Patent Description:
Use of ultrasonic waves to promote healing of wounds has become more common in recent years as its benefits are better understood and this type of therapy becomes more widely utilized. In general, ultrasonic waves have been used in medical applications for a long time, including diagnostics, therapy, and industrial applications.

A number of innovative ultrasound therapy systems and devices have previously been developed including non-contact, ultrasound mist therapy devices by the assignee of the current application, Celleration, Inc. These systems and devices have been widely used for medical treatments in medical facilities around the world. See, for example, co-owned <CIT>, entitled ULTRASONIC METHOD AND DEVICE FOR WOUND TREATMENT. Unlike most conventional wound therapies that are limited to treatment of the wound surface, Celleration, Inc. , developed therapies in which ultrasound energy and atomized normal saline solutions were used to stimulate the cells within and below the wound bed to aid in the healing process.

Although these ultrasound therapies have been effective, devices, systems and methods providing improved ultrasonic therapies that are more accessible, safer to administer to patients, and more efficient in delivery of ultrasound energy have been widely desired.

Embodiments relate to non-contact, low-frequency, highly efficient ultrasound therapy devices and systems that deliver ultrasonic therapy treatments via a mist to a patient wound to promote wound healing. One embodiment is directed to a non-contact, medical ultrasound therapy system for generating and controlling low frequency ultrasound. The ultrasound therapy system includes a non-contact treatment wand including an ultrasonic transducer configured to provide the low frequency ultrasound to a patient without contacting the patient, a generator unit, and a cable coupling the treatment wand to the generator unit. The generator unit is configured to generate electric power output to drive the ultrasonic transducer to generate and control low frequency ultrasound, the generator unit including a digital frequency generator, wherein the generator unit digitally controls energy output at resonance frequency of the ultrasonic transducer. The ultrasound therapy system further comprises a voltage vs. current phase detector configured to detect a voltage vs. current phase angle. The generator unit is also configured to adjust and lock an output frequency to the ultrasonic transducer in a phase-continuous manner at resonance for non-contact low-load conditions and for no-load conditions based on the voltage vs. current phase angle and digitally control energy output to the ultrasonic transducer. The ultrasound therapy system is driven at a constant current which maintains constant output displacement.

In some embodiments, the system may include a fluid delivery mechanism, and wherein an applicator may be coupled to the non-contact treatment wand to apply a fluid.

In some embodiments, the generator unit may comprise a Direct Digital Synthesis frequency generator configured to produce a resonance frequency that is digitally controlled to better than about <NUM> while maintaining constant energy output, and wherein the digital frequency generator may allow for selection of a frequency between about <NUM> and about <NUM> without hardware modifications.

In some embodiments, the system may allow for parameter control of at least one of voltage, current, duty cycle and phase angle.

In some embodiments, the drive voltage requirements may be less than about 50Vrms for the system.

Another embodiment is directed to a highly efficient ultrasonic generator unit. The ultrasonic generator unit includes an ultrasonic driver with digital controls to maintain system displacement at a low ultrasonic resonance frequency of a transducer coupled to the ultrasonic generator unit to provide ultrasound to a patient without contacting the patient. The ultrasonic driver in this embodiment includes a microprocessor, a digital frequency generator controlled by the microprocessor at an operating frequency, and a phase detector configured to detect a phase difference between a voltage phase angle and a current phase angle. The microprocessor is also configured to modify the operating frequency based upon the phase difference. The generator unit is also configured to adjust and lock an output frequency to the ultrasonic transducer in a phase-continuous manner at resonance for non-contact low-load conditions and for no-load conditions based on the voltage vs. current phase angle and digitally control energy output to the ultrasonic transducer. The ultrasound therapy system is driven at a constant current which maintains constant output displacement.

In some embodiments, the digital frequency generator may comprise a Direct Digital Synthesis frequency generator configured to produce a resonance frequency that is digitally controlled to better than about <NUM> while maintaining constant energy output, and wherein selection of a frequency between about <NUM> and about <NUM> may be permitted without hardware modifications.

In some embodiments, parameter control of at least one of voltage, current, duty cycle and phase angle may be permitted.

In some embodiments, the drive voltage requirements may be less than <NUM> Vrms.

In some embodiments, the generator unit may be driven at a constant current which maintains constant output displacement.

In some embodiments, the generator unit may be battery powered.

In another embodiment, the ultrasonic generator may comprise a user interface controlled by another microprocessor. In this embodiment both the microprocessor and the another microprocessor are configured to individually suspend operation of the ultrasonic generator in a fault condition corresponding to one or more of:.

The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which:.

Various embodiments may be embodied in other specific forms without departing from the essential attributes thereof, therefore, the illustrated embodiments should be considered in all respects as illustrative and not restrictive. The invention is defined in appended independent claims <NUM> and <NUM>. Further embodiments are defined in appended dependent claims.

A need for a more accessible and safer ultrasonic therapy device and system for patients to use has been recognized in this disclosure. Further, many of the substantial technical obstacles to providing such a device based on the requirements of conventional ultrasound therapy devices are recognized and overcome by this disclosure. Specifically, making devices more readily accessible to additional patient populations has been a significant problem due to the very high voltage necessary to operate conventional devices. For example, some conventional ultrasound therapy devices have operated at about <NUM> Volts (V) peak-to-peak and <NUM> Watts (W) of energy. This has necessitated qualified oversight of therapy provision, as allowing patients to operate such a high voltage machine on their own might otherwise present a significant safety risk. Further, the energy requirements of conventional devices have made the possibility of a portable battery powered device, which could be used in a homecare environment, unfeasible. Ultrasound therapy systems described herein, however, overcome many or all of the technological obstacles of the past and provide a lower-power, safer, more efficient, and more accessible ultrasound therapy system. In embodiments, an ultrasound therapy system can be monitored and controlled to operate at or near resonant frequency (Fr), which can be more efficient that operating at or near anti-resonant frequency because it requires less voltage and is more efficient. Even battery powered systems are possible in certain embodiments. Accordingly, designs for new medical ultrasound devices, systems and methods incorporating various features, concepts and improvements, are described in the following detailed description.

<FIG> shows an example of a medical ultrasound device <NUM> of an ultrasound therapy system <NUM> (refer, e.g., to <FIG>) for delivering non-contact ultrasound therapies to patient wounds via a low-frequency ultrasound mist. Medical ultrasound device <NUM> comprises both a console/generator unit <NUM> for generating power and a treatment wand <NUM> for administering therapies. In general, generator unit <NUM> supplies power to an ultrasonic transducer within the treatment wand <NUM>. Treatment wand <NUM> is ergonomically designed and can be generally pistol-shaped such that it may be conveniently positioned by a user to direct ultrasonic energy to a treatment area via atomized saline mist emitted from the end of treatment wand <NUM>. Treatment wand <NUM> also can be balanced, such as in its physical design and weight distribution, to further improve and enhance ergonomics and usability. Generator unit <NUM> further comprises an external pump <NUM> which pumps saline or other fluid through a tube (not shown) attached to the end of treatment wand <NUM>. Pump <NUM> depicted in <FIG> is a peristaltic pump but can comprise another suitable pump type or mechanism in other embodiments.

<FIG> and <FIG> show high-level block diagrams of components of ultrasound therapy system <NUM>. In general, as depicted in <FIG>, system <NUM> comprises generator unit <NUM>; treatment wand <NUM>; fluid management pump <NUM>; an ultrasonic driver <NUM>; an ultrasonic transducer <NUM>; and an applicator <NUM>.

Generator unit <NUM> and treatment wand <NUM> are connected by a cable <NUM>. Ultrasonic driver <NUM> comprises hardware mounted inside generator unit <NUM>. A basic function of the ultrasonic driver <NUM> is to generate electric power output to drive ultrasonic transducer <NUM>. Ultrasonic transducer <NUM> includes an acoustic horn <NUM> and related assembly mounted inside treatment wand <NUM>. Ultrasonic transducer <NUM> converts and transfers input electrical power into vibrational mechanical (ultrasonic) energy that will be delivered to the treatment area (i.e. to a patient wound area via atomized saline). Treatment wand <NUM> contains the system's user interface <NUM> and controls for parameters of the treatment, though in other embodiments an additional or alternative user interface can be incorporated in generator unit <NUM>. Treatment wand <NUM> is configured to appropriately position and hold applicator <NUM> relative to acoustic horn <NUM> for proper delivery of fluid during operation. The configuration also provides appropriate atomization of saline fluid and delivery of the resulting mist and ultrasound energy to a wound treatment area.

Fluid management pump <NUM> provides a fixed flow rate of saline or other fluid (e.g., about <NUM>% normal saline in one embodiment) via a tube <NUM> to the distal tip <NUM> of ultrasonic transducer <NUM> from a saline bag <NUM> or other source, as appropriate. The saline fluid is delivered to the radial surface of transducer horn near its tip <NUM>. The saline fluid is dispensed through an orifice on a superior surface of the horn <NUM>, and a portion of the saline is displaced forward to the face of horn <NUM> and atomized by horn <NUM> when it is energized and operating. The remaining volume of fluid is fed to an inferior surface of ultrasonic transducer <NUM> via gravity and capillary action. When a sufficient volume of saline is accumulated, transducer tip <NUM> atomizes the saline into a plume. The atomized saline spray plume emanates from two points on the ultrasonic transducer <NUM>, i.e., generally at the <NUM> o'clock and <NUM> o'clock positions given normal positioning of treatment wand <NUM> in operation, forming intersecting spray paths at approximately <NUM> from the front face of ultrasonic transducer <NUM> in some embodiments. In other embodiments, treatment wand <NUM>, transducer <NUM>, horn <NUM>, tip <NUM> and/or other components can be designed to provide a differently sized or configured spray plume and paths.

<FIG> is a block diagram of a more detailed schematic of generator unit <NUM> and treatment wand <NUM> of ultrasound device <NUM>. As can be understood from the following description, parameter control of voltage, current, duty cycle and phase angle is enabled, in some embodiments.

Treatment wand <NUM> houses ultrasonic transducer <NUM> and includes a microprocessor <NUM>, various interface and sensing components, and an OLED display <NUM>. Treatment wand <NUM> is pistol-shaped in embodiments to provide an improved ergonomic operator design, though other configurations can be implemented as may be advantageous in some applications. Treatment wand <NUM> comprises an acoustic horn assembly (e.g., piezo elements, back mass, horn and booster), ultrasonic transducer <NUM>, microprocessor (MCU2) <NUM>, user control key pad <NUM> and trigger <NUM>, and an LCD screen display <NUM> that displays operational information and enables control and programming of the treatment therapy (see, e.g., <FIG>). Treatment wand <NUM> also includes an RFID transceiver <NUM> in some embodiments, and RFID transceiver <NUM> can be used to identify applicator <NUM>. This feature can be used to ensure that there is only a single use of a particular applicator <NUM> and to thereby deter unwanted reuse across multiple patients and/or treatments. Treatment wand <NUM> connects to generator unit <NUM> through cable <NUM>. Cable <NUM> includes ultrasonic driver output power, communication components (such as those compatible with RS485, RS422 and/or other protocols) and power components (such as +5V and ground) in an embodiment, though other power and/or communications features can be implemented or facilitated by cable <NUM> in other embodiments. In one embodiment, <NUM>. 3V and <NUM>. 9V power can be generated from the <NUM>. 5V power provided by generator unit <NUM> for the electronics in the treatment wand <NUM>. These example power characteristics can vary and are merely examples of one embodiment.

User interface <NUM> on treatment wand <NUM> includes key pad <NUM>, trigger <NUM>, and screen display <NUM>. In some embodiments, display <NUM> can be a full-color OLED display, and key pad <NUM> can be a four button display, as shown in <FIG>. The operator can configure and control device and system operation via key pad <NUM> and initiate the delivery of therapies by depressing a trigger switch <NUM>.

Microprocessor <NUM> that controls user input requirements can also measure the internal temperature of treatment wand <NUM>, or of transducer <NUM> or horn <NUM> more specifically, from ultrasonic transducer sensor <NUM> and treatment wand sensor <NUM>. Microprocessor <NUM> also sends read/write information to applicator <NUM>. Microprocessor <NUM> communicates with generator unit <NUM> via a communications protocol transceiver <NUM> (such as one compatible with RS485, RS422 and/or other protocols) and writes information to memory <NUM>, which can be EEPROM, serial flash, or some other suitable memory. This information is stored and can be retrieved for understanding the use and performance of the system. Accordingly, greater detail can be given on data stored, how much, how long and how retrieved (USB upload/download by the user, service or other).

RFID transceiver <NUM> of treatment wand <NUM> can be used to communicate with an RFID tag (not shown) for applicator detection, as previously mentioned. The RFID tag can be located on applicator <NUM>, and microprocessor <NUM> in treatment wand <NUM> can serve as an RFID reader and writer of the signals received via RFID transceiver <NUM>. Specifically, an RFID controller can be used in treatment wand <NUM> for a Read/Write RF tag on applicator <NUM>. In each new treatment, system <NUM> will require a new applicator <NUM>. The RFID controller can read the ID tag of applicator <NUM> to identify if that particular applicator <NUM> is new or used. After a particular applicator <NUM> is used for a specified period of time, the RFID controller can write the information to an ID tag to identify that applicator <NUM> has been used to avoid reuse.

Microprocessor <NUM> of treatment wand <NUM>, or another component of system <NUM>, can be used to control input and output functions and perform control loops and calculations. Features of microprocessor <NUM> or another microprocessor or component of system <NUM> in some embodiments can include: an <NUM> maximum frequency; <NUM> DMIPS/MHz (Dhrystone <NUM>) performance; an operating voltage range of <NUM>. 3V to <NUM>. 6V; a <NUM> flash memory (plus an additional <NUM> KB of Boot Flash); a <NUM> SRAM memory; a USB <NUM>-compliant full-speed device and On-The-Go (OTG) controller; up to <NUM>-channel, <NUM>-bit Analog-to-Digital Converter; six UART modules with RS-<NUM>, RS-<NUM> and LIN support; and up to four SPI modules. These features are merely examples of one embodiment and can vary in other embodiments.

Ultrasonic transducer <NUM> generally comprises a piezoelectric ceramic element and metal horn <NUM> mounted in a sealed housing. The ultrasonic transducer input can be an AC voltage or AC current, or an AC voltage that results in a current, and the waveform can be a square form or sine form. The ultrasonic transducer output is mechanical vibration of the tip of transducer <NUM>. The amount of energy output depends on tip <NUM> displacement, frequency, size and driver load (e.g., air or liquid mist). The ratio of output to input energy is referred to as the electromechanical coupling factor. There are many variables that affect coupling factor, including frequency. In theory, it can be advantageous to operate an ultrasonic transducer (sometimes referred to as UST) by keeping the operating frequency in the resonant frequency (Fr) or anti-resonance frequency (Fa) region. At Fr, the electrical power factor is <NUM>, while near or approaching Fr the power factor only approaches <NUM>. However, due to the related, very unique impedance-frequency characteristics of transducers, which can vary from transducer to transducer, drive circuit design is very difficult. In previously designed ultrasonic drivers, Phase Loop Lock (PLL) techniques were widely used. Because of the nature of analog performance, keeping a highly accurate and stable frequency output was very difficult. In theory, an ultrasonic transducer that operates at Fr or Fa has a high efficiency output. In practice, operating a UST at Fr or Fa can be difficult or impossible with PLL technology. This is why most ultrasonic drivers with a PLL design only can operate in Fr or Fa regions rather than at Fr or Fa points, and the operational phase typically may be more than <NUM> degrees. For most systems with rapidly changing load impedance, operation at frequencies close to Fa or Fr will cause the system to be unstable. Alternatively, a system can be kept stable by setting the operation frequency lower than Fr or higher than Fa points, so long as the frequency does not drift to a resonant point. In embodiments discussed herein, however, the ultrasonic driver can be monitored and controlled to operate at or very near Fr, a significant advantage over conventional systems.

In embodiments, Fr and Fa can be equated or analogized with serial and parallel, respectively, resonance frequencies. This is shown in Table <NUM>:.

Ultrasonic transducer <NUM> is operated at relatively large displacements and a low load variation, thereby reducing loading effects and electrical impedance. Accordingly, ultrasonic medical applications can use a constant current control algorithm to achieve one or more of the following performance advantages: increased electrical safety due to lower operating voltage; lower operating voltage by running at Fr; proportional current to maximum tip velocity (displacement if frequency is held constant); tip displacement proportional to current; and the capability to limit excessive power surges by setting the voltage rail to an appropriate value, among others.

Generator unit <NUM> includes a power entry module and AC/DC power supply <NUM> as well as an ultrasonic driver <NUM>. Delivery pump <NUM> is mounted on generator unit <NUM> and is controlled by a pump driver located on ultrasonic driver <NUM>. Communications ports <NUM>, <NUM>, and <NUM> are also located on the generator unit <NUM>, though the number and arrangement of communications ports can vary from those depicted. For example, in other embodiments more or fewer ports are provided, and one or more of the ports can comprise a wireless communications port (e.g., infrared, RF, BLUETOOTH, WIFI or some other wireless technology). These ports provide an information exchange between generator unit <NUM> and treatment wand <NUM> as well as information exchange between device <NUM> and user.

With respect to the Power Entry Module & AC/DC Power Input, in some embodiments the local AC MAINS is connected to an appliance inlet with a hospital grade detachable power cord. In some embodiments, different types of power cords can be used: 15A with a 125V rate, or 10A with a 250V rate. In some embodiments, the appliance inlet is a power entry module listed for medical applications with an 10A current rating, <NUM>/250VAC voltage input, MAINS switch, integral fuse holder (<NUM>¼ x1 <NUM>/<NUM>" / 5x20mm fuses), EMC line filter for medical applications, and is mounted on the rear panel of the chassis. Although not depicted in the figures, embodiments are contemplated that use battery power as the power source in the system's design. The battery would be located within generator <NUM> in various embodiments. Battery power is made possible due to the extremely efficient design discussed herein.

In some embodiments, system <NUM> can have a universal AC power input capability accepting a range of power input from 90V to 265VAC. The local AC MAINS are connected to an appliance inlet component (IEC <NUM> C14) with a hospital grade detachable power cord. The appliance inlet is a power entry module listed for medical applications with an 115V / 230V voltage input, MAINS switch, integral fuse holder (<NUM> -5x20mm fuses), and an EMC line filter for medical applications that is mounted on the rear panel of the chassis. The MAINS switch output is connected to two AC/DC switching power modules. The two AC/DC (24V output) switching power supply modules provide +/-24V power to class-AB type amplifier use. All DC power sources +5V, +<NUM>. 5V, -<NUM>. 5V and <NUM>. 3V can be generated from a +24VDC power source via DC/DC converter. The +5VDC will provide 5V power to treatment wand <NUM> through the detached cable and medical grade connector <NUM>. While class-AB amplifiers are mentioned in examples here and elsewhere, in embodiments class-D or other amplifiers also can be used.

In some embodiments, two identical AC/DC (24V output) switching power supply modules are serially connected together to provide +/-24V power to class-AB type amplifier use. The power supply can be medical grade, Class II, BF rated with 45W output with conventional cooling. A dual color (Red/Green) LED <NUM> can be mounted at the front of generator unit <NUM>. The green color indicates normal power on without errors, and the red color indicates a system error or failure. Error detail information can also display on the interface display screen <NUM> of treatment wand <NUM>.

In some embodiments, there is a plurality of, such as three, communication ports in the on generator <NUM>. The first port is a communication port <NUM> (such as one compatible with RS485, RS422 and/or other protocols), with 5V power and UST outputs. This port <NUM> is connected to treatment wand <NUM> through cable <NUM>. Port <NUM> can be configured for full duplex communications in both directions at the same time. This port <NUM> can handle information exchange between generator unit <NUM> and treatment wand <NUM>. In operation, both sets of microcontrollers <NUM> and <NUM> can check each other to ensure none has failed to operate through this port <NUM>. The second port can be a USB-<NUM> type A port, referred to herein as port <NUM>. It can be designed for user download of information stored at the memory <NUM>, which can comprise EEPROM, serial flash, internal non-volatile, or other suitable memory, by using a flash key or other device. This port <NUM> can be used for uploading software from flash key device. A third port can be an RS232-<NUM>. 3V serial port, referred to herein as port <NUM>. Port <NUM> can be designed for use with a PC, so the PC can communicate to the system <NUM> for download, upload, system debug and calibration. Also included in generator unit <NUM> and connected to the microcontroller are RTC at numeral <NUM>, an audible signal generator <NUM> and generator temperature sensor <NUM>, though in embodiments one or more of these features can be omitted or relocated. For example, in one embodiment audible signal generator <NUM> can be located in treatment wand <NUM> instead of or in addition to being in generator unit <NUM>.

A microcontroller controlled pump delivery system <NUM> can be used for fluid delivery. Delivery system <NUM> comprises a pump <NUM> and pump driver with controls <NUM> for pump speed and pump door monitoring and can deliver fluid, such as saline, through a tube <NUM> and applicator <NUM> to the tip of ultrasonic transducer <NUM>. Microcontroller (MCU1) <NUM> of generator unit <NUM> can control peristaltic pump speed to control saline flow rate for a fixed tubing size. Pump delivery system <NUM> generally operates at constant flow rate for all operating conditions. A cooling fan <NUM> is mounted in the back of generator unit <NUM>. It is controlled by microcontroller <NUM> of ultrasonic driver <NUM>.

Ultrasonic driver <NUM> includes a microprocessor <NUM> that controls, measures and monitors the drive electronics and communicates with the hardware and software of the treatment wand <NUM>. In some embodiments, ultrasonic driver <NUM> includes a microprocessor <NUM> (such as Microchip Technology Inc. PIC32) with an <NUM> clock and <NUM>. 56DMIPS/MHz performance, though some other suitable microprocessor can be used in other embodiments. The drive electronics contain a digital frequency generator (DDS) <NUM>, AC amplifier <NUM> and voltage and current peak detection circuits <NUM> and <NUM>. Digital frequency generator <NUM> generates accurate frequencies set by microprocessor <NUM> to AC amplifier <NUM> that are output to ultrasonic transducer <NUM>. In some embodiments, AC amplifier <NUM> can be coupled to impedance matching circuitry <NUM>, though in other embodiments this circuitry <NUM> can be omitted or implemented in software or firmware rather than hardware. Voltage and current peak detection circuits <NUM> and <NUM> continually monitor the signal peaks with phase difference sensed at <NUM>. In some embodiments, internal or external timers can be used to monitor phase difference or in the monitoring of phase difference. In operation, microprocessor <NUM> can adjust the digital frequency generator output frequency based on voltage vs. current phase angle so that the frequency is locked at the resonance frequency Fr of ultrasonic transducer <NUM>. The resonance frequency Fr is not a fixed frequency, however, as it can drift with temperature and other changes. This is discussed herein below in additional detail.

Ultrasonic driver <NUM> includes a digital frequency generator <NUM>, a resonance frequency control loop <NUM>, and an output current control loop <NUM>. Microcontroller <NUM> can be of sufficiently high speed so as to handle all input measurements and output settings, especially for phase comparison of cycle by cycle frequency adjustment in real time. Ultrasonic driver <NUM> generates electrical output with an ultrasonic frequency and a required power.

At Fr and Fa, the impedance phase is <NUM> degrees, which means that ultrasonic transducer <NUM> can achieve the highest power efficiency at those points. Accordingly, it is recognized that keeping the output frequency close to Fr or Fa would be desirable, if possible. However, it is very difficult for any control systems to operate at Fr and Fa, as at those points any small increase or decrease of frequency will cause a large impedance increase or decrease. Accordingly, most ultrasonic drivers either operate at frequencies higher than Fa or lower than Fr because frequencies are relatively stable when they are farther from Fr or Fa.

For example, some conventional systems have been designed to operate in the Fa region. These designs were relatively stable and delivered effective treatment, but output power efficiency was very low and a very high operating voltage was required. Accordingly, in order to meet regulatory safety requirements, wires with high isolation and earth protection were required, adding cost and restricted user ergonomics due to a stiffer and heavier cable.

An example comparing the voltage required by a past device operating at Fa compared to an embodiment of the currently disclosed system, operating at Fr, is set forth below:
A conventional ultrasonic transducer was operated at, or above, anti-resonance, which is approximately 1KΩ~8KΩ impedance. To deliver the required power to the transducer the driver must output very high voltage (300V) to the transducer. The power calculation is: <MAT>.

If the transducer requires 7W power, ϕ =<NUM>°, Z=1500Ω, from Equation <NUM> the current will be: <MAT>.

Accordingly, a power supply voltage would be: (230mA*1500Ω) = 345V.

An embodiment of system <NUM>, in contrast, operates at Fr with constant current output control. Its impedance is about <NUM>~<NUM>Ω and voltage vs. current phase angle close to <NUM> degrees. The power efficiency is almost <NUM>%. An example with Fr impedance is 50Ω.

If the transducer requires 7W power, ϕ =<NUM>°, Z=50Ω, the current will be: <MAT> and the power supply voltage will be: 370mA*50Ω = <NUM>.

Accordingly, embodiments of system <NUM>, with a low voltage operation condition, can be much more efficient and safer than conventional designs. Any voltage surges resulting when transducer impedance is increased can be limited by setting the voltage rail to an appropriate value.

Microcontroller <NUM> of the ultrasonic driver controls all input and output functions and performs all control loops, calculations. Embodiments of microcontroller <NUM> can include one or more of the following: a <NUM> maximum frequency; <NUM> DMIPS/MHz (Dhrystone <NUM>) performance; an operating voltage range of <NUM>. 3V to <NUM>. 6V; a <NUM> flash memory (plus an additional <NUM> KB of Boot Flash); a <NUM> SRAM memory; USB <NUM>-compliant full-speed device and On-The-Go (OTG) controller; up to <NUM>-channel, <NUM>-bit Analog-to-Digital Converter; six UART modules with RS-<NUM>, RS-<NUM> and LIN support; and up to four SPI modules. These characteristics are merely examples and can vary in other embodiments.

The ultrasonic frequency generator is a digital frequency generator <NUM> that provides numerous advantages over conventional designs. In some conventional designs, PLL technology was used with or comprises part of a voltage control oscillator (VCO) for generating a fixed ultrasonic frequency. However, this produced an output frequency that is low resolution and not flexible for wide frequency range applications without hardware changes. Further, the frequency stability was imprecise since the VCO is affected by temperature, noise and power ripple.

In the current ultrasonic therapy system <NUM>, a Direct Digital Synthesis programmable frequency generator (DDS) is used as part of the frequency generator <NUM>. Because a DDS is digitally programmable, the output frequency can be easily adjusted over a wide range. DDS permits simple adjustments of frequency in real time to locate resonance frequencies or compensate for temperature drift. The output frequency can be monitored and adjusted based on phase difference measurements in embodiments, and can be continually adjusted by microcontroller <NUM> at real time speed. Advantages of using DDS to generate frequency include: digitally controlled sub-Hertz frequency-tuning resulting in sub-degree phase-tuning capability; extremely fast speed in tuning output frequency (or phase); and phase-continuous frequency hops with no overshoot/undershoot or analog-related loop setting-time anomalies, among others. In embodiments, a sine-wave output can be generated by the ultrasonic transducer, which can provide cleaner signals to sensing circuitry. Additionally, because the voltage and current maintain a very close semblance of a sine wave, peak sensing can be used without requiring more elaborate true Root Mean Square (RMS) conversion.

The digital architecture of DDS eliminates the need for the manual tuning and tweaking related to components aging and temperature drift in analog synthesizer solutions, and the digital control interface of the DDS architecture facilitates an environment where systems can be remotely controlled and optimized with high resolution under processor control. <FIG> shows the system's digital frequency generation using microcontroller <NUM> and DDS <NUM>. Specifically, frequency set <NUM> and amplitude set <NUM> are received by DDS <NUM> which generates an output frequency <NUM> (fout).

<FIG> sets forth the frequency control loop <NUM> for system <NUM>. Frequency control loop <NUM> includes a digital frequency generator (DDS) <NUM>, D/A converter <NUM>, phase detector <NUM> and microprocessor <NUM>. The drive electronics utilize the digital frequency generator <NUM>, AC amplifier <NUM> and voltage and current peak detection circuits <NUM> and <NUM>. Digital frequency generator <NUM> generates a high accuracy and precision frequency signal, set by the microprocessor <NUM>, to AC amplifier <NUM> that outputs across a transducer load <NUM> to ultrasonic transducer <NUM>. At start-up, system <NUM> performs a Power On Self-Test (POST) and communicates with ultrasonic transducer <NUM> to gather information on characteristics of ultrasonic transducer <NUM> and determine that treatment wand <NUM> is functioning properly.

Specifically, when initially energized, microprocessor <NUM> can be programmed to perform a frequency sweep using a sine wave to determine the resonant frequency by evaluating and looking for a relative minimum impedance of ultrasonic transducer <NUM>. The sweep is confined to a smaller defined interval based on the information embedded in treatment wand <NUM> regarding the operating characteristics of ultrasonic transducer <NUM>. This includes the information stored about ultrasonic transducer <NUM> at the time of manufacture or otherwise programmed or updated. During the system start, digital frequency generator <NUM> can scan frequencies from a start frequency (min <NUM>, adjustable) to an end frequency (max <NUM>, adjustable) to find the resonance frequency (Fr). Microprocessor <NUM> can adjust the digital frequency generator output frequency based on voltage vs. current phase angle so that the frequency lockup is maintained at the resonance frequency of ultrasonic transducer <NUM> (i.e., at a <NUM>° phase angle). Because the frequencies continually shift due to temperature change and other factors, the phase of output voltage and current will change as well. The voltage vs. current phase detection circuits are continually monitored for the phase difference and the frequency adjusted accordingly. Resonance frequency is not a fixed frequency. This is due to heating and other factors causing a slight drift change with temperature. Specifically, increased temperature can cause decreased resonant frequency.

In order to keep output frequency lockup at resonance frequency, frequency control loop <NUM> can monitoring output voltage vs. current phase angle in real time and continually adjust operating frequency to match the current resonance frequency. In some embodiments, microprocessor <NUM> can maintain Δϕ (as illustrated at <NUM>) to less than about <NUM> degree inaccuracy and provide sufficient capabilities to achieve accuracy of about <NUM> or better. In some embodiments, resonance frequency is digitally controlled to better than about <NUM> while maintaining constant energy output.

<FIG> sets forth output current control loop <NUM> for system <NUM>. Output current control loop <NUM> is designed to provide a constant current output. Since the transducer output displacement is a function of transducer drive current, the control output current (not voltage) will control output displacement. Displacement, of a given tip area, determines the amount of ultrasound energy delivered/output. Microprocessor <NUM> monitors the output current via a sensing resistor then adjusts the digital frequency generator <NUM> output signal level to maintain constant current output thus maintaining a constant output displacement from the tip of the horn. Current sensing circuit <NUM> can sense peak current, and in some embodiments, such as for data logging format output or other purposes, convert peak value to an RMS value. Any waveform distortion can cause converter errors, causing current control errors and ultimately displacement errors. To avoid this situation, embodiments of the system can use RMS sensing technology to reduce the errors. This can be implemented if the waveform has considerable distortion, for example.

In system <NUM>, the digital frequency generator <NUM> can be used to allow for selection and use of different frequencies via software implementation. Configurations having operating frequencies ranging from about <NUM> to about <NUM> are possible. Digital frequency generator <NUM> is digitally programmable. Accordingly, the phase and frequency of a waveform can be easily adjusted without the need to change hardware (frequency generating components), unlike VCO or PLL based generators, as would normally be required to change when using traditional analog-programmed waveform generators. Digital frequency generator <NUM> permits simple adjustments of frequency in real time to locate resonance frequencies or compensate for temperature drift or other deviations in the resonant frequency. The output frequency can be monitored via phase difference measurements and continually adjusted by microcontroller <NUM> at real time speed.

There are many advantages to using digital frequency generator <NUM> to generate frequency. For example, this provides a digitally controlled, <NUM>-Hertz frequency-tuning and sub-degree phase-tuning capability as well as extremely fast speed in tuning output frequency (or phase). The digital frequency generator <NUM> also provides phase-continuous frequency change with no overshoot/undershoot or analog-related loop setting-time anomalies. The digital architecture of the digital frequency generator <NUM> eliminates the need for the manual tuning and tweaking related to components aging and temperature drift in analog synthesizer solutions, and the digital control interface of the digital frequency generator architecture facilitates an environment where systems can be remotely controlled and optimized with high resolution under processor control.

In this system, ultrasonic driver <NUM> outputs a sine waveform through a class AB power amplifier <NUM>. It can operate at frequency from <NUM> to <NUM>, constant current mode. The ultrasonic driver <NUM> outputs current from <NUM> to <NUM>. 65A, voltage from <NUM> to 30Vrms, Max power to <NUM>. 5W, in embodiments, though these values and ranges can vary in other embodiments. The ultrasonic driver output can scan resonance frequencies from the <NUM> to <NUM> range, detect minimum impedance (<NUM>° degree phase angle of voltage vs. current), and then lock operational frequency to resonance frequency of the ultrasonic transducer <NUM> at a ±<NUM> accuracy level. Parameters may vary in various embodiments. In certain embodiments, the drive voltage requirements are less than 50Vrms for the system.

The technology of system <NUM> is unique in that it sees an essentially constant load. The no-load condition is similar to the operational load. Being a non-contact treatment and dispensing only a small amount of fluid onto the horn does not create a significant variation in the load/output, allowing the system to be run at resonance (Fr). Running and controlling the system at Fr allows improved efficiency, as previously discussed. Typical ultrasound applications such as welding, mixing, cutting, and cleaning have significant variation in the load, e.g., going from a no-load to full load condition. The variation makes control of the output very difficult and requires greater power at the cost of efficiency.

<FIG> is a graph that helps to illustrate advantages of using system <NUM>'s ultrasonic driver based on the impedance and frequency characteristics of ultrasonic transducer <NUM>. Specifically, the dramatic change in impedance magnitude <NUM> and phase <NUM> is seen for changes in frequency <NUM> for even small deviations from the resonance frequency <NUM> and anti-resonance frequency <NUM>. Ultrasonic transducer <NUM> is a component that converts electrical energy to mechanical energy. Its impedance and frequency characteristics create significant drive circuit design challenges, especially if trying to optimize for low power input and accuracy. Traditional ultrasonic driver designs typically use Phase Loop Lock (PLL) frequency control technology. However, analog system performance generally does not allow for accuracy and stable frequency output. Accordingly, this can make it difficult to control the system precisely with analog systems. In theory, an ultrasonic transducer operating at resonance frequency Fr or anti-resonance Fa frequency has a high efficiency output. In practice, when ultrasonic transducers operate at resonance frequency or anti-resonance frequency, it is almost impossible using PLL technology to maintain elegant control. Typical ultrasonic drivers utilize an analog PLL based design for control. The PLL based designs operate close to resonance frequency or anti-resonance frequency points, but due to their inherent inaccuracy, these often operate at some phase angle away from Fr or Fa leading to inefficiencies.

In system <NUM>, a constant current control algorithm can be used. It can operate at resonance frequency, rather than just close to resonant frequency. The difference between anti-resonance and resonance is that at anti-resonance the system can operate with high impedance and at resonance with lowest impedance. The high impedance can be in the range of about 5KΩ to about 50KΩ, and low impedance can be in a range of about 20Ω to about 100Ω in certain embodiments, for example.

Since ultrasonic transducer <NUM> is operated with relatively large displacements and a low load variation, there is a significant reduction in loading effects and electrical impedance variation. Many ultrasonic medical applications use a constant current control algorithm because of the following performance advantages: electrical safety (such as due to a lower operating voltage); current that is proportional to frequency and/or maximum tip velocity (displacement if frequency is held constant); fewer excessive power surges (by setting and maintaining the voltage rail to an appropriate value); and the ability to monitor and control displacement of the tip.

Some embodiments of system <NUM> have three modes of operation: a TREATMENT mode; an INFORMATION mode; and a TERMINAL mode. If the user enters the TREATMENT or normal operating mode upon power up, the user can select the length of time for a treatment and energize the acoustic output to treat a patient. If the INFORMATION mode is entered on power up with a flash key plug to the USB port, user information can be downloaded that has been stored in the memory to flash or new software can be uploaded from the flash key to the system. Finally, a TERMINAL mode can be selected that is an engineering mode for internal device calibration, system characterization, and system evaluation.

System <NUM> may also save all information of the device hardware and software as well as the user's input and treatments during operation. In some embodiments, system <NUM> has enough memory storage for all information saved for at least one year of operation. For example, system <NUM> may implement 2MB EEPROM and flexible size memory in some embodiments.

<FIG> combine to provide a flow diagram operational method <NUM> of ultrasonic system <NUM> which does not form part of the claimed invention. One or more tasks or steps can be omitted, or intervening tasks or steps can be carried out in addition those specifically depicted. Operation begins by first powering on the system at <NUM>, followed by conducting a system self-test at <NUM>.

<FIG> shows the steps of self-test <NUM>. First, system <NUM> can verify the integrity of the executable code and verifies RTC at <NUM>. Next, at <NUM>, if the self-test is passed, operation continues on to <NUM>. If the self-test is not passed, an error message is displayed at <NUM> on display <NUM> and the system may be shut down at <NUM>. The error message may be used to communicate the issue to customer service.

If <NUM> is reached (in <FIG>), the number of wounds and size of wounds are input. If a new applicator <NUM> is present at <NUM>, operation proceeds, if not, a new applicator <NUM> is loaded at <NUM>. Next, at <NUM>, tuning mode commences.

<FIG> shows tuning mode <NUM>. First, the tuning mode voltage is set at <NUM>. Next the current loop is set off at <NUM>, followed by a search for the resonance frequency Fr of ultrasonic transducer <NUM> at <NUM>. If the resonance frequency is found at <NUM>, the system continues on to <NUM>. If the resonance frequency is not found the system will try again for a set number of times at <NUM>. If resonance frequency is not found, after these attempts, an error is displayed on the system display <NUM> at <NUM>, followed by system shutdown at <NUM>.

If <NUM> is reached (in <FIG>), treatment is started following a successful tuning mode. Next, at <NUM>, the system checks the RFID tag on the applicator <NUM> for a valid state and to ensure that the treatment has proceeded for less than ninety minutes. If not, treatment is stopped at <NUM> and a new applicator is loaded at <NUM> before reengaging the operation at <NUM>. If the RFID tag indicates treatment of less than <NUM> minutes and a valid state at <NUM>, then operation continues on to pump control at <NUM>.

<FIG> shows the pump control <NUM>. First, the system <NUM> can check that the pump door of the peristaltic pump <NUM> located on the exterior of the console / generator unit <NUM> is closed at <NUM>. If not, the display <NUM> indicates a message to close the pump door at <NUM>. If the pump door is closed, operation continues to <NUM> where the pump speed is set. The system then can check the pump speed at <NUM>, and the pump speed is set again if necessary, before proceeding on to <NUM> when the pump control is complete. Checking pump speed and setting or resetting the speed (e.g., one or both of <NUM>, <NUM>) can be omitted.

When <NUM> is reached (<FIG>), the current is set for the ultrasonic transducer <NUM>. Next, the operation frequency is set at <NUM> and the voltage and current phase is measured at <NUM>. Next, monitoring the system commences at <NUM>.

<FIG> shows monitoring the system at <NUM>. First the system monitors: the temperature of the generator unit <NUM>; the temperature of the treatment wand <NUM>; the temperature of the case of the ultrasonic transducer <NUM>; the output voltage of the ultrasonic transducer <NUM>; the current of the pump <NUM>; and the communication between the two microprocessors <NUM> and <NUM> (MCU2 and MCU1). Next, error codes are generated and communicated at <NUM> before returning to <NUM>.

When <NUM> is reached (<FIG>), if the system is not determined to be in order, an error message is communicated on the display <NUM> at <NUM> and the system is shut down at <NUM>. If, however, the system is determined to be ok at <NUM>, the system checks to ensure the voltage/current phase angle is <NUM>° at <NUM>. If not, operation reverts to <NUM> in which the operation frequency is adjusted to so that a voltage/current phase angle of <NUM>° can be achieved. If voltage/current phase angle is set to <NUM>° at <NUM>, the system checks to ensure the current sensed is equivalent to the current that was set for the system at <NUM>. If the current does not match, operation reverts to <NUM> and the transducer sets the current again before continuing. If the current is appropriate at <NUM>, the system then tests to see if the treatment has timed out at <NUM>. If it has not timed out, operation reverts to <NUM> and the test of <NUM> minute RFID time limit is conducted. If treatment has timed out at <NUM>, the treatment is stopped at <NUM> followed by the option to add a further treatment or additional time at <NUM>. If another treatment or additional time is desired, another treatment is added at <NUM> and operation reverts to the tuning mode at <NUM>. If no further treatment is desired, information is saved at <NUM>.

<FIG> shows saving information <NUM> in greater detail. First, the system collects device setup information, device operation information, and user treatment information at <NUM>. Next, at <NUM>, information is saved to memory (which can be EEPROM or some other memory type or form, such as serial flash or non-volatile) before continuing to system shutdown at <NUM>.

As understood by the various system checks and protocols in this operational explanation, the operation of the system can be suspended at many points. Advantageously, in certain embodiments, both microprocessor <NUM> and microprocessor <NUM> are configured to individually suspend operation of the ultrasonic system in fault condition situations. This arrangement provides enhanced safety not present in other types of designs.

It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with an enabling disclosure for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the appended claims.

The embodiments above are intended to be illustrative and not limiting. Additional embodiments are within the claims. Although the present invention has been described with reference to particular embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the scope of the appended claims.

Claim 1:
A non-contact, medical ultrasound therapy system for generating and controlling low frequency ultrasound, comprising:
a non-contact treatment wand (<NUM>) including an ultrasonic transducer (<NUM>) configured to provide the low frequency ultrasound to a patient without contacting the patient;
a generator unit (<NUM>) configured to generate electric power output to drive the ultrasonic transducer to generate and control low frequency ultrasound, the generator unit comprising a digital frequency generator (<NUM>), wherein the generator unit digitally controls energy output at resonance frequency of the ultrasonic transducer; and
a voltage vs. current phase detector configured to detect a voltage vs. current phase angle, and
a cable (<NUM>) coupling the non-contact treatment wand to the generator unit,
wherein the generator unit (<NUM>) is configured to adjust and lock an output frequency to the ultrasonic transducer (<NUM>) in a phase-continuous manner at resonance for non-contact low-load conditions and for no-load conditions based on the voltage vs. current phase angle and digitally control energy output to the ultrasonic transducer (<NUM>);
wherein the system is driven at a constant current which maintains constant output displacement.