Method and device for subaqueous ultrasonic irradiation of living tissue Number:7,393,323 from the United States Patent and Trademark Office (PTO) owispatent Applicable to humans, animals and fish, a method for injecting thoroughly diffused ambient air or disinfectant into water prior to its delivery into a therapy tank plus an underwater PZT probe transmission of separate stable and transient cavitation signals from which a microcomputer determines, 1) the average number of transducer generated sinoidal equal amplitude alternating compression and rarefaction ultrasonic acoustic pressure waves cycles necessary to create inertial and/or transient cavitation and the required number of rectified sinoidal equal amplitude ultrasonic compression acoustic pressure waves necessary to suppress the inertial/transient cavitation and thereby maintain stable cavitation for cleaning and open-wound therapy treatment for 15-minutes, (or greater) time periods and 2) the necessary dilution of water and disinfectant and its activation by dual-mode transient cavitation to kill the pathogens shed by the "patient" following "patient" cleaning or wound-therapy treatment.<H irradiation, ultrasonic, Method, and, devi, 7393323.html, Patent, pto, 7393323

Title: Method and device for subaqueous ultrasonic irradiation of living tissue

Abstract: Applicable to humans, animals and fish, a method for injecting thoroughly diffused ambient air or disinfectant into water prior to its delivery into a therapy tank plus an underwater PZT probe transmission of separate stable and transient cavitation signals from which a microcomputer determines, 1) the average number of transducer generated sinoidal equal amplitude alternating compression and rarefaction ultrasonic acoustic pressure waves cycles necessary to create inertial and/or transient cavitation and the required number of rectified sinoidal equal amplitude ultrasonic compression acoustic pressure waves necessary to suppress the inertial/transient cavitation and thereby maintain stable cavitation for cleaning and open-wound therapy treatment for 15-minutes, (or greater) time periods and 2) the necessary dilution of water and disinfectant and its activation by dual-mode transient cavitation to kill the pathogens shed by the "patient" following "patient" cleaning or wound-therapy treatment.

Patent Number: 7,393,323 Issued on 07/01/2008 to Vago

Inventors: Vago; Robert (Osprey, FL)
Appl. No.: 11/042,607

Filed: January 25, 2005

Related U.S. Patent Documents


Application Number	Filing Date	Patent Number	Issue Date
10676061	Oct., 2003

Current U.S. Class: 600/437 ; 601/2; 601/3; 601/4

Current International Class: A61B 8/00 (20060101)

Field of Search: 601/2-4 600/437

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U.S. Patent Documents


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2004/0049134	March 2004	Tosaya et al.
2005/0017599	January 2005	Puskas
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2005/0075587	April 2005	Vago
2005/0143638	June 2005	Johnson et al.
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2007/0167880	July 2007	Vago

Foreign Patent Documents


WO 2006/017561	Feb., 2006	WO

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Primary Examiner: Casler; Brian L.
Assistant Examiner: Roy; Baisakhi
Attorney, Agent or Firm: Buchanan Ingersoll & Rooney PC

Parent Case Text

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of application Ser. No. 10/676,061 filed Oct. 1, 2003.

Claims

What is claimed is:

1. An ultrasonic treatment method comprising: feeding water to a tank; introducing air in said water; disposing a living fish in the aerated water; thereafter ultrasonically generating stable vibrating bubbles in said aerated water, the generating of said stable vibrating bubbles including energizing a transducer with first full-wave compression and rarefaction cycles, said first full-wave compression and rarefaction cycles having a first amplitude or intensity and a first pulse repetition period; automatically monitoring the aerated water in said tank to detect an onset of inertial or transient cavitation; and subsequently at the detection of the onset of inertial or transient cavitation energizing said transducer with rectified-wave compression pressure cycles, so as to suppress inertial or transient cavitation.

2. The method defined in claim 1, further comprising displaying a status of inertial of transient cavitation in the aerated water in said tank.

3. The method defined in claim 1, further comprising: removing the fish from said tank; thereafter delivering disinfectant and water to said tank; and thereafter inducing ultrasonic transient cavitation in the water and disinfectant in said tank.

4. The method defined in claim 1, further comprising subsequently energizing said transducer with periods of second full-wave compression and rarefaction cycles alternating with periods of second rectified-wave compression pressure cycles, said second full-wave compression and rarefaction cycles having a second amplitude or intensity greater or less than said first amplitude or intensity and a second pulse repetition period respectively less or greater than said first pulse repetition period and said second rectified-wave compression pressure cycles having said second amplitude or intensity and said second pulse repetition period so that said second full-wave compression and rarefaction cycles alternate with periods of said second rectified-wave compression pressure cycles.

5. The method defined in claim 4, wherein said second pulse repetition period differs from said first pulse repetition period in inverse relationship to a variation of said second amplitude relative to said first amplitude.

Description

FIELD OF THE INVENTION

This invention relates generally to a method and an associated device or apparatus for treating living tissue with ultrasonic wave energy. More specifically, this invention relates to a method and to an associated device or apparatus for irradiating living tissue disposed in water with low-frequency, low-intensity ultrasound. The tissue may be human or, more broadly, land-animal tissue and the water may be tapwater, or the tissue may be fish tissue disposed in tapwater, brackish or saline water. Even more particularly, this invention relates to such a method and to an associated apparatus for ultrasonically treating various wound types such as skin lesions, fungus infections, inflammation, decubital and venous ulcers and other surface-tissue injuries such as lacerations and local edema.

This invention also relates to an associated method for cleaning and sanitizing tanks and water contained therein.

BACKGROUND OF THE INVENTION

In the early 1990's, the present inventor introduced a low-frequency, low-intensity ultrasound device ("Hydrosound") to effect microscopic cleaning of nursing-home patients during their weekly bathing-cycle. The preferred ultrasonic center frequency was 30 kHz and the maximum acoustic intensity was limited to 3 W/cm2, spatial peak temporal peak (SPTP). The 30 kHz center frequency was swept between 29 and 31 kHz at a rate of 120 Hz to avoid acoustic standing waves within the bathtub.

Ultrasonic human patient cleaning devices are known from U.S. Pat. No. 4,942,868, U.S. Pat. No. 5,048,520, U.S. Pat. No. 5,178,134, and U.S. Pat. No. 5,305,737. Subaqueous human application of the high frequency therapy devices is described in "CLINICS IN DIAGNOSTIC ULTRASOUND 16, edited by Wesley L. Nyborg, Marvin C. Ziskin--Section 11, Therapeutic Applications of Ultrasound, Mary Dyson.

Over the past ten years, thousands upon thousands of subaqueous exposures have demonstrated the overall safety of these ultrasonic exposure parameters for full-immersion cleaning of human patients having intact tissue with no open wounds. The only use-prohibition of the low-frequency, low-intensity ultrasound device was for wound therapy because at a frequency of 30 kHz and average acoustic intensity of more than 0.5 W/cm2 (SPTP), the device produced both inertial and transient cavitation events. Inertial or transient cavitation that occurred within 15 cm of the cleaning device's transducer demonstrated that this version of an ultrasonic cleaning modality could damage open wounds. Nevertheless, accepting this limitation, the FDA listed the low-frequency, low-intensity ultrasound device as a medical device equivalent to hydromassage or whirlpool devices but suitable for only cleaning human patients who have intact tissue without the presence of open wounds.

High-intensity ultrasound (not appropriate to this invention) can expand a bubble so rapidly during a negative-pressure cycle that the bubble collapses before it has a chance to shrink during the positive-pressure cycle. At high intensity, therefore, bubbles can grow rapidly in the course of one cycle of sound to the state of inertial cavitation collapse.

In what is known as Rectified Mass Diffusion, a bubble's size oscillates in phase with the acoustic pressure expansion (rarefaction) and compression cycles. The surface area of a bubble produced by ultrasound pressure is slightly greater during rarefaction than in compression cycles. Since the amount of gas that diffuses in or out of the bubble depends on the bubble's surface area and skin thickness, diffusion into the bubble during rarefaction cycles will be slightly greater than diffusion out during compression cycles. For each cycle of sound, the bubble expands a little more than it shrinks. Over many cycles the size of bubbles will grow slowly. With Rectified Mass Diffusion, the growing bubble can eventually reach applied frequency resonant size where it will most efficiently absorb energy from the ultrasound.

At 30 kHz, for example, the resonant bubble diameter is 100 microns while the critical bubble size, where the bubble can no longer absorb acoustic energy, is roughly 120 microns in diameter. After reaching resonant size, critical bubble size can be attained in a few more cycles of sound. When this occurs, liquid inertial force will rush into the bubble and implode it. Thus, within a few microns radius, the resulting implosion generates temperatures of thousands of degrees Kelvin and increases in pressure of thousands of atmospheres. This implosion phenomena is known as inertial or transient cavitation.

Also, when a bubble reaches a critical radius Rc at the same time that Blake's critical threshold pressure is reached, unstable bubble growth and therefore transient cavitation occur, with bubble collapse results similar to inertial cavitation. However, this particular phenomenon is subject to there being sufficient time in each pressure cycle to permit bubble growth. This is determined by the relationship between the radian frequency w of the imposed oscillations and the natural frequency wN of the bubble at its current size. If the radian frequency w is much less than the natural frequency wN then the liquid inertia is relatively unimportant in the bubble dynamics and Blake's threshold pressure criteria will hold and transient cavitation will ensue. On the other hand, if the radian frequency w is much greater than the natural frequency wN, the issue will involve the dynamics of bubble growth since its inertia will determine the size of bubble perturbations.

Inertial or transient cavitation (bubble) phenomena are manifested through the dynamic interaction of many diverse physical parameters, including the relationship between the frequency w of the imposed oscillations and the natural frequency wN of the bubble, the relationship between the pressure oscillation amplitude and the mean pressure, and whether the bubble is predominantly vapor filled or gas filled. Stable oscillations are more likely with predominantly gas filled bubbles, while bubbles that contain mostly vapor will more readily exhibit transient cavitation. Other variables that have a bearing are bubble temperature, thermal damping, water purity, surface tension, viscosity, viscous damping and radiation damping.

The probability that bubbles will oscillate stably or deteriorate into inertial or transient cavitation can be forecast mathematically if appropriate values are assigned to the above variables. Such mathematical analyses and treatises have value only post-mortem or in situations where water quality and temperature can be formulated before ultrasonic irradiation of an aqueous solution.

Unfortunately, to effect cavitation control in most patient treatment environments, water quality and its temperature control have to be viewed as an amorphous mass whose critical second-order parameters are not known and cannot be formulated beforehand. Only through experimentation can the cavitation tendency of this amorphous mass be established and only by experiment can the required ratio be determined between positive and rarefaction pressure cycles needed to predictably extend the time before a cavitation bubble implodes. Fortunately, the resulting states of cavitation from such manipulations can be determined by detecting the different acoustic pressure emission from stable and inertial/transient cavitation.

On the assumption that a human patient cleaning device would only be used for patients having intact tissue without open-wounds, it was sufficient to lower its applied ultrasonic intensity until occasional tingly-sensation events from transient cavitation in the vicinity of the patient, could be tolerated by the epidermis protected corium.

As implied above, there is a need for an ultrasound treatment device for open-wound therapy, where the body's external protective covering has broken down. On the assumption that low-frequency, low-intensity ultrasound device would only be used for patients having intact tissue, without the presence of open-wounds, standard hospital whirlpool disinfection procedures used for bathtub-cleaning after patient bathing have been judged sufficient. However, where the low-frequency, low-intensity ultrasound device is to be used with patients or subjects having open wounds, it will be critical for it to incorporate an automatic therapy tank decontamination means for killing shed pathogens between patients or subjects experiencing sonic open-wound treatments.

It is well-understood by medical-researchers that the biological basis of ultrasonic non-thermal therapy for beneficial cellular, tissue changes and wound healing depends on the presence of stable cavitation and associated microstreaming without the presence of inertial or transient cavitation. They also agree that the gas bubbles involved in transient/inertial cavitation undergo irregular oscillations and then implode, producing increases in temperature of thousands of degrees Kelvin and increases in pressure of thousands of atmospheres, localized in regions of only a few microns radius. They also recognize that any live cells exposed to such conditions would clearly be destroyed.

Side by side experiments on humans have shown that at ultrasonically treated wound sites there is an increase in total area of the blood vessels in the sections examined for both low and high frequency irradiation. There were more endothelial cells present following kHz treatment than following mHz treatment. This was particularly clear 7-days following ultrasound treatment; similar but undocumented favorable results were obtained for animals.

Several animal trials have been published in which mice, rabbits and pigs were subjected to 30 kHz low intensity ultrasound to establish the degree to which their lung tissue was damaged at increasing score levels of acoustic pressure amplitude, (0, 2, 4, 6, 8, 10, where 0 score was no damage and 10 score was death). To establish the level of ultrasound pressure vs. lung damage, 30 kHz ultrasound was propagated through thoroughly filtered water so as to eliminate the possibility of cavitation occurring or attenuation of the applied ultrasonic pressure waves. At approximately 145 kPa for 10-minutes, (8-10 score), the lungs of all the mice involved (more than 270) experienced massive lung-hemorrhage, followed by death. Subsequently, another experiment repeated the same ultrasonic exposure but this time in the presence of ultrasonic vibrating bubbles. Two mice were exposed to lethal amounts of ultrasound, (145 kPa for 10-minutes); both mice had lung damage scores of 0. A third mouse was exposed at 200 kPa and a fourth at 240 kPa and those also had lung damage scores of 0.

Because of the ability of fish to detect very low levels acoustic pressure amplitude it is very important to appreciate that the 0 kPa score clinical condition for mice was a sham condition where no ultrasound exposure was applied. It follows that when the mice were exposed to lethal levels of acoustic pressure (in excess of 145 kPa) in the presence of stable vibrating bubbles, as established by follow-on post mortems, their clinical condition was the same as the mice who received no ultrasound exposure, i.e., "alive, no lesions in lungs; normal respiration; no blood in chest cavity. No lung tissue damage; lung septa and capillaries (blood vessels) are normal." The lung damage effect on humans, rabbits and pigs was far less than on mice; the lung is considered one of the most sensitive organs to the harmful effects of ultrasound exposure.

According to Hastings, (1990), a Sound Pressure Level (SPL) greater than 0.032 kPa is not harmful to fish. A Sound Pressure Level (SPL) greater than 1 kPa is harmful to many fish. According to Norris and Mohl, (1983), a Sound Pressure Level (SPL) greater than 266 kPa is fatal to most fish.

A problem area with recirculating tanks employed for aquaculture is reducing ammonia concentrations caused by the presence of fish faeces and un-eaten fish feed particulate matter. Currently, the problem is addressed by a combination of screen filtering for the removal of un-eaten fish feed particulates and faeces-ammonia by employing nitrifying bacteria to detoxify fish excretory matter by oxidizing faeces-ammonia and nitrites into non-toxic nitrates. These bacteria are located in either trickling filters, fluidized bed sand filters or thin film filters.

While effective in reducing the concentration of ammonia in recirculating aquaculture systems, this bio-technique has drawbacks when it becomes necessary to treat fish with chemicals or drugs. Cleaning and declogging static biofilters can also pose difficult problems. Some therapeutic chemicals and drugs used to treat fish are harmful to the nitrifying bacteria situated in these biofilters. These necessary maintenance actions can lead to an abrupt lowering of the population of these nitrifying bacteria resulting in the emergence of toxic NH3 (ammonia) concentrations and resulting fish-kills. Also it can take up to 3-months to populate these filters with nitrifying bacteria.

OBJECTS OF THE INVENTION

A general object of the present invention is to provide an improved low frequency, low-intensity ultrasound device of the above-discussed type.

A more particular object of the present invention is to provide such a device that is suitable for treatment of patients or subjects with one or more open wounds.

Yet another object of the present invention is to provide such a device with a means for effectively sterilizing the device after use for wound treatment.

Yet another object of the present invention is to provide an improved method and associated apparatus for reducing ammonia concentrations caused by the presence of fish faeces and un-eaten fish feed particulate matter in recirculating aquaculture tanks.

These and other objects of the present invention will be apparent from the drawings and descriptions herein. Although every object of the invention is attained in at least one embodiment of the invention, there is not necessarily any single embodiment of the invention in which all objects are attained.

SUMMARY OF THE INVENTION

The present invention provides methods and devices that overcome the limitations of current ultrasonic human patient cleaning devices and also current high frequency human therapy devices when these are used subaqueously in a non-thermal mode for cleaning, wound debridement, and wound-healing.

It is believed that the animal experiments described above demonstrate that the presence of ultrasonically induced stable vibrating bubbles surrounding a subaqueous immersed subject serve to attenuate the applied pressure amplitude to a level equal to 0 kPa. The present invention is based in part on this observation.

A wound treatment apparatus comprises, in accordance with the present invention, a tank, a water feed pipe extending to the tank, an electromechanical transducer in pressure-wave transmitting relationship to the tank for generating ultrasonic pressure waves in water contained in the tank, and an electrical signal generator operatively connected to the transducer for energizing same with an alternating electrical signal that is partially rectified. A controller is operatively coupled to the signal generator for controlling the amplitude of the alternating electrical signal, thereby determining intensity of the ultrasonic pressure waves produced in the tank by the transducer. The controller is operatively coupled to the signal generator also for varying a pulse repetition period of the electrical signal in inverse relationship to variation of the amplitude of the electrical signal.

In accordance with another feature of the present invention, an injector is posed along the feed pipe proximate to a barrier thereof. The barrier may be a wall of the pipe, formed, for instance, by an elbow-type bend in the feed pipe. The injector is operatively connected to a valve operatively on an upstream side for introducing air into a water stream flowing along the feed pipe. The injector may be alternately coupled to a disinfectant reservoir via a valve, whereby the injector introduces a disinfectant into a water stream flowing along the feed pipe. The injector is preferably a venturi injector.

The invention is effective in part because of the replacement of diffused vaporous-gas contained by water at ambient and hot temperatures with ambient-air gas to promote stable long-term bubble vibration within the wound therapy tank. The venturi injector provides the necessary ambient-air gas for vaporous-gas to ambient-air gas exchange capability within the therapy tank. Subaqueous therapeutic benefits are obtained from ultrasonically induced stable cavitation and microstreaming in water for a meaningful or predictable time period in part because of the use of a venturi air-injector, not a simple water degassing venturi.

The prior-art human patient cleaning devices use a venturi for water degassing purposes which favor the maintenance of vapor bubbles which are more likely than air bubbles to transform from stable into inertial or transient implosions. Lowering acoustic intensity can, at best, only lengthen the time a bubble is maintained in stable cavitation before bubble expansion inevitably and naturally progresses to the inertial or transient cavitation stage.

Bubbles expansion time, from bubble inception to collapse, is relatively short and unpredictable and because there's an absence of positive stable cavitation control the technique of reducing intensity may be potentially hazardous for wound therapy. The current practice of using pulsed ultrasound where the applied ultrasonic sound wave is turned on and off to give the bubbles time to shrink back in size is said to avoid the onset of inertial or transient cavitation. This is considered tenuous logic which ignores the effects of the large number of interacting variables which, at any instant of time, may serve to randomly vary the elapsed time from bubble inception until bubble collapse possibly causing the onset of inertial or transient cavitation to occur at, or just prior to, ultrasonic sound wave turn off whereupon the bubble will continue its growth to the point of collapse and implosion. Such a subaqueous inertial or transient cavitation control technique is open-ended, (ie, no outside control) and therefore considered too risky for use with water when open-wound "patient" therapy is involved.

In accordance with a further feature of the present invention, the controller is a microprocessor is operatively coupled to the signal generator and the tank for determining a percentage or proportion of rectification of the electrical signal to obviate or avoid inertial or transient cavitation. The microprocessor may be coupled to a sensor such as a PZT probe disposed in pressure-wave transmitting relationship with water in the tank for detecting inertial or transient cavitation in the water in the tank. The microprocessor iteratively operates the signal generator during a calibration procedure to produce a series of ultrasonic pressure waves of increasing proportion of rectified waves to full waves. The microprocessor is operatively coupled to the sensor for determining a rectified/full wave duty cycle at which inertial or transient cavitation disappears. The microprocessor is programmed to operate the signal generator to produce an electrical energization signal with the duty cycle.

Thus, the present invention provides an iterative, continuous full-wave to half-wave pressure-amplitude control rather than the current practice of lowering acoustic intensity or employing on/off pulsed ultrasound, or lowering acoustic intensity. The invention employs an iterative control design approach to the suppression of inertial and transient cavitation because, without such control, the vast majority of cavities created by even the lowest amplitude rarefactional ultrasonic pressure waves are likely to result in bubble formations that will eventually implode. In layman terms, this invention looks upon water as an amorphous mass whose propensity for initiating inertial or transient cavitation varies from tank-fill to tank-fill and from location to location since its constituents and temperature state and other parameters cannot be predicted or altered in advance of wound therapy treatment.

The signal generator may be controlled to produce an unrectified ultrasonic signal to induce transient cavitation in a predetermined mixture of water and disinfectant in the tank. In that case, means may be operatively coupled to the signal generator for sweeping a frequency of an electrical excitation signal produced by the signal generator.

Pursuant to another feature of the present invention, the microprocessor is operatively coupled to the signal generator and the tank for detecting and signaling the presence of stable and inertial or transient cavitation generated in water in the tank owing to energization of the transducer. A display may be operatively connected to the microprocessor for communicating to an operator a status of cavitation in the tank.

Where fish are to be subjected the wound treatment apparatus, the tank is advantageously one of two tanks communicating with one another via a barrier.

An ultrasonic treatment method comprises, in accordance with the present invention, feeding water to a tank, dissolving air in the water to aerate the water during the feeding thereof, disposing at least a portion of a living organism in the aerated water, and thereafter ultrasonically generating stable vibrating bubbles in the aerated water. The generating of the stable vibrating bubbles includes energizing a transducer with periods of full-wave compression and rarefaction cycles alternating with periods of rectified-wave compression pressure cycles sufficient to suppress inertial or transient cavitation for a predetermined interval. The full-wave compression and rarefaction cycles having a first amplitude or intensity and a first pulse repetition period. Subsequently the transducer is energized with periods of second full-wave compression and rarefaction cycles alternating with periods of second rectified-wave compression pressure cycles, where the second full-wave compression and rarefaction cycles have a second amplitude or intensity greater or less than the first amplitude or intensity and a second pulse repetition period respectively less or greater than the first pulse repetition period. The second rectified-wave compression pressure cycles have the second amplitude or intensity and the second pulse repetition period so that the second full-wave compression and rarefaction cycles alternating with periods of the second rectified-wave compression pressure cycles are sufficient to suppress inertial or transient cavitation for a predetermined interval.

The method may additionally comprise automatically monitoring the aerated water in the tank to detect inertial or transient cavitation. If so, the method may also comprise displaying a status of inertial of transient cavitation in the aerated water in the tank.

Pursuant to a yet another feature of the present invention, after the organism is removed from the tank, a disinfectant is delivered to the tank. Thereafter ultrasonic transient cavitation is induced in water and disinfectant contained in the tank. The inducing of the ultrasonic transient cavitation preferentially includes generating full-wave compression and rarefaction cycles at an ultrasonic frequency in the water and disinfectant in the tank. Also, the inducing of the ultrasonic transient cavitation may further include sweeping the frequency.

An ultrasonic treatment method comprises, in accordance with the present invention, disposing at least a portion of a living organism in aerated water, and thereafter ultrasonically generating stable vibrating bubbles in the aerated water for a first predetermined interval. The generating of the stable vibrating bubbles includes energizing a transducer with a first alternating electrical signal to suppress inertial or transient cavitation for the first predetermined interval, the first alternating electrical signal having a first amplitude and a first pulse repetition period. Thereafter stable vibrating bubbles are ultrasonically generated in the aerated water for a second predetermined interval, the generating of the stable vibrating bubbles during the second predetermined interval including energizing the transducer with a second alternating electrical signal to suppress inertial or transient cavitation for the second predetermined interval, where the second alternating electrical signal has a second amplitude and a second pulse repetition period, with the second pulse repetition period differing from the first pulse repetition period in inverse relationship to a variation of the second amplitude relative to the first amplitude.

As described above, the present invention provides a method and/or apparatus for periodically stimulating and then arresting cavitation bubble-growth as the means for perpetuating stable cavitation and the elimination of inertial or transient cavitation for a time period sufficient to permit completion of open wound therapy or cleaning, typically 10-15-minutes.

The present invention enables the application of ultrasonic frequency with stable cavitation, exhibiting subaqueous sub-harmonics above the threshold of normal human hearing so that the human patient does not detect the sub-harmonics through skeleton bone conduction. For treatment of farm-raised fish, this sub-harmonic emission precaution is not necessary as their frequency detection capability is far below ultrasound frequency.

The present invention contemplates injecting and then diffusing ambient air into the water supply before that water enters a bathing or wound-therapy treatment tank in order for the ambient air to displace vapor from vapor bubbles formed by cavitation in the therapy tank.

In an apparatus and method in accordance with the present invention, an attenuating blanket of stable vibrating air bubbles is generated that surrounds a patient or subject to prevent ultrasonic pressure waves from entering the "patient's" body and additionally, for the fish "patient," provision of a source of oxygen during its debridement and wound therapy.

To ensure bubble blanket intensity uniformity around the human or animal patient, one ultrasonic transducer is centrally located at the bottom of the therapy tank. For the fish subjects, since they are mobile and many may be treated at the same time, multiple transducers are mounted to the bottom of the therapy tank.

The present invention provides an alternative to the current 1-5 mHz, hand-held human therapy devices when used in the non-thermal, subaqueous mode with this invention's low frequency alternative because, when current high frequency (1-5 mHz) therapy devices are used subaqueously for non-thermal wound treatment, the water bubble cavitation attenuation blanket described above cannot be created so the applied ultrasonic pressure waves penetrate the human patient's body. There is risk, therefore, with these prior art devices of causing inertial or transient bubble cavitation events at various nucleation sites which exist within human or animal bodies.

The basic difference between the present invention and current high frequency devices used for subaqueous non-thermal human wound therapy is that this invention relies upon stable cavitation and microstreaming stimulated in the aqueous solution surrounding the patient or subject while the high frequency device assumes low-intensity ultrasound pressure waves will not cause transient cavitation to form within a subject's body.

To enable the microprocessor to distinguish between stable cavitation and inertial or transient cavitation events occurring in the contained tapwater within the wound therapy tank, the underwater detector circuitry pursuant to the present invention provides two separate signals, one that responds to harmonic "noise" (which is characteristic of stable cavitation) and the other that responds to broadband "noise" (which is characteristic of inertial or transient cavitation).

The present invention also contemplates a method for reducing ammonia concentrations caused by the presence of fish faeces and un-eaten fish feed particulate matter in recirculating aquaculture tanks. The method is based on the considerable research that has been done in the field of low frequency ultrasound with respect to cavitation bubble collapse and and that created a new scientific discipline known as the Sonochemistry of liquids. According to Suslick, Scientific American, 1989, due to the creation of very high temperatures (5500 degrees C.) and pressures (500 atmospheres), which develop as a cavitation bubble collapses, organic compounds in the vicinity will be highly degraded and inorganic compounds oxidized or reduced.

Since ammonia (NH4) is an inorganic compound, its oxidation through cavitation bubble collapse will serve to detoxify fish excretory matter by converting faeces-ammonia and nitrites into non-toxic nitrates.

The present method for reducing ammonia concentrations in recirculating aquaculture tanks comprises monitoring ammonia levels in fish tank water, removing fish from at least a portion of the fish tank water to thereby isolate the portion of the fish tank water, upon detecting a predetermined ammonia concentration in the fish tank water, ultrasonically generating transient cavitation bubbles in the isolated portion of the fish tank water to oxidize ammonia therein, and subsequently mixing the ultrasonically treated portion of fish tank water with an ultrasonically untreated portion of the fish tank water.

The isolated portion of fish tank water may be directed through a screen filter, for instance, after being subjected to ultrasonic pressure waves.

While effective in reducing the concentration of ammonia in recirculating aquaculture systems, the present invention's ultrasonic (non-bio) technique exhibits none of the above drawbacks listed for bio-techniques when it becomes necessary to treat fish with chemicals or drugs including the troublesome but necessary cleaning and declogging of biofilters.

The detoxification of ammonia and carbon-dioxide removal is accomplished, pursuant to the present invention, by multi-tasking the ultrasonic generator system used for wound cleaning and therapy and placing the associated management and control procedures with the microprocessor as described in U.S. patent application Ser. No. 10/676,061. The removal of un-eaten fish feed particulate matter will be accomplished by screen filtering.

Removal of un-eaten fish feed particulate matter and oxygenation of tank water is essentially a continuous ongoing process. The detoxification of ammonia and carbon dioxide removal is periodic process dependent on their toxicity levels, as indicated by suitably placed monitors or sensors.

These control means may be manual or automatic, as preferred. When automatic, they are under the control of the microprocessor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall system block diagram outlining functional interrelationships among three major elements of a human and land-animal debridement and wound-therapy supine treatment apparatus in accordance with the present invention.

FIG. 2A is a graph of a pulsed waveform used for iterative stable cavitation control in a method and apparatus in accordance with the present invention, showing a fully rectified wave portion.

FIG. 2B is a graph of another pulsed waveform used for iterative stable cavitation control in a method and apparatus in accordance with the present invention, showing a half-wave rectified wave portion.

FIG. 3 is a plan view of a two-tank fish farm with an ultrasonic therapy installation in accordance with the present invention.

FIG. 4 is an elevational view of the two-tank fish farm with ultrasonic therapy installation shown in FIG. 3.

FIG. 5 is a schematic front elevational view of a louvered barrier shown in FIGS. 3 and 5.

FIG. 6 is a side elevational view of the louvered barrier of FIG. 5.

FIG. 7 is a graph of bubble radius vs. time, illustrating stable cavitation degenerating into transient cavitation.

FIG. 8 is a graph of bubble radius vs. time, illustrating an interval of stable cavitation followed by a period of rectified half-wave transmission, in a method pursuant to the present invention.

FIG. 9 is a graph of bubble radius vs. time, illustrating an interval of stable cavitation followed by a period of rectified half-wave transmission, in turn followed by stable cavitation, in a method pursuant to the present invention.

FIG. 10 is partially an electrical circuit diagram and partially a hydraulic circuit diagram of a system for controlling or reducing ammonia levels in fish tank water pursuant to the present invention.

FIG. 11 is a schematic side elevational view of a two-tank fish farm with the system of FIG. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following operational description of a wound treatment apparatus applies to human and animal configurations of the apparatus. A configuration of the apparatus for the treatment of fish need not include provision for handling disinfectant in a therapy tank but will include all other operational features plus some additional features necessary to address the needs of fish farming.

FIG. 1 illustrates a control microcomputer or microprocessor 24 by which means an operator can cause the three processes associated with open-wound ultrasonic therapy to function, as needed. Microprocessor 24 has a control panel (not separately designated) includes an illuminated touchpad 12 for activating the wound treatment apparatus. Another illuminated touchpad 14 initiates a "one time" on-site calibration cycle. A liquid crystal display (LCD) 16 displays all relevant information and operator instructions. A further touchpad 18 is used to initiate a "start selected sequence" routine. Yet another touchpad 20 initiates a "stop selected sequence" routine. A sequencer touchpad 22 is accessed by microcomputer or microprocessor 24 to assist the operator in initiating the required operation.

The wound treatment apparatus described herein operates in either a manual or an automatic operational mode and either mode is selectable at the operator's choice.

Sequencer touchpad 22 runs the LCD 16 through a menu so the operator can make selections as required. The menu is set forth in the normal sequence of operation, i.e., therapy tank fill, wound debridement/cleaning, wound healing, decontamination/auto therapy tank drain, therapy tank drain, fish conditioning and fish excrement removal. Each of these operations, other than therapy tank fill, may be taken in the operator preferred order, e.g., if for humans and animals the operator wanted to disinfect the therapy tank before wound therapy, this is possible but the microcomputer 24 will instruct the operator not to install the patient and will empty the therapy tank at the completion of the automatic decontamination cycle time.

Before the wound treatment apparatus can be used for routine therapy treatment it must first be calibrated onsite. When a therapy tank 26 (FIG. 1) is filled the first time, the operator activates the system by depressing the illuminated "ON" touchpad 12. This activates all electronic circuits but stops ultrasound transmission to the therapy tank 26 by opening a switch K7 to disable an amplifier A3. The operator, by means of the sequencer touchpad 22 and LCD 16 selects from the menu option "THERAPY TANK FILL." Microcomputer 24 then asks the operator via LCD 16 to select "AUTO, (FILL)." After making the required selections the operator is instructed by microcomputer 24 via LCD 16 to depress the "START" touchpad 18. Microcomputer 24 closes a switch K4, which energizes a solenoid S3 and closes a drain 28. Then a switch K6 is closed, which energizes a solenoid S2 and commences aerated tub fill. The therapy tank fill components are turned off when a preset level is reached as determined by a sensor D2.

Calibration

Until microcomputer 24 has conducted its first on-site calibration, it will only respond to an instruction to fill the therapy tank 26. Microcomputer 24 will tell the operator via LCD 16 why and ask the operator to depress calibration (CAL) touchpad 14. The calibration cycle is fully automatic and operates as follows.

An initial step in an iterative control technique is to test the number of full sinusoidal cycles of equal amplitude ultrasonic compressional and rarefactional pressure waves needed to stimulate inertial or transient cavitation in water. This is accomplished by running ten discrete sets of tests of which the longest and the shortest number of cycles are discarded and the average number of cycles is calculated from the remaining eight tests.

This average number of cycles is the pulse repetition period, i.e., the time from the beginning of one pulse to the beginning of the next. There is no ultrasound "off" time in this pulse repetition period since it is made up of two different pulse types, one immediately following the other. The pulse duration (PD) is the length of time required for the first type pulse to occur and is equal to the period times the number of sinusoidal cycles in the pulse. The duty factor is the fraction of time that the first type pulse is on and consists of full sinusoidal compressional and rarefaction pressure waves. The balance of the pulse repetition period is occupied by the second pulse type, which consists of half sinusoidal (rectified) compressional pressure waves

The iterative stable cavitation control technique consists essentially of decreasing the above-defined duty factor from 0.8 in increments of 0.1, for example, until the setting is reached where it takes transient cavitation 15 minutes or more to manifest itself, whereupon, the duty factor is reduced, for example, by an increment of 0.1 to provide a safety margin.

The above iterative control technique is conducted with the average time to transient cavitation calculated from the above ten discrete sets of tests corresponding to the duty factor 1.0 and using the precision microcomputer clock as the determinant for setting the trial duty factors where it takes transient cavitation 15 minutes or more and whose value and increments are adjusted from tank to tank location to suit water quality.

Upon completion of the above calibration cycle the microcomputer 24 through its LCD 16 confirms that stable cavitation is in effect. Thereafter, the calibrated ultrasound wave configuration is transmitted continuously while the 15-minute "patient" cleaning, wound debridement or wound healing therapy is in progress.

In an example of a wave configuration arrived at via the above-described iterative calibration technique, the duty factor is 0.4, with full-wave rectification, the applied frequency is 60 kHz, and the pulse repetition period (PRP) is 15 seconds. Then the number of alternate compressional and rarefaction cycles is (15.times.60,000.times.0.4)/2 or 180,000. For a duty factor of 0.6, the number of alternate compressional and rarefaction cycles is 270,000. The number of follow-on compressional half-cycles is 15.times.60,000.times.0.6 or 540,000 and, for a duty factor of 0.6, the number of alternate compressional and rarefaction cycles is 360,000.

After the 15-minute therapy period is completed, or transient cavitation is detected, the microcomputer 24 shuts down the ultrasound for a time period sufficient for cavitation to dissipate, whereafter therapy can be resumed for another 15-minute time period, and so on.

This calibration cycle is more likely a one-time event necessary upon device site installation because water quality varies widely depending on geographical location.

The final waveform resulting from this calibration at a particular location is placed into the memory of microcomputer 24 and is applied for all subsequent device activations at this particular site location.

The presence or absence of inertial or transient cavitation is determined by a signal from a PZT probe X1 (FIG. 1) situated in close proximity to a transducer T1 and in combination with an appropriately configured detection circuit 30. PZT probe X1 generates a signal fed to microcomputer 24, which manages all associated signals, system components and processes.

Operator control over microcomputer 24 is provided by a control unit 10 including LCD component 16, which are situated on or near wound treatment therapy tank 26.

Microcomputer 24 induces the energization of transducer T1 with a full-wave ultrasonic waveform alternating with a rectified alternating waveform, defined by parameters selected during the calibration process as discussed above. This ultrasound generation method suppresses inertial and transient cavitation. The system generates bubbles at the applied frequency and compresses the bubbles so that they are smaller than their resonant size at the applied frequency, thereby prolonging stable cavitation.

Because vibrating bubble-to-bubble interaction causes bubbles to assume a non-spherical shape, their vibratory response is non-sinusoidal and therefore contains harmonics and sub-harmonics of the applied frequency. A limitation of the above-discussed prior-art human patient cleaning device was the 30 kHz applied frequency because its third sub-harmonic 10 kHz, proved detectable by all immersed human patients through conduction of the 10 kHz subharmonic by their bony prominances to their inner-ear, some patients finding the noise either irritating or intolerable. For the prior human patient cleaning device, lowering the applied intensity served to decrease the amplitude of the third sub-harmonic which lowered the noise to an acceptable level in most but not all cases. This necessary lowering of intensity proved to be at the expense of cleaning process effectiveness for the patient.

The present apparatus has removed this limitation by increasing the applied frequency to 60 kHz for human and animal exposure and therefore its third sub-harmonic to 20 kHz, which is above the threshold of human hearing. The detection circuit 30 may also employ harmonics for detection of stable cavitation.

For fish treatment, the applied ultrasonic frequency is lowered to 30-kHz, because the frequency detection capability of farm-raised fish is, at the highest, in the low hundreds of Hz.

The present apparatus provides four levels of intensity, one for decontamination at more than 5 W/cm.sup.2 SPTP, the second for cleaning and open-wound debridement at 3 W/cm2 SPTP (maximum), the third for wound healing at 1.5 W/cm2 SPTP (maximum), and the fourth for fish conditioning at 0.5 W/cm2 SPTP. The 30 or 60 kHz applied frequency is swept up to +/-5 kHz at 120 Hz to provide the likelihood of increased microorganism kill.

The limitation exhibited by 1-mHz-and -above hand-held therapy device is its inability at 0.1-0.5 W/cm2 intensity to stimulate any form of cavitation in the water thus enabling ultrasonic pressure waves to penetrate a human patient's body without attenuation, thereby exposing nucleation sites within the patient to cell damage and free radicals from inertial or transient cavitation. This limitation of these hand-held devices can only be removed by lowering their applied frequency and increasing the acoustic intensity of the devices. There's no better example than the 1 mHz hand-held therapy device for demonstrating that water's reaction to ultrasonic pressure waves may have unanticipated major harmful effects on the desired therapeutic clinical result and that reliance on first-order, open-ended controls to effect stable cavitation may only serve to increase the risk of cell damage due to the non-visible presence of inertial or transient cavitation within the human patient's body.

An advantageous element of the present apparatus is an ability to differentiate between occurrences of stable and inertial or transient cavitation within contained tapwater within a wound-therapy tank 26. An inertial or transient cavitation detection signal always overrides the stable cavitation detection signal so that microcomputer 24 can suppress or maintain inertial or transient cavitation depending on the required mode of operation.

The location of PZT probe X1 of detector circuit 30 is in-line with a face 32 of transducer T1 at the highest intensity within the wound-therapy tank 26. In response to a signal from PZT probe X1, microcomputer 24 displays on LCD 16 the cavitation status within the water contained within the wound-therapy tank 26 at all times during operation.

PZT probe X1 and detection circuitry 30, inter alia, overcome the limitation of prior human patient cleaning devices in their inability to detect inertial or transient cavitation and to thereby maintain stable cavitation suitable for wound-therapy.

Decontamination

The need is recognized for disinfection of a tank 26 used for ultrasound wound treatment. After completion of a wound-therapy procedure in therapy tank 26, the tank must be decontaminated from pathogens shed by the patient or subject. A number of microorganisms have been found to withstand hot-water temperatures and chemical disinfectants, which suggests that chemical means alone are not 100% effective. Also, experimental data suggests that ultrasound in the low-kilohertz frequency range is capable to some measure of inactivating certain human disease agents that may reside in water. This experimental ultrasound data states that the human pathogens tested were selected on their normal routes of infection, for example, skin or intestinal tract, or their structural similarities to such agents, which would make them likely candidates of whirlpool or hot tubs.

In an experiment, ultrasound killed within 1 hour a variable percentage of the following microorganisms: bacteria (Pseudomonas aeruginosa, Bacillus subtilis Escherichia coli), fungus (Trichophyton mentagrophytes) and viruses (feline herpes virus type 1; this sub-family also includes the human herpes viruses, herpes simplex virus types 1 and 2). This experiment concluded that 100% microorganism killing was a dose-effect dependent on time of exposure and level of ultrasound intensity but the mechanism of microorganism "kill" appeared to be inertial or transient cavitation.

This microorganism "kill" principle appeared to be the high forces and high temperatures associated with inertial or transient implosions which can disintegrate cell walls and membranes of bacteria and certain enveloped virus but only in the immediate vicinity of these micro-sized implosions. Because an apparent defense mechanism of pathogens is to gather at the antinodes of a constant frequency ultrasonic wave where the amplitude of the ultrasound pressure wave is at a minimum, the present apparatus employs a rapid frequency-sweep modality which serves to oscillate the location of the antinodes in space thereby exposing the microorganisms to an increased number of cavitation implosion events.

Experimental data reveals that ultrasonic cavitation enhances the effect of different antibiotics and disinfectants. Clearly, disinfectant plays no part in the deactivating of pathogens exposed to the high forces and temperatures created by cavitation implosion events. Reasons for the synergism of water, ultrasound and disinfectant having an apparently enhancing germicidal effect over water and disinfectant alone are largely unknown. Since experiments have demonstrated acoustic pressure waves used in conjunction with disinfectant does exhibit an increased germicidal effect, the synergism hypothesis is that like vibrating bubbles the pathogens are subjected to alternating compression and rarefaction ultrasonic pressure waves. Since the pathogen's internal contents are normally equalized in pressure corresponding to ambient pressure, in the pre