U.S. patent number 3,735,755 [Application Number 05/157,160] was granted by the patent office on 1973-05-29 for noninvasive surgery method and apparatus.
Invention is credited to Reginald C. Eggleton, Francis J. Fry.
United States Patent |
3,735,755 |
Eggleton , et al. |
May 29, 1973 |
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.
Inventors: |
Eggleton; Reginald C.
(Champaign, IL), Fry; Francis J. (Champaign, IL) |
Family
ID: |
22562583 |
Appl.
No.: |
05/157,160 |
Filed: |
June 28, 1971 |
Current U.S.
Class: |
601/3 |
Current CPC
Class: |
A61B
8/0808 (20130101); A61B 17/22004 (20130101); A61B
8/00 (20130101); A61N 7/02 (20130101) |
Current International
Class: |
A61B
17/22 (20060101); A61B 8/00 (20060101); A61N
7/02 (20060101); A61N 7/00 (20060101); A61h
029/00 () |
Field of
Search: |
;128/24,24A,303,303.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Trapp; Lawrence W.
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.
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.
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