Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods
  • A61B17/22—Implements for squeezing-off ulcers or the like on inner organs of the body; Implements for scraping-out cavities of body organs, e.g. bones; for invasive removal or destruction of calculus using mechanical vibrations; for removing obstructions in blood vessels, not otherwise provided for
  • A61B17/22004—Implements for squeezing-off ulcers or the like on inner organs of the body; Implements for scraping-out cavities of body organs, e.g. bones; for invasive removal or destruction of calculus using mechanical vibrations; for removing obstructions in blood vessels, not otherwise provided for using mechanical vibrations, e.g. ultrasonic shock waves
  • A61B17/22012—Implements for squeezing-off ulcers or the like on inner organs of the body; Implements for scraping-out cavities of body organs, e.g. bones; for invasive removal or destruction of calculus using mechanical vibrations; for removing obstructions in blood vessels, not otherwise provided for using mechanical vibrations, e.g. ultrasonic shock waves in direct contact with, or very close to, the obstruction or concrement
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods
  • A61B2017/00017—Electrical control of surgical instruments
  • A61B2017/00022—Sensing or detecting at the treatment site
  • A61B2017/00106—Sensing or detecting at the treatment site ultrasonic
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods
  • A61B17/22—Implements for squeezing-off ulcers or the like on inner organs of the body; Implements for scraping-out cavities of body organs, e.g. bones; for invasive removal or destruction of calculus using mechanical vibrations; for removing obstructions in blood vessels, not otherwise provided for
  • A61B17/22004—Implements for squeezing-off ulcers or the like on inner organs of the body; Implements for scraping-out cavities of body organs, e.g. bones; for invasive removal or destruction of calculus using mechanical vibrations; for removing obstructions in blood vessels, not otherwise provided for using mechanical vibrations, e.g. ultrasonic shock waves
  • A61B2017/22005—Effects, e.g. on tissue
  • A61B2017/22007—Cavitation or pseudocavitation, i.e. creation of gas bubbles generating a secondary shock wave when collapsing
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
  • A61B2018/00005—Cooling or heating of the probe or tissue immediately surrounding the probe
  • A61B2018/00011—Cooling or heating of the probe or tissue immediately surrounding the probe with fluids

Definitions

• the invention relates generally to medical devices and more particularly to a method and apparatus for delivering ultrasound energy to a treatment location within a human or other mammal.
• ultrasound devices for ablating, lysing or removing material obstructing blood vessels in humans and to otherwise apply ultrasound to locations within the body for therapeutic purposes.
• One such device for removing material obstructing blood vessels is in the form of an elongated ultrasound transmitting probe.
• This device includes a cavitation generating tip at the distal end of an elongated transmission member.
• a transducer is used to convert an electrical signal into longitudinal mechanical vibration, which is transmitted to the tip by the transmission member and causes cavitation within the blood vessel to ablate or lyse the obstruction.
• One drawback to such a device is the need to insert and advance the device through a blood vessel to the treatment location.
• an apparatus and method for the application of ultrasound to a location within the body is provided.
• the apparatus can advantageously operate at a pulse duration below about 100 milliseconds and in the range 0.1 milliseconds to 100 milliseconds and a pulse repetition period below about 1 second and in the range of 1 millisecond to 1 second. Duty cycle ratios over 5 and preferably over 8 are also advantageous.
• Therapeutic applications of ultrasound such as for assisting in the treatment of medical conditions such as cancer and/or other ailments are also provided. Accordingly, it is an object of the invention to provide an improved apparatus and method for treating locations within the body with ultrasound.
• a further object of the invention is to provide a method and apparatus for determining ultrasound application parameters.
• Yet another object of the invention is to provide an apparatus and method for therapeutic applications of ultrasound.
• FIG. IA is a schematic perspective view of a system for the non- invasive use and testing of ultrasound energy
• FIG. IB and 1C are front and side views of the transducer shown in FIG IA;
• FIG. 2 is a graph showing hydrophone output, in decibels, as a function of transversal displacement of the hydrophone along the Y axis to establish the focal width of ultrasound in the Y direction;
• FIG. 3 is a graph showing hydrophone output voltage as a function of transducer input voltage, showing that electric potential above 160 volts, and therefore increased wattage, caused a decrease in hydrophone output as a result of exceeding the cavitation threshold of the medium;
• FIG. 4 is a graph showing hydrophone output voltage as a function of displacement of the transducer along the Z-axis for both short duration pulses and relatively longer duration pulses, showing that a longer pulse duration ( ⁇ ) can initiate cavitation;
• FIG. 5 is a graph showing hydrophone output voltage as a function of Z- axis displacement for various pulse durations, showing that longer pulse durations were associated with larger decreases in acoustic amplitude after exceeding the cavitation threshold;
• FIG. 6 is a graph showing hydrophone output voltage as a function of Z- axis displacement for transducer inputs of varying voltage, showing that cavitation was evidenced by a decrease in actual hydrophone output from the theoretical output;
• FIG. 7 is a graph showing change in percentage of clot mass dissolution as a function of change in the pulse repetition period (T), showing that an appropriate pulse repetition period has a significant effect on the efficiency of clot lysis;
• FIG. 8 is a graph showing percentage of clot mass dissolution as a function of pulse duration ( ⁇ ), showing a strong dependency of clot dissolution and danger to the blood vessel on pulse duration;
• FIG. 9 is a graph showing rate of clot mass dissolution as a function of intensity at the focal area;
• FIGS. 10A and 10B are ultrasound images of a clot within an artery segment, before and after ultrasound treatment
• FIGS. 11 and 12 are graphs showing microphone output voltage as a function of ultrasound peak intensity in a buffer solution and in a clot, showing that ultrasound initiated randomly, but that once initiated, it could be maintained at decreased intensities and that the threshold and slope are different for the buffer and clot;
• FIGS. 13 and 14 are graphs showing microphone output as a function of ultrasound intensity, when blood is acted upon by ultrasound of different pulse repetition periods (T), showing that shorter T's correlate to lower intensity thresholds and ultimately lower cavitation intensity;
• FIGS. 15 and 16 are graphs showing the influence of pulse duration on cavitation activity of a buffer solution and blood, respectively;
• FIG. 17 is a graph showing microphone output, which is related to cavitation activity, as a function of pulse duration in both a blood and a buffer solution;
• FIG. 18 is a graph showing percentage of weight loss of a clot as a function of ultrasound intensity for a non-degassed and degassed sample, showing a lower intensity threshold and lower intensity requirement for the non-degassed system;
• FIGS. 20 A, 20B and 20C are three graphs showing percentage of clot dissolution as a function of pulse duration ( ⁇ ), pulse repetition period (T), and pulse duration ( ⁇ ), respectively, at intensities of 1400 W/cm 2 , 1400 W/cm 2 and 1300 W/cm 2 respectively and shows that optimal parameters can be intensity independent;
• FIG. 21 is a graph showing percentage of clot dissolution as a function of ultrasound intensity, manifesting threshold for clot lysis
• FIG. 22 is a graph showing the weight of unlysed clot as a function of ultrasound intensity, manifesting a threshold for clot lysis
• FIG. 23 is a perspective view of an invasive type ultrasound transmission system, constructed in accordance with an embodiment of the invention.
• FIGS. 24-27 are graphs showing cavitation activity as a function of transducer power, showing the difference between continuous and pulsed activation.
• FIGS. 28-30 show ultrasound probe temperature in activated and unactivated states, both with and without the use of cooling fluid, in a continuous wave mode of probe operation, and in duty cycles of 8.
• a transducer converts an electrical signal to mechanical vibration, which causes the propagation of ultrasound waves through some medium or media. If these waves are of sufficient intensity, they create cavitation within a medium at a desired location as micro bubbles are formed and collapse. This generates extraordinarily high activity at the cavitation site.
• a transducer can be operated in a continuous mode or in a pulsed mode.
• a continuous mode the signal to the transducer is always causing the transducer to generate sufficient vibration to maintain cavitation at the desired location.
• a pulse mode the signal amplitude is reduced sufficiently (or eliminated) to permit cavitation to pause between pulses of high amplitude during which cavitation occurs.
• Certain conventional pulsing methods apply ultrasound in one to several second doses, followed by pauses of approximately equal duration or even durations longer than the duration of the activating signal. This is conventionally performed to permit objects which became hot during the activation process to cool down. It has been discovered that applying ultrasound in an improved pulsed mode can provide substantial advantages, compared to conventional pulsing modes of operation.
• Non-invasive ultrasound system 100 includes a therapeutic focused ultrasound transducer 110, which is activated by an electrical signal from a signal generator 120.
• Therapeutic transducer 110 can be constructed to operate at up to 750 KHz and can be formed with a 1-3 ceramic composite.
• a 1-3 composite transducer includes rods of PZT inserted into a polymer support and has very high energy transfer efficiency. Front and side views of one embodiment of transducer 110 are shown in FIGS. IB and 1C.
• Therapeutic transducer 110 includes a hole 111 at the center thereof. Hole 111 permits the use of an optional ultrasound imaging probe (not shown) which can guide and monitor the therapy with ultrasound during application.
• an optional ultrasound imaging probe (not shown) which can guide and monitor the therapy with ultrasound during application.
• One example of a suitable transducer which was used in experiments presented herein, is about 45 mm thick, has an overall radius of 46 mm, a central active area with a radius of 40 mm and a central bore with a radius of about 10 mm. Electrical connections are on either side of the central bore at disk shaped depressions having an 8 mm radius. Alternative transducers can be substituted.
• generator 120 sends a signal 121 through a pair of electric wires 112, which are coupled to transducer 110 at attachment points 113a and 113b.
• Signal 121 is formed with a plurality of energy pulses 122 of duration ⁇ at an amplitude (A) and a frequency (f).
• a pulse will be considered the "on" portion 122 of signal 121, which is of sufficient amplitude to maintain cavitation and is followed by an "off section 123 of signal 121 of insufficient amplitude to maintain cavitation.
• the duration of time between the beginning of successive pulses 122 is referred to as pulse repetition period T. It has been determined that pulse duration ⁇ is advantageously significantly smaller than pulse repetition period T.
• Model system 140 includes an open Plexiglas water tank 141 with a hole in a front side 142 for inserting therapeutic transducer 110.
• Tank 141 was filled with water, which was either degassed or non-degassed, depending on the particular experiment to be run. When water was not degassed, it included small air bubbles which served as a nuclei for cavitation initiation. Decreasing the number of bubbles in the water increases the energy needed to initiate cavitation.
• a hydrophone (not shown) was positioned at various locations within a dedicated tank. It was found that when activated by generator 120 at low intensities below the cavitation threshold, transducer 110 creates an acoustic field with a focal region having an elongated ellipsoid or cigar shape.
• a bovine vessel 150 having a clot 151 therein or a clot attached to the front of a bovine vessel wall was suspended within tank 141 by a specimen holder 152. Depending on the experiment to be run, vessel 150 was filled with either blood or a buffer solution.
• the vessel 150 and the clot 151 were moved by a computerized x-y positioning a system 180 through a mounting 181 and a computer controller 182.
• Certain information regarding the effects of applied ultrasound were compiled with an ultrasound imaging device 160, formed with an imaging ultrasound transducer 161, coupled to a processor 162 for interpreting information received from transducer 161 and displaying an image thereof. Additional information was compiled through the use of a microphone 170 attached to tank 141, coupled to a frequency analyzer 171 through an amplifier 173, which also receives a trigger signal 172 from generator 120.
• Trigger signal 172 corresponds to transducer activation signal 121, so that only sound transmitted from microphone 170 when transducer 110 is activated will be analyzed.
• Non-invasive therapeutic ultrasound can be practiced at a frequency of about 100 to 1000 KHz and far broader.
• Invasive-type (probe-based) therapeutic ultrasound can be practiced at a frequency range of 20 to 100 KHz and far broader.
• These parameters are particularly well suited for a non-invasive-type device, particularly one applying ultrasound at I > about 750 W/cm 2 , more preferably > about 1000 W/cm 2 .
• advantageous operating parameters include T ⁇ about 1000 milliseconds preferably ⁇ about 600 milliseconds, more preferably about 100 to 500 milliseconds and/or ⁇ ⁇ about 100 milliseconds, preferably about 10 to 100 milliseconds, more preferably 20 to 60 milliseconds. These parameters are particularly well suited for use with an invasive- type device, especially one operated at a peak power output of over 10 watts, such as one operated at 10-40 watts, preferably 15-30 watts. When pulse parameters are correctly selected, an invasive-type probe can be operated with substantially no cooling fluid.
• Example 1 The following examples illustrating the non-invasive application of ultrasound were conducted in a water tank with a system having the general construction shown in FIG. IA. These examples are provided for purpose of illustration only, and are not intended to be construed in a limiting sense.
• Example 1
• the hydrophone output was measured in decibels as a function of transversal displacement in mm along the Y axis, parallel to the transducer plane and corresponded to the predicted cigar shape at a distance of 5 cm from the transducer. The results are shown in FIG. 2.
• curve 80 shows a theoretical plot at 190 volts, if no cavitation had occurred, curve 81 is from 100 volts, curve 82 is from 142 volts, curve 83 is from 155 volts and curve 84 is from 190 volts.
• Higher electrical input corresponded to higher amplitude and larger decreases in acoustic amplitude, compared to a theoretical prediction and hence, greater cavitation effect.
• Example 6 The apparatus shown in FIG.
• IA was used to dissolve a blood clot attached to the front of a wall taken from a bovine blood vessel.
• the operating parameters including a duty cycle of about 8 were deemed acceptable.
• Example 9 The use of an ultrasound imaging system similar to system 160 shown in FIG. IA provided additional information regarding the use of ultrasound for blood clot lysis. It is possible to visualize the clot during ultrasound application.
• a bovine artery segment was filled with non-degassed PBS.
• Bright reflection images corresponding to cavitation were seen only at the posterior artery wall. This indicated that the transducer was located too close to the vessel. After the transducer was moved away from the vessel, reflection spots, indicating cavitation within the vessel were observed, indicating proper positioning of the transducer.
• Example 10 After the transducer was moved still farther away, bright reflection corresponding to cavitation was observed only at the anterior artery wall, indicating that the transducer was located too far from the vessel. Thus, by combining conventional imaging ultrasound with non-invasive ultrasound lysis, it is possible to assure that the ultrasound focal point is at a desirable location within the body.
• FIG. 10A an ultrasound image of a clot (right side) and buffer solution (dark left side) within a bovine vessel is shown. The focal point of the therapeutic transducer was advanced along the longitudinal axis of the artery segment from left to right. Ultrasound treatment was stopped at approximately the middle of the clot. Referring to FIG. 10B, it can be seen that the dark section indicative of liquid has grown from left to right in the vessel, and the clot has been reduced in size from the ultrasound treatment.
• driving frequency 650 KHz
• transducer excitation voltage 116 V
• T 7 millisecond
• FIG. 10B an ultrasound image of a clot (right side) and buffer solution (dark left side) within a bovine vessel is shown. The focal point of the therapeutic transducer was advanced along the longitudinal axis of the artery segment from left to right. Ultrasound treatment was stopped at approximately the middle of the clot.
• FIG. 10B it can be seen that the dark section indicative
• microphone output acoustic emission in the audible range was conducted as a manifestation of the degree of cavitation activity by placing a microphone on a water filled tank.
• a microphone on the outside of the body of the subject receiving ultrasound treatments can provide an excellent method of obtaining feedback regarding whether cavitation is occurring.
• the microphone output can be fed to a data processor, which can display a warning signal or deactivate the ultrasound device if the device is fully powered, but cavitation is not being detected by the microphone.
• the feedback can permit an operator to reduce power to the transducer to obtain the minimal amount of power needed to sustain cavitation.
• the voltage could be decreased to decrease the ultrasound intensity, but maintain cavitation, i.e., it is an inertial phenomenon.
• the intensity can be decreased to maintain cavitation within the blood vessel but diminish a chance to injure the vessel itself.
• the cavitation threshold for non-degassed buffer and blood was in the range of 1000 to 1500 W/cm 2 , closest to about 1200 W/cm 2 . With respect to degassed buffer and blood, the cavitation threshold centered around 2000 W/cm 2 #
• a pulse repetition period T between about 10 and 50 ms created maximum cavitation activity for pulse durations from about 150 ⁇ s to about 700 ⁇ s, correlating to duty ratios ranging from about 15 to 500.
• a buffer solution was subjected to ultrasound at an intensity of 2400 W/cm 2 .
• Example 16 Another experiment similar to that discussed with reference to FIG. 15 was performed, except that the medium tested was blood, rather than a buffer solution. Referring to FIG. 16, the intensity was set at 2400 W/cm 2 and results are shown for pulse durations of 0.100 ms, 0.150 ms, 0.250 ms, 0.400 ms and 0.700 ms for curves 251, 252, 253, 254 and 255 respectively. The parameters for causing cavitation in blood were found to be different than those for causing cavitation in the buffer solution.
• I 1400 W/cm 2
• Probe 1200 is formed with a tapered member 1225, formed with a proximal end 1229 of diameter A; constructed to be coupled to a source of ultrasound energy such as a transducer 1248.
• proximal end 1229 is preferably located at a displacement maximum relative to the standing ultrasound wave supported by the overall device. From proximal end 1229, tapered member 1225 tapers to a reduced diameter distal end of diameter A f .
• Proximal end 1229 must be large enough to receive sufficient energy to treat a thrombus, occlusions and the like. However, in order to provide optimal flexibility, it is desirable to reduce the diameter of distal portions of probe 1200 as much as possible, without significant loss of energy, strength or guidability. Furthermore, the reduction in diameter is preferably accomplished in such a manner as to amplify, or increase the amplitude of, the ultrasound vibrations.
• Ultrasound device 1200 is understood to operate in the resonant frequency mode; i.e., it supports a standing wave when energized by ultrasonic stimulation at proximal end 1229. Consequently, it is preferred that a cavitation tip 1250 is located at a displacement maximum (anti-node).
• a probe in accordance with the invention can be bathed with a coolant.
• the coolant can be directed over and around the probe, for example, by incorporating a sheath 1245 around some or all sections of the probe.
• Sheathing 1245 may be affixed to the probe at one or more of the displacement nodes of the standing wave. Additional sheathing may be incorporated for providing a passageway for a guidewire or other auxiliary tool which may serve to steer or position the device to its intended location.
• Sheathing 1245 if formed of a high-strength, thin-walled, low- friction material, preferably polyimide.
• Probe 1200 includes a horn 1225, having a tapered section T and a first constant diameter section S, is constructed to be coupled to an ultrasound energy source. Ultrasound energy is provided by the controller at a power source 1246 via a coaxial cable 1247 to a quick disconnect 1249, which connects coaxial cable 1247 to transducer 1248. Transducer 1248 is intimately connected to horn 1225. Probe 1200 also includes a transmission member 1240 coupled to horn 1225 and a tip 1250 coupled to the distal end of transmission member 1240. Ultrasound energy sources disclosed in U.S. Patent No. 5,269,297, and in a copending application entitled FEEDBACK CONTROL SYSTEM FOR ULTRASOUND PROBE under Application Serial No. 60/046,938, filed may 19, 1997, the contents of which are incorporated herein by reference, are suitable.
• Tip 1250 is coupled to three fine wires joining section 1240 and tip 1250 by means of three openings in tip 1250.
• the three openings in tip 1250 are spaced so as to form an equilateral triangle, concentric with the central axes of coupling tip 1250.
• Tip 1250 may also be provided with an opening for a guidewire, and a guidewire tube may be installed in the opening and extended proximally from the distal end.
• the fine wires may be separately sheathed, and any sheathing may extend between tip 1250 and a coupling joint.
• Wire 1240 may also be sheathed and the sheathing may be connected to the separate sheathing of the fine wires and may extend proximally to a coolant port through which coolant may be injected to bathe all or part of the transmission member.
• the entire probe was placed in a straight configuration in a Plexiglas tube with an inner diameter of 3.5 mm and the tube was placed inside a water tank.
• a microphone was placed on the outside of the water tank and measured acoustic output which correlates to cavitation activity.
• the probe was operated in both continuous mode and pulse mode under various operating parameters and data was compiled.
• the invasive-type probe was operated under 18 watts of power.
• a thermocouple in contact with the tip inside the tube provided real time data with respect to temperature. Referring to FIG. 28, the system was initially at 37°C, 10 ml/min of 24°C cooling water was pumped through the tube. As shown in FIG. 28, this reduced temperature at the probe tip to approximately 24°C. At point 681, the probe was turned on and activated with 18 watts of power. This quickly raised the temperature to over 41°C (point 682).
• the techniques described for the invasive and non- invasive application of ultrasound are also applicable to systems that promote or focus ultrasound energy to enhance the absorption of drugs, induce apoptosis in cells, and/or treat tissue, tumors, obstructions, and the like, within and without the body, systems to be utilized in or for laproscopic surgery, for ultrasonic scalpels, and to induce tissue hyperthermia such as for cancer radiation therapy, for example.
• drugs such as streptokinase, urokinase, whose function or efficacy would be enhanced by ultrasound or that would enhance the application of ultrasound at the treatment site, may be infused within the coolant fluid for cooling the ultrasound probe or delivered through a separate passageway within or without the ultrasound probe to the treatment site.
• Clot lysis Cell function manipulation eg. Migration, adhesion, etc.
• Cancer treatment Biological product manipulation eg. Genes, anti-sense DNA

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• 1997
  • 1997-09-29 US US08/939,289 patent/US6113558A/en not_active Expired - Fee Related
• 1998
  • 1998-09-25 TW TW087116026A patent/TW386883B/zh active
  • 1998-09-28 ZA ZA9808832A patent/ZA988832B/xx unknown
  • 1998-09-29 BR BR9815387-0A patent/BR9815387A/pt unknown
  • 1998-09-29 AU AU95128/98A patent/AU9512898A/en not_active Abandoned
  • 1998-09-29 WO PCT/US1998/020455 patent/WO1999016360A1/en not_active Ceased
  • 1998-09-29 EP EP98948587A patent/EP1022985A4/en not_active Withdrawn
  • 1998-09-29 CA CA002305636A patent/CA2305636A1/en not_active Abandoned
  • 1998-09-29 AR ARP980104873A patent/AR017276A1/es not_active Application Discontinuation
  • 1998-09-29 JP JP2000513507A patent/JP2001517525A/ja active Pending
• 2001
  • 2001-10-09 US US09/973,601 patent/US20020111569A1/en not_active Abandoned

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