Noninvasive Surgery Method And Apparatus

Abstract

A method and apparatus for performing human and animal surgery in which the tissue field including all soft tissue fluid space interfaces can be visualized along with other soft tissue features by appropriate ultrasonic visualization means such as transmitting a scanning ultrasonic beam and receiving echoes from the desired areas and presenting a picture of said areas on a suitable display monitor such as a cathode ray tube for two-dimensional presentation where the presentation may be compared with standard atlases of normal tissue. Means and apparatus for transmitting ultrasonic energy at substantially higher level than that used for visualizing the area are provided so as to selectively destroy tissue without requiring a surgical incision. The extent of the surgery may be observed with the visualizing apparatus and the surgery may be performed and monitored by the visualizing apparatus. The visualizing and the tissue destructing means are under the control of a computer which is suitably programmed for the particular operation being performed.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates in general to method and apparatus for performing human and animal surgery.

2. Description of the Prior Art

It is at times desirable to destroy or excise tissue at locations within the human and animal bodies which are displaced from the surface of the body thus requiring that healthy tissue be cut to arrive at the tissue to be destroyed or excised. Surgical techniques have been developed for operating in the brain and other portions of the body but substantial risks to the patient occur due to the incision through the healthy tissue to the area to be excised or destroyed.

It has also been known to utilize X-ray and radiating sources to destroy tissue. However, such radiation does not have a selective capability for destroying certain cells and not destroying others. Thus, the placement of radium capsules adjacent an area to be destroyed often destroys many healthy cells in its vicinity. The placement of radiation capsules in or near internal organs of the body also at times requires that surgery be utilized for proper placement.

SUMMARY OF THE INVENTION

The present invention comprises apparatus and method for performing ablative surgery while utilizing noninvasive ultrasonic techniques. The visualization system is a component of the invention and is useful for providing the physician with detailed information concerning the morphology of the tissues under treatment. Ultrasonic energy is transmitted and scans the tissues under treatment and echoes return from the tissue and are displayed for the physician's study. A computer forms a part of the invention and contains a suitable atlas of healthy tissue which may be presented on the visualization of the tissue under study so as to assist in tissue identification and also to identify any abnormalities or disease in the tissue under study.

High-intensity ultrasonic generating means are provided capable of producing lesions or tissue modification for treatment purposes may be generated in the organ by means of precise control from the computer. Appropriate dosage control permits the use of selective effects of ultra sound by which certain tissue components may be selectively destroyed and simultaneously the operator can see and/or select regions to be modified with reference to the appropriate display. An index marker may be visible in the display so that the location of the focus for the lesioning beam with respect to the anatomy may be identified.

The computer controls the dosage and the intensity varies as a function of I = I.sub.o e.sup.1.sup..alpha. where I.sub.o is the incident acoustic intensity, I is the intensity at the focus, 1 is the path length through the tissue and .alpha. is the absorption coefficient which in a typical example might be 0.2 The half power point of the beam might be 2 mm in width and thus very small lesions may be formed by controlling the radiated energy level and the time of radiation such that the threshold for acoustic lesion formation occurs only at a very small area.

Thus, the object of this invention is to present an entirely new concept for certain types of surgery for humans and other animals. The concept allows the surgeon to visualize the body tissue under study without requiring that an incision be made due to the ability of ultrasonic energy to pass through body tissue and be reflected back to a detecting receiver. After the area of interest has been surveyed, a high intensity ultrasonic beam may be focused within the tissue to be treated such that only at the focus will sufficient sound energy exist to produce changes in the tissue. The lesions thus formed in animal and human tissue by high intensity ultrasonic waves can also be visualized by the ultrasonic visualization equipment of this invention and thus surgery can be performed with this apparatus such that the lesions formed appear on the visualization apparatus and the surgeon can control the position, size and result of his surgery while directly observing it. Thus the present invention provides method and apparatus for exploratory examination into parts of the body which are unaccessible such as the human brain, for example, and where the structure of the brain may be clearly presented and compared with an atlas of healthy tissue such that abnormalities and diseases may be recognized. While observing the tissue, the surgeon may focus an ultrasonic beam of high intensity on the tissue being observed and selectively destroy undesired tissue. As the lesions from the lesion-forming beam are produced the surgeon may observe with the visualization system the production of the lesions so that he knows exactly where the lesion producing beam is effective.

Thus the present invention allows a surgeon to perform brain surgery, for example, without making an incision into the depths of the brain where such surgery is required and after observing the structure of the tissue with a visualization system which transmits ultra sound and receives reflections from the area under investigation, he can identify abnormalities and then produce lesions with a lesion-producing beam and simultaneously observe the effect and locations of the lesions thus produced. Since the ultrasonic energy may be transmitted into tissue far below the surface of the skin, the patient is not subject to shock and infection resulting from surgical incisions and only the desired unhealthy tissue will be destroyed.

Other objects, features and advantages of the invention will be readily apparent from the following description of certain preferred embodiments thereof taken in conjunction with the accompanying drawings, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure, and in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating the apparatus of this invention;

FIG. 2 is a block diagram of the visualization system of the invention;

FIG. 3 is a block diagram of the lesion generation system of the invention;

FIG. 4 illustrates the calibration system of this invention;

FIG. 5 is a graph of acoustic intensity versus single pulse time to produce threshold lesions in white matter of the brain;

FIG. 6 is a schematic of the pulser of this invention; and

FIG. 7 is a schematic view of the clamper and video amplifier of the receiver.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a patient designated generally as 10 supported on a treatment and visualization table 11. The apparatus and method of this invention utilizes ultra sound to observe a wide variety of internal body structures. For example, in the present invention, ultra sound is transmitted into the brain of the patient 10 for visualization by scanning an ultrasonic beam in a pulse-echo manner such that the ultrasonic pulses are reflected from soft tissue fluid-filled space interfaces and in particular the ventricular system, sulci, fissures and large blood vessels. It is also possible to observe directly gray-white matter interfaces. For visualization frequency in the range of 1 to 5 MHz, for example, is transmitted into the brain by removing a section of skull bone and replacing it with an open stainless steel mesh which might typically be 1 .times. 1 inch mesh made from 0.023 inch diameter wire. Such a grid provides adequate protection for the brain and provides acoustic transparency. The overlying muscle and skin are allowed to heal resulting in a transcutaneous ultrasonic window. The present invention allows the brain to be visualized through the acoustically transparent opening described above and great detail can be achieved in delineating internal brain structures. A 2.25 MHz transducer was used for pulse-echo visualization and is constructed of a spherically-shaped lead zirconate-titanate dish (having a 9-cm diameter) with an included beam angle of 26.degree.. The transducer was positioned by a specially adapted Cincinnati turret drill (Cintimatic Model DE) and was moved in X, Y and Z coordinates under the control of a computer. The mechanical coordinate system and sweep unit comprising the Cintimatic Model DE is designated by numeral 15 and it is to be noted that it supports the transducer 16. The computer 34 controls the scanning of the transducer 16 and since the acoustic system may employ a sharply focused transceiver, the focal region can be moved in space so that any given echogram comprising a composite of a number of echogram bands taken at different depths in the specimen may be obtained. Sector scanning is commonly used for routine examination and may also be employed in combination with linear scanning as a form of compound scanning. In omnidirectional scanning, interfaces within the plane of an echogram are viewed not only with the axis of the incident beam within the plane of section, but also with the axis oriented to a variety of angles with respect to this plane. Thus by adjusting the position of the transducer 16 with the mechanical coordinate system in sweep unit 15 such that the distance from the transducer to a plane within the brain equals the focal distance allows the echogram of the brain at that plane to be observed.

It has been found very desirable to couple the ultrasonic energy to the window in the head of the patient such that a matched and non-reflective interface is obtained. The use of a liquid coupling medium successfully accomplishes this. In FIG. 1, for example, a flexible bag 60 containing a suitable liquid is placed against the patient's head adjacent the window and the transducer 16 is directly coupled to the liquid in the bag 60 and through the liquid to the brain of the patient. Thus, maximum efficiency of coupling of the energy from the ultra sound transducer 16 is obtained. The liquid in the bag 60 might contain protein and organic substances so as to closely match the tissue inside the head of the patient, for example.

FIG. 1 illustrates the over-all apparatus of the invention and includes a visualization system 61 which is connected to a computer input unit 33 and computer 34 and through the computer to the mechanical coordinate and sweep unit 15 which positions the transducer 16. The visualization system 61 includes a pulser unit 1 for providing pulses that are coupled through the computer to the transducer 16 and these pulses pass from the transducer 16 through the fluid bag 60 into the head of the patient and are reflected from the tissue under observation. The mechanical coordinate and sweep unit 15 scans the beam of the transducer 16 and the pulses shock and excite the transducer 16 thus causing its ferro-electric element to be displaced and thus causing an acoustic pulse to be generated in the coupling medium 60 and into the tissue of the patient. When this pulse propagates through the coupling medium to the tissue and encounters various interfaces, a portion of the energy will be reflected at the interfaces and return to the transducer 16. The transducer 16 will generate a voltage due to the ferro-electric element of the transducer being effected by the returning echoes. Such echoes are amplified by the receiver of the visualization system and are presented on a visual display unit 5. The echoes may also be displayed on the graphic display unit 6 which may be used in conjunction with a camera 7 so as to photograph the display 6. Atlas overlay information 10 may be contained in the computer 34 or might be formed of plastic transparent overlays which may be placed over the display units 5 and 6 so as to allow orientation of the echograms under consideration.

The atlas overlay information from storage 10 of the computer provides a means of adding to the visual display standard anatomical data for aid in the interpretation of the echoes. The computer may also display other information such as the coordinates of the visualized structures, the aiming point of the lesioning system and other pertinent information required by the physician to adequately control the treatment procedure.

A time-sweep generator 12 is part of the visualization system 61 and generates a raster on the visual display unit 5 which corresponds to the actual sweep executed by the coordinate and sweep unit 15 so that these units are synchronized. The computer 34 controls the sweep generator 12 as well as the coordinate sweep system and sweep unit 15.

The computer 34 also processes the acoustic data of the digital to analog converter 13 and the analog to digital converter 14, and such control makes it possible to vary the intensity of the display as a function of depth of the examination in the tissue to compensate for absorption loss within the tissue.

The coordinate system 62 allows the mechanical sweep of the transducer to be made as specified by the physician and is under control of the computer 34.

A lesion generation system 63 includes an oscillator which may be of the crystal control type and is connected to drive a driver amplifier 20 through a timer 19. The driver amplifier 20 might be a class A moderate power amplifier producing approximately 50 watts r.f. output. The power amplifier 21 receives the output of the driver amplifier 20 and may be a class A amplifier capable of delivering up to 2,000 watts r.f. power to the transducer 16. A matching unit 23 provides an impedance match between the power amplifier and the transducer 16. The matching unit 23 also contains a precision voltage divider thus allowing a portion of the voltage to be applied to the stabilization unit to ensure that the output remains at the desired level and that it remains constant for the duration of the treatment. This feedback is under control of the computer 34. An automatic keying unit 25 operates the timer 19 during the treatment and calibration cycles.

A sound-field calibration system 65 is provided for properly calibrating and testing the unit. This unit allows the various parameters of the system to be monitored and checked. The peak output versus time intensity and the distribution of the acoustic output in the sound beam relate directly to the rate of lesion formation in tissue. Thus by determining the peak output as a result of 1 second duration of c.w. pulse of ultra sound multiplied by the probe calibration factor determines the peak output. The peak intensity is localized by plotting the intensity along the three major axes of the sound beam and a thermocouple probe is contained in a stainless steel housing 27 and has a pair of thin plastic windows between which is mounted an absorbing medium. A thermocouple probe which has very small dimensions compared to the wave length of the sound beam is mounted in the housing 27 and measures the temperature rise in the absorbing medium resulting from the absorption of the acoustic energy. The output of the probe is linear as a function of the acoustic intensity. The calibration may be periodically checked to assure accuracy.

A sensitive amplifier 28 amplifies the output of the thermocouple probe within the housing 27 and displays it on a dual trace oscilloscope 29. The other channel of the oscilloscope 29 may be used to display the excitation voltage applied to the ultrasonic transducer 16 and a camera 30 may be utilized to record the input-output relative to the transducer 16. The sensitivity of the amplifier 28 and the oscilloscope 29 is checked by using the microvolt calibration unit standard 32 and the time/mark generator 31 is coupled to the oscilloscope 29. Thus the calibration system 65 allows the visualization and lesion generation system to be carefully checked before applying ultra sound to the patient for lesion producing purposes.

FIG. 2 is a detailed block diagram of the visualization system 61. As previously described, the visualization system 61 allows the surgeon or other observer to observe tissue and obtain an echogram from the tissue. A computer 34 controls the output of a pulser 1 which produces a pulse 66 of the shape as illustrated in block 1. This pulse is supplied to the transducer 16 which propagates a wave in response to the pulse 66 through the medium 60 and into the patient's head where a portion of the energy will be reflected at interfaces and reflected energy will be returned to the transducer 16. The transducer will produce an electrical output based on the returning echoes and supply such electrical signals to a receiver 2 which detects the electrical signals and amplifies them. These amplified signals are passed to the attenuator 3 which adjusts the optimum output of the received signals to an appropriate level for optimum interpretation and passes it to an amplifier 4 which drives the visual display unit 5. The signals are also applied to a photograph display unit 6 which is used in conjunction with a camera 7 so that permanent records of the echo may be obtained. Camera unit 7 might be a Polaroid-type camera and a photocell detecting unit 9 observes the intensity of the display on the photographic display 6 and provides an input to a dynamic range control 8 which is connected to the camera unit 7. Atlas data storage 10 adds visual display standard anatomical data which are stored within the computer 34 on the visual display unit 5 and the photographic display 6 so as to allow the echogram received from the tissue to be identified and analyzed. The atlas data storage and computer 34 may also provide other reference information such as the coordinate position of the visualized structures, the aiming point of the lesioning system and other pertinent information required by the physician to adequately control the treatment procedure.

A sweep generator 12 generates the raster on the visual display unit 5 and 6 and is synchronized with the actual mechanical coordinate system and sweep unit 15 through the computer 34. Thus the display units 5 and 6 are synchronized with the mechanical sweep system so that the echoes will appear in their correct orientation. The coordinate system 62 provides three output shafts 91, 92 and 93 for moving the transducer in the X, Y and Z directions.

Radar sweep and synchronization systems are well known to those skilled in the art and the detailed circuitry for such systems will not be described herein as such techniques are well known in electrical engineering fields. Control of the transducer in the Z direction allows the transducer to be focused on tissue at a desired level in the patient.

An analog to digital converter 14 receives the output of the amplifier 4 and supplies it to the computer 34 and such information may be processed within the computer 34 so as to allow the intensity of the display to be controlled as a function of depth of the examination in the tissue or other regional enhancement to compensate for absorption loss within the tissue. After processing such information it may be fed from the computer 34 through the digital to analog converter 13 to the amplifier 4 and the visual display units 5 and 6 so as to control the units.

Since the mechanical coordinate system and sweeping unit 62 is under direct computer control, any mode of sweeping appropriate for treatment of the patient can be specified by the physician and thus the transducer 16 will be moved appropriately for the visualization and treatment of the patient.

Thus the visualization system 61 allows the physician to produce an echogram of tissue of the patient without making an incision to such tissue and further provides means for comparing such echograms with standard anatomical atlas data so as to determine if any abnormalities are present in the tissue under examination. Due to the accuracy of the mechanical coordinate system and sweep unit which is synchronized with the display units 5 and 6, the surgeon knows exactly the location of the tissue under study so that he can, if desired, produce lesions deep within the structures of the body without disturbing overlying tissues and can simultaneously observe the position of the lesions thus produced.

FIG. 3 is a block diagram of the lesion generation system 63 and comprises a crystal oscillator 18 which is connected to a driver amplifier 20 through a timer 19. An automatic keying unit 25 controls the timer 19 to allow an output of the oscillator 18 to be supplied to the driver amplifier 20. The automatic keying unit 25 is under the control of the computer 34. The computer 34 also supplies output to the attenuator 26 to control the crystal oscillator 18.

The driver amplifier 20 supplies an output to the power amplifier 21 which also receives an input from the power supply 22. The power amplifier 21 supplies an output to the matching unit 23 which drives the transducer 16. The matching unit 23 contains a precision voltage divider for permitting a portion of the voltage to be applied to the stabilization unit 24 which provides a feedback to the driver amplifier 20. The stabilization unit 24 also receives an input from the computer 34. This feedback system assures that the output to the transducer remains at the desired level and remains constant. The automatic keying unit 25 operates the timer during both treatment and calibration modes of operation. The attenuator 26 controls the output of the crystal oscillator 18.

The lesion generation system provides a means for producing small discrete focal lesions anywhere within the deep structures of the body without disturbing overlying tissue. The acoustic energy for lesion production is approximately 1,000 times the energy required for visualization and thus the lesion producing transducer may differ from that of the visualization transducer. However, for purposes of explanation, transducer 16 is illustrated as being used for both visualization and lesion generation systems. It is to be realized, of course, that it is well within the skill of those in the art to utilize one or two transducers for these two purposes.

During the lesion generation mode of operation, it has been discovered that specific tissue effects are found for exposure to high intensity ultra sound. For example, levels of energy above a certain threshold produce irreversible tissue modification whereas levels of energy below the threshold level do not permanently alter the tissue. It has also been discovered that the threshold energy levels for all tissue are not the same. The utilization of a focused transducer allows energy to be supplied to tissue at the focus point which has an intensity just above the threshold and thus tissue at the focus will be modified but other overlying or underlying tissue will not be affected by the ultrasonic irradiation.

FIG. 5 is a graph of acoustic intensity versus single pulse time duration to produce threshold lesions in white matter of the mammalian brain. There are three distinct types of lesions which are identifiable based on the intensity level and the time of application of the energy to the tissue. For short time, high intensity levels as, for example, for times of 10 milliseconds or less, along the curve of FIG. 5, cavitation generated lesions form. Cavitation generated lesions destroy all surrounding tissue and produce hemorrhaging at the site and have no selective effect. Cavitation generated lesions are immediately discernible. The cavitation generated lesions occur where there are cavitation nuclei which is generally in the vascular system fluid-material interface and does not exhibit the desired selective effect of acoustic lesions which occur in the range of 10 seconds to 10 milliseconds with the energies illustrated on the curve of FIG. 5. Such acoustic lesions formed in the 10 second to 10 milliseconds range on the curve of FIG. 5 has the selective capability of destroying certain cells and not destroying other cells. The acoustic energy in this time and energy range has an effect on the chemistry of the cell and has a threshold which varies for different cells. Also, it has been observed that there is no cumulative effect of energy in the range from 10 second to 10 milliseconds of the curve of FIG. 5, thus repetitive exposure to energy level below those illustrated in FIG. 5 do not accumulate. The lesions formed with the energy intensity and the time between 10 seconds and 10 milliseconds on the curve of FIG. 5 have different characteristics than lesions formed from cavitation generated lesions particularly in brain tissue. Acoustic generated focal lesions occur at the focus of the energy and thus may be very accurately formed with a focused ultrasonic transducer.

Also, the effect of forming acoustically generated focal lesions is more subtle. Surrounding cells are not destroyed as in the cavitation generated lesion process. The ultra sound causes the irradiated cells to cease to function instantaneously and there is a change in the transmembrane potential which causes dipolarization. For example, a nerve cell when subjected to acoustical energy above the threshold level will no longer propagate an electrical impulse and the myelin sheath of the nerve cells start to break up.

Acoustic generated lesions appear slowly and effect tertiary cellular structure. The changes occur from 10 minutes to an hour after radiation.

For radiations longer than 10 seconds on the curve of FIG. 5, thermal lesions occur. Forty-six degrees centigrade is the threshold of heat for the formation of thermal lesions and the selective effects for thermal lesions are not as good as acoustic generated lesions in the range of 10 seconds to 10 milliseconds.

The size of focus of an ultrasonic beam is related to the wave length and a frequency of 4 MHz can be focused to a volume as small as 0.04 cubic millimeters. Also, arrays can be used to produce lesions of any size.

The ability of acoustic radiation for destroying the ability of cells to transmit electrical pulses can be used in Parkinson's disease wherein the tremor condition caused by unbalance in the neural servo system often exists. Neural systems generally have a direct system and an excitatory system and by radiating the excitatory side, the tremor can be stopped without destroying the function served by the direct system. FIG. 4 illustrates the sound field calibration system wherein a very sensitive thermocouple probe is contained in a stainless steel housing 27 which has two thin plastic windows between which is mounted an absorbing medium. The thermocouple probe measures the temperature rise in the absorbing medium resulting from the absorption of acoustic energy when placed in the output path of the transducer 16 and supplies an output to amplifier 28. Amplifier 28 amplifies the output of the thermocouple probe and presents the output on a dual trace oscilloscope 29. The second channel of the oscilloscope 29 may be used to display the excitation voltage applied to the ultrasonic transducer 16. The oscilloscope display may be photographed with a camera 30 to record the input-output relative to the transducer 16. The sensitivity of the amplifier 28 and the oscilloscope 29 is checked by using a microvolt calibration standard 32 which may be selectively connected to apply an input to the amplifier 28. The time base of the display oscilloscope may be checked with a time-mark generator 31.

FIG. 6 is an electrical schematic view of a pulser 1 for producing the pulses 66 of the visualization system illustrated in FIG. 2. An input is applied from computer 34 to a transistor T1 through a capacitor C1 and a resistor R2. The resistor R1 is connected from terminal 71 to ground. The emitter of transistor T1 is connected to ground and the resistor R3 is connected between the emitter and collector. The resistor R13 is connected between the collector of transistor T1 and a suitable biasing source. A zener diode D1 is connected between the collector of transistor T1 and ground. A capacitor C2 and the primary of a transformer L1 are connected from the collector of transistor T1 to ground.

The secondary of transformer L1 is connected to the gate of an SCR through a resistor R4. Resistor R5 is connected between the gate and ground. The cathode of the SCR is connected to ground and the anode is connected to a suitable biasing source through a resistor R6 and an inductance L2. The anode is coupled through a capacitor C3 to a pair of output terminals 72 and 73 which are respectively connected to the transducer 16 and the receiver 2. The output pulse 66 is illustrated above the output terminals 72 and 73.

The pulser unit 1 provides the means of shock exciting the transducer with 1/4 -waves of phase excitation. Following excitation the phase is shifted such that the voltage supplied to the transducer provides actual dynamic breaking. The maximum range resolution of the system is obtained when the shortest possible excitation is utilized.

FIG. 7 illustrates the clamper and video amplifier portion of the receiver 2 of this invention. The clamper circuit is mounted ahead of the video amplifier of the receiver so as to protect the amplifier from high energy level signals from the pulser which are applied to the transducer 16. The input terminal 73 is connected to the transducer 16 and to the output of the pulser 1. The input terminal 73 is coupled through the capacitor C4 and inductor L3 to a pair of resistors R16 and R17 and to the base of a transistor T2. A pair of diodes D2 and D3 are connected between the junction point of the inductor L3 and resistor R16 and ground. The anode of diode D3 is connected to ground and the cathode of diode D2 is connected to ground.

The emitter of transistor T2 is connected to the input of the video amplifier through capacitor C10. Operational amplifier 94 which might be for example type MC 151OG receives the output of the clamper circuit and applies an output through resistor R26 and capacitor C12 to the base of output transistor T3. The collector of transistor T3 is coupled to the output terminal 85 through a capacitor C14.

In the clamper circuit, the collector of transistor T2 is connected to a suitable biasing source through a resistor R21. A capacitor C8 is connected between the collector of transistor T2 and ground. A resistor R19 is connected between a suitable biasing source and the resistor R20 which is connected to the emitter of T2. A capacitor C9 is connected from the resistor R20 to ground. Diode D7 has its cathode connected to the base of transistor T2 and its anode to ground. A diode D6 has its anode connected to the base of transistor T2 and its cathode connected to a capacitor C7 which has its other side grounded. A resistor R18 is in parallel with capacitor C7.

A capacitor C5 is connected to the junction point between resistors R16 and R17 and has its other side connected to a pair of diodes D4 and D5. The diode D5 has its cathode connected to ground and the diode D4 has its anode connected to a capacitor C6 and a resistor R15. The other side of the resistor R15 is connected to a wiper contact 90 which engages a resistor R14. A suitable biasing voltage is connected to one end of the resistor R14 and the other end is connected to ground.

The emitter of transistor T3 is connected to a suitable bias source through resistor R30 which has a capacitor C13 in parallel with it. A diode D8 has its cathode connected to ground and its anode connected to resistors R25 and R31. The other side of resistor R25 is connected to the operational amplifier 94 and to a capacitor C11 which has its other side connected to ground. Resistor R31 is connected between the resistor R30 and resistor R25. A resistor R29 is connected from the base of transistor T3 to the resistor R31. A resistor R32 is connected between resistors R22 and R28 which has its other side connected to the collector of transistor T3. Resistor R33 is connected between the base of transistor T3 and resistor R32.

In operation when the pulser 1 puts out a signal it is received on input terminal 73 of the of the clamper and the diodes D2, D3, D5, D6 and D7 clamp the high energy pulses to ground thus preventing the input of the video amplifier from being saturated. If it were saturated it would not recover in time to detect the very low level echo pulses reflected from the tissue under study. After the pulser signal has been turned off an echo from the tissue under study will be received from the transducer 16 and will pass to input terminal 73 and through the transistor T2 to the video amplifier comprising the operational amplifier 94 and the output transistor T3. The amplifier will not be saturated due to the clamping action which occurred when the high power output signal was received at input terminal 73 from the pulser 1.

The dynamic range of ultrasonic echoes may extend over several orders of magnitude and as such, is beyond the capability of most display units. Compression of the dynamic range to fit within the limits of the display is not the best solution; rather, a selection of the appropriate proportion of the dynamic range of the returning echoes which contain information of diagnostic value is the best approach to the display problem.

To achieve this objective, the ultrasonic instrumentation described in this invention provides means for examining the A-mode display of returning echoes. The magnitude of the echoes may be adjusted such that the important echoes fall within the display capabilities of this unit. The video display unit is designed so that 1 v of video input signal produces the maximum z-axis intensity which can be recorded on the photographic material with the aperture set at f16, and 0.1 v is the least detectable z-axis intensity which can be recorded. This 10 to 1 range is the limitation imposed only by the photographic material; it is not an inherent limitation of the other parts of the system. By increasing the aperture to large values, the dynamic range can be expanded to correspond to a smaller change in voltage. At f4, the full range from minimal detectable signal to saturation is increased to 0.1 v change in video input level, i.e., 0.2 v results in saturation and 0.1 v is the minimum detectable signal. Thus, a small change in input signal can be represented by a large change in the z-axis intensity.

The operator is provided with a control over: (1) the video intensity which is the voltage range of the video signal; (2) the camera intensity, which is a D.C. offset on the video signal; and, (3) the aperture.

By appropriately adjusting these controls, the operator can select any portion of a video signal to correspond with any part of the dynamic range of the display unit. In order to quantitate the intensity of the specific echoes which may be important in differential diagnosis, it is desirable to be able to measure the intensity of specific echoes. This can be done best by making voltage measurements from the raw video data. The probelm arises as to determining the correspondence between the anatomical information on the one hand and the video signal on the other. This is accomplished by the use of an electronic marker to display a specific line of the two-dimensional B-mode raster, which identifies for the operator the relationship between the anatomy and the corresponding video signal.

An alternative method of measuring the intensity of signals, that makes use of a relative rather than absolute intensity measurment, is the photocell unit connected to the display. The photocell can be utilized to determine the boundaries of the signal in some specific location corresponding to a particular morphological feature. Control of the display can be accomplished either manually or automatically by varying the three controls mentioned above.

Identification of ultrasonic echo data and interpretation of echograms are materially aided by the availability of atlas overlay data. These data may be stored as acetate transparencies which can be moved over the face of the display unit to achieve a one-to-one correspondence between atlas overlay and anatomical features depicted by the ultrasound. Atlas information may also be stored within the computer and displayed electronically by adding this input to the video signals. Reference coordinates, as well as other pertinent information, may be printed on the margin of the echogram through signals generated by the computer. Thus, the physician is able to relate the anatomical atlas to the echogram by a simple inspection of the composite picture.

The transducer utilized in this invention may have a large aperture, high sensitivity and comprise a high resolution device. The transducer may be made of a ferro-electric element mounted in a stainless steel housing and electrical input and output may be connected to the element through a matching circuit which receives a coaxial cable fitting. Matching layers and damping layers are provided to improve the resolution capability and to provide for better energy transfer. Damping of the acoustic element is important for range resolution although excessive viscous damping may produce losses which are important in the high energy handling capacity of the transducer. Thus, electrical damping is desirable for achieving the desired damping. Heat dissipation is also minimized through the selection of an appropriate ferro-electric material.

Lead metaniobate crystals provide a suitable ferro-electric material for the transducer of this invention. Such crystals effectively dissipate heat. Heat dissipation becomes important when the transducer is used in the lesioning mode. Means are provided to improve the heat exchange between the transducer and the coupling medium in which the transducer is immersed. The energy coupled to the coupling medium from the transducer transmits the sound to the tissue under treatment.

Thus, it is seen that this invention provides means for studying tissue within the body of an animal by transmitting ultrasonic energy with a focusing transducer which is scanned over tissue and echoes are received from the tissue at the focal point of the transducer and are returned for presentation to the operator. The transducer may be moved to vary the distance from the patient such that the focal point of the transducer will occur at different layers in the tissue such that echograms can be obtained from the desired tissue layer. The presentation means is synchronized with the scanning means of the transducer so that a suitable echogram may be received. After the echogram has been studied, tissue may be destroyed by selectively subjecting it to much higher levels of ultra sound energy which is applied by a transducer focused on the desired points of lesioning. The formation of the lesions may be observed by utilizing the visualization mode of the equipment so as to assure that lesions occur at the desired locations.

Thus, the invention provides means for performing surgery at internal portions of the body without incision to such portions and without injury to tissue on either side of the destroyed tissue. Thus the chance of infection and shock to the patient are substantially reduced and the time required for the patient to remain in the hospital is substantially decreased.

Although the invention has been described with respect to preferred embodiments, it is not to be so limited as changes and modifications may be made therein which are within the full intended scope as defined by the appended claims.

Claims

What we claim is:

1. Apparatus for observing and diagnosing animal tissue and selectively destroying tissue comprising:

a computer having first means for transmitting and scanning a focused ultrasonic beam having a relatively low energy level into said animal;

said computer including means for receiving an echo of ultrasonic energy from said tissue and presenting said echo for observation or by holographic and transmission methods;

said computer having means for calculating and indicating the aiming point of a focused ultrasonic beam,

second means for transmitting into said animal said focused ultrasonic beam having an energy level high enough to selectively destroy cells of said animal,

comprising means for scanning and focusing said first and second means on the same tissue,

including alternately transmitting and scanning said tissue with said first and second means such that lesions formed by said second means are visually presented for observation.

2. Apparatus according to claim 1 comprising means for superimposing anatomical atlases on said echoes for comparing said tissue under observation with standard tissue.

3. Apparatus according to claim 1 including anatomical atlas information stored in said computer for presentation with the echoes of said first means.

4. Apparatus according to claim 1 wherein said first means includes a transducer for transmitting and receiving ultra sound energy from said tissue, a pulser attached to said transducer for transmitting ultra sound energy, and a receiver attached to said transducer for detecting said echoes.

5. Apparatus according to claim 4 including a clamping circuit connected between said receiver and said transducer for preventing energy above a predetermined level from passing into said receiver.

6. Apparatus according to claim 1 comprising third means for calibrating said first and second means.

7. Apparatus according to claim 5 wherein said third means includes a thermocouple for detecting and calibrating energy in the beam of said first and second means.

8. A method for performing human and animal surgery on the tissue field including focusing a low energy ultrasonic beam on a certain region of the body, receiving with a computer producing and displaying the aiming point for a second ultrasonic beam, focusing the second ultrasonic beam for producing the surgical lesions in correct geometrical relationship with respect to the surgical field and appropriate tissues and receiving and displaying with said computer the surgical lesions as they are formed.