the detection signal I/F 26 is unused in the
second AEC mode.
[0052] In Fig. 3, as is widely known, the electronic cassette
13 is composed of a flat panel detector (FPD) 35 and a portable
housing for containing the FPD 35. The housing of the electronic
22
cassette 13 is in an approximately rectangular and flat shape,
and of the same size (a size compatible with International
Standard ISO4090:2001) as the size of the film cassette and the
IP cassette (also called a CR cassette) in plane. Therefore, the
electronic cassette 13 is attachable to an existing imaging stand
or table designed for the film cassette and the IP cassette.
[0053] A plurality of electronic cassettes 13 are provided in
each examination room installed with the X-ray imaging system 2,
for example, one electronic cassette 13 for the imaging stand 15
and one electronic cassette 13 for the imaging table 16. The
electronic cassette 13 is detachably set in a holder 15a, 16a (see
Fig. 1) of the imaging stand 15 or the imaging table 16 in such
a position that an imaging surface 36 of the FPD 35 is opposed
to the X-ray source 10. The electronic cassette 13 can be used
separately from the imaging stand 15 or the imaging table 16 in
a state of being put on a bed under the object lying or held by
the object himself/herself.
[0054] The electronic cassette 13 contains an antenna 37 and a
battery 38, and can have wireless communication with the console
14. The antenna 37 transmits and receives a radio wave for use
in the wireless communication to and from the console 14. As a
wireless communication method between the electronic cassette 13
and the console 14, one having a relatively low communication
speed and requiring lower power consumption, for example, a
wireless LAN, Bluetooth (trademark), Zigbee (trademark), or the
like is available. The battery 38 supplies the electric power
to operate each part of the electronic cassette 13. The battery
38 is of a relatively small type so as to be contained in the slim
electronic cassette 13. As shown in Fig. 1, the battery 38 can
be taken out of the electronic cassette 13 and set in the specific
cradle 17 for recharging.
[0055] The electronic cassette 13 is provided with a socket 39
23
in addition to the antenna 37. The socket 39 is provided for
having wired communication with the console 14, and used in the
case of a malfunction of the wireless communication between the
electronic cassette 13 and the console 14 owing to poor signal
quality. Upon connecting a cable of the console 14 to the socket
39, the wired communication is established between the electronic
cassette 13 and the console 14. Note that, the console 14 may
feed power to the electronic cassette 13 using a power feedable
multi-cable as the communication cable. This allows operating
the electronic cassette 13 and recharging the battery 38 by the
power fed by the console 14, even in the case of running out of
the battery 38.
[0056] The antenna 37 and the socket 39 are provided in a
communication unit 40. The communication unit 40 mediates
transmission and reception of various types of information
including image data and signals (including a life check signal
for checking whether or not communication is performed normally
and the like) between the antenna 37 or the socket 39 and a
controller 41, and between the antenna 37 or the socket 39 and
a memory 42. The antenna 37 functions as a low speed wireless
communicator, and the socket 39 functions as a low speed wired
communicator.
[0057] The FPD 35 has a TFT active matrix substrate. In the
substrate, a plurality of pixels 45 each for accumulating signal
charge in accordance with an X-ray amount incident thereon are
arranged to form the imaging surface 36. The plurality of pixels
45 are arranged into a two-dimensional matrix with n rows (X
direction) and m columns (Y direction) at a predetermined pitch.
“n” and “m” are integers of two or more. The pixel number of the
FPD 35 is, for example, approximately 2000 by approximately 2000.
[0058] The FPD 35 is of an indirect conversion type, having a
scintillator (phosphor) for converting the X-rays into visible
24
light. The pixels 45 perform photoelectric conversion of the
visible light converted by the scintillator. The scintillator
is made of CsI (cesium iodide), GOS (gadolinium oxysulfide), or
the like, and is opposed to the entire imaging surface 36 having
the matrix of pixels 45. Note that, the scintillator and the FPD
35 may adopt either a PSS (penetration side sampling) method in
which the scintillator and the FPD 35 are disposed in this order
from an X-ray incident side, or an ISS (irradiation side sampling)
method in which the FPD 35 and the scintillator are disposed in
this order oppositely to the PSS method. Also, a direct
conversion type FPD, which has a conversion layer (amorphous
selenium) or the like for directly converting the X-rays into the
electric charge, may be used instead of the scintillator.
[0059] The pixel 45 is composed of a photodiode 46, a capacitor
(not shown), and a thin film transistor (TFT) 47. The photodiode
46, being a photoelectric conversion element, produces the
electric charge (electron and hole pairs) upon entry of the
visible light. The capacitor accumulates the electric charge
produced by the photodiode 46. The thin film transistor 47
functions as a switching element.
[0060] The photodiode 46 is composed of a semiconducting layer
(of a PIN type, for example) for producing the electric charge
and an upper electrode and a lower electrode disposed on top and
bottom of the semiconducting layer. The lower electrode of the
photodiode 46 is connected to the TFT 47. The upper electrode
of the photodiode 46 is connected to a bias line 48. There are
the same number of bias lines 48 provided as the number (n rows)
of the rows of the pixels 45 in the imaging surface 36. All the
bias lines 48 are coupled to a bus 49. The bus 49 is connected
to a bias power supply 50. A bias voltage Vb is applied from the
bias power supply 50 to the upper electrodes of the photodiodes
46 through the bus 49 and the bias lines 48. Since the application
25
of the bias voltage Vb produces an electric field in the
semiconducting layer, the electric charge (electron and hole
pairs) produced in the semiconducting layer by the photoelectric
conversion is attracted to the upper and lower electrodes, one
of which has a positive polarity and the other of which has a
negative polarity. Thereby, the electric charge is accumulated
in the capacitor.
[0061] A gate electrode of the TFT 47 is connected to a scan line
51. A source electrode of the TFT 47 is connected to a signal
line 52. A drain electrode of the TFT 47 is connected to the
photodiode 46. The scan lines 51 and the signal lines 52 are
routed into a lattice. The number of the scan lines 51 coincides
with the number of the rows (n rows) of the pixels 45. The number
of the signal lines 52 coincides with the number of the columns
(m columns) of the pixels 45. The scan lines 51 are connected
to a gate driver 53, and the signal lines 52 are connected to a
signal processor 54.
[0062] The gate driver 53 drives the TFTs 47 to carry out a charge
accumulation operation for accumulating the signal charge in the
pixel 45 in accordance with the amount of the X-rays incident
thereon, a readout operation (actual readout operation) for
reading out the signal charge from the pixels 45, and a reset
operation (idle readout operation). The controller 41 controls
a start timing of each of the above operations carried out by the
gate driver 53.
[0063] In the charge accumulation operation, the signal charge
is accumulated in the pixels 45 while the TFTs 47 are turned off.
In the readout operation, the gate driver 53 sequentially issues
gate pulses G1 to Gn each of which drives the TFTs 47 of the same
row at a time. Thereby, the scan lines 51 are activated one by
one to turn on the TFTs 47 connected to the activated scan line
51 on a row-by-row basis. Upon turning on the TFT 47, the electric
26
charge accumulated in the capacitor of the pixel 45 is read out
to the signal line 52 and inputted to the signal processor 54.
[0064] Dark charge occurs in the semiconducting layer of the
photodiode 46 irrespective of the presence or absence of entry
of the X-rays. Due to the application of the bias voltage Vb,
the dark charge is accumulated in the capacitor. The dark charge
occurring in the pixels 45 becomes noise of the image data, and
therefore the reset operation is carried out to remove the dark
charge. The reset operation is an operation to discharge the dark
charge occurring in the pixels 45 through the signal lines 52.
[0065] The reset operation adopts a sequential reset method, for
example, by which the pixels 45 are reset on a row-by-row basis.
In the sequential reset method, as with the readout operation of
the signal charge, the gate driver 53 sequentially issues the gate
pulses G1 to Gn to the scan lines 51 to turn on the TFTs 47 of
the pixels 45 on a row-by-row basis. While the TFT 47 is turned
on, the dark charge flows from the pixel 45 through the signal
line 52 into an integration amplifier 60. In the reset operation,
in contrast to the readout operation, a MUX 61 does not read out
the electric charge accumulated in the integration amplifier 60.
In synchronization with the issue of each of the gate pulses G1
to Gn, the controller 41 outputs reset pulses RST to reset the
integration amplifiers 60.
[0066] Instead of the sequential reset method, a parallel reset
method or all pixels reset method may be used. In the parallel
reset method, a plurality of rows of pixels are grouped together,
and sequential reset is carried out in each group, so as to
concurrently discharge the dark charge from the rows of the number
of the groups. In the all pixels reset method, the gate pulse
is inputted to every row to discharge the dark charge from every
pixel at a time. The parallel reset method and the all pixels
reset method allow speeding up the reset operation.
27
[0067] The signal processor 54 includes the integration
amplifiers 60, the multiplexer (MUX) 61, an A/D converter (A/D)
62, and the like. The integration amplifier 60 is connected to
each signal line 52 on a one-by-one basis. The integration
amplifier 60 is composed of an operational amplifier and a
capacitor connected between input and output terminals of the
operational amplifier. The signal line 52 is connected to one
of the input terminals of the operational amplifier. The other
input terminal of the operational amplifier is connected to a
ground (GND). The integration amplifier 60 converts by
integration the electric charge inputted from the signal line 52
into each of voltage signals D1 to Dm, and outputs each of the
voltage signals D1 to Dm. An output terminal of the integration
amplifier 60 of each column is connected to the MUX 61 through
another amplifier 63 and a sample holder (S/H) 64. An output of
the MUX 61 is connected to the A/D 62.
[0068] The MUX 61 sequentially selects one of the plurality of
integration amplifiers 60 connected in parallel, and inputs the
voltage signals D1 to Dm outputted from the selected integration
amplifiers 60 in series to the A/D 62.
[0069] The A/D 62 converts the inputted analog voltage signals
D1 to Dm of one row into digital values, and outputs the digital
values to the memory 42 embedded in the electronic cassette 13.
The memory 42 stores the digital values of one row with being
associated with coordinates of individual pixels 45 as image data
of one row of the X-ray image. Thereby, the readout operation
of one row is completed.
[0070] After the MUX 61 reads out from the integration amplifiers
60 the voltage signals D1 to Dm of one row, the controller 41
outputs the reset pulse RST to the integration amplifiers 60 to
turn on reset switches 60a. Thus, the signal charge of one row
accumulated in the integration amplifiers 60 is reset. Upon
28
resetting the integration amplifiers 60, the gate driver 53
outputs the gate pulse of the next row to start reading out the
signal charge from the pixels 45 of the next row. By sequential
repetition of this operation, the signal charge is read out from
the pixels 45 of every row.
[0071] After completion of the readout from every row, the image
data representing the X-ray image of one frame is stored in the
memory 42. This image data is read out from the memory 42, and
outputted to the console 14 through the communication unit 40.
Thereby, the X-ray image of the object is detected.
[0072] Upon receiving the emission start request signal from the
controller 21 of the source control device 11, the controller 41
of the electronic cassette 13 makes the FPD 35 perform the reset
operation and sends the emission permission signal to the source
control device 11. Upon receiving the emission start signal, the
controller 41 of the electronic cassette 13 shifts the operation
of the FPD 35 from the reset operation to the charge accumulation
operation.
[0073] The FPD 35 has, in the same imaging surface 36, a plurality
of detection pixels 65 each of which is connected to the signal
line 52 without through the TFT 47, in addition to the pixels 45
each connected to the signal line 52 through the TFT 47. The
detection pixels 65 are pixels for use in detecting the X-ray dose
applied to the imaging surface 36 through the object. The
detection pixels 65 function as an AEC sensor, just as with the
previous AEC sensor 25. The detection pixels 65 occupy, for
example, on the order of approximately 0.01 of the pixels 45
in the imaging surface 36.
[0074] As shown in Fig. 4, the detection pixels 65 are disposed
along a waveform line 66 that is horizontally symmetric with
respect to the center of the imaging surface 36 as shown by a broken
line, so as to be uniformly distributed in the imaging surface
29
36 without being localized. For example, one detection pixel 65
is laid out in the column of the pixels 45 connected to the single
signal line 52. The columns having the detection pixel 65 are
arranged at intervals of two to three columns without having the
detection pixel 65. The positions of the detection pixels 65 are
known in manufacturing the FPD 35, and the FPD 35 has a nonvolatile
memory (not shown) that stores the position (coordinates) of every
detection pixel 65 in advance.
[0075] Since the detection pixel 65 is connected to the signal
line 52 directly without through the TFT 47, the signal charge
produced in the detection pixel 65 immediately flows into the
signal line 52. The same holds true, even while the TFTs 47 of
the normal pixels 45 of the same column are turned off and the
normal pixels 45 of the same column are in the charge accumulation
operation. Thus, the electric charge produced in the detection
pixel 65 always flows into the integration amplifier 60 in the
signal line 52 connected to the detection pixel 65. During the
charge accumulation operation, the electric charge that is
produced by the detection pixel 65 and accumulated in the
integration amplifier 60 is outputted as a voltage value (new AEC
detection signal) through the MUX 61 to the A/D 62 at predetermined
sampling intervals. The new AEC detection signal is outputted
from the A/D 62 to the memory 42. The memory 42 stores the new
AEC detection signal in correspondence with the coordinate
information of each detection pixel 65 in the imaging surface 36.
The FPD 35 repeats this dose detection operation in the execution
of the AEC.
[0076] The controller 41 controls the operation of an AEC unit
67. The AEC unit 67 accesses the memory 42 to read out the recorded
new AEC detection signal. In Fig. 5, the AEC unit 67 has a dose
measurement area selector 75, a corrector 76, an integrator 77,
a comparator 78, and a threshold value generator 79.
30
[0077] The dose measurement area selector 75 selects which signal
to use in the AEC out of the new AEC detection signals of the
plurality of detection pixels 65 distributed in the imaging
surface 36, based on the coordinate information of the new AEC
detection signals read out of the memory 42. The corrector 76
corrects the new AEC detection signal to a value corresponding
to the previous AEC detection signal.
[0078] As described later on, the previous AEC sensor 25 and the
detection pixel 65 embedded in the electronic cassette 13 are
different from each other in sensitivity, a range of an outputted
voltage value, and the like. Thus, even if the same X-ray dose
is applied, an output value of the previous AEC sensor 25 is
different from an output value of the detection pixel 65. In the
electronic cassette 13, in the case of executing the AEC in the
first AEC mode, the new AEC detection signal is sent to the
detection signal I/F 26 of the source control device 11, just as
with the previous AEC detection signal. The source control device
11 has no function of distinguishing which one of the previous
AEC sensor 25 and the electronic cassette 13 has outputted the
detection signal. Accordingly, the corrector 76 corrects the
output value of the new AEC detection signal so as to equalize
the output value of the new AEC detection to the output value of
the previous AEC detection signal.
[0079] In the first AEC mode, in the case of outputting the new
AEC detection signal as an instantaneous value to the source
control device 11, the new AEC detection signal outputted from
the corrector 76 is sent to the source control device 11. In this
case, neither the integrator 77, the comparator 78, nor the
threshold value generator 79 works.
[0080] The integrator 77 integrates the new AEC detection signal.
In the first AEC mode, in the case of outputting the new AEC
detection signal as an integrated value to the source control
31
device 11, the new AEC detection signal outputted from the
integrator 77 is sent to the source control device 11. In this
case, neither the comparator 78 nor the threshold value generator
79 works.
[0081] The comparator 78 and the threshold value generator 79
work in the second AEC mode. In the second AEC mode, upon
detecting the start of X-ray emission, the comparator 78 starts
monitoring the integrated value of the detection signal from the
integrator 77. The comparator 78 compares the integrated value
with the emission stop threshold value provided by the threshold
value generator 79 in appropriate timing. At the moment when the
integrated value has reached the threshold value, the comparator
78 issues the emission stop signal.
[0082] The emission stop threshold value can be set more
specifically in the electronic cassette 13 in the second AEC mode,
as compared with the case of executing the first AEC mode using
the emission stop threshold value preset in the X-ray generating
apparatus 2a.
[0083] To be more specific, according to the imaging conditions
preset in the source control device 11, only one imaging condition
(including the emission stop threshold value) is set relative to
one tube voltage, which depends on the body part to be imaged,
as shown in Fig. 2. On the other hand, according to the imaging
conditions settable in the electronic cassette 13, a plurality
of imaging conditions are settable relative to one tube voltage,
as shown in Fig. 6. Taking Fig. 6 as an example, emission stop
threshold values (S values) different in accordance with an
imaging direction (PA, AP) and the like are settable relative to
one tube voltage (120 kV) corresponding to the chest radiography.
The information settable to the electronic cassette 13 is stored
in a storage device 87 of the console 14.
[0084] Note that, an S value is used as the emission stop
32
threshold value set in the electronic cassette 13. The S value,
which is obtained by a histogram analysis of the X-ray image data,
is a representative index value of a radiation dose, similarly
to an EI value and a REX value. Although the S value differs from
a value representing a radiation dose itself just as with the
emission stop threshold value preset in the source control device
11, the S value can be converted into a dose value similar to the
emission stop threshold value present in the source control device
11.
[0085] The emission stop threshold value set in the electronic
cassette 13 is set as a value to be compared with the new AEC
detection signal before being corrected by the corrector 76. The
new AEC detection signal inputted to the comparator 78 has been
corrected by the corrector 76, as described above, so the emission
stop threshold value that is set to be compared with the
uncorrected new AEC detection signal needs to be converted. The
threshold value generator 79 replaces the emission stop threshold
value set in the electronic cassette 13 with a value comparable
with the corrected new AEC detection signal.
[0086] More specifically, the threshold value generator 79
converts the emission stop threshold value set as a form of the
S value to the electronic cassette 13 into a form of the dose value.
Then, the converted dose value is multiplied by a ratio between
an output value of the previous AEC detection signal and an output
value of the uncorrected new AEC detection signal, to obtain the
emission stop threshold value comparable to the corrected new AEC
detection signal. Taking a case as an example where the emission
stop threshold value converted from the S value set in the
electronic cassette 13 is “6”, and a ratio between the output value
(4) of the previous AEC detection signal and the output value (5)
of the uncorrected new AEC detection signal is “4/5 (0.8)”, the
emission stop threshold value to be compared with the corrected
33
new AEC detection signal is calculated by 60.8=4.8. The ratio
between the output value of the previous AEC detection signal and
the output value of the uncorrected new AEC detection signal is
obtained from source information 99 described later on.
[0087] Note that, the replacement of the emission stop threshold
value, as described above, is required in this embodiment, because
the new AEC detection signal after being corrected by the
corrector 76 is inputted to the comparator 78 in the second AEC
mode. However, inputting the new AEC detection signal before the
correction to the comparator 78 eliminates the need for replacing
the emission stop threshold value.
[0088] The communication unit 40 includes a detection signal I/F
80 and an emission signal I/F 81, in addition to the antenna 37
and the socket 39 described above. The detection signal I/F 80
is wirelessly connected to the detection signal I/F 26 of the
source control device 11, and the emission signal I/F 81 is
wirelessly connected to the emission signal I/F 27 of the source
control device 11. The communication between the detection
signal I/Fs 26 and 80 and between the emission signal I/Fs 27 and
81 adopts a relatively high speed wireless communication method,
for example, an optical wireless communication, notably infrared
communication such as IrDA. The detection signal I/F 26 and the
emission signal I/F 27 function as a high speed communication
unit. The detection signal I/F 80 and the emission signal I/F
81 function as a high speed communication unit.
[0089] To the detection signal I/F 80, the corrector 76 and the
integrator 77 of the AEC unit 67 are connected. The detection
signal I/F 80 outputs one of an output from the corrector 76 i.e.
the new AEC detection signal and an output of the integrator 77
i.e. the integrated value of the new AEC detection signal. The
emission signal I/F 81 performs the transmission and reception
of the start synchronization signal (emission start request
34
signal and the emission permission signal), the output of the
comparator 78 i.e. the transmission of the emission stop signal.
In the execution of the AEC, the detection signal I/F 80 is used
in the first AEC mode, and the emission signal I/F 81 is used in
the second AEC mode. The emission signal I/F 81 is used for the
transmission and reception of the start synchronization signal
in both of the first AEC mode and the second AEC mode.
[0090] The console 14 is communicatably connected to the
electronic cassette 13 in a wired or wireless method, to control
the operation of the electronic cassette 13. To be more specific,
the console 14 transmits the imaging condition to the electronic
cassette 13 to set a signal processing condition (including a gain
of the amplifier for multiplying a voltage corresponding to the
accumulated signal charge) of the FPD 35. Additionally, the
console 14 turns on and off the electronic cassette 13, and puts
the electronic cassette 13 into a power saving mode, an exposure
preparation mode, and the like.
[0091] The console 14 applies various types of image processes
including an offset correction, a gain correction, a defect
correction, and the like to the X-ray image data transmitted from
the electronic cassette 13. In the defect correction, pixel
values of the row having the detection pixel 65 are interpolated
using the pixel values of the adjacent row without having the
detection pixel 65. The X-ray image after subjected to the image
processes is displayed on a display 89 (see Fig. 7) of the console
14, and its data is stored to the storage device 87 and a memory
86 (both are shown in Fig. 7) of the console 14, or a data storage
such as an image storage server connected to the console 14 through
a network.
[0092] The console 14 receives an input of an examination order
including information about sex and age of a patient, a body part
to be imaged, and an examination purpose, and displays the
35
examination order on the display 89. The examination order is
inputted from an external system e.g. HIS (hospital information
system) or RIS (radiography information system) that manages
patient data and examination data related to radiography, or
inputted manually by the operator. The examination order
includes the body part to be imaged e.g. head, chest, abdomen,
and the like, and an imaging direction e.g. anterior, medial,
diagonal, PA (X-rays are applied from a posterior direction), and
AP (X-rays are applied from an anterior direction). The operator
confirms the contents of the examination order on the display 89,
and inputs the imaging condition corresponding to the contents
through an operation screen of the console 14.
[0093] In Fig. 7, the console 14 is composed of a computer having
a CPU 85, the memory 86, the storage device 87, a communication
I/F 88, the display 89, and an input device 90. These components
are connected to each other via a data bus 91.
[0094] The storage device 87 is a hard disk drive (HDD), for
example. The storage device 87 stores a control program and an
application program (hereafter called AP) 92. The AP 92 is a
program to make the console 14 execute various functions related
to the radiography including a display process of the examination
order and the X-ray image, the image process of the X-ray image,
a setup of the imaging condition, and the like.
[0095] The memory 86 is a work memory used when the CPU 85 executes
a process. The CPU 85 loads the control program stored on the
storage device 87 into the memory 86, and performs a process in
accordance with the program for centralized control of each part
of the computer. The communication I/F 88 is a network interface
for performing wireless or wired transmission control from/to an
external device such as the RIS, the HIS, the image storage server,
or the electronic cassette 13. The communication I/F 88
corresponds to a low speed wireless communication unit and a low
36
speed wired communication unit. The input device 90 includes a
keyboard and a mouse, or a touch panel integrated with the display
89.
[0096] In Fig. 8, by running the AP 92, the CPU 85 of the console
14 functions as a store and retrieval processor 95, an input and
output controller 96, and a main controller 97. The store and
retrieval processor 95 performs a storing process of various types
of data to the storage device 87, and a retrieval process of the
various types of data stored in the storage device 87. The input
and output controller 96 reads out drawing data from the storage
device 87 in response to an operation on the input device 90, and
outputs to the display 89 various operation screens of GUIs based
on the read drawing data. The input and output controller 96
receives an input of operation commands from the input device 90
through the operation screen. The main controller 97 has a
cassette controller 98 for controlling the operation of the
electronic cassette 13, and performs centralized control of each
part of the console 14.
[0097] The storage device 87 stores source information 99 as
shown in Fig. 9. The source information 99 is referred to
determine a setting and a connection method of the X-ray imaging
apparatus 2b, in the combined use of the X-ray generating
apparatus 2a having the X-ray source 10 and the X-ray imaging
apparatus 2b having the electronic cassette 13. The source
information 99 includes specifications of the X-ray generating
apparatus 2a, specifications of the previous AEC sensor 25 that
has been used together with the X-ray generating apparatus 2a from
before installation of the X-ray imaging apparatus 2a, the imaging
condition preset in the X-ray generating apparatus 2a, and a
region type by which a connection type considered to be
appropriate in accordance with a geographic region where the X-ray
generating apparatus 2a is installed is specified, which are
37
stored on a source ID basis. The source ID represents the model
of the X-ray generating apparatus 2a.
[0098] The region type is information representing that which
form is suited for use in the connection between the X-ray imaging
apparatus 2b and the X-ray generating apparatus 2a in accordance
with the geographic region (region such as Japan, North America,
Europe, and Asia) where the X-ray generating apparatus 2a has
already been present and the X-ray imaging apparatus 2b is newly
installed. In the region type, there are two forms in the
connection, that is, a connection method of giving a priority to
ease of installation (easy installation priority type) with a
penalty in performance (e.g. performance contributing to
improvement in X-ray image quality) to some extent, and a
connection method of making full use of the performance of the
X-ray imaging apparatus 2b (easy installation non-priority type)
with a penalty in the ease of installation to some extent. Which
connection method to use is set in advance from region to region,
and therefore the connection method is chosen in accordance with
the geographic region where the X-ray imaging apparatus 2b is
installed. According to the set connection method, the
electronic cassette 13 is put into one of the first AEC mode and
the second AEC mode.
[0099] In a case where a medical facility having the X-ray
generating apparatus 2a intends to be newly equipped with the
X-ray imaging apparatus 2b, a serviceman is in charge of the
installation of the X-ray imaging apparatus 2b, including an
initial setting of the X-ray imaging apparatus 2b and a connection
to the X-ray generating apparatus 2a. However, depending on an
geographic area, it may be difficult to make arrangements for a
skilled serviceman.
[0100] As described above, the electronic cassette 13 does not
need to be connected to the detection signal I/F 26 of the source
38
control device 11 in the second AEC mode. However, the previous
AEC sensor 25 used conventionally is connected to the detection
signal I/F 26. Therefore, a serviceman who does not have enough
knowledge of the connection method of the electronic cassette 13
may mistakenly connect the electronic cassette 13 to the detection
signal I/F 26 to which the previous AEC sensor 25 has been connected
in the instance of detaching the previous AEC sensor 25 from the
X-ray generating apparatus 2a and connecting the electronic
cassette 13 thereto, though the electronic cassette 13 has to be
connected to the emission signal I/F 27 in actual fact.
[0101] Placing a priority on ease of installation, the detection
signal I/F 26 is preferably used, because the electronic cassette
13 is connected in a manner similar to the connection of the
conventionally used previous AEC sensor 25 and the skill of the
serviceman has no effect on a connection result. This is because
the electronic cassette 13 has the first AEC mode in which the
detection signal I/F 26 is used as in the case of the previous
AEC sensor 25. The electronic cassette 13 is connected to the
detection signal I/F 26 and operated in the first AEC mode, in
the easy installation priority type.
[0102] On the other hand, as explained in Figs. 2 and 6 with
comparison, the number of the imaging conditions (including the
emission stop threshold values) preset in the source control
device 11 is limited, and hence a precise setting cannot be made
in performing the AEC by the source control device 11. In
performing the AEC by the electronic cassette 13, it is possible
to make a more precise setting (including the emission stop
threshold value). Therefore, the second AEC mode in which the
electronic cassette 13 performs the AEC based on a precise imaging
condition is superior to the first AEC mode using the emission
stop threshold value preset in the source control device 11 in
the X-ray image quality and the like, except for the ease of
39
installation.
[0103] As described above, the electronic cassette 13 can be
selectively switchable between the two types, that is, the
connection method of putting a priority on ease of installation
that has a high degree of commonality to the connection method
of the previous AEC sensor 25 (first AEC mode is chosen) and the
connection method of putting a higher priority on improvement in
the image quality than the ease of installation (second AEC mode
is chosen). Note that, in this embodiment, these types are
related to the geographic regions and set as the region types,
but one of the easy installation priority type (first AEC mode)
and the easy installation non-priority type (second AEC mode) may
be selectable in accordance with a user’s preference irrespective
of the geographic region.
[0104] The imaging conditions of the source information 99 are
the same as those stored in the source control device of each X-ray
source, other than the emission stop threshold values that can
be adjusted by the operator. The AEC specifications have items
of the presence or absence of the integrator for integrating the
AEC detection signal, the positions of the dose measurement areas
in the previous AEC sensor 25 (X and Y coordinates of two points
on a diagonal line if the dose measurement area is rectangular),
which value to output out of a value of each individual dose
measurement area, a sum value of the dose measurement areas, and
an average value of the dose measurement areas in the previous
AEC sensor 25 (not shown).
[0105] The X and Y coordinates correspond to the position of the
pixels 45 (including the detection pixels 65) of the electronic
cassette 13 in the imaging surface 36. An X axis extends to a
direction parallel to the scan line 51. A Y axis extends to a
direction parallel to the signal line 52. The coordinates of the
top left pixel 45 are designated as an origin point (0, 0).
40
Information about the positions of the dose measurement areas is
referred by the dose measurement area selector 75 to determine
which output to select, out of outputs of the detection pixels
65 in the electronic cassette 13. The dose measurement area
selector 75 selects the new AEC detection signal of the detection
pixel 65 that is situated in an area corresponding to the dose
measurement area of the previous AEC sensor 25, out of the AEC
detection signals of the plurality of detection pixels 65 based
on the information on the dose measurement areas.
[0106] Note that, there is an imaging stand or table on which
the electronic cassette 13 can be mounted in an orientation
rotated by 90 such as a portrait orientation and a landscape
orientation. In the case of using such an imaging stand or table,
if the dose measurement area selector 75 selects the dose
measurement area by accepting the information on the dose
measurement areas of the previous AEC sensor 25 without
questioning, as described above, the dose measurement area is
selected in a completely different position depending on the
orientation of the electronic cassette 13. To prevent this, as
described in Japanese Patent Laid-Open Publication No.
2011-067314, for example, it is preferable that a mounted
orientation of the electronic cassette on the imaging stand or
table is detected using a photosensor or the like and the dose
measurement area selector 75 selects the dose measurement area
based on information of the detection result.
[0107] More specifically, when the information on the positions
of the dose measurement areas in the previous AEC sensor 25
corresponds to the portrait orientation and the electronic
cassette 13 is mounted in the landscape orientation, the
information (coordinates) on the dose measurement areas in the
previous AEC sensor 25 is used after being rotated by 90 or 270
with respect to the center of the imaging field of the cassette.
41
Otherwise, the source information 99 has information on the
positions of the dose measurement areas in the previous AEC sensor
25 corresponding to the portrait orientation and the landscape
orientation in advance, and information to be used may be selected
in accordance with the detection result of the mounted orientation
of the cassette.
[0108] The source information 99 also includes correction
information. The correction information is referred by the
corrector 76 and used for making the output value of the new AEC
detection signal correspond to the output value of the previous
AEC detection signal. Also, the correction information is
referred by the threshold value generator 79 in the execution of
the second AEC mode. The threshold value generator 79 calculates
the ratio between the output value of the new AEC detection signal
and the output value of the previous AEC detection signal based
on the correction information. The calculated ratio is used in
replacing the emission stop threshold value. The correction
information represents the correlation between the new AEC
detection signal and the previous AEC detection signal of each
X-ray source on a tube voltage basis and stored in a form of a
data table or an arithmetic expression.
[0109] The previous AEC sensor 25 and the detection pixels 65
of the electronic cassette 13 are different in an installation
state and the like, in addition to a sensitivity property. Thus,
a difference occurs between the output value of the previous AEC
sensor 25 and the output value of the detection pixels 65 even
if the same X-ray dose is applied.
[0110] Since the previous AEC sensor 25 is used in a state of
being put in front of the imaging surface of the cassette, the
previous AEC sensor 25 itself causes reduction in the amount of
the X-rays to be incident from the X-ray source to the imaging
surface of the cassette. Therefore, the emission stop threshold
42
value of the previous AEC sensor 25, which is preset in the source
control device 11, is determined by adding a radiation dose
absorbed by the previous AEC sensor 25 to a radiation dose required
for obtaining desired image quality. On the other hand, the
electronic cassette 13 uses the detection pixels 65 as the new
AEC sensor, and an intermediate member such as the housing of the
electronic cassette 13 is disposed between the X-ray source and
the new AEC sensor. When the electronic cassette 13 adopts the
PSS method in which the scintillator and the FPD 35 are disposed
in this order from the X-ray incident side, the scintillator
corresponds to the intermediate member too (on the contrary, the
scintillator does not correspond to the intermediate member in
the ISS method). If a grid for eliminating the X-rays scattered
inside the object is provided between the X-ray source 10 and the
electronic cassette 13 in the introduction of the electronic
cassette 13, the grid corresponds to the intermediate member too.
In the case of using the detection pixels 65 of the electronic
cassette 13 for the AEC, instead of the previous AEC sensor 25,
if an application of a radiation dose causes the previous AEC
detection signal of a value of “1”, an application of the same
radiation dose may possibly cause the new AEC detection signal
of “0.8” due to the disposition of the intermediate member.
[0111] Furthermore, an output range may differ between the
previous AEC detection signal and the new AEC detection signal,
such that the previous AEC detection signal is represented in a
range having a minimum value of -5 V and a maximum value of 5 V,
while the new AEC detection signal is represented in a range having
a minimum value of 0 mV and a maximum value of 5 mV. Thus, in
the case of using the electronic cassette 13, it is required to
correct a deviation between the previous AEC detection signal and
the new AEC detection signal caused by the existence of the
intermediate member and the difference in the output range. The
43
correction information facilitates eliminating the deviation
between the output value of the previous AEC detection signal and
the output value of the new AEC detection signal in the application
of the same X-ray dose.
[0112] The correction information is calculated in advance by
experiment and simulation in consideration of the structure of
the previous AEC sensor 25 and the structure of the electronic
cassette 13 (the PSS method or the ISS method, the presence or
absence of the scintillator and a material of the scintillator
if it is present, the presence or absence of the grid and a material
of the grid if it is present, and the like). Note that, the
presence or absence of the scintillator is obtained from the
specifications of the electronic cassette 13, i.e. the PSS method
or the ISS method. The presence or absence of the grid is chosen
through a GUI displayed on the display 89 of the console 14.
Irrespective of the intermediate member, the previous and new AEC
sensors have different X-ray detection principles, so a detection
value is different therebetween even if the same radiation dose
is applied. The above experiment and simulation also eliminate
a deviation in the detection value due to the difference in the
detection principles.
[0113] The source information 99 is setting information employed
in using the electronic cassette 13 together with the X-ray
generating apparatus 2a. Thus, the source information 99 is
produced on a model-by-model basis of the electronic cassette 13.
The source information 99, which is produced on a model-by-model
basis of the electronic cassette 13, is updated anytime to the
latest information provided through the network, whenever a new
product of the X-ray source is released. Instead of the automatic
update, X-ray source information that is possibly used in the
system may be obtained from a manufacturer and inputted manually
through the input device 90.
44
[0114] A table of Fig. 10 shows the setting and the like of the
electronic cassette 13 in each region type, that is, in each of
the easy installation priority type (first AEC mode) and the easy
installation non-priority type (second AEC mode). The operation
of the above structure will be hereinafter explained with
referring to the table of Fig. 10, a flowchart of an initial setting
process shown in Fig. 11, a flowchart of an AEC execution process
in radiography shown in Fig. 12, and Figs. 13 to 15 representing
operation states of the communication unit 40 and the AEC unit
67.
[0115] A case of newly introducing the X-ray imaging apparatus
2b having the electronic cassette 13 and the console 14 into the
X-ray imaging system 2, instead of the film cassette, the IP
cassette, and the previous AEC sensor 25 that are conventionally
used, will be described as an example.
[0116] In installing the X-ray imaging apparatus 2b, the
electronic cassette 13 and the console 14 are wirelessly connected
using the antenna 37 of the electronic cassette 13. Then, the
communication I/F 88 of the console 14 is connected to the
communication I/F 22 of the source control device 11 through a
network such as a LAN.
[0117] As shown in a step 10 (S10) of Fig. 11 representing the
initial setting process, upon establishing communication between
the console 14 and the source control device 11, the store and
retrieval processor 95 obtains information of the source ID and
the emission stop threshold value preset in the source control
device 11 through the communication I/F 22 of the source control
device 11, and stores the information to the storage device 87
(see Fig. 8 too).
[0118] The store and retrieval processor 95 retrieves and
extracts a type that corresponds to the source ID received by the
source control device 11 and the geographic region set in advance
45
in shipping (the region to which the X-ray imaging apparatus 2b
is to be installed) from the item of the region type of the source
information 99 (S11). The imaging condition, the AEC
specifications, and the correction information corresponding to
the source ID are extracted from the source information 99. This
information extracted by the store and retrieval processor 95 is
provided from the cassette controller 98 to the electronic
cassette 13 together with the information of the emission stop
threshold value. The information extracted by the store and
retrieval processor 95 is also displayed on the display 89 of the
console 14.
[0119] The serviceman in charge of the installation of the X-ray
imaging apparatus 2b checks the display on the display 89, and
establishes physical connection between the electronic cassette
13 and the X-ray generating apparatus 2a in accordance with the
geographic region set in shipping the X-ray imaging apparatus 2.
In the region where the ease of installation is prioritized, the
emission signal I/F 27 of the source control device 11 is connected
to the emission signal I/F 81 of the electronic cassette 13, and
the detection signal I/F 26 of the source control device 11 is
connected to the detection signal I/F 80 of the electronic
cassette 13 as the connection I/F for the AEC signal. The
detection signal I/F 26 has been used with the previous AEC sensor
25, so the serviceman is hardly confused at the connection method
even if the serviceman does not have enough knowledge. In the
region where the ease of installation is not prioritized, only
the emission signal I/F 27 and the emission signal I/F 81 are
connected each other, while the detection signal I/Fs 26 and 80
are not used.
[0120] The controller 41 of the electronic cassette 13 chooses
the AEC mode to be executed by the electronic cassette 13 based
on information of the region type provided by the console 14, from
46
between the first AEC mode and the second AEC mode. In accordance
with the chosen mode, an output destination and the output format
of the AEC signal are determined.
[0121] To be more specific, in a case where the region type is
the easy installation priority type (YES in S12), the first AEC
mode is chosen (S13). Thus, the detection signal I/F 80 is
designated as the output destination of the communication unit
40, and the detection signal (new AEC detection signal) is
designated as the output format (S14). In a case where the region
type is the easy installation non-priority type (NO in S12), the
second AEC mode is chosen (S15). The emission signal I/F 81 is
designated as the output destination, and the emission stop signal
is designated as the output format (S16). In the case of choosing
the first AEC mode, the output format is chosen in further detail
depending on the presence or absence of an integrator usable in
the AEC and information about which value to output out of the
value of each individual dose measurement area, the sum value of
the dose measurement areas, and the average value of the dose
measurement areas.
[0122] The dose measurement area selector 75 selects the new AEC
detection signal of the detection pixel 65 that is present in the
area corresponding to the dose measurement area of the previous
AEC sensor 25, out of the new AEC detection signals of the plurality
of detection pixels 65 outputted from the A/D 62, based on the
information on the position of the dose measurement area of the
previous AEC sensor 25 provided by the console 14. The dose
measurement area selector 75 outputs the selected new AEC
detection signal to the corrector 76 (S17). Taking the case of
a source ID “0001” in this embodiment as an example, the dose
measurement area selector 75 selects the new AEC detection signals
of the detection pixels 65 that are present within frames A’ to
C’ as shown in Fig. 4, corresponding to the dose measurement areas
47
A to C. Then, the initial setting is completed.
[0123] In the radiography using the X-ray imaging system 2 after
the completion of the initial setting, the imaging condition is
set based on the examination order. Upon inputting the warm-up
start signal from the emission switch 12, the source control
device 11 sends the emission start request signal to the
electronic cassette 13 through the emission signal I/F 27. The
electronic cassette 13 performs the preparation process, and
sends the emission permission signal to the source control device
11 as soon as the electronic cassette 13 is ready for receiving
the X-ray emission. Upon receiving the emission permission
signal, the source control device 11 makes the X-ray source 10
start the X-ray emission.
[0124] As shown in Fig. 12, upon sending the emission permission
signal, the electronic cassette 13 judges that the X-ray emission
has been started and makes the detection pixels 65 start the dose
detection operation (YES in S21).
[0125] Upon starting the dose detection operation, the new AEC
detection signals are recorded from the detection pixels 65 to
the memory 42. In the AEC unit 67, the dose measurement area
selector 75 reads out the selected new AEC detection signal from
the memory 42. The corrector 76 converts the new AEC detection
signal inputted from the dose measurement area selector 75 into
the detection signal based on the correction information
corresponding to the source ID of the X-ray generating apparatus
2a (S22). The corrector 76 calculates the sum value, the average
value, or the like of the detection signals if necessary, based
on the information about which value to output out of the value
of each individual dose measurement area, the sum value of the
dose measurement areas, and the average value of the dose
measurement areas. The selection of the dose measurement area
and the correction, as described above, are necessarily carried
48
out irrespective of the selected AEC mode (see Fig. 10 too).
[0126] In a case where the first AEC mode is chosen in the initial
setting (YES in S23) and the source control device 11 is judged
to have an integrator based on the information on the presence
or absence of the integrator usable in the AEC (YES in S24), the
controller 41 of the electronic cassette 13 transmits the
instantaneous value of the new AEC detection signal outputted from
the corrector 76 at constant transmission intervals through the
detection signal I/F 80 to the detection signal I/F 26 of the source
control device 11 (S25). In this case, in the AEC unit 67, only
the dose measurement area selector 75 and the corrector 76
function as shown in Fig. 13.
[0127] On the other hand, when the first AEC mode is chosen and
the source control device 11 has no integrator (NO in S24), the
corrector 76 outputs the new AEC detection signal to the
integrator 77. The integrator 77 integrates the new AEC detection
signal (S26). The integrated value of the new AEC detection
signal is transmitted at constant transmission intervals from the
integrator 77 through the detection signal I/F 80 to the detection
signal I/F 26 of the source control device 11 (S27). The
instantaneous value or the integrated value of the detection
signal is continuously transmitted until electronic cassette 13
receives an emission end signal from the source control device
11 (YES in S28). In this case, as shown in Fig. 14, the dose
measurement area selector 75, the corrector 76, and the integrator
77 function in the AEC unit 67.
[0128] In the first AEC mode, the instantaneous value of the
integrated value of the new AEC detection signal is transmitted
from the electronic cassette 13 to the source control device 11.
The source control device 11, which receives the instantaneous
value or the integrated value of the new AEC detection signal,
makes a judgment on the stop of X-ray emission. Just as in the
49
case of using the previous AEC sensor 25, the judgment of the stop
of X-ray emission is made by comparison of the integrated value
of the new AEC detection signal with the emission stop threshold
value. After the completion of the X-ray emission, the electronic
cassette 13 reads out the X-ray image from the FPD 35, and transmits
the X-ray image data to the console 14 through the antenna 37.
[0129] When the second AEC mode is chosen (NO in S23), the
comparator 78 and the threshold value generator 79 function in
addition to above, as shown in Fig. 15. First, just as in a case
where the source control device 11 has no integrator in the first
AEC mode, the corrector 76 outputs the new AEC detection signal
to the integrator 77, and the integrator 77 integrates the new
AEC detection signal (S29).
[0130] The comparator 78 compares the integrated value of the
new AEC detection signal from the integrator 77 with the emission
stop threshold value from the threshold value generator 79 (S30).
As soon as the integrated value reaches the threshold value (YES
in S31), the emission stop signal is outputted. The emission stop
signal outputted from the comparator 78 is transmitted through
the emission signal I/F 81 to the emission signal I/F 27 of the
source control device 11 (S32). Upon receiving the emission stop
signal, the source control device 11 stops the X-ray emission.
Also in the second AEC mode, upon the completion of the X-ray
emission, the electronic cassette 13 reads out the X-ray image
from the FPD 35, and transmits the X-ray image data to the console
14 through the antenna 35.
[0131] In the second AEC mode, the corrector 76 corrects the new
AEC detection signal from the detection pixel 65 into the
detection signal corresponding to the previous AEC detection
signal. The corrected new AEC detection signal is compared with
the emission stop threshold value to make a judgment of the stop
of X-ray emission. In other words, the electronic cassette 13
50
carries out exactly the same process in the second AEC mode as
the process of the AEC that the controller 21 of the source control
device 11 carries out in the radiography using the previous AEC
sensor 25 or in the first AEC mode. However, the emission stop
threshold value varies in accordance with each of the plurality
of imaging conditions, so it is possible to realize the precise
AEC, as compared with the AEC performed by the source control
device 11. Therefore, the image quality is improved in the second
AEC mode, as compared with the image quality in the first AEC mode.
[0132] The electronic cassette 13 is switchable between the first
AEC mode and the second AEC mode, which have different connection
methods to the X-ray generating apparatus 2a, in accordance with
the region type, that is, the easy installation priority type or
the easy installation non-priority type. Therefore, it is
possible to flexibly meet a situation of a site where the X-ray
imaging system 2 is installed.
[0133] Since the electronic cassette 13 has the first AEC mode
in which the new AEC detection signal, being equivalent to the
previous AEC detection signal outputted from the previous AEC
sensor 25, is outputted to the source control device 11, the source
control device 11 can use the electronic cassette 13 just as in
the case of using the previous AEC sensor 25 without correcting
the preset emission stop threshold value and changing a preset
judging process. When the X-ray generating apparatus and the
X-ray imaging apparatus are made by different makers, correcting
the emission stop threshold value of the source control device
11 requires a serviceman of the source maker on site and hence
expenses much time and effort. The present invention, however,
facilitates less burdensome because the correction is completed
just in the electronic cassette 13, and this becomes a sales point
in introducing the new system. Furthermore, it is possible to
inherit a tendency of an operator and a policy of a hospital, e.g.
51
reducing radiation exposure of a patient by using a low radiation
dose or increasing an X-ray image density by using a high radiation
dose.
[0134] Also, the dose measurement area selector 75 selects the
detection pixel 65 such that the electronic cassette 13 has the
same dose measurement area as the dose measurement area of the
previous AEC sensor 25, so the AEC can be carried out in a like
manner as previous.
[0135] As shown in a flowchart of Fig. 16, the electronic cassette
13 uses the detection signal I/F 80 and the emission signal I/F
81, being the high speed communication unit, as the communication
unit in both of the first AEC mode and the second AEC mode, in
a case where a signal is to be sent to the X-ray generating
apparatus 2a, just as in the case of sending the AEC signal (new
AEC detection signal and the emission stop signal). Thus, the
AEC signal can be sent quickly in the AEC process, which is carried
out within extremely short emission time. Accordingly, this
prevents a delay in timing of the stop of X-ray emission and hence
unnecessary radiation exposure of a patient.
[0136] On the other hand, the electronic cassette uses the
antenna, being the low speed wireless communication unit, as the
communication unit, in a case where a signal e.g. the X-ray image
is to be sent to the console 14. The electronic cassette 13 and
the console 14 are connected by a wireless method without a cable,
and therefore the handleability and the portability of the
electronic cassette 13 and the console 14 are ensured. The
electronic cassette 13 and the console 14 are sometimes situated
away from each other, such that the electronic cassette 13 is
disposed in an examination room while the console 14 is installed
in an operators room. Thus, connecting the electronic cassette
13 and the console 14 without a cable is highly effective.
Especially, the cableless connection produces a beneficial effect
52
in using the electronic cassette 13 in a state of being put on
a bed or held by the object himself/herself.
[0137] In addition to the X-ray image, the imaging condition,
the life check signal, and the like are communicated between the
electronic cassette 13 and the console 14. Transmission of these
signals requires less rapidity than the AEC signal, and therefore
uses a lower speed communication unit than a communication speed
of the communication unit of the AEC signal.
[0138] In this embodiment, since the battery 38 supplies the
drive power of the electronic cassette 13, the power cable for
feeding the electric power to the electronic cassette 13 is
unnecessary. Thus, the handleability and the portability of the
electronic cassette 13 are further improved.
[0139] The battery 38 is taken out of the electronic cassette
13 and set in the cradle 17 for recharging. Thus, it is
unnecessary to connect a cable for feeing the electric power to
the electronic cassette 13. This further facilitates handling
of the electronic cassette 13.
[0140] Moreover, in this embodiment, not only the electronic
cassette 13 and the console 14, but also the source control device
11 and the electronic cassette 13 are connected by a wireless
method. A connection cable is completely eliminated from the
electronic cassette 13, so the handleability and the portability
of the electronic cassette 13 is further improved. Thus, the
electronic cassette 13 can be easily moved among examination
rooms.
[0141] Note that, in this embodiment, the start synchronization
signal (emission start request signal and the emission permission
signal) and the emission end signal are communicated between the
source control device 11 and the electronic cassette 13 through
the emission signal I/Fs 27 and 81. However, the electronic
cassette 13 may have the function of detecting the start and end
53
of the X-ray emission by itself. In this case, the communication
of the start synchronization signal and the emission end signal
becomes unnecessary.
[0142] The electronic cassette 13 detects the start and end of
the X-ray emission by itself with the use of the new AEC detection
signal outputted from the detection pixel 65 provided for the AEC,
for example. Upon receiving the X-rays, the detection pixel 65
outputs the new AEC detection signal of a value corresponding to
the amount of the X-rays incident thereon. The controller 41 of
the electronic cassette 13 compares the instantaneous value of
the new AEC detection signal with the predetermined threshold
value for judging the start of emission. When the new AEC
detection signal exceeds the threshold value, the start of
emission is judged and detected. The controller 41 keeps
monitoring the new AEC detection signal after the start of
emission. When the new AEC detection signal has fallen below the
threshold value for judging the end of emission, the end of
emission is judged and detected.
[0143] Providing the self detection function of the start and
end of emission, as described above, negates the need for
communication of the start synchronization signal and the
emission stop signal between the electronic cassette 13 and the
source control device 11. Thus, in the first AEC mode in which
the AEC signal is outputted to the detection signal I/F 26, the
detection signal I/Fs 26 and 80 are connected each other, and the
emission signal I/Fs 27 and 81 are connected each other in the
above embodiment. Out of these connections, the connection
between the emission signal I/Fs 27 and 81 becomes unnecessary.
In other words, only the connection between the detection signal
I/Fs 26 and 80 is required in the first AEC mode. In the second
AEC mode, since the AEC signal (emission stop signal) is outputted
to the emission signal I/F 27, the emission signal I/Fs 27 and
54
81 are connected as described above.
[0144] Second Embodiment
In the above first embodiment, the optical wireless
communications is used as an example of high speed communications
of the detection signal or the emission stop signal for the AEC
between the source control device 11 and the electronic cassette
13, and the wireless LAN or the like is used as an example of low
speed wireless communications of various types of information and
signals other than the detection signal and the emission stop
signal for the AEC between the electronic cassette 13 and the
console 14. However, ad-hoc communications may be used in the
former communications, and infrastructure communications may be
used in the latter communications.
[0145] The ad-hoc communications is a method in which wireless
communication devices (the source control device 11 and the
electronic cassette 13) have a routing function of a wireless
communication channel and each wireless communication device
performs communication on an autonomous basis. Thus, the ad-hoc
communications is established without mediation of a relay device
having the routing function such as a switching hub or a router
between the wireless communication devices. The ad-hoc
communications is a so-called specific line method used only in
the X-ray imaging system 2. Thus, the ad-hoc communications
hardly causes a delay (time lag) in data communication, and
average delay time in the data communication becomes small.
[0146] On the contrary, the infrastructure communications is a
method for establishing communication with mediation of a relay
device having a routing function. In the infrastructure
communications, the relay device having the routing function is
a component of a network such as a hospital LAN that performs
communication of medical equipment including the X-ray imaging
system 2 and other devices, and therefore used in data
55
communication of signals and data sent and received by the devices
other than the X-ray imaging system 2, such as an electronic
medical chart, a medical report, and account data. Thus, the
infrastructure communications more easily causes a delay (time
lag) in data communication than the ad-hoc communications. The
ad-hoc communications has higher communication speed than the
infrastructure communications.
[0147] The ad-hoc communications includes a wireless method
using a radio wave, in addition to the optical wireless
communication method as described above. In the ad-hoc
communications, it is preferable that the source control device
11 and the electronic cassette 13 establish direct communication
without mediation of any relay device. Note that, in the ad-hoc
communications, a relay device having no routing function, e.g.
a repeater having the function of just transferring a received
signal, an amplifier for amplifying a signal in the middle of
transfer for restraining attenuation of the signal, and the like
may be provided. This is because such a relay device does not
cause much data delay.
[0148] Note that, if a communication speed is the same in the
specifications, an actual communication speed differs in reality
depending on average delay time in the data communication. In
other words, in the present invention, a high communication speed
and a low communication speed are defined in consideration of not
only the communication speed itself but also the average delay
time in the data communication. Therefore, “the high speed
communication unit” of the present invention includes a device
that has relatively small average delay time in the data
communication, and “the low speed wireless communication unit”
includes a device that has relatively large average delay time
in the data communication. The ad-hoc communications described
above corresponds to high speed communications having relatively
56
small average delay time in the data communication. The
infrastructure communications corresponds to low speed
communications having relatively large average delay time in the
data communication.
[0149] The source control device 11 is usually disposed in the
examination room. Thus, using the ad-hoc communications in the
communication of the detection signal and the emission stop signal
for the AEC between the source control device 11 and the electronic
cassette 13 allows stable communication, because the source
control device 11 and the electronic cassette 13 are close to each
other and the radio wave reaches easily, and hence actualizes the
high speed communications without the occurrence of a delay in
the data communication. The communication of the various types
of information and signals other than the detection signal and
the emission stop signal for the AEC between the electronic
cassette 13 and the console 14, which is usually installed in a
room different from the examination room, is performed by the
infrastructure communications, so the electronic cassette 13 is
connected without a cable and easily handled, just as with the
above embodiment.
[0150] Third Embodiment
In the above first and second embodiments, the controller 41 is
in charge of controlling the operation of parts including the gate
driver 53, the signal processor 54, and the AEC unit 67. The
antenna 37 and the socket 39 for making communication with the
console 14, and the detection signal I/F 80 and the emission signal
I/F 81 for making communication with the source control device
11 are disposed integrally into one communication unit 40. Thus,
a process related to the communication with the console 14
conflicts with a process related to the communication with the
source control device 11 in the controller 41, or the
communication with the console 14 overlaps with the communication
57
with the source control device 11 in the controller 41. As a
result, there is a possibility of delaying the transmission timing
of the detection signal or the emission stop signal from the
detection signal I/F 80 or the emission signal I/F 81.
[0151] Therefore, in the electronic cassette 13 according to a
third embodiment, a control section and a communication section
are structured as shown in Fig. 17. Namely, there are provided
an AEC controller 160 dedicated to controlling the operation of
the AEC unit 67 and another controller 161 for controlling the
operation of each part other than the AEC unit 67, which are made
of different hardware resources. Also, as for the communication
section, there are provided an AEC communication unit 162 having
the detection signal I/F 80 and the emission signal I/F 81 and
another communication unit 163 having the antenna 37 and the
socket 39, which are made of different hardware resources. To
be more specific, the AEC controller 160 and the controller 161
are incorporated into different IC chips and operated
independently each other. In a like manner, the AEC communication
unit 162 and the communication unit 163 are incorporated into
different IC chips and operated independently each other.
[0152] Since the hardware resources of the control section and
the communication section related to the AEC are operated
separately from the hardware resources of the other control
section and the other communication section, it is possible to
prevent the occurrence of the conflict between the process related
to the communication with the console 14 and the process related
to the communication with the source control device 11 in the
control section and the overlap between the communication with
the console 14 and the communication with the source control
device 11 in the communication section. Thus, the detection
signal and the emission stop signal are securely transmitted in
desired timing, and the X-ray emission can be stopped precisely.
58
[0153] Fourth Embodiment
In the above first to third embodiments, the detection signal I/Fs
26 and 80 are wirelessly connected each other, and the emission
signal I/Fs 27 and 81 are wirelessly connected each other.
However, the detection signal I/Fs 26 and 80 may be connected each
other with a cable, and the emission signal I/Fs 27 and 81 may
be connected each other with a cable. In this case, for example,
an optical fiber cable or the like having a relatively high
communication speed is used as the cable. The wired communication
consumes less electric power than the wireless communication in
general, so it is possible to cut a drain of the battery 38 as
compared to the above embodiments.
[0154] Since a cable is connected to the electronic cassette 13,
the electronic cassette 13 is hard to handle more or less.
However, signals transmitted through the cable are limited to some
types, i.e. the detection signal and the emission stop signal,
so the cable is thinner and more flexible than a cable that is
used in connection between the electronic cassette 13 and the
console 14 for sending and receiving various types of signals and
information. For this reason, the electronic cassette 13 is easy
to handle as compared with the case of connecting the electronic
cassette 13 and the console 14 with the relatively thick and rigid
cable.
[0155] Note that, the signals and information other than the AEC
signal, such as the image data, may be communicated through a wired
connection line of the high speed communications for the AEC
signal. In this case, a cable is split in its middle, in such
a manner that one is for the AEC signal and the other is for the
other signals, and the split cable is connected to the source
control device 11 and the console 14. In a case where whether
or not the AEC is performed using the detection pixel 65 is set
in each of the imaging conditions choosable in the console 14,
59
the controller 41 judges in accordance with the setting that
whether or not the imaging condition that executes the AEC is
chosen. When the imaging condition that executes the AEC is
judged to be chosen, the controller 41 adopts the wireless
communication in sending and receiving the image data and the like
between the electronic cassette 13 and the console 14, as with
the above embodiments. When the imaging condition that does not
execute the AEC is judged to be chosen, the controller 41 switches
the communication between the electronic cassette 13 and the
console 14 to the wired connection line for the AEC. The
controller 41 constitutes a judging section and a communication
switching section.
[0156] To be more specific, when the imaging condition that does
not execute the AEC is chosen, the input and output controller
96 of the console 14 displays a message that advises the operator
to connect the cable into the socket 39 to establish the wired
communication on the display 89. Upon detecting the connection
of the cable into the socket 39 to establish the wired
communication with the console 14, the controller 41 stops the
operation of a function part related to the wireless
communication, such as the communication unit 40, and shifts to
the wired communication using the cable. In the case of not
executing the AEC, no AEC signal is transmitted through the wired
connection line for the AEC. Thus, transmitting the signals and
information other than the AEC, such as the image data, through
the wired connection line for the AEC signal facilitates reducing
a drain of the battery 38 due to the wireless communication without
a problem of signal collision and the like.
[0157] Fifth Embodiment
In the above first to fourth embodiments, the battery 38 is taken
out of the electronic cassette 13 and set in the cradle 17 for
recharging, but the present invention is not limited to this. The
60
electronic cassette 13 may have a power receiving function of
noncontact power feeding. The battery 38 may be recharged in a
state of not being taken out of the electronic cassette 13 with
electric power fed from a noncontact power feeding device.
[0158] As a method of the noncontact power feeding, there are
an electromagnetic induction method, a magnetic resonance method,
and an electric field coupling method. Any method is available,
but the electric field coupling method has simpler and smaller
structure than the other methods, and allows cost reduction and
easy control. Also, the electric field coupling method has a
relatively high degree of flexibility in positioning and does not
require precise positioning, though poor positioning between the
power feeding device and a power receiving device (the electronic
cassette 13 in this case) significantly reduces electric power
transmission efficiency in the other methods. Thus, the electric
field coupling method is preferably adopted.
[0159] Fig. 18 shows a noncontact power feeding device 150 of
the electric field coupling method, as an example. An electronic
cassette 151 is provided with a power receiving electrode 152 and
a recharging circuit 153. The power receiving electrode 152 is
made of metal such as copper or aluminum into a flat plate of
approximately the same size and shape as a rear cover of a housing
of the electronic cassette 151, so as to be attached to the rear
cover, for example.
[0160] The power feeding device 150 is contained in the holder
15a of the imaging stand 15 and the holder 16a of the imaging table
16, so that the electronic cassette 151 is fed with power in a
state of being mounted on the imaging stand 15 or the imaging table
16. The power feeding device 150 has a power feeding electrode
154. The power feeding electrode 154 is connected to an AC power
supply 155. The power feeding electrode 154 is made of the same
material as the power receiving electrode 152, and is a flat plate
62
The electronic cassette may be supplied with power from a utility
power supply through a cable. For example, in a case where the
electronic cassette is disposed in the examination room and the
console is installed in the operators room, the electronic
cassette is fed with power from a wall outlet of the utility power
supply in the examination room. Eliminating the power cable is
preferable as a matter of course in consideration of the
handleability and the portability, but the handleability and the
portability of the electronic cassette and the console are ensured
to some extent because of the cableless connection between the
electronic cassette and the console.
[0164] Sixth Embodiment
In the first to fifth embodiments, the electronic cassette 13
configured by one housing is provided with all fundamental
structures for performing the AEC, which include the AEC unit 67,
the detection signal I/F 80, and the emission signal I/F 81.
However, in a sixth embodiment as shown in Fig. 19, an electronic
cassette 104 is composed of a cassette main body 105 and a
supplemental device 110 having a part of a function performing
the AEC.
[0165] The cassette main body 105 includes the FPD 35 having the
detection pixels 65. Furthermore, the cassette main body 105 is
provided with a detection signal I/F 106 for outputting the new
AEC detection signal from the detection pixel 65 to the
supplemental device 110. The supplemental device 110 has all the
functions of the AEC unit 67 and the communication unit 40 of Fig.
5. Furthermore, the supplemental device 110 is provided with a
detection signal I/F 109, which is connected to the detection
signal I/F 106 of the cassette main body 105 to receive the new
AEC detection signal. The supplemental device 110 chooses an
output format (the new AEC detection signal or the emission stop
signal) and an output destination (the detection signal I/F 26
61
electrode of the same size as the power receiving electrode 152.
In setting the electronic cassette 151 in the power feeding device
150, the power feeding electrode 154 is opposed to the power
receiving electrode 152 in parallel with leaving space of the
order of several millimeters to the power receiving electrode 152.
The noncontact power feeding of the electric field coupling method
is performed from the power feeding electrode 154 to the power
receiving electrode 152. The recharging circuit 153 is
constituted of an AC/DC converter (rectifier) and a DC regulator.
The recharging circuit 153 converts AC power that is fed from the
power feeding electrode 154 and received by the power receiving
electrode 152 into DC power, and outputs a voltage suitable for
recharging the battery 38.
[0161] The power feeding device 150 is provided with a full charge
detector 156 and a detachment detector 157. The full charge
detector 156 detects whether or not the battery 38 is full. The
detachment detector 157 detects detachment of the electronic
cassette 151 from the holder 15a or 16a. When the full charge
detector 156 detects that the battery 38 is full, or the detachment
detector 157 detects the detachment of the electronic cassette
151 from the holder 15a or 16a, a power feeding operation is
interrupted by cutting the connection between the power feeding
electrode 154 and the AC power supply 155 or stopping the operation
of the AC power supply 155.
[0162] Recharging the battery 38 with the electric power fed from
the noncontact power feeding device 150 eliminates the need for
connecting a power feeding cable to the electronic cassette, as
with the above embodiments, and hence the electronic cassette is
easy to handle.
[0163] Note that, the above first to fifth embodiments describe
the electronic cassette that can be driven by the integral
battery, but the integral battery is not necessarily provided.
63
or the emission signal I/F 27) of the AEC signal.
[0166] In this case, the supplemental device 110 is connected
to the console 14, and receives the region type, the imaging
condition, the AEC specifications, the correction information,
the emission stop threshold value, and the like of the source
information 99 from the console 14. Each part of the supplemental
device 110, including a dose measurement area selector 111, a
detection signal I/F 116, an emission signal I/F 117, and the like
is identical to that of the AEC unit 67 and the communication unit
40 of Fig. 5, though they are referred to by different reference
numbers. The supplemental device 110 determines the output
destination and the output format in accordance with the region
type sent from the console 14, and maintains that state until the
X-ray source 10 is exchanged.
[0167] Since the functions of the AEC unit 67 and the like are
provided in the supplemental device 110, the cassette main body
105 can be small in size and light in weight. In a case where
the cassette main body 105 is shared among a plurality of
examination rooms of a hospital, if the X-ray generating
apparatuses 2a of the examination rooms have different region
types, the electronic cassette 13 of the above first embodiment
has to change the output destination and the output format from
one region type to another. However, since the supplemental
device 110 is provided with the changing function, the cassette
main body 105 does not have to change the output destination and
the output format. A communication method between the detection
signal I/F 106 of the cassette main body 105 and the detection
signal I/F 109 of the supplemental device 110 may be a wired method
or a wireless method. However, the AEC signal that requires the
rapidity is communicated between the cassette main body 105 and
the supplemental device 110, so the high speed communication unit
is adopted, as described as the communication method between the
64
electronic cassette 13 and the source control device 11 in the
above first to fifth embodiments.
[0168] Note that, it is described in the above first to sixth
embodiments that either of the wired connection and the wireless
connection is available to connect the source control device 11
and the electronic cassette 13, 104. This does not intend just
one of the wired connection and the wireless connection. The
present invention includes the case of using both of the wired
connection and the wireless connection together, as a matter of
course. For example, a communication channel between the source
control device 11 and the electronic cassette 104 (more
particularly, the supplemental device 110) may be a mixture of
the wireless method and the wired method.
[0169] Note that, the present invention is not limited to above
embodiments, and is modified into various configurations within
the scope of the present invention.
[0170] In the above embodiments, the source ID is transmitted
and received upon establishing the communication between the
source control device 11 and the console 14 after completely
installing the X-ray imaging apparatus 2b, to retrieve and extract
the region type of the X-ray source 10 corresponding to the source
ID from the source information 99. However, the region type may
be manually inputted by the operator. In this case, a type
selection window 100, as shown in Fig. 20, is displayed on the
display 89 of the console 14 or a monitor (not shown) of the
electronic cassette 13. The type selection window 100 has radio
buttons 101 for selecting one of the easy installation priority
type (first AEC mode) and the easy installation non-priority type
(second AEC mode). The operator chooses one of the two types by
clicking on the radio button 101 using a pointer 102 or the like
through the input device 90 or an operation section (not shown)
of the electronic cassette 13. In a like manner, the source ID
65
may be manually inputted by the operator, instead of being
obtained automatically.
[0171] Also, the easy installation priority type and the easy
installation non-priority type are set just as settings of the
electronic cassette 13, and the maker of the electronic cassette
13 or a dealer thereof may set one of the types in advance in
shipping. The electronic cassette 13 switches its operation in
accordance with the set type. This eliminates time and effort
to choose the type in a hospital being a customer. This also saves
the maker from having to prepare software of both types for
controlling the electronic cassette 13 and having to selectively
install the software that adheres to each geographic region, and
increases productivity.
[0172] In the above embodiments, in a case where the region type
is the easy installation priority type (first AEC mode), the
detection signal I/F is set as the output destination, and the
voltage value (new AEC detection signal) is set as the output
format. The source control device 11, which has a limited number
of imaging conditions (emission stop threshold values), makes a
judgment on the stop of emission, so the image quality
deteriorates more or less as compared with a case where the
electronic cassette 13 performs the AEC in accordance with the
precise imaging conditions. Accordingly, a contrivance as shown
in Fig. 21 is made to perform the AEC based on the emission stop
threshold values corresponding to the precise imaging conditions
with the use of the detection signal I/F, in a case where source
control device 11 has a less number of imaging conditions than
those of the electronic cassette 13.
[0173] First, exactly the same process is carried out as the
process of the first AEC mode in the first embodiment from the
selection of the dose measurement area to the judgment of the stop
of emission. However, the detection signal I/F 80 is used instead
66
of the emission signal I/F 81. As soon as the integrated value
of the detection signal has reached the emission stop threshold
value produced by the threshold value generator 79, a voltage
value that is equivalent to the emission stop threshold value
(TH1’, TH2, or the like of Fig. 2) of the source control device
11 at the corresponding tube voltage is transmitted through the
detection signal I/F 80, instead of transmitting the emission stop
signal through the emission signal I/F 81.
[0174] The emission stop threshold value produced by the
threshold value generator 79 takes various values (see Fig. 6)
even at the same tube voltage, in accordance with the imaging
condition set in the console 14. Since the judgment of the stop
of X-ray emission is made based on the threshold value
corresponding to the imaging condition, the timing of the judgment
varies depending on the imaging condition. According to this
method, however, a signal to be transmitted from the electronic
cassette 13 to the source control device 11 is only the voltage
value (one type in this embodiment) equivalent to the emission
stop threshold value of the source control device 11. In other
words, the voltage value equivalent to the emission stop threshold
value of the source control device 11 functions as the emission
stop signal, the detection signal I/Fs 26 and 80 function as I/Fs
dedicated to the transmission and reception of the emission stop
signal. The electronic cassette 13 makes the judgment of the stop
of emission in actual fact, but it is seen that the source control
device 11 itself judges the stop of emission by receiving the
voltage value equivalent to the emission stop threshold value.
[0175] This embodiment has both of an advantage of the easy
installation priority type using the detection signal I/F 80 and
an advantage of high image quality using the emission signal I/F
81 at the same time. This embodiment may be added as an easy
installation and high image quality compatible type in the region
67
type of the above embodiments. Note that, if the source control
device 11 has two or more types of imaging conditions at the same
tube voltage, the imaging conditions of the console 14 are grouped
in advance, and each group is linked to one of the imaging
conditions of the source control device 11 having the same tube
voltage, so as to transmit a voltage value that is equivalent to
the emission stop threshold value of the linked imaging condition
of the source control device 11.
[0176] As described above, in the second AEC mode, the emission
signal I/F 27 of the source control device 11 transmits and
receives not only the emission stop signal (AEC signal) but also
the signals other than the AEC signal, such as the emission start
request signal and the emission permission signal, to and from
the emission signal I/F 81 of the electronic cassette 13. Thus,
a branch step for judging the type of a received signal and
determining a course of a process is required and causes decrease
in rapidity. Also there is a possibility of receiving the same
type of signals in the same timing. This may cause a delay in
the AEC, especially, in a process of the stop of X-ray emission.
For example, in chest radiography, X-ray emission time is
extremely short i.e. on the order of 50 ms, so the process of the
stop of X-ray emission has to be performed rapidly.
[0177] Accordingly, a source control device 122 and an electronic
cassette 123 may be used, as shown in Fig. 22. The source control
device 122 is provided with an I/F 120 dedicated to the emission
stop signal, independently of the emission signal I/F 27, to
transmit and receive only the emission stop signal therethrough.
The electronic cassette 123 is provided with an I/F 121 dedicated
to the emission stop signal to transmit and receive only the
emission stop signal therethrough. In this case, the same process
as that of the second AEC mode in the above embodiments is
performed, but the I/Fs 120 and 121 dedicated to the emission stop
68
signal, instead of the emission signal I/Fs 27 and 81, are
necessarily in charge of the transmission and reception of the
emission stop signal. Transmitting and receiving the emission
stop signal, which is related to the judgment of the stop of X-ray
emission, through the dedicated I/Fs independent of the I/Fs for
transmitting the other signals eliminates the need for performing
the branch process for judging the type of the signal and
determining a process in accordance with the judgment. Also, it
is possible to prevent the reception of the different types of
signals in the same timing, so the process of the stop of X-ray
emission can be made rapidly.
[0178] Note that, in transmitting and receiving the emission stop
signal between the source control device and the electronic
cassette, the source control device is prevented from receiving
the different types of signals in the same timing by controlling
that the electronic cassette does not transmit another signal.
In this method, however, the signal transmission control of the
electronic cassette becomes complicated. In this embodiment,
since the emission stop signal related to the judgment of the stop
of X-ray emission is transmitted and received through the
dedicated I/Fs, the electronic cassette does not need to perform
the signal transmission control and becomes simple.
[0179] Also, there are many cases that the X-ray generating
apparatus and the X-ray imaging apparatus are made by different
makers and the details of processes cannot be known each other.
Thus, in the case of combining the X-ray source, the source control
device, the electronic cassette, and the console made by the
different makers, it is difficult to ensure that the X-ray
emission stop process is performed without delay. In this
embodiment, however, the emission stop signal related to the
judgment of the stop of X-ray emission is transmitted and received
through the dedicated I/Fs. Thus, if execution of the X-ray
69
emission stop process without delay is ensured by assessing signal
transmission performance of the electronic cassette and signal
reception performance of the source control device, an operation
of the system into which the above parts are combined is preferably
ensured.
[0180] Although there is a problem of the complication more or
less, as described above, with the aim of accelerating the X-ray
emission stop process, not only the emission stop signal but also
another signal may be transmitted through the I/Fs dedicated to
the emission stop signal, only in a case where no collision between
the signals is ensured in consideration of a sequence of the
process of the system. This does not adversely affect the
rapidity of the X-ray emission stop process in actual fact. More
specifically, the start synchronization signal is never issued
in timing of stopping the X-ray emission, and hence can be
transmitted and received through the I/Fs dedicated to the
emission stop signal. A signal that can be issued in arbitrary
timing (irregular timing) such as a battery level check signal
is transmitted and received through the different I/Fs.
[0181] Note that, in an example of Fig. 22, the signals other
than the emission stop signal may be wirelessly transmitted and
received between the emission signal I/F 27 of the source control
device 11 and the emission signal I/F 81 of the electronic cassette
13, in addition to the wireless communication with the console
14. While the emission stop signal is securely transmitted and
received through the wired communication, transmitting the other
signals through the wireless communication secures the
portability of the electronic cassette 13.
[0182] If a malfunction occurs in the detection pixel 65 of the
electronic cassette 13 or the communication between the source
control device 11 and the electronic cassette 13 is interrupted
by a wiring disconnection, the AEC may not work due to a failure
70
in the transmission and reception of the AEC signal. In the AEC,
the source control device 11 sets as the X-ray emission time the
maximum value allowable under safety restrictions, so a
malfunction of the AEC poses the risk of excessive radiation
exposure to a patient beyond the target dose. Therefore, the
electronic cassette 13 has a test mode, and test radiography is
performed in all the imaging conditions that the console 14 has,
immediately after the installation and before radiography of one
day. The detection pixels 65 keeps detecting the X-rays even
after the electronic cassette 13 sends the AEC signal to the source
control device 11. In a case where the stop of X-ray emission
is detected within predetermined time, the AEC is judged to be
performed normally. If not, it is judged that any breakdown
occurs and a warning message is displayed on the display 89 of
the console 14.
[0183] In a case where the source control device 11 and the
electronic cassette 13 are connectable through both the wired and
wireless communication between the detection signal I/Fs 26 and
80 or between the emission signal I/Fs 27 and 81, if the wireless
communication is judged to be unstable as a result of monitoring
radio field intensity or the like, a warning message may be
displayed to recommend switching to the wired communication.
[0184] In the above embodiments, one X-ray generating apparatus
2a, one electronic cassette 13, and one console 14 are connected
on a one-by-one basis for the sake of convenience in explanation.
However, the present invention is intended for use in a case where
one pair of X-ray generating apparatus and console is disposed
in each examination room or each medically equipped vehicle and
a several number of electronic cassettes are shared in the rooms
or the vehicles, or one console performs centralized control of
a plurality of X-ray generating apparatuses. In the former case,
since an individual structure is the same as the structures of
71
the above embodiments i.e. the connection on a one-by-one basis,
the source ID is transmitted and received upon establishing the
communication between the X-ray generating apparatus and the
console, as with the above embodiments. In the latter case, the
operator chooses which apparatus to use, out of the plurality of
X-ray generating apparatuses, through the GUI (graphical user
interface) on the display of the console, and the source ID of
the chosen X-ray generating apparatus is transmitted and received
between the X-ray generating apparatus and the console.
[0185] In the above embodiments, the source information 99 is
stored in the storage device 87 of the console 14 and the region
type, the correction information, and the like are transmitted
from the console 14 to the electronic cassette 13, but the present
invention is not limited to this. The source information 99 may
be stored in an internal memory (not shown) of the controller 41
of the electronic cassette 13. In this case, the source ID is
sent to the electronic cassette through the console. If there
are a plurality of X-ray generating apparatuses, the electronic
cassette may have information about the correlation between the
source ID and a unique ID of the console or a wireless access point
(in a case where the console and the electronic cassette are
wirelessly connected) such as an IP address, an SSID, or an ESSID.
The unique ID may be obtained upon connecting the console or the
wireless access point, and the source ID corresponding to the
obtained unique ID of the console or the wireless access point
may be read out from the information on the correlation. In
obtaining the unique ID of the wireless access point, a wireless
access point that has the most favorable communication
characteristics including the radio field intensity and the like
is chosen. In the case of a medically quipped vehicle, a unique
ID of the medically equipped vehicle may be used instead of the
unique ID of the console or the wireless access point.
72
[0186] In the above embodiments, the detection pixel 65 that is
directly connected to the signal line 52 without through the TFT
47 is used as the new AEC sensor. However, the radiation dose
may be detected by monitoring an electric current flowing through
the bias line 48 connected to a specific pixel 45, taking advantage
of the fact that the electric current flowing through the bias
line 48 for supplying the bias voltage Vb to each pixel 45 is based
on electric charge produced in the pixel 45. Otherwise, the
radiation dose may be detected based on a leak current that leaks
from the pixel 45 when all the TFTs 47 are turned off.
Furthermore, an AEC detection pixel that has a different structure
and an independent output may be provided besides the pixels 45
in a plane coplanar to the imaging surface 36. Also, the radiation
dose may be detected by nondestructive readout of the electric
charge from the pixel by using a CMOS type image sensor as an FPD.
[0187] Note that, instead of integrating the detection signal
by the integrator after the correction of the detection signal
by the corrector, the integrated value of the detection signal
outputted from the integrator may be corrected. In this case,
the new AEC detection signal is inputted from the dose measurement
area selector to the integrator, and the integrator calculates
the integrated value. Then, the integrated value is inputted to
the corrector to make a correction similar to the correction of
the above embodiments.
[0188] In the above embodiments, the detection pixel 65 of the
electronic cassette 13 is newly used as the AEC sensor, instead
of the previous AEC sensor attached to the X-ray generating
apparatus 2a, in other words, a retrofit. However, the present
invention is applicable in the same manner to a case where the
X-ray generating apparatus and the like are made by a maker while
only the electronic cassette is made by an OEM supplier, because
the OEM supplier of the electronic cassette has to change the
73
output format of the AEC signal so as to be compatible with the
format of the X-ray generating apparatus and the like made by the
different maker.
[0189] The console 14 and the electronic cassette 13 are separate
from each other in the above embodiments, but the console 14 is
not necessarily an independent device, and the electronic
cassette 13 has the function of the console 14. The present
invention may be applied to an X-ray image detecting device to
be mounted on the imaging stand, instead of or in addition to the
electronic cassette, being a portable X-ray image detecting
device.
[0190] In the above embodiments, the corrector 76 is provided
to correct the new AEC detection signal to the detection signal
corresponding to the previous AEC detection signal due to
incompatibility in the specifications related to the AEC between
the source control device and the electronic cassette. However,
if the specifications are compatible, the corrector 76 is
unnecessary.
[0191] The present invention is applicable to an imaging system
using another type of radiation such as -rays, instead of the
X-rays.
DESCRIPTION OF THE REFERENCE NUMERALS
[0192] 2 X-ray imaging system
10 X-ray source
11, 122 source control device
13, 105, 123, 151 electronic cassette
14 console
21 controller
25 previous AEC sensor
26, 80, 106, 116 detection signal I/F
27, 81, 117 emission signal I/F
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35 FPD
40, 163 communication unit
41, 161 controller
45 pixel
65 detection pixel
67 AEC unit
75, 111 dose measurement area selector
76, 112 corrector
77, 113 integrator
78, 114 comparator
79, 115 threshold value generator
88 communication I/F
120, 121 I/F dedicated to emission stop signal
150 power feeding device
160 AEC controller
162 AEC communication unit
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We Claim:
1. A radiation imaging system characterized in comprising:
a radiation source for emitting radiation to an object;
a source control device for controlling an operation of said
radiation source;
a radiographic image detecting device for detecting a
radiographic image by measuring said radiation passed through
said object, said radiographic image detecting device having an
AEC sensor for performing automatic exposure control that stops
a radiation emission from said radiation source based on a
radiation dose passed through said object;
a console for receiving said radiographic image from said
radiographic image detecting device;
a high speed communication unit having a relatively high
communication speed, for communicating an AEC signal related to
said automatic exposure control between said source control
device and said radiographic image detecting device; and
a low speed wireless communication unit having a
communication speed lower than said communication speed of said
high speed communication unit, for wirelessly communicating a
signal other than said AEC signal between said radiographic image
detecting device and said console.
2. The radiation imaging system according to claim 1,
characterized in that
average delay time of data communication is small in said
high speed communication unit; and
said delay time of said low speed wireless communication
unit is larger than said delay time of said high speed
communication unit.
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3. The radiation imaging system according to claim 1 or 2,
characterized in that said high speed communication unit performs
wireless communication of said AEC signal.
4. The radiation imaging system according to claim 3,
characterized in that
said high speed communication unit performs communication
of said AEC signal by ad-hoc communications; and
said low speed wireless communication unit performs
communication of said signal other than said AEC signal by
infrastructure communications.
5. The radiation imaging system according to claim 4,
characterized in that said radiographic image detecting device
directly communicates said AEC signal with said source control
device by said ad-hoc communications.
6. The radiation imaging system according to claim 1 or 2,
characterized in that said high speed communication unit performs
wired communication of said AEC signal.
7. The radiation imaging system according to claim 6,
characterized in that said high speed communication unit also
performs wired communication of said signal other than said AEC
signal.
8. The radiation imaging system according to claim 7
characterized in further comprising:
a judging section for judging whether or not to perform said
automatic exposure control in radiography in accordance with an
imaging condition inputted through said console; and
a communication switching section for making said high
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speed communication unit, instead of said low speed wireless
communication unit, communicate said signal other than said AEC
signal, in a case where said judging section judges that said
automatic exposure control is not performed.
9. The radiation imaging system according to one of claims
1 to 8, characterized in that
said high speed communication unit and said low speed
wireless communication unit are made of different hardware
resources; and
said radiographic image detecting device includes a first
control section for performing control of a process and
communication of said AEC signal and a second control section for
performing control of a process and communication of said signal
other than said AEC signal.
10. The radiation imaging system according to one of claims
1 to 9, characterized in further comprising:
a low speed wired communication unit for performing wired
communication of said signal other than said AEC signal at a
communication speed lower than said communication speed of said
high speed communication unit.
11. The radiation imaging system according to one of claims
1 to 10, characterized in that
said AEC signal is one of a dose detection signal of said
AEC sensor and an emission stop signal that is outputted as soon
as an integrated value of said dose detection signal of said AEC
sensor has reached a predetermined emission stop threshold value;
and
said radiographic image detecting device has two modes,
including a first AEC mode for transmitting said dose detection
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signal of said AEC sensor and a second AEC mode for transmitting
said emission stop signal to said source control device through
said high speed communication unit.
12. The radiation imaging system according to claim 11,
characterized in that as said high speed communication unit, each
of said source control device and said radiographic image
detecting device has a detection signal I/F for communicating said
dose detection signal and an emission signal I/F for communicating
said emission stop signal.
13. The radiation imaging system according to claim 12,
characterized in that
said radiographic image detecting device has a main body
and a supplemental device, and said main body has an image detector
for detecting said radiographic image and said AEC sensor, and
said supplemental device has said detection signal I/F and said
emission signal I/F; and
communication between said supplemental device and said
main body adopts a same communication method as a communication
method of said high speed communication unit.
14. The radiation imaging system according to one of claims
1 to 13, characterized in that said radiographic image detecting
device is an electronic cassette having a portable housing.
15. The radiation imaging system according to claim 14,
characterized in that said electronic cassette can be driven by
a battery contained in said housing.
16. The radiation imaging system according to claim 15
characterized in further comprising:
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a noncontact power feeding device for supplying electric
power to recharge said battery, wherein
said battery is rechargeable in a state of being contained
in said electronic cassette with said electric power from said
noncontact power feeding device.
17. The radiation imaging system according to claim 16,
characterized in that said noncontact power feeding device is
embedded in a holder of an imaging stand into which said electronic
cassette is detachably loaded.
18. The radiation imaging system according to one of claims
1 to 17, characterized in that
said radiographic image detecting device includes an image
detector that has an imaging surface and detects said radiographic
image; and
said AEC sensor is disposed in said imaging surface.
19. A communication method of a radiation imaging system
including:
a radiation source for emitting radiation to an object;
a source control device for controlling an operation of said
radiation source;
a radiographic image detecting device for detecting a
radiographic image by measuring said radiation passed through
said object, said radiographic image detecting device having an
AEC sensor for performing automatic exposure control that stops
a radiation emission from said radiation source based on a
radiation dose passed through said object; and
a console for receiving said radiographic image from said
radiographic image detecting device,
said communication method characterized in comprising:
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a high speed communication step for communicating at a
relatively high communication speed an AEC signal related to said
automatic exposure control between said source control device and
said radiographic image detecting device; and
a low speed communication step for wirelessly communicating
a signal other than said AEC signal between said radiographic
image detecting device and said console at a communication speed
lower than said communication speed of said AEC signal.
20. A radiographic image detecting device to be used in
combination with a radiation source for emitting radiation to an
object and a source control device for controlling an operation
of said radiation source, for detecting a radiographic image by
measuring said radiation passed through said object, said
radiographic image detecting device characterized in comprising:
an AEC sensor for performing automatic exposure control
that stops a radiation emission from said radiation source based
on a radiation dose passed through said object;
a high speed communication unit for communicating an AEC
signal related to said automatic exposure control with said source
control device at a relatively high communication speed; and
a low speed wireless communication unit for wirelessly
communicating a signal other than said AEC signal with a console
for receiving said radiographic image at a communication speed
lower than said communication speed of said AEC signal.
21. The radiation imaging system according to one of claims
1 to 18, characterized in that in said automatic exposure control,
said radiation emission is stopped as soon as an integrated value
of said radiation dose detected by said AEC sensor has reached
a predetermined emission stop threshold value.
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22. A radiation imaging system characterized in comprising:
a radiation source for emitting radiation to an object;
a source control device for controlling an operation of said
radiation source;
a radiographic image detecting device for detecting a
radiographic image by measuring said radiation passed through
said object, said radiographic image detecting device having an
AEC sensor for performing automatic exposure control that stops
a radiation emission from said radiation source based on a
radiation dose passed through said object;
a console for receiving said radiographic image from said
radiographic image detecting device;
a high speed communication unit having small average delay
time of data communication, for communicating an AEC signal
related to said automatic exposure control between said source
control device and said radiographic image detecting device; and
a low speed wireless communication unit having delay time
larger than said delay time of said high speed communication unit,
for wirelessly communicating a signal other than said AEC signal
between said radiographic image detecting device and said
console.
23. The radiation imaging system according to claim 22,
characterized in that said high speed communication unit
wirelessly communicates said AEC signal.
24. The radiation imaging system according to claim 23,
characterized in that
said high speed communication unit performs communication
of said AEC signal by ad-hoc communications; and
said low speed wireless communication unit performs
communication of said signal other than said AEC signal by
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infrastructure communications.
25. The radiation imaging system according to claim 24,
characterized in that said radiographic image detecting device
directly communicates said AEC signal with said source control
device by said ad-hoc communications.
26. The radiation imaging system according to claim 22,
characterized in that said high speed communication unit performs
wired communication of said AEC signal.
27. The radiation imaging system according to claim 26,
characterized in that said high speed communication unit also
performs wired communication of said signal other than said AEC
signal.
28. The radiation imaging system according to claim 27
characterized in further comprising:
a judging section for judging whether or not to perform said
automatic exposure control in radiography in accordance with an
imaging condition inputted through said console; and
a communication switching section for making said high
speed communication unit, instead of said low speed wireless
communication unit, communicate said signal other than said AEC
signal, in a case where said judging section judges that said
automatic exposure control is not performed.
29. The radiation imaging system according to one of claims
22 to 28, characterized in that
said high speed communication unit and said low speed
wireless communication unit are made of different hardware
resources; and
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said radiographic image detecting device includes a first
control section for performing control of a process and
communication of said AEC signal and a second control section for
performing control of a process and communication of said signal
other than said AEC signal.
30. The radiation imaging system according to one of claims
22 to 29, characterized in further comprising:
a low speed wired communication unit for performing wired
communication of said signal other than said AEC signal at a
communication speed lower than said communication speed of said
high speed communication unit.
31. The radiation imaging system according to one of claims
22 to 30, characterized in that
said AEC signal is one of a dose detection signal of said
AEC sensor and an emission stop signal that is outputted as soon
as an integrated value of said dose detection signal of said AEC
sensor has reached a predetermined emission stop threshold value;
and
said radiographic image detecting device has two modes,
including a first AEC mode for transmitting said dose detection
signal of said AEC sensor and a second AEC mode for transmitting
said emission stop signal to said source control device through
said high speed communication unit.
32. The radiation imaging system according to claim 31,
characterized in that as said high speed communication unit, each
of said source control device and said radiographic image
detecting device has a detection signal I/F for communicating said
dose detection signal and an emission signal I/F for communicating
said emission stop signal.
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33. The radiation imaging system according to claim 32,
characterized in that
said radiographic image detecting device has a main body
and a supplemental device, and said main body has an image detector
for detecting said radiographic image and said AEC sensor, and
said supplemental device has said detection signal I/F and said
emission signal I/F; and
communication between said supplemental device and said
main body adopts a same communication method as a communication
method of said high speed communication unit.
34. The radiation imaging system according to one of claims
22 to 33, characterized in that said radiographic image detecting
device is an electronic cassette having a portable housing.
35. The radiation imaging system according to claim 34,
characterized in that said electronic cassette can be driven by
a battery contained in said housing.
36. The radiation imaging system according to one of claims
22 to 35, characterized in that in said automatic exposure
control, said radiation emission is stopped as soon as an
integrated value of said radiation dose detected by said AEC
sensor has reached a predetermined emission stop threshold value.
37. A communication method of a radiation imaging system
including:
a radiation source for emitting radiation to an object;
a source control device for controlling an operation of said
radiation source;
a radiographic image detecting device for detecting a
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radiographic image by measuring said radiation passed through
said object, said radiographic image detecting device having an
AEC sensor for performing automatic exposure control that stops
a radiation emission from said radiation source based on a
radiation dose passed through said object; and
a console for receiving said radiographic image from said
radiographic image detecting device,
said communication method characterized in comprising:
a high speed communication step for communicating an AEC
signal related to said automatic exposure control between said
source control device and said radiographic image detecting
device with small average delay time of data communication; and
a low speed wireless communication step for wirelessly
communicating a signal other than said AEC signal between said
radiographic image detecting device and said console with delay
time larger than said delay time of the communication of said AEC
signal.
38. A radiographic image detecting device to be used in
combination with a radiation source for emitting radiation to an
object and a source control device for controlling an operation
of said radiation source, for detecting a radiographic image by
measuring said radiation passed through said object, said
radiographic image detecting device characterized in comprising:
an AEC sensor for performing automatic exposure control
that stops a radiation emission from said radiation source based
on a radiation dose passed through said object;
a high speed communication unit having small average delay
time of data communication, for communicating an AEC signal
related to said automatic exposure control with said source
control device; and
a low speed wireless communication unit having delay time
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larger than said delay time of said high speed communication unit,
for wirelessly communicating a signal other than said AEC signal
with a console for receiving said radiographic image.