THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE NATURE OF THE INVENTION

IMPROVED ULTRASONIC DEVICE FOR BONE ASSESSMENT
A) Technical Field
1. The invention relates to a device which is used for assessing various bone conditions.
More particularly the invention is related to assessment of bone properties and
characteristics such as bone density in humans and thus can be used for diagnosing
bone conditions, one of them Osteoporosis and more particularly to an apparatus that
uses ultrasound for the analysis.
B) Background and prior art
2. Osteoporosis is a condition resulting in weakening of the bones with reduction in bone mineral density, changes in bone microarchitecture due to depletion of calcium and bone protein. Osteoporosis or loss of bone mineralization and its cure or prevention are important areas of medical and biological interest. Osteoporosis can be detected by using tests that measure bone density.
3. Various devices are known for measuring bone density, including X Ray, Gamma photon apparatus and ultrasound apparatus. Typically, the equipment for conducting the bone analysis using ultrasound contains two transducers between which the part of the body to be analyzed is placed. One of the transducer emits ultrasonic waves and the other transducer receives these ultrasonic waves. It has been known that the velocity of the Ultrasonic Signal through a patients bone is a measure of elasticity and density of the bone. Also by measuring the Broadband Ultrasonic Attenuation we can get a picture of bone density and structure i.e., micro-architecture of cancellous bone. The data is

expressed as the attenuation of ultrasound in the frequency range of 200KHz to 6OOKH2.
4. An early measurement of speed of sound through bone in vivo is described in US Pat. No 3,847,141 to Hoop issued Nov 12 1974. A pulse from a transmitting transducer was propagated through a finger and heel to be received by a receiving transducer.
5. A Doctoral thesis by Langton entitled "The measurement of Broadband Ultrasonic Attenuation in cancellous Bone" dated July 1984 describes the measurement of Speed of Sound and Broadband Ultrasonic Attenuation through the os calcis of the heel. One such device described in US patent application 5054490 where the patients heel is immersed in water for the measurement and BUA and SOS is measured. A second such device described in UK patent application GB 2257253 describes equipment which includes a pair of ultrasonic transducers which are in contact with heel with the help of Silicone Pad.
6. The techniques discussed above represent improvement over their predecessors but still have room left for further improvements. Like other bone densitometry techniques, QUS technique measures the physical properties of the bone .There are many sources of error (accuracy and precision) that can affect the measurement and cause varying results. Various factors contribute to lower accuracy. Assuming a fixed Soft Tissue Thickness surrounding the heel while determining Speed of Sound parameter may result in an error in SOS measurement. Precision and accuracy can be affected by variations in soft tissue thickness, which might be caused due to gaining or losing weight or developing ankle edema. As also, the BUA result obtained from these techniques may be erroneous due to inter subject variability of bone width. Since both the parameters independentiy give a picture of Bone Mineral Density, therefore there is a need for improvement in accuracy in measurement of these parameters and hence a final reported diagnostic parameter.

7. In addition, a multi variable approach (present bone ultrasound bone densitometers usually use one, two or three parameters) using more than three, ideally four parameters has to be adapted. This may improve the accuracy in the final reported diagnostic value which is derived from all the individual diagnostic parameters by reducing the effect of error caused in the measurement of any individual parameter.
8. Also with the use of dry coupling i.e., use of pads instead of water, error may be induced in Speed Of Sound Measurement due to different amount of squish in coupling pad on contact with the heel of the subject depending on subjects heel's shape. So instead of assuming a fixed amount of squish compensation it is appropriate to measure the accurate Squish in the coupling pads.
9. Yet there can be an error in measurement of Diagnostic parameters like SOS due to variation in timing signals (like timing of firing of ultrasound transducers, switching timings etc) due to hardware limitations. Even a small variation may induce unacceptable variations in various diagnostic parameters. So there is a need to accurately control the various timing signals. One such device mentioned in US6364837 Bl mentions a digitally controlled Ultrasonic Bone Densitometer for better accuracy. But by using modern programmable logic devices like Field Programmable Gate Array much better accuracy can be achieved.
10. The present Ultrasound based equipment uses a fixed foot receptacle to receive various foot sizes. But this may induce error in measurement as for various foot sizes the desired Region of Interest i.e., the calcaneus cannot be achieved. The positioning of the transducer at the desired region at heel will depend on Foot Size.
11. All Ultrasound based equipment which use dry coupling (Gel pads instead of water) do not to provide sufficient safety from cross infection as the same set of coupling pads are used on number of subjects. So for maintaining proper hygiene and safety from cross

infection use of disposable gel pads is required. Also there is a necessity that this gel pads can be easily removed.
C) Objects of the present invention
12. A primary object of the invention is to additionally analyze the reflected and scattered ultrasonic signals in addition to transmitted signals for the bone status assessment.
13. An object of the invention is to provide greater accuracy and sensitivity in bone characterization by using a multi variable approach more than three and ideally four in order to enable a more complete assessment of bone status and also improve the accuracy of diagnosis.
14. Another object of the invention is to improve the accuracy in calculating Speed of Sound through the heel by calculating the tissue thickness instead of assuming a fixed soft tissue thickness surrounding the calcaneus.
15. Yet another object of the invention is to improve the accuracy in calculating Speed of Sound through the heel by calculating coupling pad thickness (amount of squish) on both sides of the Heel instead of assuming a fixed amount of squish in coupling pads for SOS measurements.
16. Still another object of the invention is to enable multi Site measurement instead of taking the measurement only at the heel as it also uses the reflected signal for evaluation of bone status. Use of reflected signal for evaluation of Bone status employs one transducer and thus may be employed for multi site assessment easily as compared to using two transducers.

17. One more object of the invention is use of advanced programmable logics like Field Programmable Gate Array along with Digital Signal Processor instead of conventional analog, digital and microprocessor based designs to accurately control various timing signals which may reduce the inaccuracies in measurement of various diagnostic parameters.
18. One more object of invention is the use of easily replaceable and disposable coupling pads(gel pads). The use of easily replaceable and disposable gel pads will help in prevention of cross infection. The gel pads used are also bacteriostatic.
19. Another object of invention is to use a foot pad which can be removed for subjects having foot size above a specified foot size to accommodate various foot sizes and to ensure a desired Region Of Interest.
D) Summary of the invention
20. Accordingly the present invention provides an apparatus to determine bone condition accurately by using plurality of parameters derived from transmitted and reflected ultrasound signals from bone. The invention operates on the principle that the speed of ultrasound signal characteristics are influenced by the medium through which it propagates. Based on that various parameters are obtained which gives the property of the medium through which ultrasound has propagated.
21. The present invention provides mulri mode operation and in each mode different operations are performed and different parameters are obtained. The present invention consists of two ultrasonic transducers which can emit and receive ultrasound signals containing frequency components from 10 KHz to 1.2 MHz or more. The transducer configuration i.e., receiver or emitter depends on the mode of operation. When recording the transmitted signal one transducer acts as a transmitter and the other acts

as a receiver. The role of the transducers may be changed. While recording the reflected signal one transducer acts as a transmitter as well as a receiver depending upon the mode of operation. Both the transducers on both side of the heel can act as transmitter and a receiver. The transmitter transducer is connected to a programmable firing circuit which controls the emitted Ultrasound power and Frequency characteristics. The receiver transducer is connected to a receive circuit which conditions (filter, amplify) the received signal for future processing. From the received signal various parameters like time of arrival of the received signal after being transmitted from the transmitter, attenuation of specific frequency components, attenuation in the reflected signal and shape of the received signal is calculated. In addition, accurate measurement of soft tissue thickness surrounding the heel which is also an object of invention is obtained instead of assuming fixed soft tissue thickness. Also, squish in the coupling pads is obtained from the received signal. Accordingly, from the obtained multiple parameters (ideally four) a diagnostic parameter is obtained which gives a picture of Bone condition. A Field programmable gate array controls the timing and functioning of receive, transmit and various other blocks. A digital signal processor processes the received signals and calculates the desired parameters. The received signal can also be transferred to a PC, which can process and calculate the various parameters. Use of a field programmable gate array which is an object of invention reduces the variations in calculations and enables precise timing control.
22. The use of removable foot pad enables the positioning of transducers at the desired region of interest. As the anatomy and foot size changes from one person to other so with the use of removable Foot pad we can ensure that the Region of interest for various foot sizes will be at the calcaneus region. So if the foot size is above a predetermined size the pad may be removed to ensure that the required region of interest for the person with bigger foot sizes.

23. The use of easily replaceable and disposable coupling pads(gel pads) will help in
maintaining hygiene. The use of easily replaceable, bacteriostatic and disposable gel pads
will help in prevention of cross infection.
E) Brief Description of the Drawings
24. Fig 1 shows the diagram of ultrasound bone analyzer for measuring the bone condition in accordance with the present invention.
25. Fig 2 shows the basic principle and arrangement of the transducer in a specific mode of operation wherein one transducer launches ultrasound signals and the other transducer receives the ultrasound signals.
26. Fig 3 shows a mode of operation of the bone densitometer wherein a single transducer transmits and receives signals reflected for calculation of coupling pad and heel tissue thickness.
27. Fig4 shows a mode of operation of the bone densitometer wherein a single transducer transmits and receives signals reflected from the bony member for analyzing the bone condition.
28. Fig5 shows the removable foot pad for achieving the desired region of interest.
29. Fig 6 shows the design and mechanism of easily replacing the disposable and bacteriostatic gel pads.
30. Fig 7 depicts the overall system block diagram.
31. Fig 8 shows the system flow chart.

F) Detailed Description of the invention
32. Referring to Fig 1, it shows a portable ultrasound bone analyzer for evaluating the bone status. The bone analyzer consists of a movable assembly which moves towards or opposite to each other. On both end of the assembly ultrasonic transducers are housed which functions as a transmitter as well as a receiver or transreceiver. The transducers may or may not be in direct contact with the subjects body part preferably heel or any other bone which is to be analyzed. The transducers are removable and may be used as a single entity to measure or analyze the bone status without the requirement of the other transducer. So the measurement site is not restricted to heel and can be used in any location. There is a foot receptacle where any body part say heel can be placed.
33. Referring to Fig 2, it shows the basic principle and arrangement of the transducer in a specific mode of operation. Here one transducer emits the ultrasound, which is received by the other transducer. Between the two transducers the part which is to be analyzed is placed. The arrangement is designed to accommodate body part of any size and adjusts the separation between them accordingly. From this arrangement we can obtain the Speed of Ultrasound through the bone (Speed of Sound) through the body part under examination. Another parameter obtained is the amount of attenuation the ultrasound encounters while passing through the body part which is referred here as Broadband Ultrasonic Attenuation. Yet another parameter obtained can be the change in shape of the received ultrasound in time domain, i.e., Width Of Received Maximum which is also an important parameter.
34. Referring to Fig 3, it shows the basic principle and arrangement of the transducer in another mode of operation. Here the same transducer transmits and receives the ultrasound signals from the body member under diagnosis. This arrangement enables us

to calculate the squish in the coupling pads and to calculate the tissue thickness surrounding the heel instead of assuming a fixed amount of squish and tissue thickness.
35. Referring to Fig 4, it shows the basic principle and arrangement of the transducer in a mode of operation where the same transducer transmits and receives the ultrasound signals from the body member under diagnosis. This arrangement enables us to analyze the back scattered and reflected signals for bone characterization.
36. Referring to Fig 5, it shows the arrangement of the removable foot pad which can be removed easily depending on subjects foot size. This kind of removable foot pad is required to achieve desired region of interest at die calcaneus for different subjects having different foot anatomy such as foot size.
37. Fig 6 depicts the mechanism and principle of easily removable, disposable Coupling Pads which are bacteriostatic and can be changed easily between two measurements. Here the outer case holding the disposable coupling pads can be removed easily from the transducer assembly. After replacing the pads the outer case can be fixed back to the transducer assembly as depicted in the figure.
38. Fig 7 depicts the system block diagram of the bone densitometer. Transducer 1 and 2 are connected to the firing circuitry which is responsible to trigger the ultrasonic pulse. The field programmable gate array (FPGA) controls the timing of the firing circuit activation for achieving the desired emitted ultrasound bandwidth and the relay switch activation/deactivation. FPGA controls the mode of firing and receiving of the Transducer, i.e. transmitting mode, receiving mode or Transceiver mode. Once the ultrasonic pulse (High voltage pulse) is launched through the Transducer 1, the FPGA triggers the relay switch (analog switch) to accept received signals from Transducer 2(Transmitting mode) or Transducer 1 (Transceiver mode). Upon receiving ultrasonic signals from Transducer 1, Transducer 2 transmits the signals to a variable gain amplifier. The amplified analog signal is converted to digital format using an analog to

digital converter (ADC). The resulting digital signals are passed on to the digital signal processor (DSP) or PC that processes the signals received to calculate the various parameters to give out a final picture of status of the bone. Signal processing is performed in Time domain as well as frequency domain. The frequency domain calculation are used for calculation of Broadband Ultrasonic Attenuation which is calculated in transmission mode and Attenuation in received signal in reflection mode i.e., Broadband Ultrasonic Backscatter. The time domain signal processing is used for calculation of Speed of Sound and Width of Received Maximum from the received signal. The FPGA is also connected to a clock circuitry and also a distance measurement unit. The distance measurement unit obtains the separation between the two transducers. This obtained data is used in the measurement of speed of ultrasound through the bone and measurement of the squish in the coupling pads and also the tissue surrounding the bone. Also the transmitted and received ultrasound signals are used for squish, tissue thickness and speed of ultrasound calculation by calculating the time of arrival of various received and transmitted signals. This information is provided to the DSP or PC for further calculations of the Speed of Ultrasound through the bone after removing the affect of tissue and coupling pad on speed of ultrasound measurement.
39. Additionally, an optional USB and parallel port interface between the digital signal processor (DSP) and the PC. The signals can be processed in the DSP as well as the PC.
40. Fig 8 shows the system flow chart for the present invention. As the flow chart shows, the system operates in multiple modes. In the BUA reference mode, both the transducers are brought in contact with each other. One transducer transmits and other transducer being in receive mode. Reference data for signals received will be recorded as BUA reference data for further calculations. In BUB reference mode Transducer 1 is set in a transceiver mode , A perfect reflector placed in contact with the transducer and same transducer will transmit and receives the reflected echo . Signals received will be recorded as BUB reference data for further calculations. In the left tissue mode, the left

transducer is in reflection (Transceiver) mode. Using the signals reflected from the left side of the heel, the left tissue thickness and the coupling pad squish is calculated from the time of arrival of various signals from various interfaces. Similarly, in the right tissue mode the right transducer is kept in reflection (Transceiver) mode. Using the reflected signals from the right side of the heel, the right tissue thickness and the coupling pad squish is calculated. Using the left and right side tissue thickness and squish measurement, speed of sound through the bone could be derived during final calculations after removing the affect of surrounding tissue and coupling pads. In the BUA mode, one transducer acts as a transmitter and the other transducer is kept in receiving mode. The signal received is used to compare against the reference data collected during reference mode to calculate the attenuation. In the BUB mode, one transducer it may be left or right acts as transmitter as well as a receiver. The reflection signals from the second transducer are analyzed to check the backscattered signal attenuation. In the WORM mode the width of the received maximum is measured from the received signal in transmission mode when one of the transducer functions as a transmitter and other functions as a receiver. The accuracy of the timing of the various modes and the calculations are enhanced using the FPGA that controls the system control through various modes and the calculations.

Claims
We claim:
1. An ultrasound based diagnostic equipment for analyzing bone conditions in human
oscalcis comprising:
two Ultrasonic transducers which may function as a transmitter, a receiver or transceiver;
a set of replaceable and disposable gel pads;
a removable foot pad; and
a signal processing and acquisition circuit.
2. The ultrasound based diagnostic equipment as claimed in claim 1, wherein the two ultrasonic transducers are initially separated by a fixed distance and can move closer to accommodate a subjects heel
3. The ultrasound based diagnostic equipment as claimed in claim 1, analyzes both the scattered and reflected signals in addition to the transmitted signals.
4. The ultrasound based diagnostic equipment as claimed in claim 1, operates multiple modes and automatically shifts from one mode to another and measures BUB, tissue thickness at heel, coupling pad squish from the reflected signal when the transducers function as transceivers and BUA and FWHM from the transmitted signals when one transducer functions as transmitter and other as receiver.

5. The ultrasound based diagnostic equipment as claimed in claim 1, which utilizes multi-
variable approach wherein the equipment measures at least four diagnostic parameters
instead of usual two from the reflected, scattered and transmitted ultrasound signals for
improving the accuracy of diagnosis.
The diagnostic parameters measured may include:
• Speed of sound
. BUA
. BUB
• Width of received maximum
6. The ultrasound based diagnostic equipment as claimed in claim 1, wherein the equipment measures tissue thickness at both sides of the heel of the subject instead of considering a fixed heel tissue thickness.
7. The ultrasound based diagnostic equipment as claimed in claim 1, wherein the equipment measures the squish in the coupling pads from the reflected ultrasound signals instead of considering a fixed amount of squish in the coupling pads on contact with the subjects heel.
8. The ultrasound based diagnostic equipment as claimed in claim 1, wherein the signal processing uses a digital signal processor (DSP) for processing the acquired signals from the subjects heel and a field programmable gate array (FPGA) for various timing control.
9. The ultrasound based diagnostic equipment as claimed in claim 1, may be used for multi site measurement in addition to heel as a single transducer functions as a transmitter as well as a receiver.

10. The ultrasound based diagnostic equipment as claimed in claim 1, uses easily
replaceable, disposable and bacteriostatic coupling pads (gel pads) for preventing cross
infection and contamination.
11. The ultrasound based diagnostic equipment as claimed in claim 1, uses a removable foot
pad enabling the positioning of transducers at the desired region of interest.
12. The ultrasound based diagnostic equipment as claimed in claim 1, wherein the signal
processing and acquisition circuit managers system control, firing, reception and
processing of Ultrasonic signals received from human Os Calcis, with being done both
in time as well as in frequency domain.

To,
The Controller of Patents,
Patent Office,
Chennai.