US20100063422A1 - Ultrasound therapy transducer head and ultrasound therapy system incorporating the same - Google Patents

Abstract

An ultrasound therapy transducer head comprises an ultrasound source emitting ultrasonic radiation, the ultrasound source comprising a plurality of transducer elements, integrated driving electronics coupled to the transducer elements, the electronics generating at least one output ultrasound waveform and driving at least some of the transducer elements independently based on the at least one output ultrasound waveform and temperature control structure providing cooling for the electronics.

Description

CROSS-REFERENCE TO RELATED APPLICATION
• This application claims the benefit of U.S. Provisional Application No. 61/095,171 filed on Sep. 8, 2008 entitled “Ultrasound Transducer Head and Ultrasound Therapy System Incorporating the Same”, the contents of which are incorporated herein by reference.
FIELD OF THE INVENTION
• The present invention relates generally to ultrasound therapy and in particular, to an ultrasound therapy transducer head and to an ultrasound therapy system incorporating the same.
BACKGROUND OF THE INVENTION
• Ultrasound therapy uses high-frequency sound waves to produce heat that can reduce some types of acute and chronic pain and is often employed during physical, occupational or manipulation therapy to treat conditions such as musculoskeletal injuries, arthritis and fibromyalgia. Therapeutic ultrasound is typically delivered at frequencies between about 200 to about 10000 kHZ. Lowering the frequency of therapeutic ultrasound provides for deeper penetration of the sound waves. Sound waves penetrating the tissue of the subject cause molecules in the tissue to vibrate, producing heat and mechanical energy allowing for deep heating of tissues such as muscles, tendons, ligaments, joint capsules and bone. As is well known, therapeutic ultrasound differs from diagnostic ultrasound, which uses less-intense sound waves to create images of internal structure.
• In the case of diagnostic ultrasound systems, compact electronics have been developed. For example, U.S. Pat. No. 5,924,993 to Hadjicostis et al. discloses an ultrasound mixed signal multiplexer/pre-amplifier application specific integrated circuit (ASIC) for supplying voltages to a group of transducer elements of an ultrasound array, receiving voltages from the same or another group of transducer elements of the ultrasound array, and amplifying the received voltages for transmission to external circuitry. The transmit and receive groups of transducer elements are shifted to provide accurate visual images with a minimal number of transmit and receive cycles.
• U.S. Pat. No. 6,497,664 to Randall et al. discloses a medical diagnostic ultrasound receive beamformer including an upsampler upstream of both a time delay device and a summer, and a smoothing filter downstream of both the time delay device and the summer. The receive beamformer is automatically programmed into a gate array as a single-beam, dynamic-focus receive beamformer when the user selects B-mode and as a dual-beam, fixed-focus receive beamformer when the user selects color flow mode.
• U.S. Pat. No. 6,969,352 to Chiang et al. discloses a hand-held ultrasound system including integrated electronics within an ergonomic housing. The integrated electronics include control circuitry, beamforming circuitry and transducer drive circuitry. The integrated electronics communicate with a host computer using an industry standard high speed serial bus. The ultrasound system is operable on a standard, commercially available, user computing device such as a personal computer (PC) without specific hardware modifications, and is adapted to interface with an external application without modification to the ultrasound system. This allows a user to gather ultrasonic data on the standard user computing device, and employ the data so gathered via the external application without requiring a custom system, expensive hardware modifications, or system rebuild. An integrated interface program allows such ultrasonic data to be invoked by a variety of external applications having access to the integrated interface program via a standard, predetermined platform such as Visual Basic or C++.
• U.S. Pat. No. 7,169,108 to Little et al. discloses a continuous wave Doppler beam former application specific integrated circuit (CW-ASIC). The beam former may be a transmit or receive beam former. In one mode, the CW-ASIC is used in a diagnostic medical ultrasound system comprising a plurality of channels forming a CW analog receive path, wherein each channel is connected with a digital beam former. The plurality of channels are mixed down in quadrature to base band using a mixer and a local oscillator (LO) generator in quadrature. The outputs of the mixer are summed and wall/high pass filtered to provide a beam formed base band signal. A sub circuit provides a digital serial control function to interface to a real time control bus providing per channel enable/disable of the mixer and the LO generator, and LO delay as well as global local oscillator frequency select. The digital serial control function also has an external delay enable signal to start the LO generator and synchronize all the internal LO delays.
• Although considerable attention has been paid to diagnostic ultrasound imaging systems, the same cannot be said as regards ultrasound therapy systems. The technologies described above relating to diagnostic ultrasound imaging systems are not applicable to therapeutic ultrasound delivery mainly due to the longer ultrasound bursts and higher time average power required. As a result, there are still numerous barriers to the construction of fully electronically steerable, focused ultrasound devices for therapy including the number of transducer array elements, interconnects and driving and monitoring electronics that are required. As will be appreciated, further improvements in the design of ultrasound therapy systems are desired.
• It is therefore an object of the present invention to provide a novel ultrasound therapy transducer head and ultrasound therapy system incorporating the same.
SUMMARY OF THE INVENTION
• Accordingly, in one aspect there is provided an ultrasound therapy transducer head comprising an ultrasound source emitting ultrasonic radiation, said ultrasound source comprising a plurality of transducer elements; integrated driving electronics coupled to said transducer elements, said electronics generating at least one output ultrasound waveform and driving at least some of said transducer elements independently based on said at least one output ultrasound waveform; and temperature control structure providing cooling for said electronics.
• In one embodiment, the electronics drive each of the transducer elements independently. The transducer elements are arranged in groups and wherein circuitry is provided for each group of transducer elements. The circuitry comprises digital and analog circuit components. For each group, the digital circuit comprises digital memory storing a digital waveform for each transducer element of the group and at least one digital to analog converter to convert each digital waveform output by the digital memory to an analog signal. The analog circuit comprises at least one amplification stage receiving the analog signal output of the at least one digital to analog converter and provides a variable driving signal to each transducer element of the group. The digital circuit and analog circuit for each group may be implemented on one integrated circuit chip or on separate integrated circuit chips.
• According to another aspect there is provided an ultrasound therapy transducer head comprising an ultrasound source comprising at least one transducer element for generating an ultrasound beam; and an acoustic power sensing arrangement through which said ultrasound beam passes, said acoustic power sensing arrangement sensing the acoustic power of the ultrasound beam generated by said at least one transducer element.
• In one embodiment, the ultrasound source comprises an array of transducer elements and wherein the acoustic power sensing arrangement senses the acoustic power of the ultrasound beam generated by each transducer element. The acoustic power sensing arrangement comprises a pressure sensitive layer and an electrode pair generally aligned with each transducer element. The electrodes of each electrode pair are positioned on opposite sides of the pressure sensitive layer. In one form, the pressure sensitive layer is a piezoelectric membrane and wherein each electrode pair develops a potential voltage between the electrodes thereof generally proportional to the power of the ultrasound beam generated by the associated transducer element. Readout circuitry electively reads out the potential voltages developed by the electrode pairs. Control circuitry communicates with the readout circuitry and the ultrasound source. The control circuitry provides feedback to the ultrasound source based on the potential voltages readout by the readout circuitry.
• According to yet another aspect there is provided an ultrasound therapy transducer head comprising an ultrasound source comprising at least one transducer element for generating an ultrasound beam; and temperature control structure to control temperature within said ultrasound therapy transducer head.
• In one embodiment, a coupling fluid reservoir containing coupling fluid is positioned adjacent the ultrasound source through which the ultrasound beam passes before exiting the transducer head. A heat exchanger cools the coupling fluid in response to at least one first sensor monitoring the temperature of the coupling fluid. The heat exchanger also cools the ultrasound source in response to at least one second sensor monitoring the temperature of the ultrasound source.
BRIEF DESCRIPTION OF THE DRAWINGS
• Embodiments will now be described more fully with reference to the accompanying drawings in which:
• FIG. 1 is a schematic diagram of an ultrasound therapy system comprising an ultrasound transducer head and an external controller;
• FIG. 2 is an enlarged schematic diagram of a portion of the ultrasound transducer head;
• FIGS. 3 and 4 show an acoustic power sensing arrangement, a switching circuit and a voltage measuring circuit forming part of the ultrasound transducer head;
• FIG. 5 is a schematic block diagram of electronics forming part of the ultrasound therapy system ofFIG. 1;
• FIG. 6 is a circuit diagram of an analog amplifying stage forming part of the electronics ofFIG. 5;
• FIG. 7 is a schematic block diagram of one implementation of the electronics ofFIG. 5; and
• FIG. 8 is a schematic block diagram of another implementation of the electronics ofFIG. 5.
DETAILED DESCRIPTION OF THE EMBODIMENTS
• Turning now toFIGS. 1 and 2, a system for ultrasound therapy comprising an ultrasoundtherapy transducer head10 coupled to anexternal controller11 is shown. As can be seen,ultrasound transducer head10 comprises ahousing12 that physically supports and protects internal ultrasound therapy source components. An acousticallytransparent membrane13 is provided at one end of thehousing12. Anultrasound source14 that emits ultrasonic radiation15 (i.e. acoustic signals or sound waves) that pass through themembrane13 for application to atarget region16 of a subject selected for ultrasound therapy is mounted within thehousing12. Theultrasound source14 comprises an array ofpiezoelectric transducer elements20, only a small number of which are shown for illustrative purposes only. Eachtransducer element20 has animpedance backing21 thereon comprised of material with different impedance properties than the ultrasonic impendence properties of the associatedtransducer element20.
• Aconnection layer22 in the form of a flex circuit or circuit board provides a mechanical mount for thetransducer elements20 and theimpendance backing21 as well as electrical connections between drivingelectronics24 and thetransducer elements20. The drivingelectronics24 also communicate withtemperature sensing electronics26 and aheat exchanger28 disposed within thehousing20 as well as with theexternal controller11. Acoupling fluid reservoir32 filled with acoupling fluid34 is provided in thehousing12 adjacent themembrane13. Atemperature sensor36 is positioned within thecoupling fluid reservoir32 and communicates with thetemperature sensing electronics26. The distal end of eachtransducer element20 extends into thecoupling fluid reservoir32 and is immersed in thecoupling fluid34.
• An acousticpower sensing arrangement38 spaced from the array oftransducer elements20 is also disposed in thecoupling fluid reservoir32 and is positioned so that ultrasonic radiation emitted by thetransducer elements20 passes through the acousticpower sensing arrangement38 before exiting thehousing12 via themembrane13. The acousticpower sensing arrangement38 is connected to aswitching circuit42 which in turn is connected to avoltage measuring circuit44. Thevoltage measuring circuit44 communicates with theexternal controller11.
• Turning now toFIGS. 3 and 4, the acousticpower sensing arrangement38, switchingcircuit42 andvoltage measuring circuit44 are better illustrated. In this embodiment, the acousticpower sensing arrangement38 comprises a polarizedpiezoelectric membrane40 formed of polyvinylidene fluoride (PVDF). As is known, membranes of this nature are commonly used in hydrophones to measure ultrasound pressure waves in a medium such as water. A set ofupper electrodes40ain the form of generally parallel, laterally spaced strips and a set oflower electrodes40bsimilarly in the form of generally parallel, laterally spaced strips are provided on opposite sides of thepiezoelectric membrane40. The electrode strips40aof the upper set are generally orthogonal to the electrode strips40bof the lower set. The upper electrode strips40aand the lower electrode strips40boverlap to form electrode pairs, with each electrode pair being aligned with a respective one of thetransducer elements20.
• Switching circuit42 comprises a pair ofmultiplexers42aand42b. Each channel ofmultiplexer42ais connected to a respective one of the upper electrode strips40aand each channel of themultiplexer42bis connected to a respective one of the lower electrode strips40b. Themultiplexers42aand42breceive address data from theexternal controller11 allowing the voltage developed between each electrode pair to be readout.
• Thevoltage measuring circuit44 comprises anamplifier44areceiving input from themultiplexers42aand42b. Theamplifier44aprovides output to an analog-to-digital converter44bwhich in turn provides output to amemory44c.Memory44ccommunicates with theexternal controller11.
• In this embodiment, thetransducer elements20 are arranged in groups with each group comprising forty-eight (48)transducer elements20 although this number may be increased or decreased as desired. The drivingelectronics24 in this embodiment are formed of discrete components and comprise adigital circuit50 and ananalog circuit52 for each group oftransducer elements20.FIG. 5 better illustrates one of thedigital circuits50 and one of theanalog circuits52. Thedigital circuit50 comprises anaddress counter60, anaddress counter memory62, forty-eight (48) digital waveform memories64 (only one of which is shown), forty-eight (48) waveform digital-to-analog converters (DACs)66 (only one of which is shown) and areference voltage DAC68. Theaddress counter memory62, thedigital waveform memories64 and thereference voltage DAC68 are connected to theexternal controller11 via a 16-bit highspeed data bus70. Theaddress counter60 and the waveform DACs66 are connected to theexternal controller11 via ORlogic72 that is driven by arun clock74. Theaddress counter60,address counter memory62,digital waveform memories64, waveform DACs66 andreference voltage DAC68 also communicate with theexternal controller11 via control lines76.
• Eachdigital waveform memory64 in this embodiment comprises 64K x10 bit static random access memory (RAM) that stores a digital waveform received from theexternal controller11 via the highspeed data bus70. The digital values of the digital waveform at sampled time points are directly and serially loaded into each digital waveform memory66 via the highspeed data bus70. The frequencies, amplitudes and phases of digital waveforms loaded into the digital waveform memories66 by the external controller are selected so that theultrasonic radiation15 output by the ultrasoundtherapy transducer head10 provides the desired therapeutic ultrasound to the subject. Parallel loading of the digital waveform into eachdigital waveform memory64 is also feasible and will reduce the time required for the digital waveform loading procedure. Theaddress counter memory62 supplies rolling memory addresses to theaddress counter60 at 20 MHz as theexternal controller11 outputs data onto the highspeed data bus70 which in turn enables thedigital waveform memories64 so that the digital waveform data is stored in the properdigital waveform memories64. Eachdigital waveform memory64 is also addressed by theaddress counter60 to ensure synchronization during output of digital waveforms by the digital waveform memories.
• Once thedigital waveform memories64 have been loaded with the desired digital waveforms, each digital waveform memory is used to provide 10-bit digital waveform data to its associated waveform DAC66 during the sonication. Each waveform DAC66 converts the 10-bit digital waveform seen at its input to an analog signal with a dynamic range of 0 to 1 volt. The waveform DAC66 is fast enough to allow adequate time resolution. During the sonication, therun clock74 to theaddress counter60 and the waveform DACs66 is switched to a higher frequency oscillator (for example 65 MHz) to allow for adequate time resolution. Each waveform DAC66 may also have additional features such as power down lines to allow individual channels to be disabled in the event of a channel down condition. Such a channel down condition occurs for example if the channel driving line becomes disconnected from its associatedtransducer element20 or if thetransducer element20 is damaged. Thereference voltage DAC68 and its associated latch (not shown) are used to set the reference voltage for all the waveform DACs66. This allows the total power level of theultrasound source14 to be adjusted in real time during sonication without requiring reloading of the digital waveform memories66.
• Theanalog circuit52 comprises forty-eight (48) amplication circuits (only one of which is shown), each of which receives the analog signal output of an associated waveform DAC66 and outputs a corresponding analog radio frequency (RF) signal that is applied to the channel driving line extending to an associatedtransducer element20. The advantages of having eachtransducer element20 connected to its own driving line include the reduction of the driving system size, cost, and power loss when the energy is transmitted from the driving electronics to the transducer element array.
• One of the amplification circuits is better illustrated inFIG. 6 and comprises a first Op-Amp stage80 that provides a voltage gain to the analog signal, and a second Op-Amp stage82 that provides a high current analog signal output. In this embodiment, the first Op-Amp stage80 applies a voltage gain of eleven (11) to the DAC analog output signal augmenting the voltage swing from 0 to 11 volts. The Op-Amp stage80 cuts out high frequencies and can be used to cut the quantization noise frequency. The signal output by the Op-Amp stage80 is high-pass filtered with a first order resistor-capacitor (RC)circuit84 to remove DC offset. The second Op-Amp stage82 employs a high power Op-Amp to amplify the voltage, in this embodiment by a gain of two (2), and provide a high current analog output signal with a maximum peak-to-peak voltage swing of 22 volts.
• The components shown in the shaded region ofFIG. 5 represent the circuitry of the digital andanalog circuits50 and52 that is repeated for each of the forty-eight (48) channels. The digital andanalog circuits50 and52 can be constructed from discrete components or can be constructed using application specific integrated circuit (ASIC) chips. Thedigital circuit50 can be combined on oneASIC chip90 and theanalog circuit52 on anotherASIC chip92 as shown inFIG. 7. Alternatively, both the digital andanalog circuits50 and52 can be combined on onechip96 using a multiple-chip package (MCP) process as shown inFIG. 8. The Op-Amp stages80 and82 can be embedded in the module by integrating semiconductor intellectual property (SIP) blocks with ASIC/memories. Thechip90 or96 may include a line that allows the status of thedigital waveform memories64 to be monitored to assure that each digital waveform is properly loaded.
• Theexternal controller11 in this embodiment comprises a computing device such as for example, a Microsoft Windows based personal computer (PC) with a NI PCI-6534 (National Instruments, Austin, Tex.), an 80 Mbytes/second data transfer rate, and a 32-bit digital I/O board. The I/O board is controlled through a program executing on the computing device that uses the dynamic link library (DLL) supplied by the I/O board manufacturer. Binary data on thirty-two (32) data lines can be simultaneously transmitted for example at 20 MHz if an 80 Mbytes/s transfer rate is desired. Of the 32 data lines, 16 data lines form the highspeed data bus70 for transmitting digital waveform values, etc. to the drivingelectronics24. The other 16 data lines are used as thecontrol lines76 for selecting, programming and manipulating different components of the drivingelectronics24 and for higher level functions such as powering on and off individualdigital circuits50 and/or individual channels of thedigital circuits50.
• Theanalog circuits52 can be controlled by theexternal controller11 for example through a parallel port. Theexternal controller11 can control electronic components of theultrasound transducer head10 via a serial port, universal serial bus (USB) or other suitable communications protocol. Each operation or instruction issued by theexternal controller11 is coded with a specific 16-bit word that is used to directly control the appropriate component elements. 16-bit data arguments can be sent by the electronic components to theexternal controller11 when required.
• During operation, when theultrasound transducer head10 is conditioned to outputultrasonic radiation15, the digital waveform data in eachdigital waveform memory64 is output to its associated digital waveform DAC66 and converted into an analog signal. Each analog signal is input to its associated amplification circuit resulting in an output RF signal that is fed to its associatedtransducer element20. In response, eachtransducer element20 outputs a beam of ultrasonic radiation corresponding to the digital waveform.
• The ultrasound beam transmitted by eachtransducer element20 passes through the acousticpower sensing arrangement38 before exiting thetransducer head10 via themembrane13. As each ultrasound beam passes through the acoustic power sensing arrangement, a varying voltage is formed in thepiezoelectric membrane40 between the electrode pair aligned with thetransducer element20 that is outputting the ultrasound beam as a result of the pressure variation created across thepiezoelectric membrane40. When thecontroller11 addresses an electrode pair by enabling themultiplexers42aand42bconnected to the upper and lower electrode strips40aand40bforming the electrode pair, the voltage across thepiezoelectric membrane40 between the electrode pair is sensed by theamplifier44a.Amplifier44ain turn outputs a voltage signal to the analog-to-digital converter44bwhich converts the voltage signal to a digital value for storage in thememory44c. Since the sensed voltage is proportional to the ultrasound pressure wave, the acoustic power delivered by eachtransducer element20 can be measured. These measurements can be relative or they can be calibrated to provide absolute power measurements.
• The generated voltage measurement signal output from thememory44cby thevoltage measuring circuit44 is used by theexternal controller11 to assure the proper operation of thetransducer elements20 and/or the drivingelectronics24 allowing theultrasonic radiation15 output by the ultrasoundtherapy transducer head10 to be precisely controlled. The generated voltage measurement signal may also be used to assure proper operation of the software executed by theexternal controller11 during generation and loading of digital waveforms, to measure, display and/or control the amplitude of the emitted ultrasound beams, to measure, display and/or control the phase of the emitted ultrasound beams, and as a feedback signal to assure desired operation of the ultrasoundtherapy transducer head10 such as by adjusting ultrasound beam amplitudes to stabilize power output.
• Thetemperature sensing electronics26 in this embodiment monitor the temperature of thecoupling fluid34 viatemperature sensor36 and the temperature of the drivingelectronics24 via another temperature sensor (not shown) and provide output to theheat exchanger28. In response to output from thetemperature sensing electronics26, the heat exchanger cools thecoupling fluid34 and/or the drivingelectronics24 by circulating coolant through thehousing12 thereby to control temperature within thehousing12 and assure stable and reliable operation of the ultrasoundtherapy transducer head10. Thetemperature sensing electronics26 can signal theheat exchanger28 so that it operates generally continuously to maintain a desired temperature within the housing or can cycle theheat exchanger28. If desired, thetemperature sensing electronics26 may store temperature measurement and control data for transfer to theexternal controller11.
• If desired, the ultrasoundtherapy transducer head10 may further comprise a controller to maintain and control the performance of the ultrasound therapy transducer head. Memory may be provided to store sonication, control and/or safety limit data as well as other data generated during ultrasound therapy transducer head monitoring. Additional electronics to enable automatic control and provide enhanced safety may also be included.
• By integrating the array oftransducer elements20 with drivingelectronics24 using custom integrated circuits in thetransducer housing12 and by using piezoelectric film technology integrated into thetransducer housing12 to monitor acoustic power output, the manufacturing costs of the ultrasoundtherapy transducer head10 are significantly reduced providing for the ability to make ultrasound therapy systems that are not feasible with the current approaches.
• Although the drivingelectronics24 are described above as being connected to the array oftransducer elements20 via theconnection layer22, if desired, the drivingelectronics24 may be directly connected to thetransducer elements20 obviating the need for the connection layer. If the connection layer does not provide the mechanical mounting then additional material is used to provide the mechanical mounting for thetransducer elements20. Also, if desired, the acousticpower sensing arrangement38 can be positioned directly on the transducer element array face rather than being spaced from it as shown.
• The form of the drivingelectronics24 can of course vary from the examples described above and illustrated in the drawings. For example, if desired the amplification circuits may only include the high power Op-Amps. The analog output provided to the amplification circuits may be generated by individual waveform generators. In the example ofFIG. 7, it is possible to realize only thedigital circuits50 in ASICs while using discrete components for theanalog circuits52.
• Although embodiments have been described above with reference to the drawings, those of skill in the art will appreciate that variation and modifications may be made without departing from the spirit and scope thereof as defined by the appended claims.

Claims (62)

1. An ultrasound therapy transducer head comprising:

an ultrasound source emitting ultrasonic radiation, said ultrasound source comprising a plurality of transducer elements;

integrated driving electronics coupled to said transducer elements, said electronics generating at least one output ultrasound waveform and driving at least some of said transducer elements independently based on said at least one output ultrasound waveform; and

temperature control structure providing cooling for said electronics.

2. An ultrasound therapy transducer head according toclaim 1 wherein said electronics drives each of said transducer elements independently.

3. An ultrasound therapy transducer head according toclaim 2 wherein said electronics comprise digital and analog circuit components.

4. An ultrasound therapy transducer head according toclaim 3 wherein said transducer elements are arranged in groups and wherein circuitry is provided for each group of transducer elements, each said circuitry comprising digital and analog circuit components.

5. An ultrasound therapy transducer head according toclaim 4 wherein each said circuitry comprises a digital circuit and an analog circuit.

6. An ultrasound therapy transducer head according toclaim 5 wherein for each group, said digital circuit comprises digital memory storing a digital waveform for each transducer element of said group and at least one digital to analog converter to convert each digital waveform output by said digital memory to an analog signal and wherein said analog circuit comprises at least one amplification stage receiving the analog signal output of said at least one digital to analog converter and providing a variable driving signal to each transducer element of said group.

7. An ultrasound therapy transducer head according toclaim 6 wherein said digital circuit comprises a digital memory and a digital to analog converter for each transducer element of said group and wherein said analog circuit comprises at least one amplification stage for each transducer element of said group.

8. An ultrasound therapy transducer head according toclaim 7 wherein each analog circuit comprises a pair of serially connected amplification stages.

9. An ultrasound therapy transducer head according toclaim 8 wherein each analog circuit further comprises a high-pass filter between said amplification stages.

10. An ultrasound therapy transducer head according toclaim 9 wherein a first of said amplification stages applies a voltage gain to the analog signal output of the associated digital to analog converter and the second of said amplification stages generates a high current analog output signal based on the high-pass filtered output of the first of said amplification stages.

11. An ultrasound therapy transducer head according toclaim 7 wherein for each group, said digital circuit further comprises addressing circuitry communicating with each of the digital memories, said addressing circuitry controlling output of the digital waveforms by said digital memories and the loading of the digital waveforms into the digital memories.

12. An ultrasound therapy transducer head according toclaim 11 wherein said addressing circuitry comprises memory storing count values and an address counter responsive to said memory for conditioning said digital memories to output the digital waveforms.

13. An ultrasound therapy transducer head according toclaim 11 wherein said digital circuit further comprises a reference voltage source communicating with each of the digital to analog converters.

14. An ultrasound therapy transducer head according toclaim 7 wherein for each group, said digital circuit and analog circuit are implemented on at least one integrated circuit chip.

15. An ultrasound therapy transducer head according toclaim 14 wherein said digital circuit and analog circuit are implemented on separate integrated circuit chips.

16. An ultrasound therapy transducer head according toclaim 15 wherein each of said integrated circuit chips is an application specific integrated circuit chip.

17. An ultrasound therapy transducer head according toclaim 14 wherein said digital circuit and analog circuit are implemented on a single integrated circuit chip.

18. An ultrasound therapy transducer head according toclaim 17 wherein said single integrated circuit chip is formed using a multi-chip package process.

19. An ultrasound therapy transducer head according toclaim 2 wherein said temperature control structure comprises a heat exchanger for cooling said electronics.

20. An ultrasound therapy transducer head according toclaim 19 further comprising a coupling fluid reservoir containing coupling fluid positioned adjacent said ultrasound source through which emitted ultrasonic radiation passes before exiting said ultrasound therapy transducer head.

21. An ultrasound therapy transducer head according toclaim 20 wherein said heat exchanger also cools said coupling fluid.

22. An ultrasound therapy transducer head according toclaim 21 wherein a wall of said coupling fluid reservoir is an acoustically transparent membrane forming an external surface of said ultrasound therapy transducer head.

23. An ultrasound therapy transducer head according toclaim 22 wherein said transducer elements are immersed in said coupling fluid.

24. An ultrasound therapy transducer head according toclaim 22 further comprising at least one sensor monitoring the temperature of said coupling fluid.

25. An ultrasound therapy transducer head according toclaim 23 wherein said heat exchanger cools said coupling fluid in response to said at least one sensor.

26. An ultrasound therapy transducer head according toclaim 2 further comprising an acoustic power sensing arrangement positioned adjacent said ultrasound source through which emitted ultrasonic radiation passes before exiting said ultrasound therapy transducer head, said acoustic power sensing arrangement sensing the acoustic power of the emitted ultrasonic radiation.

27. An ultrasound therapy transducer head according toclaim 26 wherein said acoustic power sensing arrangement senses the acoustic power of ultrasonic radiation generated by each transducer element.

28. An ultrasound therapy transducer head according toclaim 27 wherein said acoustic power sensing arrangement comprises a pressure sensitive layer and an electrode pair generally aligned with each transducer element, the electrodes of each electrode pair being positioned on opposite sides of said pressure sensitive layer.

29. An ultrasound therapy transducer head according toclaim 28 wherein said pressure sensitive layer is a piezoelectric membrane and wherein each electrode pair develops a potential voltage between the electrodes thereof generally proportional to the power of the ultrasonic radiation emitted by the associated transducer element.

30. An ultrasound therapy transducer head according toclaim 29 further comprising readout circuitry for reading out the potential voltages developed by the electrode pairs.

31. An ultrasound therapy transducer head according toclaim 30 wherein the readout circuitry selectively reads out the potential voltages developed by the electrode pairs.

32. An ultrasound therapy transducer head according toclaim 31 further comprising control circuitry communicating with said readout circuitry and said electronics, said control circuitry providing feedback to said electronics based on the potential voltages readout by said readout circuitry.

33. An ultrasound therapy transducer head according toclaim 32 wherein said temperature control structure provides cooling to said electronics based on said feedback.

34. An ultrasound therapy transducer head according toclaim 28 further comprising a coupling fluid reservoir containing coupling fluid positioned adjacent said ultrasound source through which emitted ultrasonic radiation passes before exiting said transducer head.

35. An ultrasound therapy transducer head according toclaim 34 wherein a wall of said coupling fluid reservoir is an acoustically transparent membrane forming an external surface of said ultrasound transducer head.

36. An ultrasound therapy transducer head according toclaim 35 wherein said transducer elements and said acoustic power sensing arrangement are immersed in said coupling fluid.

37. An ultrasound therapy transducer head according toclaim 36 further comprising readout circuitry for reading the sensed, ultrasonic radiation acoustic power.

38. An ultrasound therapy transducer head according toclaim 37 further comprising control circuitry communicating with said readout circuitry and said electronics, said control circuitry providing feedback to said electronics based on the sensed, ultrasonic radiation acoustic power readout by said readout circuitry.

39. An ultrasound therapy transducer head comprising:

an ultrasound source comprising at least one transducer element for generating an ultrasound beam; and

an acoustic power sensing arrangement through which said ultrasound beam passes, said acoustic power sensing arrangement sensing the acoustic power of the ultrasound beam generated by said at least one transducer element.

40. An ultrasound therapy transducer head according toclaim 39 wherein said ultrasound source comprises an array of transducer elements and wherein said acoustic power sensing arrangement senses the acoustic power of the ultrasound beam generated by each transducer element.

41. An ultrasound therapy transducer head according toclaim 40 wherein said acoustic power sensing arrangement comprises a pressure sensitive layer and an electrode pair generally aligned with each transducer element, the electrodes of each electrode pair being positioned on opposite sides of said pressure sensitive layer.

42. An ultrasound therapy transducer head according toclaim 41 wherein said pressure sensitive layer is a piezoelectric membrane and wherein each electrode pair develops a potential voltage between the electrodes thereof generally proportional to the power of the ultrasound beam generated by the associated transducer element.

43. An ultrasound therapy transducer head according toclaim 42 further comprising readout circuitry for reading out the potential voltages developed by the electrode pairs.

44. An ultrasound therapy transducer head according toclaim 43 wherein the readout circuitry selectively reads out the potential voltages developed by the electrode pairs.

45. An ultrasound therapy transducer head according toclaim 44 further comprising control circuitry communicating with said readout circuitry and said ultrasound source, said control circuitry providing feedback to said ultrasound source based on the potential voltages readout by said readout circuitry.

46. An ultrasound therapy transducer head according toclaim 40 further comprising a coupling fluid reservoir containing coupling fluid positioned adjacent said ultrasound source through which the generated ultrasound beams pass before exiting said ultrasound therapy transducer head.

47. An ultrasound therapy transducer head according toclaim 46 wherein a wall of said coupling fluid reservoir is an acoustically transparent membrane forming an external surface of said ultrasound transducer head.

48. An ultrasound therapy transducer head according toclaim 47 wherein said transducer elements and said acoustic power sensing arrangement are immersed in said coupling fluid.

49. An ultrasound therapy transducer head according toclaim 48 further comprising readout circuitry for reading sensed the ultrasound beam powers.

50. An ultrasound therapy transducer head according toclaim 49 further comprising control circuitry communicating with said readout circuitry and said ultrasound source, said control circuitry providing feedback to said ultrasound source based on the read ultrasound beam powers.

51. An ultrasound therapy transducer head according toclaim 46 further comprising a heat exchanger for cooling said coupling fluid.

52. An ultrasound therapy transducer head according toclaim 51 further comprising at least one first sensor monitoring the temperature of said coupling fluid.

53. An ultrasound therapy transducer head according toclaim 52 wherein said heat exchanger cools said coupling fluid in response to said at least one first sensor.

54. An ultrasound therapy transducer head according toclaim 53 further comprising at least one second sensor monitoring the temperature of said ultrasound source.

55. An ultrasound therapy transducer head according toclaim 54 wherein said heat exchanger cools said ultrasound source in response said at least one second sensor.

56. An ultrasound therapy transducer head comprising:

an ultrasound source comprising at least one transducer element for generating an ultrasound beam; and

temperature control structure to control temperature within said ultrasound therapy transducer head.

57. An ultrasound therapy transducer head according toclaim 56 further comprising a coupling fluid reservoir containing coupling fluid positioned adjacent said ultrasound source through which the ultrasound beam passes before exiting said transducer head.

58. An ultrasound therapy transducer head according toclaim 57 further comprising a heat exchanger for cooling said coupling fluid.

59. An ultrasound therapy transducer head according toclaim 58 further comprising at least one first sensor monitoring the temperature of said coupling fluid.

60. An ultrasound therapy transducer head according toclaim 59 wherein said heat exchanger cools said coupling fluid in response to said at least one first sensor.

61. An ultrasound therapy transducer head according toclaim 60 further comprising at least one second sensor monitoring the temperature of said ultrasound source.

62. An ultrasound therapy transducer head according toclaim 61 wherein said heat exchanger cools said ultrasound source in response to said at least one second sensor.

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