BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This disclosure relates to the generation of ultrasound signals and, more particularly, to an ultrasonic controller for use with an ultrasonic transducer to accelerate the process of healing in both hard and soft tissue. 
     2. Description of the Related Art 
     The therapeutic value of ultrasonic waves is known. Various techniques and devices are used to apply ultrasound waves to various areas of the body. In one known technique a pulsed radio-frequency ultrasonic signal applied via a transducer to the skin of a patient and is directed to the site of the wound. The radio-frequency signal is in the range of 1.3 to 2 MHZ, and it consists of pulses at a repetition rate of 100 to 1000 Hz, with each pulse having a duration in the range of 10 to 20,000 microseconds. See, e.g. U.S. Pat. No. 4,530,360 to Duarte and U.S. Pat. No. 5,520,612 to Winder et al. 
     U.S. Pat. Nos. 5,003,965 and 5,186,162 both to Talish and Lifshey (“Talish &#39;965” and “Talish &#39;162”, respectively) describe an ultrasonic delivery system where the R-F generator and transducer are both part of a modular applicator unit that is placed at the skin location. The signals controlling the duration of ultrasonic pulses and the pulse repetition frequency are generated apart from the applicator unit. Talish &#39;965 and Talish &#39;162 also describe fixture apparatus for attaching the applicator unit so that the operative surface is adjacent the skin location. In Talish &#39;965 and Talish &#39;162, the skin is surrounded by a cast, while in U.S. Pat. No. 5,211,160 to Talish and Lifshey (“Talish &#39;160”) fixture apparatus is described for mounting on uncovered body parts (i.e., without a cast or other medical wrapping). Talish &#39;160 also describes various improvements to the applicator unit. Duarte, Talish &#39;965, Talish &#39;162 and Talish &#39;160, are all incorporated into this application by reference. 
     As ultrasonic self-treatment becomes more popular, a need arises to make ultrasonic delivery systems easier and more convenient to use. Current ultrasonic transducers for home use create opportunities for the patient, participating in self-treatment, to make errors in time of exposure or improperly setting up the apparatus, for example, inadequate amounts of ultrasound coupling gel being used on the interface between the ultrasound transducer and the skin over the region where the defect exists. A daily 20 minute treatment session has been established as effective in accelerating healing of certain bone fractures. The effects of longer treatment are usually of no benefit to the patient. However patient compliance is necessary in order for the true benefits of ultrasound treatment to be realized. Therefore, self-treatment programs should be monitored and controlled. 
     Rigidly adhering to a 24 hour delay between treatment sessions often puts an unrealistic constraint on a patient with a self administrated treatment device. Non-routine occurrences or unexpected events often interfere forcing a patient to advance or delay treatment rather than skip the treatment session. A contiguous 20 minute session is preferred for each treatment with ultrasound, however, this period can be interrupted by common everyday events, for example, the door bell ringing. Therefore, a need exists for a treatment system that allows a patient to advance or delay treatment and which automatically prevents any unnecessary over treatment. There also exists a need to provide the flexibility to stop a treatment session and start up again within a reasonable time, with automatic protection against over treatment. 
     In order for a treatment session to be beneficial to a patient, at least a portion of the ultrasound wave must penetrate the body and reach the injury to accelerate the healing process. In order to minimize excessive attenuation of the ultrasound waves produced by the transducer, an ultrasonic wave coupling material, e.g. a conductive gel, is used between the surface of the skin and the transducer head. If an inadequate amount of gel is used or it is improperly applied by the patient to herself, the treatment session will not be as effective as it should be. Therefore, a need exists for determining whether or not a gel layer is properly applied or even if the patient forgets to apply the gel before treatment. 
     Ultrasonic treatment systems are made up of many components. Variations in component tolerances in the output driver circuitry or the output transducer, for example, create a need to perform minor adjustments to the output power level in order to achieve the required level of compliance. Although a manual tuning component traditionally works, its use requires a labor intensive process which can raise the cost of the final product. Therefore, a need to reliably set power levels and perform minor adjustments for ultrasonic transducers exists. 
     Patients often forget to keep and maintain accurate treatment logs. The duration of each treatment session and the time interval between treatments can prove to be important information for a treating physician or a patient. It would be advantageous to have a device that was capable of logging time efficiently and accurately to create a cumulative treatment history without relying on the patient to keep appropriate records. 
     SUMMARY OF THE INVENTION 
     A controller for driving an ultrasonic transducer is disclosed and includes a processor, responsive to a feedback signal, for generating control signals to an output driver which is responsive to the control signals, to cause the ultrasonic transducer to generate ultrasound having a power level corresponding to the control signal. The controller is preferably attached to a sensing circuit to determine the presence of a sufficient amount of ultrasound conductive gel associated with the ultrasonic transducer, and for generating the feedback signal therefrom. The controller includes data logging capabilities to record treatment data and prevent inappropriate treatment delivery. The processor creates the desired operating frequency. 
     The controller creates an environment for a simple, safe and efficient ultrasonic self-treatment by patients. The microprocessor used in the controller creates the operating frequency and can warn of a low battery condition or insufficient amount of ultrasound conducting gel. It can limit the usage of the transducer to prevent over treatment by comparing use data with acceptable limits and disabling the transducer if the limits have been exceeded. It can also be used as a switching regulator to improve lithium battery life. The device is contemplated to be portable for ease of transport by patients and can be configured for use with a wide variety of power supplies at a number of different anatomical treatment sites. 
     An ultrasound delivery controller system for driving ultrasonic transducers includes a plurality of controller boards, each board for controlling an ultrasound transducer wherein one of the plurality of boards is a master board for controlling and sequencing the other boards. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     The invention will be described in detail in the following description of preferred embodiments with reference to the following figures wherein: 
     FIG. 1 is a schematic diagram of an ultrasonic transducer controller with an AC current detector connected to an ultrasonic transducer; 
     FIG. 1A is a schematic diagram of an ultrasonic transducer controller with a reflected signal receiver connected to an ultrasonic transducer; 
     FIG. 2 is a schematic of the transducer controller with digital output ports connected to an output driver; 
     FIG. 3 is a time plot of several control signals corresponding to different power levels with a constant duty cycle; 
     FIG. 4 illustrates a memory allocation scheme for recording the time of treatment and the interval between treatments; 
     FIG. 5 shows the ultrasonic transducer head prior to installation within an insert which is mounted in a cast; 
     FIG. 6 shows the transducer head installed in the insert and secured by a cover; 
     FIG. 7 is a block diagram of a controller having a display driver therein for driving a display; and 
     FIG. 8 is a block diagram showing an ultrasound delivery controller system for driving ultrasonic transducers includes a plurality of controller boards. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present invention includes the use of a microprocessor to receive and output electrical signals from a feedback circuit and to an ultrasonic transducer. The microprocessor can receive signals from a sensing circuit and produce a warning sign to the user of the ultrasonic treatment device. The microprocessor can be used to log treatment times and intervals between treatments. The microprocessor can also be used to output varying power levels to the ultrasonic transducer. A compliance indicator may also be provided to, inter alia, inform the patient as to whether they have been complying with the prescribed treatment regimen. The microprocessor can be input with treatment, use and/or control parameters to facilitate, e.g., compliance, return and/or disabling of the unit. For example, the microprocessor can be programmed for 1 treatment sequence, two or more sequences or an unlimited number of sequences. The microprocessor can also limit the number of times per day the unit can be used to avoid potential misuse. Further details are described herein. 
     Referring now in specific detail to the drawings, with like reference numerals identifying similar or identical elements, FIG. 1 shows a schematic diagram of an ultrasonic transducer controller  10  with an AC current detector circuit  12  connected to an ultrasonic transducer  14 . The transducer controller includes a processor  16 , which could be a microprocessor used in conjunction with an ultrasonic transducer  14 . The processor  16  generates control signals which are a amplified by an output driver  18  to the desired power level and imparted to the ultrasonic transducer  14 . A preferred transducer could be an air backed quarter wave matched transducer. 
     The delivery of ultrasound to a target  20  requires an efficient coupling path between the transducer and the patient&#39;s skin and soft tissue. A material for ultrasound coupling is used, typical characteristics include coupling, hypoallergenic composition and slow to dry. Commonly used materials are sonically conductive materials, such as glycerol, water, oils, lotions, etc. A layer of gel  22  is preferred and often used to effect a proper interface for propagating ultrasonic waves  24  into the body  20 . The application of gel to the surface of an ultrasonic transducer changes the acoustic load impedance on the transducer such that the electrical current flowing through the transducer tends to be reduced. If gel is absent or present in an insufficient amount, the current through the transducer will be excessive. Thus, the amount of current flowing through the transducer can be used as an indicator as to whether gel is available to couple the ultrasonic waves through the interface between the transducer and the patient&#39;s body. Conversely, if no current is flowing (zero current) then there may have been a malfunction of the transducer or more often of a cable or connection to the transducer. Also, because ultrasound is reflected from the gel/tissue media, a receiver can be used to sense reflected ultrasound signals. If little or no reflected signal is received, an insufficient gel signal can be given. 
     The detector circuit  12  is in series with the transducer  14 . A current sensing resistor R 1  is connected between a transducer side which contacts a patient&#39;s skin and electrical common. When current flows through the transducer, it induces a proportional but small voltage across the current sensing resistor R 1 . This voltage will be referenced to common since the current sensing resistor R 1  is connected to electrical common. The current sensing function of R 1  can be performed with either an inductor or a capacitor to provide an equivalent impedance magnitude as R 1 . Whereas the resistor is dissipative, the inductor or capacitor is nearly without loss. This has the advantage of saving battery power. 
     The current sensing resistor R 1  is wired in parallel with a peak detector circuit  24 . The peak detector circuit  24  includes a diode D 1  in series with a capacitor C 1  and resistor R 2  which are in parallel with one another. The peak detector circuit  24  is also referenced to common. The purpose of the peak detector circuit  24  is to rectify the periodic alternating voltage across the current sensing resistor R 1 . The alternating signal is filtered and a proportional DC magnitude is derived. The diode D 1  rectifies the signal, capacitor C 1  smooths the DC signal and resistor R 2  discharges C 1  when there is no signal on R 1 . The equivalent function of R 2  can be performed in the processor  16  if the A/D sense port for A/D converter  26  can be selectively changed to a digital ground to discharge C 1 . The DC signal&#39;s magnitude can be sampled by the processor  16  to determine if adequate gel is present or if the transducer  14  is not functioning. One method of detection includes the conversion of the analog DC magnitude, or the feedback signal, into a digital value through the use of an analog to digital converter  26  (herein A/D converter). The A/D converter  26  is shown integrated with the processor  16 . Alternately, the A/D converter  26  can be placed on a printed circuit board (not shown) along with other components of the processor  16 . The software code is preferably encrypted for security. 
     The feedback signal is read from a connection point between the diode D 1  and C 1  of the peak detector circuit. The feedback signal is proportional to the transducer current and is a function of the motional impedance of the transducer which varies as a function of the acoustic impedance at the face of the transducer  28 . The processor  16  senses the acoustic impedance through the analog to digital conversion from the current detector circuit  12 . The motional impedance will be lowest with good skin contact at the face of the transducer. If an unsatisfactory acoustic coupling is detected, the user is given an indication by means of an alarm, for example a light emitting diode  34  on the unit next to the word “GEL”. 
     FIG. 1A shows an alternative embodiment of the gel sensing means wherein a reflected signal receiver  31  is used to receive a reflected portion of an ultrasound signal. If a reflected signal of insufficient magnitude is received, a low gel warning is generated and the signal can be suspended. 
     It is desirable to have a portable ultrasonic transducer so that the patient who is self-treating can have the unit available wherever they are. With this in mind, a processor or microprocessor  16  and transducer  14  can be powered by an energy storage device  30 , such as a battery. It is therefore necessary to give a patient warning when the energy storage device runs low. A similar scheme can be used as before. For example, the power from the energy storage device  30  is sampled. The value of the voltage is converted from an analog signal to a digital signal by means of an A/D converter  32 . The digital signal can be compared to a predetermined value stored in the memory of the microprocessor  16 . If the energy source is low an alarm is activated, such as a liquid crystal display  36 , indicating “Bat Low”, for example, or a light emitting diode. 
     The transducer controller can be activated by a switch  38  or a button located on or near the processor. 
     FIG. 2 is a schematic of the transducer controller  10  with digital output ports connected to an output driver  18 . Output bits b 0 , b 1 , and b 2  can be generated by the microprocessor  16  or stored in the microprocessor&#39;s memory for retrieval at the appropriate time. The bits represent a high or low voltage (“1” or “0”, respectively). Output bits b 0 , b 1  and b 2  are passed through resistors having a magnitude proportional to the bits place value, thereby creating more current for a given bit value of “1”. For example a “high” bit on line b 3  generates a current proportionally greater than a “high” on line b 1  because the resistance in the line is greater at b 1 . The resistors, R 3 , R 4 , R 5  and diode D 2  are connected to the same node, or control signal line  40 , to produce an ultrasound control signal proportional to the output bits. The control signal line is connected to common through a capacitor C 2 . The control signal line current can be varied by the line resistances R 3 , R 4  and R 5  which set the charging rate of the capacitor C 2 . R idle  sets a minimum charge rate. C 2  drives the voltage in the control signal line  40  which is then amplified by an output driver  18 . Different charge rates of capacitor C 2  create varied power levels in the transducer  14  once the signal is amplified. The amount of variation of the signal can be controlled by the word size at the output of the controller. For example, if the word has three bits b 0 , b 1 , and b 2  and each bit has a possible value of high or low then 23 or 8 possibilities exist. For “N” bit words  2   N possibilities exist. To use “N” bits requires “N” digital ports with weighted resistors. A possible output bit pattern creating  8 distinct power levels is shown in TABLE 1, below, for a digital word. The control signal is obtained by cyclically alternating between the codes for “ON and “OFF” at an ultrasonic carrier frequency. Note, that an idle pin, b idle , is always driven cyclically. 
     Larger words may be implemented by adding more outputs (b 3 , b 4 , etc.)from the processor  16 . More resistors may be connected to these additional output with magnitudes adjusted by a factor of 2, for example, R/ 2 , R/ 4 , etc. 
     
       
         
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 ON 
                 OFF 
               
               
                   
                 Output Bits 
                 Output Bits 
               
               
                 Power Level 
                 b 2  b 1  b 0  b idle   
                 b 2  b 1  b 0  b idle   
               
               
                   
               
             
             
               
                 0 
                 000 1 
                 000 0 
               
               
                 (Low Power) 
               
               
                 1 
                 001 1 
                 000 0 
               
               
                 2 
                 010 1 
                 000 0 
               
               
                 3 
                 011 1 
                 000 0 
               
               
                 4 
                 100 1 
                 000 0 
               
               
                 5 
                 101 1 
                 000 0 
               
               
                 6 
                 110 1 
                 000 0 
               
               
                 7 
                 111 1 
                 000 0 
               
               
                 (High Power) 
               
               
                   
               
             
          
         
       
     
     The control signal must be amplified prior to being applied across the transducer  14 . Any stable AC voltage amplifier providing a gain in the range of about 3 to 5 and capable of driving a 50 Ω load is possible. In one embodiment, the amplifier could contain a Field Effect Transistor (FET) having its gate coupled to the control signal line  40 . Diode D 2  can be connected between the b idle  bit output and an end of the capacitor C 2  opposite the common connection. D 2  would allow for a fast discharge of C 2  once a predetermined time has elapsed which may be determined by the digital bits cyclically switching to OFF. This would disable the output driver  18  and, therefore, the transducer. 
     A switching regulator  70  may be connected to L 1  of the output driver  18  and the resistors at a node A. The switching regulator  70  is powered by battery  30  and controlled by the processor  16 , i.e., turned on for treatment and off for sleep. The switching regulator  70  enables the use of any size battery because the output voltage supplied, V variable supply , can be regulated. Thus, alkaline batteries, etc. can be used. Typical batteries provide 6-12 volts. Using the regulator allows the battery voltage to be adjusted to a higher value, for example, 10-15 volts. This enables a higher voltage to be supplied to the output driver  18  for ultrasound treatment. The output of switching regulator  70  may be set by adjusting the values of the resistors R 3 -R 5 , for example. 
     In a preferred embodiment, a CMOS digital buffer  72  may be included. The buffer  72  includes two invertors which are connected in-line on the control signal line  40 . Control signal line  40  connects to the FET of the output driver  18 . The buffer  72  increases the switching efficiency of FET. The buffer switches from low to high when the control signal amplitude as shown in FIG. 3 rises to approximately 50% full amplitude and off when falling below approximately 50% control signal amplitude. In this manner, the slowly rising control signals in FIG. 3 are converted to a pulse width modulated square wave drive signal for the FET. The buffer  72  is more temperature stable since it comprises CMOS transistors and reduces the temperature dependency of the FET for switching the output driver  18  on and off. This is advantageous in a battery powered system since battery power is conserved in efficiently switched systems. 
     In another embodiment, the sensing circuit can provide an estimate of and control the input power to the transducer  14 . The circuit includes a current sensor, a voltage sensor, a multiplier and an averaging circuit, such as a low pass filter. The analog power estimate at the output of the averager is converted to a digital signal by means of the A/D converter  26  in the processor  16 . This digital value can then be compared to a stored reference and the differential used to adjust the control signal to the FET of the output driver, thereby controlling the acoustic power output of the transducer to within prescribed limits. 
     FIG. 3 shows a time plot of several control signals corresponding to a given output power level. The power level numbers correspond to the example outlined in TABLE 1, above. The highest power level,  7 , is achieved by the fastest charge up of capacitor C 2 . Hence the steep leading edge of control signal  7  when plotted verses time. The y-axis represents voltage, for example, and is limited by the capacitor C 2  and other circuit parameters. The maximum voltage is achieved quickly when the largest charging current corresponding to the highest bit word value is encountered. For intermediate power settings charging the capacitor is delayed resulting in a shorter duty cycle as shown in FIG.  3 . 
     The processor  16  has the capability of memory storage. FIG. 4 demonstrates a memory allocation scheme for recording the time of treatment and the interval between treatments. An optimized daily treatment time has been shown to be a consistent 20 minute session. The effects of longer daily treatments (over 20 minutes per session) are not in the overall treatment plan for a patient. Therefore, a mechanism for ensuring correct treatment time is desirable. Information recording can be employed through processor memory. An electrically erasable programmable read only memory (EEPROM) device (not shown) could be used, for example. Each recorded entry consists of 3 bytes or 24 bits of memory. A first byte (8 bits) would contain the number of whole days that have elapsed since the previous treatment. Eight (8) bits allow the storage of an integer numbers form 0 to 255. If the number of days exceeds 255 than it can be recorded as 255. This can also be used as an indicator to disable the unit after a set number of days. For example if treatment is to be for 3 weeks, a limit of 21 may be used in conjunction with a rule in software to disable the unit. 
     A second byte  44  and part of a third byte  48   a  (11 bits) can be used to store the number of minutes that have elapsed since the last treatment. Eleven (11) bits are capable of storing an integer from 0 to 2047. Since there are only 1440 minutes in a day, only the integers 0 to 1439 are needed in these bits. In this way the number of days and minutes is recorded since the last treatment session. The remaining five (5) bits of the 24 would represent the amount of time in minutes of a given session. The five bits can contain an equivalent binary number from 0 to 31, of which only 0 to  20  would be needed since the time of the session would be monitored by software to automatically end the session at 20 minutes. 
     The data collected by the processor  16  can be used to not only log the patient&#39;s treatment, but also to prevent the patient from extending the treatment. A first counter (not shown) is provided in the processor that allows a patient to reinitiate a session that has been interrupted. Once a patient begins a new 20 minute treatment session, a four hour clock is started. If the patient is interrupted during the session the remaining treatment time remains available to continue treatment within the four hour time limit. When the four hour time period expires the patient can no longer receive treatment and the remaining time left in the session is no longer available. For example, a patient begins a new 20 minute treatment session, after 10 minutes the patient is interrupted. The remaining ten minutes of treatment must be used within the next 3 hours and 50 minutes or that treatment time is lost. To prevent excessive treatment, a minimum of 12 hours must lapse between treatment sessions, but 2 treatment sessions should not occur within the same 36 hour period. Counters (not shown) on the processor can keep track of treatment frequency and disable the transducer if the patient attempts treatment sessions within the 12 hour period or 2 times in 36 hours. For example, if a patient desires to move up a treatment session by 12 hours from the normally prescribed 24 hour period, it is possible. However, he must wait 24 hours before the next treatment can be performed to satisfy the requirement of a maximum of 2 sessions per 36 hour period. 
     A further use for the processor includes providing a means for defining the number of treatments a given unit can perform without being recharged or reprogrammed. In one embodiment, a unit is programmed using an EEPROM, which does not require battery power, to store a set number of sessions or the total amount of time available to the patient. Different types of injuries may require a different number of treatment sessions. By using an electronic key (input code) or a smart battery (a battery which identifies itself by an input code) the processor  16  could be enabled. However, when the number of allocated minutes or number of sessions expires the electronic key is erased disabling the circuit. In the case of the smart battery, it is necessary to prevent the patient from switching the battery with a different battery having the same electronic key which would allow more treatments or renew the amount of time on the unit. In other words switching the battery should not refresh the unit to allow more time or sessions. This enablement feature allows sale of treatment minutes rather than the sale of the actual equipment. 
     The processor may also include programming which requires prepayment prior to activation or payment prior to or contemporaneous with a treatment or sequence of treatments. This feature could facilitate return of the unit and avoid potential unauthorized use. Similarly, an end-of-file disabling program can be provided which inactivates/disables the unit after a predetermined number of uses and/or the passage of a predetermined time period. 
     FIG. 5 and 6 show a preferred embodiment of the controller in practical use. The processor  16 , output driver  18 , battery  30 , sensing circuit  12  and related circuitry (not shown in FIGS. 5 and 6) can all be assembled into housing  54 . A “GEL” alarm  62 , a “BAT LOW” alarm  66  and a compliance indicator  67  can be positioned on top of the housing  54  in plain view of the patient. Also, a power button  64  can be located on the housing for easy access by the patient. FIG. 5 shows the ultrasonic transducer head  50  prior to installation within an insert  52  which is mounted in a cast  60 . The unit  68  can be secured to the patient by straps  56 . A flexible cable  58  can be used to connect the unit  68  to transducer head  50 . FIG. 6 shows the transducer head  50  installed in the insert  52  and secured by a cover  62 . The insert  52  and therefore the transducer head  50  are located over the injured area and the ultrasound conductive material (not shown) is placed between the transducer head  50  and the patients skin. 
     In other embodiments, unit  68  is configurable into different housings. Ultrasonic transducer controller  10  (FIG. 1) may be included within commercially available devices, for example an SAFHS 2000 available commercially from Exogen, Inc, Piscataway, N.J. Ultrasonic transducer controller  10  (FIG. 1) may be configured with appropriate inputs and outputs to work with or control the SAFHS 2000 unit in accordance with the present invention. 
     The microprocessor of the present invention is also contemplated for use in passivation of the battery power supply. Lithium batteries, while exhibiting long shelf life, on the order of about 8 years are subject to oxide buildup which increases the internal resistance of the battery. When the internal resistance increases to a point where there is insufficient current to drive the controller, the unit will not function. In one embodiment, the microprocessor senses this oxide layer buildup, also referred to as the passivation layer, and applies a resistance less than the resistance of the controller to effectively burn off at least a portion of the passivation layer thus permitting full operation of the controller without the need to replace the battery. Further, the microprocessor can be provided with two clock circuits with one circuit assigned to time keeping and the other circuit activating the processor at a reduced power level on a periodic basis to clear the passivation layer. For example, the processor could be activated once a day to run for about 5 seconds at a power level of 100 mA. This step keeps the battery chemistry in good operating condition and maximizes useful battery life. 10 The main operating unit is configurable for use with other devices. Referring to FIG. 7, a preferred embodiment of a main operating unit  100  includes a liquid crystal display (LCD) interface board or display driver  102 . A transducer  104  connects to unit  100  where feedback is processed and transferred to board  102  and output to a liquid crystal display  106 . Display  106  is preferably mounted on unit  100 . Information displayed on display  106  includes treatment time elapsed or remaining, number of days left in the treatment regimen, warnings or error messages, etc. 
     Referring to FIG. 8, a plurality of controller boards  202  may be included in a main operating unit  200 . A master board  204  is included and comprises circuitry for controlling, synchronizing and or sequencing slave boards  206 . Each board controls outputs to a transducer  208 . Transducers  208  may be positioned about a treatment site to form an array of transducers appropriately located to better treat an injury, for example at different locations about a patient&#39;s thigh to treat a tibia. Transducers  208  are sequenced so as to minimize interference between ultrasound waves supplied by each transducer. To apply ultrasound to the treatment site, master board  204  supplied time shifted enable signals to slave boards  206  to provide time staggering treatment delivery from different transducers. In a preferred embodiment, time shifts between transducers are between about 200 microseconds to about 800 microseconds. 
     Having described preferred embodiments of a novel processor control device (which are intended to be illustrative and not limiting), it is noted that modifications and variations can be made by persons skilled in the art in light of the above teachings. It is therefore to be understood that changes may be made in the particular embodiments of the invention disclosed which are within the scope and spirit of the invention as defined by the appended claims. Having thus described the invention with the details and particularity required by the patent laws, what is claimed and desired protected by Letters Patent is set forth in the appended claims.
A controller for driving an ultrasonic transducer is disclosed and includes a processor, responsive to a feedback signal, for generating control signals to an output driver which is responsive to the control signals, to cause the ultrasonic transducer to generate ultrasound having a power level corresponding to the control signal. The controller is preferably attached to a sensing circuit to determine the amount of ultrasound conductive gel associated with the ultrasonic transducer, and for generating the feedback signal therefrom. The controller includes data logging capabilities to record treatment data and prevent unnecessary extended treatment. The controller creates an environment for safer ultrasonic self-treatment by patients. The microprocessor used in the controller can be used to warn of a low battery condition or insufficient amount of ultrasound conducting gel. It can limit the usage of the transducer to prevent over treatment by comparing use data with acceptable limits and disabling the transducer if the limits have been exceeded. The device is contemplated to be portable for ease of transport by patients.