BACKGROUND OF THE INVENTION
Embodiments of the invention relate generally to diagnostic imaging and,
more particularly, to a method and apparatus of maintaining image quality while
reducing system fabrication cost.
Typically, in computed tomography (CT) imaging systems, an x-ray source
emits a fan-shaped beam toward a subject or object, such as a patient or a piece of
luggage. Hereinafter, the terms "subject" and "object" shall include anything capable of
being imaged. The beam, after being attenuated by the subject, impinges upon an array
of radiation detectors. The intensity of the attenuated beam radiation received at the
detector array is typically dependent upon the attenuation of the x-ray beam by the
subject. Each detector element of the detector array produces a separate electrical signal
indicative of the attenuated beam received by each detector element. The electrical
signals are transmitted to a data processing system for analysis which ultimately
produces an image.
Generally, the x-ray source and the detector array are rotated about the gantry
within an imaging plane and around the subject. X-ray sources typically include x-ray
tubes, which emit the x-ray beam at a focal point. X-ray detectors typically include a
collimator for rejecting scatter x-rays from the patient, a scintillator for converting xrays
to light energy adjacent the collimator, and photodiodes for receiving the light
energy from the adjacent scintillator and producing electrical signals therefrom.
Typically, each scintillator of a scintillator array converts x-rays to light energy. Each
scintillator discharges light energy to a photodiode adjacent thereto. Each photodiode
detects the light energy and generates a corresponding electrical signal. The outputs of
the photodiodes are then transmitted to the data processing system for image
reconstruction.
2
Typically, the detector array is fabricated from a large number of detector
modules that are each separately fabricated, tested, and installed into the detector array
during assembly. For instance, in one design the detector array is fabricated from 57
modules, each having 16 channels along a channel or x-direction of the detector array.
The modules of known designs may include 8, 16,32,64, or more pixels in a slice or zdirection
of the detector array.
However, because of the complexity of the design of the modules: to include
high density interconnects, array bonding of a backlit diode, underfill, and myriad other
issues, the modules are very expensive to fabricate and test. And, as complexity
increases, the possibility for yield losses during module fabrication and testing increases
as well. Further, the modules that make up the detector array are aligned and positioned
with a high degree of accuracy with respect to one another, typically on the order of
microns are required. As such, the detector array is typically fabricated in a test bay as
a stand-alone unit and then the unit is installed and tested in a larger assembly bay.
In addition, in some system designs or applications it may be desirable to
reduce an amount of detector coverage along the slice direction (to, for instance 8 slices
of coverage) in order to reduce system cost, enabling a cost tradeoff to be made between
coverage and cost. However, in other system designs or applications it may be desirable
to increase an amount of coverage along the slice direction (to, for instance 16,64, or
256 slices as examples). As such, there are multiple configurations of designs that may
be desired based on z-coverage and cost tradeoffs. Each detector design, though,
includes different amounts of z coverage. That is, an 8-slice detector is typically
designed from 8-slice detector components, a 16-slice detector is typically designed
from 16-slice detector components, etc ... , resulting in a different system design for each
amount of coverage that is desired. As such, there is typically not a lot commonality in
designs of different slice coverage, resulting in separate components and assembly and
test procedures for each unique design.
Thus, there are therefore not only myriad issues associated with fabrication
and testing of individual detector modules, but overall system cost, complexity, and
3
yield are also affected because of the different detector designs having differing
amounts of z-coverage. And, in some markets, such as in the developing world, there is
less need for a "high-end" imaging capability as such systems may be priced out of the
market while providing functionality that is of less demand (such as 64 slice or 256 slice
coverage). For instance, systems having 64-slice capability or greater are directed
increasingly toward the desire to image a full organ in a single rotation. However, in
many markets it is more desirable to have a much more basic scanning capability, with
system cost a much more important driver than high-end scanning capability. In other
words, in some markets it is desirable to have an option to purchase a system that is
skewed toward low cost, with users willing to forego a more high-end scanning
capability.
As such, there is a need to reduce cost and complexity of detector arrays in
imaging application, particularly in system designs having a more limited amount of zcoverage
that are directed toward a value end of the market. Therefore, it would be
desirable to design an apparatus and method to reduce cost of a CT system, while
providing a basic amount of detector coverage, system and performance capability.
4
BRIEF DESCRIPTION OF THE INYENTION
The invention is a directed method and apparatus for imaging using a cost
effective, highly reliable, and serviceable module.
According to one aspect, a CT system includes a rotatable gantry having an
opening to receive an object to be scanned, the rotatable gantry having a detector
mounting surface, an x-ray source attached to the gantry and configured to project an xray
beam toward the object, a plurality of detector modules each mounted within one
field-of-view (FOY) and mounted directly to the detector mounting surface of the
rotatable gantry, a data acquisition system (DAS) configured to receive outputs from at
least one of the plurality of detector modules, and a computer programmed to acquire
projections of imaging data of the object from the DAS, and generate an image of the
object using the imaging data.
According to another aspect, a method of fabricating a CT system includes
fabricating a gantry having a detector mounting surface, attaching an x-ray source to the
gantry such that x-rays emit from the x-ray source and through the rotational axis, and
attaching, within one field-of-view (FOY), each detector module directly to the detector
mounting surface such that the x-rays also emit to the two or more detector modules.
According to yet another aspect, a CT detector module includes an
electronics board, a first mounting surface, and a second mounting surface; wherein the
first mounting surface is configured to be mounted directly onto a rotatable gantry of a
CT system, the second mounting surface is configured such that the electronics board is
mounted orthogonal with respect to x-rays emitted from an x-ray source that is
positioned on the rotatable gantry.
Yarious other features and advantages will be made apparent from the
following detailed description and the drawings.
5
BRIEF DESCRIPTION OF THE DRAWINGS
The drawings illustrate preferred embodiments presently contemplated for
carrying out the invention.
In the drawings:
FIG. 1 is a pictorial view of a CT imaging system.
FIG. 2 is a block schematic diagram of the system illustrated in FIG. 1.
FIG. 3 is a plan view of a rotatable gantry according to an embodiment of the
invention.
FIG. 4 is a perspective view of a perspective view of one module, according
to an embodiment of the invention.
FIG. 5 is a plan view of a module having both an 8-slice and a 16-slice
configuration.
FIG. 6 illustrates a set of curves representing a geometric amount of
correction for modules installed according to an embodiment of the invention.
FIG. 7 is a pictorial view of a CT system for use with a non-invasive package
inspection system.
6
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The operating environment of the invention is described with respect to a
eight and sixteen-slice computed tomography (CT) system. However, it will be
appreciated by those skilled in the art that the invention is equally applicable for use
with other multi-slice configurations. Moreover, the invention will be described with
respect to the detection and conversion of x-rays. However, one skilled in the art will
further appreciate that the invention is equally applicable for the detection and
conversion of other high frequency electromagnetic energy. The invention will be
described with respect to a "'third generation" CT scanner, but is equally applicable with
other CT systems.
Referring to FIGS. I and 2, a computed tomography (CT) imaging system 10
is shown as including a rotatable gantry 12 representative of a "third generation" CT
scanner. Rotatable gantry 12 has an x-ray source 14 that projects a beam of x-rays 16
toward a detector assembly 18 on the opposite side of the rotatable gantry 12. Imaging
system 10 includes a pre-patient collimator 27 and a bowtie filter 29. Pre-patient
collimator 27 is configured to control a beam width, in a z-direction and as known in the
art, between x-ray source 14 and detector assembly 18. Detector assembly 18 is formed
by a plurality of detectors 20 that are directly attached to rotatable gantry 12. The
plurality of detectors 20 sense the projected x-rays 16 that pass through medical patient
22. Detectors 20 include a DAS 32 that converts the data from detectors 20 to digital
signals for subsequent processing. Each detector 20 produces an analog electrical signal
that represents the intensity of an impinging x-ray beam and hence the attenuated beam
as it passes through the patient 22. During a scan to acquire x-ray projection data,
rotatable gantry 12 and the components mounted thereon rotate about an axis of rotation
24.
Rotation of rotatable gantry 12 and the operation of x-ray source 14 are
governed by a control mechanism 26 of CT system 10. Control mechanism 26 includes
a controller 28 that provides power and timing signals to an x-ray source 14 as well as
motion control for operation of pre-patient collimator 27 and bowtie filter 29, and
control mechanism 26 includes a gantry motor controller 30 that controls the rotational
7
speed and position of rotatable gantry 12. An image reconstructor 34 receives sampled
and digitized x-ray data from DAS 32 and performs high speed reconstruction. The
reconstructed image is applied as an input to a computer 36 which stores the image in a
mass storage device 38.
Computer 36 also receives commands and scanning parameters from an
operator via console 40 that has some form of operator interface, such as a keyboard,
mouse, voice activated controller, or any other suitable input apparatus. An associated
display 42 allows the operator to observe the reconstructed image and other data from
computer 36. The operator supplied commands and parameters are used by computer
36 to provide control signals and information to DAS 32, x-ray controller 28 and gantry
motor controller 30. In addition, computer 36 operates a table motor controller 44
which controls a motorized table 46 to position patient 22 and rotatable gantry 12.
Particularly, table 46 moves patients 22 through a gantry opening 48 of FIG. 1 in whole
or in part.
As commonly understood in the art, patient 22 is generally translated along a
z-direction 21, commonly referred to as a slice-direction, of rotatable gantry 12. As also
commonly understood in the art, detector assembly 18 is caused to rotate
circumferentially in an x-direction 23, or channel direction, of rotatable gantry 12.
Thus, x-rays 16 travel generally in a y-direction 25 and through detector assembly 18 as
they emit from x-ray source 14 and pass through patient 22.
As illustrated in FIGS. 1 and 2 and as will be further discussed, CT system 10
includes a plurality of detectors 20 that are mounted directly to rotatable gantry 12.
And, although five modules 20 are illustrated therein, it is contemplated that less than or
more than 5 modules may be included, dependent on desired field of view (FOV),
according to the invention.
Referring now to FIG. 3, a plan view of rotatable gantry 12 includes a
detector mounting surface 50 and five modules 20 that are attached directly thereto
having collimator plates 68 that are generally fanned and angled such that they
collimate x-rays emanating from a focal spot 54, as will be further described in FIG. 4.
8
Detector mounting surface 50 includes a removable module 51 having its own
collimator plates 68. Removable module 51 thereby serves as a reference for x-rays 17
that pass outside of a field-of-view (FOY) 58 and removable module 51 may include
only a limited number of collimator plates 68, and corresponding detector elements, as
illustrated. Thus, in contrast to a conventional system design where detector modules
are attached to, for instance, a collimator assembly, which is then attached as a whole
unit to a gantry, modules 20 of the present invention are attached directly to the
rotatable gantry and are thus standalone units which may be separately fabricated, pretested
and attached thereto, according to the invention. Such a modular design enables
simple repair and replacement of individual modules, as opposed to having to remove
an entire detector unit, having a plurality of detector modules attached thereto, as is
conventionally done.
Each module 20 includes a surface 52 that is generally perpendicular to focal
spot 54 that emanates from an x-ray tube (not shown), such as x-ray tube 14 illustrated
in FIGS. 1 and 2. Circumferential coverage 56 of modules 20 defines FOY 58, which
defines an imaging region over which imaging data may be obtained from modules 20
as rotatable gantry 12, that comprises detector mounting surface 50, and is rotated about
axis of rotation 24. As will be further discussed, each module 20 includes an array of
pixels in both the x-direction or channel direction 23, and in the slice or z-direction
(direction 21 illustrated in FIG. 1). As such and as understood in the art, the total
number of channels in x-direction 23 is a product of the number of channels in each
module and the number of modules. Accordingly, it is contemplated that
circumferential coverage 56 that defines FOY 58 is a function of a number of
geometrical parameters related to rotatable gantry 12, including but not limited to the
number of channels in each module 20 in x-direction 23, the pitch thereof, the number
of modules 20 employed, and their placement with respect to focal spot 54, as
examples.
Referring now to FIG. 4, a perspective view of one module 20 is illustrated,
of the five modules 20 of FIGS. 1-3, positioned on detector mounting surface 50 with
respect to focal spot 54, according to one embodiment of the invention. Module 20
9
includes an L-shaped bracket 60 having a planar module mounting surface 62 that is
attachable to detector mounting surface 50 via, for instance, a bolt (not shown) through
aperture 64. According to this embodiment, module mounting surface 62 is generally at
a right angle to a surface 66 (surface 66 corresponds to surface 52 of FIG. 3, and is
orthogonal to x-rays 16 passing from focal spot 54), toward which x-rays 16 emanate
from focal spot 54. Likewise, module mounting surface 62 is orthogonal, in the
illustrated embodiments, to rotational axis 24 of system 10. It is to be recognized that
module mounting surface 62 need not be orthogonal to rotational axis 24, and that the
angle therebetween may be varied based on the design of rotatable gantry 12 and the
surfaces used to mount modules 20. However, the angle of L-shaped bracket 60 would
change accordingly, so long as surfaces 52 are maintained generally orthogonal to xrays
16 passing from focal spot 54.
Module 20 includes a collimator array 68 attached to L-shaped bracket 60 via
bolts, screws, or other known methods. Collimator 68 is configured to reject scatter
from the patient, corresponding to x-rays coming from angle outside the primary beam
angle and collimate x-rays that emit toward module 20 from focal spot 54 using. For
instance, high-density plates (such as tungsten) that are generally positioned in a fanned
angle toward focal spot 54, as is known in the art. Module 20 includes an electronics
board 70 attached to collimator 68 and L-shaped bracket 60, having mounted thereon a
photodiode array and scintillator 72, as known in the art. According to the invention,
photodiode array of photodiode array and scintillator 72 includes either a backlit
photodiode array or a frontlit photodiode array. As understood in the art, a backlit
photodiode array is configured to be electrically attached to a board, such as electronics
board 70, such that electrical signals are read through the back side of the scintillator,
whereas a frontlit photodiode array is read out from the front side using electrical traces
positioned on the front side (i.e., toward the x-ray source).
Electronics board 70 also includes electrical components such as ASICS 74
and other components that comprise DAS 32. Electronics board 70 is, for instance, a
printed circuit board (PCB) having multiple layers therein that enable readout from
photodiode array and scintillator 7'f to ASJCS 74, and to an image reconstructor and/or
10
computer (via a cable, not shown), as illustrated in FIG. 2. According to the invention,
electronics board 70 may include a heat sink 76 attached thereto and thermally coupled
to ASICS 74 and other components of electronics board 70.
Thus, referring to FIGS. 1-4, a plurality of modules 20 are attached directly to
detector mounting surface 50 of rotatable gantry 12 and form FOV 58 therewith. As
can be seen particularly in FIG. I, when rotatable gantry 12 is rotated, detector
mounting surface 50 thereof is generally orthogonal to axis of rotation 24. Modules 20
formed as such are formed of L-shaped bracket 60, which enables modules 20 to be
mounted directly to detector mounting surface 50 while presenting a surface 52/66 that
is orthogonal to x-rays 16 that emit from focal spot 54.
X-rays 16 are caused to emit from focal spot 54, toward surface 52/66, pass
into the scintillator of photodiode array and scintillator 72. Resultant photons pass to
photodiode array of photodiode array and scintillator 72, where electrical signals are
generated and read out using electronics board 70.
According to the invention, module 20 is configured so that either an 8-slice
or a 16-slice can be included therewith. That is, during fabrication, either 8-slice or 16slice
components may be selected, based on the desired design that is being fabricated.
In other words, module 20 is designed in order that common components may be used
for system to, except for the components that are used in module(s) 20. Such an
arrangement is illustrated in FIG. 5. Referring to FIG. 5, module 20 is illustrated as a
plan view of surface 52 of FIG. 3 and surface 66 of FIG. 4 (but without collimator 68
and without a corresponding scintillator placed on the diode array, for simplicity of
illustration purposes).
In the 8-slice illustration 100, diode arrays 102 (here illustrated as frontlit
diodes) are positioned on electronics board 70, having positioned thereon (illustrated in
phantom to show that they are on a side of electronics board 70 that is opposite the
surface being viewed) DAS 32 that includes ASICS 74 and other electronic
components. Diode arrays 102 define a total amount of z-coverage 104 over 8-slices
(Le., 8 pixels of slice information), which corresponds to z-direction 21 as shown in
II
FIG. 1. As illustrated, electronics board 70 includes a total width in z-direction 106 and
includes a backplane 108 that receives digital signals from DAS 32 via a flex cable 110.
Wirebonds 112 are positioned, in this embodiment that shows frontlit diodes, to
electrically connect diode arrays 102 to electronics board 70. Although not illustrated,
it is to be understood that collimator 68 of FIG. 4 is configured having a z-width of
coverage that corresponds to total amount of z-coverage 104 and 8 slices of pixel
coverage.
In another arrangement of this embodiment, still referring to FIG. 5, I6-slice
configuration 150 includes diode arrays 152 that are positioned on electronics board 70.
In this arrangement, a total amount of z-coverage 154 over 16-slices (i.e., 16 pixels of
slice information), which corresponds to z-direction 21. As illustrated in this
configuration, and in contrast to 8-slice illustration 100, electronics board 70 includes a
total width in z-direction 156 that is different from total width in z-direction 106 of 8slice
illustration 100, and includes a backplane 158 that receives digital signals from
DAS 32 via a flex cable 160. Wirebonds 162, in this arrangement, electrically connect
diode arrays 152 to electronics board 70 on both sides of the arrays. Although not
illustrated, it is to be understood that collimator 68 of FIG. 4 is configured having a zwidth
of coverage that corresponds to total amount of z-coverage 154 and 16 slices of
pixel coverage.
As such, illustrations 100 and 150 of FIG. 5 include both 8 and 16 slice
configurations that may be incorporated into system 10, and components thereof, of
FIGS. 1-4. That is, module 20 may be configured to accommodate an 8 or 16 slice
collimator, 8 slices of pixel coverage with a scintillator/diode array combination, and
corresponding DAS components. In the 8-slice arrangement, electronics board 70 is
narrower in width 106 than that of the 16-slice arrangement, requiring two types of
board 70 for each respective configuration. However, the invention is not to be so
limited and it is contemplated that a single design of board 70 may be included that
includes accommodation of either an 8 or 16 slice arrangement. For instance, according
to this embodiment, a single board 70 may be included such as that illustrated for 16slice
configuration 150, but it may be depopulated for an 8-slice arrangement. Thus,
12
board 70 having total width in z-direction 21 156 may be used for either arrangement,
but in the 8-slice arrangement, additional diode arrays 164 and additional DAS
components 166 may be foregone such that only an 8-slice arrangement is fabricated.
Thus, in this arrangement, a single design of components, including but not limited to
electronics board 70 and collimator 68, may be used to accommodate either an 8 or a 16
slice configuration. Accordingly, the total number of components is decreased,
significantly reducing overall manufacturing costs, while enabling fabrication of either
system.
As such, the design of module 20, according to the invention, enables a
simple design where parts commonality may be simplified and a total number of parts
can be reduced. Embodiments include separate boards 70 and other corresponding
components for each slice configuration, and embodiments include a single dedicated
board 70 and other corresponding components that may include more than one
configuration. Further and as stated, the invention is not to be limited to 8 and 16 slice
configurations, and may include any combination of slice options for system
fabrication, such as 16/32 slice options, 32/64 slice options, and the like. Also, each
single module 20 can be separately tested during manufacturing, because of the modular
design thereof. It is also expected that the collimator can be fabricated having an
improved tolerance and therefore quality because the collimator is fabricated as a
modular unit. Further, because DAS functionality can be increased having with more
functionality built into the FPGA than in a conventional module. The modules 20
disclosed herein are self-structuring and stand-alone modules, removing the need for
external support rails or other methods - allowing modules 20 to be separately tested
and then directly attached to the rotatable gantry, according to the invention. Because
the module includes the complete image chain (Collimator, Scintillator, Diode, AID,
FPGA, Thermal management circuit), it can be fully tested before assembly on the
detector and qualified against system specifications..
Still further, the invention is not limited to only two slice options (i.e., 8 and
16 slices), but is applicable to additional combinations of slice options. That is,
multiple board 70 types may be included that are specific to a configuration that may be
13
simply and easily be incorporated into the manufacturing process, to provide yet
additional manufacturing flexibility into a single overall system configuration while
providing multiple slice options. For instance, referring back to 8-slice illustration 100
of FIG. 5, numerous board designs may be provided that incorporate essentially any
overall z-coverage, and any number of slices in z-direction 21. For instance, as
discussed a board may be designed that is dedicated to an 8-slice configuration, and
another board may be designed that is dedicated to a 16-s1ice configuration. However,
additional board designs may include 32, 64, or any number of slices, according to the
invention.
As illustrated in FIG. 3, a limited number surfaces 52 (i.e., from 5 modules
20) are presented that are orthogonal to focal spot 54. This is in contrast to a more
conventional system that may include, for instance, 57 modules. In a conventional
system, because the number of modules is much greater than the 5 illustrated in FIG. 3,
typically the angular correction from the outermost portions of the modules is small, and
thus unaccounted for. That is, in order to cover FOV 58 with 57 modules, each module
includes pixels having a small enough angle with respect to focal spot 54 so as to make
the angle negligible. However, when the number of modules decreases to for instance 5
modules, outermost channels of each module include significant angles that can be
accounted for in acquired imaging data, according to the invention. For instance,
referring back to FIG. 3, one module 78 includes a ray 80 from focal spot 54 that is
orthogonal to surface 52 and impinges approximately on a centermost channel of
module 78. Thus, at the extreme edges of module 78, rays 82 impinge module 78 at
angles 84 that are significantly (from an imaging data point of view) different from a
90° angle. Thus, data obtained within modules 20 may be geometrically corrected to
account for the measurable geometric effect of modules that are significantly wider than
modules in a system having 57 modules.
Thus, referring to FIG. 6, a set of 5 curves 86 are illustrated that represent an
angular amount of correction that corresponds to the physical and geometrical angle that
results from modules 20 of FIG. 3 along x-direction 23. As one skilled in the art will
recognize, the angle of correction for each modules, occurring as it corresponds to
14
surfaces 52 of FIG. 3, is a function of parameters that include but are not limited to a
width of each module, their distance from the focal spot, total number of channels in
each module, and the like. Thus, according to the invention, acquired data may have a
geometric correction associated therewith that is calculable based on representative
curves 86 and based on the foregoing discussion.
Referring now to FIG. 7, package/baggage inspection system 500 includes a
rotatable gantry 502 having an opening 504 therein through which packages or pieces of
baggage may pass. The rotatable gantry 502 houses a high frequency electromagnetic
energy source 506 as well as a detector assembly 508 having scintillator arrays
comprised of scintillator cells similar to that shown in FIGS. 1 and 2. A conveyor
system 510 is also provided and includes a conveyor belt 512 supported by structure
514 to automatically and continuously pass packages or baggage pieces 516 through
opening 504 to be scanned. Objects 516 are fed through opening 504 by conveyor belt
512, imaging data is then acquired, and the conveyor belt 512 removes the packages 516
from opening 504 in a controlled and continuous manner. As a result, postal inspectors,
baggage handlers, and other security personnel may non-invasively inspect the contents
of packages 516 for explosives, knives, guns, contraband, etc.
A technical contribution for the disclosed method and apparatus is that it
provides for a computer implemented method and apparatus of maintaining image
quality while reducing system fabrication cost.
One skilled in the art will appreciate that embodiments of the invention may
be interfaced to and controlled by a computer readable storage medium having stored
thereon a computer program. The computer readable storage medium includes a
plurality of components such as one or more of electronic components, hardware
components, andlor computer software components. These components may include
one or more computer readable storage media that generally stores instructions such as
software, firmware and/or assembly language for performing one or more portions of
one or more implementations or embodiments of a sequence. These computer readable
storage media are generally non-transitory andlor tangible. Examples of such a
15
computer readable storage medium include a recordable data storage medium of a
computer and/or storage device. The computer readable storage media may employ, for
example, one or more of a magnetic, electrical, optical, biological, and/or atomic data
storage medium. Further, such media may take the form of, for example, floppy disks,
magnetic tapes, CD-ROMs, DVD-ROMs, hard disk drives, and/or electronic memory.
Other forms of non-transitory and/or tangible computer readable storage media not list
may be employed with embodiments of the invention.
A number of such components can be combined or divided in an
implementation of a system. Further, such components may include a set and/or series
of computer instructions written in or implemented with any of a number of
programming languages, as will be appreciated by those skilled in the art. In addition,
other forms of computer readable media such as a carrier wave may be employed to
embody a computer data signal representing a sequence of instructions that when
executed by one or more computers causes the one or more computers to perform one or
more portions of one or more implementations or embodiments of a sequence.
According to an embodiment of the invention, a CT system includes a
rotatable gantry having an opening to receive an object to be scanned, the rotatable
gantry having a detector mounting surface, an x-ray source attached to the gantry and
configured to project an x-ray beam toward the object, a plurality of detector modules
each mounted within one field-of-view (FOV) and mounted directly to the detector
mounting surface of the rotatable gantry, a data acquisition system (DAS) configured to
receive outputs from at least one of the plurality of detector modules, and a computer
programmed to acquire projections of imaging data of the object from the DAS, and
generate an image of the object using the imaging data.
According to another embodiment of the invention, a method of fabricating a
CT system includes fabricating a gantry having a detector mounting surface, attaching
an x-ray source to the gantry such that x-rays emit from the x-ray source and through
the rotational axis, and attaching, within one field-of-view (FOV), each detector module
16
directly to the detector mounting surface such that the x-rays also emit to the two or
more detector modules.
According to another embodiment of the invention, a CT detector module
includes an electronics board, a first mounting surface, and a second mounting surface;
wherein the first mounting surface is configured to be mounted directly onto a rotatable
gantry of a CT system, the second mounting surface is configured such that the
electronics board is mounted orthogonal with respect to x-rays emitted from an x-ray
source that is positioned on the rotatable gantry.
This written description uses examples to disclose the invention, including
the best mode, and also to enable any person skilled in the art to practice the invention,
including making and using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defined by the claims, and may
include other examples that occur to those skilled in the art. Such other examples are
intended to be within the scope of the claims if they have structural elements that do not
differ from the literal language of the claims, or if they include equivalent structural
elements with insubstantial differences from the literal languages of the claims.

WE CLAIM :
1. A CT system comprising:
a rotatable gantry having an opening to receive an object to be scanned,
the rotatable gantry having a detector mounting surface;
an x-ray source attached to the gantry and configured to project an x-ray
beam toward the object;
a plurality of detector modules each mounted within one field-of-view
(FOV) and mounted directly to the detector mounting surface of the rotatable gantry;
a data acquisition system (DAS) configured to receive outputs from at
least one of the plurality of detector modules; and
a computer programmed to:
acquire projections of imaging data of the object from the DAS;
and
generate an image of the object using the imaging data.
2. The CT system of claim I wherein the computer is programmed to
geometrically correct for an angular position of pixels within one of the plurality of
detector modules that is a function of their position along an x-direction of the CT
system.
3. The CT system of claim 1 wherein the detector mounting surface is
orthogonal to a rotational axis of the rotatable gantry.
4. The CT system of claim 3 wherein one detector module of the plurality
of detector modules is comprised of a mounting bracket having a first leg and a second
leg, the first and second legs formed in a shape of an L, wherein the first leg is
comprised of a module mounting surface that is attached to the detector mounting
surface.
18
5. The CT system of claim 4 wherein the one detector module is mounted
such that the second leg includes an electronics board mounting surface that is generally
orthogonal to x-rays passing thereto from the x-ray source.
6. The CT system of claim 5 comprising an electronics board having a
planar mounting surface that is attached to the electronics board mounting surface ofthe
second leg.
7. The CT system of claim 6 comprising:
a diode array coupled to the electronics board, the diode array comprised
of one or several front lit diode array or a backlit diode array; and
a scintillator coupled to the diode array.
8. The CT system of claim 7 wherein the electronics board is configured
such that the CT system includes optionally both of the following arrays:
the diode array coupled to the electronics board having a first amount of
pixels in a slice direction and a first electronics readout capability of the DAS that
corresponds with the first amount of pixels; or
the diode array coupled to the electronics board having a second amount
of pixels, twice that of the first amount of pixels, in the slice direction and a second
electronics capability of the DAS that corresponds with the second amount of pixels.
9. The CT system of claim 6 wherein the DAS comprises several AID
conversions chips (ASIC) and a heat sink attached to the electronics board.
10. The CT system of claim 9 comprising a cover attached to the electronics
board and configured to cover all of the ASIC and the heat sink.
11. A method of fabricating a CT system comprising:
fabricating a gantry having a detector mounting surface;
19
attaching an x-ray source to the gantry. such that x-rays emit from the xray
source and through the rotationat axis; and
attaching, within one field-of-view (fOY), each detector module directly
to the detector mounting surface such that the x-rays also emit to the detector modules. .
12. The method of claim 11 comprising:
configuring a DAS incorporated in the detector module to acquire image
projection data of the object; and
programming a computer to geometrically correct an angular position of
the acquired image projection data as a function of a position along a channel direction
of the CT system.
13. The method of claim II comprising, when the gantry is rotated about a
rotational axis and about an object to be imaged, the detector mounting surface is at a
right-angle to the rotational axis
14. The method of claim 13 comprising fabricating the detector modules
each having:
a first leg that includes a module mounting surface that is attached to the
detector mounting surface; and
a second leg having attached thereto an electronics board that is
generally orthogonal to x-rays passing there through and from the x-ray source.
15. The method of claim 14 comprising:
coupling a diode array comprised of several frontlit diode array and
backlit diode array to the electronics board such that the x-rays pass generally
orthogonal to a surface of the diode array; and
coupling a scintillator to the surface of the one diode array.
16. The method of claim 14 comprising configuring the electronics board
such that the CT system includes optionally:
20
the diode array coupled to the electronics board having a first amount of
pixels in a slice direction and a first electronics readout capability of the DAS that
corresponds with the first amount of pixels; or
the diode array coupled to the electronics board having a second amount
of pixels, twice that of the first amount of pixels, in the slice direction and a second
electronics capability of the DAS that corresponds with the second amount of pixels.
17. A CT detector module comprising:
an electronics board;
a first mounting surface; and
a second mounting surface; wherein:
the first mounting surface is configured to be mounted directly
onto a rotatable gantry of a CT system;
the second mounting surface is configured such that the
electronics board is mounted orthogonal with respect to x-rays emitted from an x-ray
source that is positioned on the rotatable gantry.
18. The CT detector module of claim 17 comprising:
several diode arrays coupled to a surface of the electronics board such
that a planar surface of the diode array is orthogonal to the x-rays emitted from the x-ray
source; and
a scintillator coupled to the planar surface of the diode array.
19. The CT detector module of claim 18 wherein the first mounting surface
is an x-y planar surface of the rotatable gantry, and the second mounting surface is
orthogonal to the first mounting surface.
20. The CT detector module of claim 18 wherein:
the diode array is one of a frontlit diode array and a backlit diode array;
and
when the diode array is a backlit diode array, the attachment of the diode
to the board is achieved by conductive epoxy joints and when the diode array is frontlit,
the connection to the board is achieved by wirebonds.
21. The CT detector module of claim 18 wherein:
each module comprises several diode arrays to achieve 8 or 16 slices by
64 or 128 or more channels on a flat surface, defined by the electronics board.