U.S. patent application number 10/171149 was filed with the patent office on 2003-01-23 for method and apparatus for medical procedures using high-intensity focused ultrasound.
Invention is credited to Carter, Stephen J., Crum, Lawrence A., Gaps, Michael, Helton, W. Scott, Kaczkowski, Peter J., Keilman, George, Martin, Roy W., Proctor, Andrew, Vaezy, Shahram.
Application Number | 20030018255 10/171149 |
Document ID | / |
Family ID | 25505252 |
Filed Date | 2003-01-23 |
United States Patent
Application |
20030018255 |
Kind Code |
A1 |
Martin, Roy W. ; et
al. |
January 23, 2003 |
Method and apparatus for medical procedures using high-intensity
focused ultrasound
Abstract
Methods and apparatus for enabling substantially bloodless
surgery and for stemming hemorrhaging. High intensity focused
ultrasound ("HIFU") is used to form cauterized tissue regions prior
to surgical incision, for example, forming a cauterized tissue
shell around a tumor to be removed. The procedure is referred to as
"presurgical volume cauterization." In one embodiment, the method
is particularly effective for use in surgical lesion removal or
resection of tissue having a highly vascularized constitution, such
as the liver or spleen, and thus a propensity for hemorrhaging. In
further embodiments, methods and apparatus for hemostasis using
HIFU is useful in both surgical, presurgical, and medical emergency
situations. In an apparatus embodiment, a telescoping, acoustic
coupler is provided such that depth of focus of the HIFU energy is
controllable. In other embodiments, apparatus characterized by
portability are demonstrated, useful for emergency medical
situations.
Inventors: |
Martin, Roy W.; (Seattle,
WA) ; Crum, Lawrence A.; (Seattle, WA) ;
Vaezy, Shahram; (Seattle, WA) ; Carter, Stephen
J.; (LaConner, WA) ; Helton, W. Scott;
(Kirkland, WA) ; Gaps, Michael; (Seattle, WA)
; Kaczkowski, Peter J.; (Seattle, WA) ; Proctor,
Andrew; (Duvall, WA) ; Keilman, George;
(Woodinville, WA) |
Correspondence
Address: |
Office of Eugene H. Valet
PMB 3
4742 42nd Ave SW
Seattle
WA
98116
US
|
Family ID: |
25505252 |
Appl. No.: |
10/171149 |
Filed: |
June 13, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10171149 |
Jun 13, 2002 |
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09390032 |
Sep 3, 1999 |
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6432067 |
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09390032 |
Sep 3, 1999 |
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08961972 |
Oct 31, 1997 |
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6007499 |
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Current U.S.
Class: |
600/437 |
Current CPC
Class: |
A61B 2017/22008
20130101; A61B 2017/320052 20130101; A61N 2007/027 20130101; A61B
8/4209 20130101; A61B 17/22004 20130101; A61B 90/50 20160201; A61N
2007/0065 20130101; A61N 7/02 20130101; A61B 2017/320069 20170801;
A61B 2090/0472 20160201; A61N 2007/0091 20130101; A61B 2017/320071
20170801; A61B 8/4281 20130101; A61B 8/14 20130101; A61B 8/4254
20130101; A61B 2017/320082 20170801; A61B 8/4218 20130101; A61B
17/2255 20130101; A61B 2017/12004 20130101; A61N 2007/0069
20130101; A61B 17/2251 20130101; A61N 2007/0078 20130101; A61B
2017/320095 20170801; A61B 8/4461 20130101 |
Class at
Publication: |
600/437 |
International
Class: |
A61B 008/00 |
Goverment Interests
[0001] The invention described herein was made in the course of
work under a grant or award from the U.S. Department of Defense,
Office of Naval Research.
Claims
What is claimed is:
1. A method of performing surgery with minimized bleeding,
comprising the steps of: a) determining each path of incision to be
made in a tissue volume; b) cauterizing each path using ultrasonic
energy to form at least one surgical pathway in the tissue volume
prior to incising; and c) making surgical incisions only along a
surgical pathway formed in accordance with step b).
2. The method as set forth in claim 1, the step of cauterizing
further comprising the step of: isolating a region of tissue from
the blood supply to the region.
3. The method as set forth in claim 1, the step of cauterizing
further comprising the step of: encapsulating a volume of tissue
with an encasement of coagulative necrosed tissue.
4. The method as set forth in claim 1, the step of cauterizing
further comprising the step of: surrounding a tissue volume to be
surgically excised with a coagulated necrotized surface of tissue
having a predetermined thickness.
5. The method as set forth in claim 1, said step of cauterizing
further comprising the step of: using high intensity focused
ultrasound energy at a level sufficient to produce coagulation and
necrosis in the tissue along each pathway.
6. The method as set forth in claim 1, said step of cauterizing
further comprising the step of: applying ultrasonic energy having a
frequency in the range of 0.5 MHZ to 20 MHz.
7. The method as set forth in claim 1, said step of cauterizing
further comprising the steps of: A) determining a first point on an
edge of a plane of a path to be cut; B) focusing the energy to have
a first focal point at the first point; C) moving the first focal
point to follow the edge of the plane, producing a first line of
coagulation having a cross-sectional width; D) refocusing the
energy to have a second focal point aligned with the first line and
proximate to the first point; E) moving the second focal point to
follow the plane of the path to be cut, producing a second line of
coagulation along said plane; and F) repeating said steps of
refocusing and moving until the plane for incision is substantially
entirely coagulated.
8. The method as set forth in claim 7, further comprising the steps
of: repeating steps A) through F) for each path of incision.
9. The method as set forth in claim 7, said step of cauterizing
further comprising the step of: applying ultras sonic energy
causing a temperature gradient at each focal point in a range of
approximately 59.degree. C. to approximately 99.degree. C.
10. The method as set forth in claim 7, said step of cauterizing
further comprising the step of: applying ultrasonic energy causing
an intensity of acoustic radiation at each focal point in a range
of approximately 1000 W/cm.sup.2 to approximately 3000
W/cm.sup.2.
11. A method for presurgical treatment of highly vascularized
organic tissue to minimize bleeding during surgical procedures, the
method comprising the steps of: determining each path of incision
to be made in the tissue; and exposing each path to high intensity
focused ultrasound energy having a predetermined frequency for a
time period sufficient to form at least one coagulative necrosed
pathway in the tissue such that making subsequent surgical
incisions only along a coagulative necrosed pathway is subject to
minimized bleeding.
12. The method as set forth in claim 11, further comprising the
steps of: determining each path of incision necessary to remove a
volume of tissue including a lesion from the tissue; and
surrounding the volume of tissue to be surgically excised with a
coagulated necrotized surface having a predetermined thickness
permitting surgical incisions there through.
13. The method as set forth in claim 11, further comprising the
steps of: determining each path of incision necessary to resection
the tissue; and prior to incising the tissue, cauterizing each path
using high frequency focused ultrasound energy to form at least one
coagulative necrosed pathway in the tissue such that making
surgical incisions only along a coagulative necrosed pathway
minimizes bleeding.
14. The method as set forth in claim 11, further comprising the
step of: applying ultrasound energy having a frequency in the range
of 0.5 MHZ to 20 MHz.
15. The method as set forth in claim 11, the step of exposing
further comprising: the ultrasonic energy causing an intensity of
acoustic radiation at each focal point in a range of approximately
1000 W/cm.sup.2 to approximately 3000 W/cm.sup.2 for a duration of
time such that hyper-thermic effects or a combination of
hyper-thermic effects and cavitation effects are produced in the
tissue.
16. A method for causing hemostasis comprising the steps of: baring
a hemorrhaging blood vessel or parenchyma; and exposing said blood
vessel or parenchyma to sonic energy comprising high intensity
focused ultrasound such that said hemorrhaging blood vessel or
parenchyma is cauterized by said sonic energy.
17. The method as set forth in claim 16, the step of exposing
further comprising the step of: applying ultrasound energy having a
frequency in the approximate range of 0.5 MHZ to 20 MHz.
18. A method for causing hemostasis in a visible hemorrhaging
wound, comprising the steps of: using a transducer means, having an
ultrasonic transducer having a transmitting surface emitting high
frequency focused ultrasound having a frequency in the approximate
range of 0.5 MHZ to 20 MHz and a depth of focus substantially
immediately adjacent said transducer means, applying high intensity
focused ultrasound energy onto outer regions of a hemorrhaging
vessel adjacent to a vascular breach; and controlling energy level
and the duration of exposure to cause closure of fibrous sheath
tissue surrounding the breach of the hemorrhaging vessel without
substantially damaging wall tissue of the vessel itself.
19. A presurgical device for preparing an organ of a patient for
surgical incisions, comprising: a transducer means for emitting
energy as high frequency focused ultrasound; and means for
controlling focal position and focal intensity of energy emissions
from said transducer means such that acoustic energy at selective
focal zones produces coagulative necrosed tissue in the form of
predetermined surgical pathways within the tissue such that
surgical incisions along the surgical pathways is subject to
substantially no bleeding.
20. The device as set forth in claim 19, further comprising: tissue
backing means for protecting tissue beyond a selective focal zone
from exposure effects of emitted energy from the transducer.
21. The device as set forth in claim 20, said tissue backing means
further comprising: an acoustic energy absorber having an acoustic
impedance approximately equal to acoustic impedance of the tissue
at the frequency of the emitted energy and a thickness and thermal
properties such that abutting the tissue does not become heated by
said absorber.
22. The device as set forth in claim 20, said tissue backing means
further comprising: means for reflecting said emitted energy back
to said focal zone.
23. The device as set forth in claim 19, further comprising: said
transducer means emits high intensity focused ultrasound energy
having a depth of focus and depth of field in respective ranges in
combination with said means for controlling such that the device
provides cauterization of visible hemorrhaging.
24. The device as set forth in claim 19, said transducer means
further comprises: said transducer means having at least one
surface for emitting acoustic energy having a frequency in the
range of 0.5 MHZ to 20 MHz; and mounted to said transducer, means
for acoustically coupling said energy to the tissue, including a
liquid-filled chamber mounted proximate said surface and having an
acoustic energy window at a position distal from said surface and a
means for varying gap distance from said surface to said window
such that depth of said selective focal zone position changes as
said gap distance is increased and decreased using said means for
varying gap distance.
25. The device as set forth in claim 24, wherein said means for
acoustically coupling further comprises: a telescoping construct
having a fully retracted position providing a shallow tissue
penetration depth of focus, a fully extended position providing a
predetermined deep tissue penetration depth of focus, and providing
a substantially continuous range of depth of focus positions
between said shallow tissue penetration depth of focus and said
deep tissue penetration depth of focus.
26. The device as set forth in claim 25, said telescoping construct
further comprising: first means for mounting a high intensity
focused ultrasound transducer and for providing an acoustic
coupling medium chamber adjacent the transducer; and second means
for mounting an acoustic window for focusing ultrasound energy
emitted by said transducer, wherein said second means is coupled to
said first means by a screw-type interface such that a gap between
said transducer and said acoustic window is variable such that
depth of focus of the ultrasound energy is selected by using said
screw-type interface to vary the gap.
27. The device as set forth in claim 25, said telescoping construct
further comprising: first means for mounting a high intensity
focused ultrasound transducer and for providing an acoustic
coupling medium chamber adjacent the transducer; and second means
for mounting an acoustic window for focusing ultrasound energy
emitted by said transducer, wherein said second means is coupled to
said first means by a bellows-type interface such that a gap
between said transducer and said acoustic window is variable such
that depth of focus of the ultrasound energy is selected by using
said bellows-type interface to vary the gap.
28. A method of using high intensity focused ultrasound for
surgical procedures, comprising the steps of: prior to incising
tissue of a surgery patient, applying ultrasonic energy at a
combination of frequency, time of exposure, and power intensity to
cause controlled coagulation and necrotization of tissue in the
patient such that a volume cauterized tissue region is formed in
said tissue at predetermined locations within said tissue that are
to be cut.
29. A high intensity focused ultrasound medical instrument for use
with an electronic controller means, the instrument comprising: a
pencil-like handle; fixedly mounted on a tip of the handle, sealed
acoustic coupling means for interfacing ultrasonic energy into a
patient; mounted subjacent the acoustic coupling means, ultrasound
transducer means, including at least one transducer for emitting
ultrasonic energy through the acoustic coupling means such that a
focal region is produced immediately adjacent the acoustic coupling
means; and incorporated through the handle, means for coupling the
transducer means to the electronic controller.
30. A high intensity focused ultrasound medical instrument for use
with an electronic controller means, the instrument comprising: a
palm-of-the-hand shaped and dimensioned handle; fixedly mounted on
a first surface of the handle, sealed acoustic coupling means for
interfacing ultrasonic energy into a patient; mounted on a second
surface of the handle subjacent the acoustic coupling means,
ultrasound transducer means, including at least one transducer for
emitting sonic energy through the acoustic coupling means; and
mounted on a third surface of the handle opposing the first
surface, means for coupling the transducer means to the electronic
controller.
31. The instrument as set forth in claim 30, said transducer means
further comprising: at least one imaging transducer; at least one
high intensity focused ultrasonic transducer means for emitting
ultrasonic energy through said acoustic coupling means in a
frequency in an approximate range of 0.5 MHZ to 20 MHz.
32. The instrument as set forth in claim 31, said high intensity
focused ultrasonic transducer means further comprising: a plurality
of transducers forming a discretely targetable set of ultrasonic
emitters.
33. The instrument as set forth in claim 31, said high intensity
focused ultrasonic transducer means further comprising: an annular
array transducer system.
34. A method for causing hemostasis of an internal hemorrhage,
comprising the steps of: without surgical incision, exposing a
blood vessel or parenchyma source of said hemorrhage to sonic
energy comprising high intensity focused ultrasound such that said
hemorrhaging blood vessel or parenchyma is cauterized by said sonic
energy.
35. The method as set forth in claim 34, the step of exposing
further comprising the step of: closing a shunt or other internal
bleeding without affecting or cutting through adjacent tissue.
36. The method as set forth in claim 35, the step of exposing
further comprising the step of: occluding a blood vessel feeding
the shunt, the shunt itself, or the vessel receiving shunt blood
flow.
37. The method as set forth in claim 35, the step of exposing
further comprising the step of: coagulating a specific volume of
tissue encompassing a whole tissue region or malformation of a
blood vessel feeding the shunt, the shunt, and the vessel receiving
the shunt.
Description
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to uses of
ultrasonics in medical technology applications, more particularly
to a method and apparatus for performing presurgical and surgical
procedures using high-intensity focused ultrasound.
[0004] 2. Description of Related Art
[0005] Studies in the use of ultrasound--sound with frequency above
20,000 Hz, the upper limit of human hearing--began in the early
1940's [see e.g., A New Method for the Generation and Use of
Focused Ultrasound in Experimental Biology, Lynn et al., Focused
Ultrasound in Experimental Biology, Journal of General Physiology,
1943, pp. 179-193]. It is widely accepted that the first refined
system for the use of ultrasound in the medical arts was developed
by William and Francis Fry at the University of Illinois, Urbana,
in the 1950's (a paper was published as part of the Scientific
Program of the Third Annual Conference of the American Institute of
Ultrasonics in Medicine, Washington D.C., Sep. 4, 1954, pp.
413-423).
[0006] In the main, research and development has been concerned
with diagnostic and therapeutic applications. Therapeutic
ultrasound refers to the use of high intensity ultrasonic waves to
induce changes in tissue state through both thermal
effects--induced hyperthermia--and mechanical effects--induced
cavitation. High frequency ultrasound has been employed in both
hyper-thermic and cavitational medical applications, whereas low
frequency ultrasound has been used principally for its cavitation
effect. Diagnostic medical ultrasonic imaging is well known, for
example, in the common use of sonograms for fetal examination.
[0007] Various aspects of diagnostic and therapeutic ultrasound
methodologies and apparatus are discussed in depth in an article by
G. ter Haar, Ultrasound Focal Beam Surgery, Ultrasound in Med.
& Biol., Vol. 21, No. 9, pp. 1089-1100, 1995, and the IEEE
Transactions on Ultrasonics, Ferroelectrics, and Frequency Control,
November 1996, Vol. 43, No. 6 (ISSN 0885-3010). The IEEE journal is
quick to point out that: "The basic principles of thermal effects
are well understood, but work is still needed to establish
thresholds for damage, dose effects, and transducer characteristics
. . . . " Id., Introduction , at page 990.
[0008] In high-intensity focused ultrasound (HIFU) hyperthermia
treatments, intensity of ultrasonic waves generated by a highly
focused transducer increases from the source to the region of focus
where it can reach a very high temperature, e.g. 980 Centigrade.
The absorption of the ultrasonic energy at the focus induces a
sudden temperature rise of tissue--as high as one to two hundred
degrees Kelvin/second which causes the irreversible ablation of the
target volume of cells, the focal region. Thus, for example, HIFU
hyperthermia treatments can cause necrotization of an internal
lesion without damage to the intermediate tissues. The focal region
dimensions are referred to as the depth of field, and the distance
from the transducer to the center point of the focal region is
referred to as the depth of focus. In the main, ultrasound is a
promising non-invasive surgical technique because the ultrasonic
waves provide a non-effective penetration of intervening tissues,
yet with sufficiently low attenuation to deliver energy to a small
focal target volume. Currently there is no other known modality
that offers noninvasive, deep, localized focusing of non-ionizing
radiation for therapeutic purposes. Thus, ultrasonic treatment has
a great advantage over microwave and radioactive therapeutic
treatment techniques.
[0009] A major issue facing the use of HIFU techniques is
cavitation effects. In some quarters, it is recognized that
cavitation can be used advantageously. See e.g., Enhancement of
Sonodynamic Tissue Damage Production by Second-Harmonic
Superimposition: Theoretical Analysis of Its Mechanism, Unmemura et
al. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency
Control, Vol. 43, No. 6, 11/96 at page 1054. Cavitation can occur
in at least three ways important for consideration in the use of
ultrasound for medical procedures. The first is gaseous cavitation,
where dissolved gas is pulled from solution during a negative
pressure phase of an acoustic wave. The second is vaporous
cavitation due to the negative pressure in the negative pressure
phase becoming low enough for a fluid to convert to its vapor form
at the ambient temperature of the tissue fluid. The third is where
the ultrasonic energy is absorbed to an extent to raise the
temperature above boiling at ambient pressure. At lower
frequencies, the time that the wave is naturally in the negative
pressure phase is longer than at higher frequencies, providing time
for gas or vapor to come out of the fluid. All other factors being
equal, a lower frequency will have a lower intensity level for
cavitation than a higher frequency. Higher frequencies are more
rapidly absorbed and therefore raise the temperature more rapidly
for the same applied intensity than a lower frequency. Thus,
gaseous and vaporous cavitation are promoted by low frequencies and
boiling cavitation by high frequency.
[0010] For HIFU applications it has been found that ultrasonically
induced cavitation occurs when an intensity threshold is exceeded
such that tensile stresses produced by acoustic rarefaction
generates vapor cavities within the tissue itself. Subsequent
acoustic compressions drive the cavities into a violent, implosive
collapse; because non-condensing gases are created, there are
strong radiating pressure forces that exert high shear stresses.
Consequently, the tissue can shred or be pureed into an essentially
liquid state. Control of such effects has yet to be realized for
practical purposes; hence, it is generally desirable to avoid
tissue damaging cavitation whenever it is not a part of the
intended treatment.
[0011] Another problem facing the designer of ultrasound medical
devices is that the attenuation and absorption rate of ultrasound
in tissue is known to exponentially increase in proportion to the
frequency. In other words, a very high frequency, e.g., 30 MHz wave
would be absorbed nearly immediately by the first tissue it is
applied to. Yet, lower frequencies, e.g., 30 KHz-60 KHz, are
associated with cavitation effects because of the longer
rarefaction time periods, allowing gaseous vapor formation. Thus,
the effect of ultrasound energy is quite different at a frequency
of 30 KHz versus 30 MHz. The rate of heat generation in tissue is
proportional to the absorption constant. For example, for the
liver, the attenuation constant is approximately 0.0015 at 30 KHz,
but is approximately 0.29 at 3 MHz. Therefore, all other variables
being equal, the heat generated in liver tissue is about 190 times
greater at 3 MHz than at 30 KHz. While this means hyperthermia can
be achieved more quickly and to a much greater level with high
frequencies, the danger to intervening tissue between the
transducer and the focal region is much more prevalent.
[0012] Thus, there is a continuing need in the field for means of
improving heating penetration, spatial localization, and dynamic
control of ultrasound for medical applications, along with the
discovery of new methodologies of their use.
[0013] An even less explored field of ultrasound use is as a direct
surgical tool for non-invasive surgical procedures. While
ultrasound has been used as a electromechanical driver for cutting
tool implementations (see e.g., U.S. Pat. No. 5,324,299 to Davison
et al. for an ultrasonic scalpel blade, sometimes referred to as a
"harmonic scalpel"), the use of ultrasonic radiation directly in a
device for performing presurgical and surgical procedures, rather
than therapeutic procedures, has been limited. An ultrasonic
diagnostic and therapeutic transducer assembly and method of use
for ophthalmic therapy is shown by Driller et al. in U.S. Pat. No.
4,484,569. The acoustic coupler in the Driller device is a
fluid-filled, conical shell, mounted to a transducer apparatus and
having a flexible membrane across the apertured, distal end of the
cone. Depth of focus is controlled by changing the aperture size
and the spacing from the focal point of a fixed focal point
transducer by using cones of varying axial length. The problem with
this construct is that the focal point is fixed and that the cones
must be manually changed (compare Driller's FIG. 2 and FIG. 5).
[0014] During invasive surgery, an obvious primary problem is
bleeding. The most common surgical technique in the state of the
art for coagulating bleeding vessels is to apply an electrical
cauterizing probe to the bleeding site (see, e.g., U.S. Pat. No.
4,886,060, to Wiksell for an ultrasonically driven, oscillating
knife having a means for emitting high-frequency electrical energy
which induces heat in the tissue). However, if a bleeding vessel is
more than about 1.5 mm in diameter, or in an organ such as the
liver, which is highly vascularized and where uncontrolled
hemorrhage is the primary cause of death in hepatic trauma, direct
electro-cauterization is ineffective. A more complicated technique
of clamping of a large blood vessel and electrical cauterization
via the clamp or with laser light can sometimes be effective. A
major problem that is not solved with either electrical or laser
cauterization techniques is the control of a rapidly bleeding
vessel because the blood egress is often sufficiently large enough
to carry the heat away before coagulation or tissue necrosis is
accomplished. In liver surgery, neither is effective. Moreover,
organs such as the liver and spleen are subject to bleeding
profusely from cracks in the parenchyma, which is usually diffuse
and non-pulsatile due to the large number of small vessels. In
another example, the control of bleeding is the most important
variable in determining the length of neurosurgical craniotomy
procedures.
[0015] Another important application in need of technologically
advanced medical treatment is for emergency hemorrhaging
situations, e.g., an accidently severed femoral artery, massive
internal bleeding, or puncture wounds due to bullets, knives, or
automobile accidents. Prompt stemming of visible hemorrhaging is
literally a matter of life or death. Standard procedure to arrest
visible bleeding is to maintain pressure on the puncture site until
coagulation is sufficient to stem the flow of blood. Without
sophisticated hospital equipment and invasive surgery, the problem
of internal bleeding lacks suitable emergency treatment
devices.
[0016] The present invention meets the various needs in the field
of technology by presenting a method and apparatus using high
intensity focused ultrasound for inducing coagulative necrosis and
hemostasis that can be used in presurgical procedures such that
substantially bloodless surgery can be achieved. The present
invention further provides methods and apparatus using high
intensity focused ultrasound for stemming hemorrhaging in emergency
situations or with organs where tradition methodologies are
ineffective.
SUMMARY OF THE INVENTION
[0017] In its basic aspects, the present invention provides a
method of performing surgery with minimized bleeding, including the
steps of: determining each path of incision to be made in a tissue
volume; cauterizing each path using ultrasonic energy to form at
least one surgical pathway in the tissue volume prior to incising;
and making surgical incisions only along a surgical pathway.
[0018] In another basic aspect, the present invention provides a
method for presurgical treatment of highly vascularized organic
tissue to minimize bleeding during surgical procedures including
the steps of: determining each path of incision to be made in the
tissue; and prior to incising the tissue, exposing each path to
high intensity focused ultrasound energy having a predetermined
frequency for a time period sufficient to form at least one
coagulative necrosed pathway in the tissue such that making
surgical incisions only along a coagulative necrosed pathway is
subject to minimized bleeding.
[0019] In another basic aspect, the present invention provides a
method for causing hemostasis including the steps of: exposing a
hemorrhaging blood vessel or parenchyma; and exposing said blood
vessel or parenchyma to sonic energy comprising high intensity
focused ultrasound such that said hemorrhaging blood vessel or
parenchyma is cauterized by said sonic energy.
[0020] In another basic aspect, the present invention provides a
presurgical device for preparing an organ of a patient for surgical
incisions. The device includes: a transducer mechanism for emitting
energy as high frequency focused ultrasound; and a mechanism for
controlling focal position and focal intensity of energy emissions
from said transducer such that acoustic energy at selective focal
zones produces coagulative necrosed tissue in the form of
predetermined surgical pathways within the tissue such that
surgical incisions along the surgical pathways is subject to
substantially no bleeding. Various embodiments of devices are
disclosed, including screw-type and bellows-type focusing
apparatus.
[0021] In another basic aspect, the present invention provides a
method for causing hemostasis in a visible hemorrhaging wound,
including the steps of: using a transducer means, having an
ultrasonic transducer having a transmitting surface emitting high
frequency focused ultrasound having a frequency in the approximate
range of 0.5 MHZ to 20 MHz and a depth of focus substantially
immediately adjacent said transducer means, applying high intensity
focused ultrasound energy onto outer regions of a hemorrhaging
vessel adjacent to a puncture; and controlling energy level and the
duration of exposure to cause closure of fibrous sheath tissue
surrounding the puncture of the hemorrhaging vessel without
substantially damaging wall tissue of the vessel itself.
[0022] In another basic aspect, the present invention provides a
method for causing hemostasis of an internal hemorrhage, without
surgical incision, by exposing a blood vessel or parenchyma source
of the hemorrhage to sonic energy comprising high intensity focused
ultrasound such that the hemorrhaging blood vessel or parenchyma is
cauterized by the sonic energy.
[0023] In another basic aspect, the present invention provides a
method of using high intensity focused ultrasound for surgical
procedures, including the steps of: prior to incising tissue of a
surgery patient, applying ultrasonic energy at a combination of
frequency, time of exposure, and power intensity to cause
controlled coagulation and necrotization of tissue in the patient
such that a volume cauterized tissue region is formed in said
tissue at predetermined locations within said tissue that are to be
cut.
[0024] In another basic aspect, the present invention provides a
high intensity focused ultrasound medical instrument. The
instrument includes a pencil-like handle; fixedly mounted on a tip
of the handle, a sealed acoustic coupling mechanism for interfacing
ultrasonic energy into a patient; mounted subjacent the acoustic
coupling mechanism, a ultrasound transducer mechanism, including at
least one transducer for emitting ultrasonic energy through the
acoustic coupling mechanism such that a focal region is produced
immediately adjacent the acoustic coupling mechanism; and,
incorporated through the handle, mechanisms for coupling the
transducer mechanism to an electronic controller.
[0025] In another basic aspect, the present invention provides a
high intensity focused ultrasound medical instrument including a
palm-of-the-hand shaped and dimensioned handle; fixedly mounted on
a first surface of the handle, a sealed acoustic coupling mechanism
for interfacing ultrasonic energy into a patient; mounted on a
second surface of the handle subjacent the acoustic coupling
mechanism, an ultrasound transducer mechanism, including at least
one transducer for emitting sonic energy through the acoustic
coupling mechanism; and mounted on a third surface of the handle
opposing the first surface, mechanisms for coupling the transducer
mechanism to an electronic controller.
[0026] It is an advantage of the present invention that it provides
a method for performing surgery while limiting hemorrhaging.
[0027] It is an advantage of the present invention that it provides
a device for performing HIFU surgical procedures, particularly
suited to performing percutaneous cauterization, hemostasis, and
coagulative necrosis of tissue.
[0028] It is an advantage of the present invention that it provides
a surgical device which can produce hemostasis along a defined
focal path without deep penetration into tissues, without
substantial charring of a cut tissue interface, and without harmful
cavitation-related tissue damage.
[0029] It is another advantage of the present invention that it
provides a method and apparatus for medical situations where
conventional hemostatic mechanisms are either too slow or not
functioning properly due to blood platelet or coagulation factor
deficiencies.
[0030] It is another advantage of the present invention that it
provides a method and apparatus that can substantially shorten the
time of surgery, thereby reducing costs.
[0031] It is another advantage of the present invention that it
provides a method and apparatus that decrease both the risk of
bleeding and the need for transfusions.
[0032] It is still another advantage of the present invention that
it provides a method and apparatus for reducing the morbidity and
death associated with surgical procedures in which hemorrhaging is
a frequent problem.
[0033] It is yet another advantage of the present invention that it
allows the use of HIFU for medical procedures with the ability to
focus and localize HIFU effects without effecting intervening or
subjacent tissue and organs.
[0034] It is still another advantage of the present invention that
it provides for a device that can be adapted to either open or
laparoscopic surgical procedures.
[0035] It is a further advantage of the present invention that it
provides a device for performing percutaneous embolization and
partial resection operations, eliminating the need for organ
removal.
[0036] It is yet a further advantage of the present invention that
it provides a device suited for emergency surgical procedures for
stemming bleeding due to vascular breaches.
[0037] It is a further advantage of the present invention that it
provides a device for non-invasively stemming internal
hemorrhaging.
[0038] It is still a further advantage of the present invention
that it can be used in an emergency medical situation to decrease
the effects of traumatic injury while the injured is transported to
a fully equipped medical facility.
[0039] Other objects, features and advantages of the present
invention will become apparent upon consideration of the following
explanation and the accompanying drawings, in which like reference
designations represent like features throughout the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIGS. 1A and 1B are schematic depictions of a presurgical
medical procedure methodology in accordance with the present
invention in which:
[0041] FIG. 1A is a top view of a section of a body organ having a
tumor, and FIG. 1B is a side view of the depiction of FIG. 1A in
which presurgical volume cauterization has been performed.
[0042] FIGS. 2A through 2D are schematic depictions of various
steps of the procedure as shown in FIGS. 1A-1B in which:
[0043] FIG. 2A depicts a first step involved in producing a
vertical coagulated and necrotized line or plane,
[0044] FIG. 2B depicts a second step involved in producing a
vertical coagulated and necrotized line or plane,
[0045] FIG. 2C depicts a third step involved in producing a
vertical coagulated and necrotized line or plane, and
[0046] FIG. 2D depicts a final step involved in producing a
vertical coagulated and necrotized line or plane.
[0047] FIGS. 3A through 3F are perspective views depicting steps in
the procedure as shown in FIGS. 1A-2D in which:
[0048] FIG. 3A depicts bottom burn paths using an apparatus as
depicted in FIGS. 1A-2D,
[0049] FIG. 3B is a subsequent step depicting a completed bottom
burn as shown in FIG. 3A,
[0050] FIG. 3C is a subsequent step depicting side burn paths,
[0051] FIG. 3D is a subsequent step depicting a partially complete
cauterization shell,
[0052] FIG. 3E depicts a subsequent step depicting further side
burn paths, and
[0053] FIG. 3F depicts a subsequent step depicting a completed
bottom and side plane cauterization shell.
[0054] FIGS. 4A through 4C are schematic drawings of an apparatus
in accordance with the present invention for performing the
procedures depicted in FIGS. 1A-3F in which:
[0055] FIG. 4A is a top view of the apparatus,
[0056] FIG. 4B is a side view of the apparatus,
[0057] FIG. 4C is a perspective view, schematic drawing of the
mechanism of element 401 of FIGS. 4A and 4B,
[0058] FIG. 4D is a perspective view, schematic drawing showing
detail of element 411 of FIG. 4C, and
[0059] FIG. 4E is a perspective view, schematic drawing showing
detail of the dynamic operating mechanism of element 401 of FIGS.
4A-4C.
[0060] FIGS. 5A through 5C are schematic diagrams in cross section
(side view) showing an alternative embodiment of the apparatus as
shown in FIGS. 4A-4C in which:
[0061] FIG. 5A is a top view of the apparatus,
[0062] FIG. 5B is a side view of the apparatus, and
[0063] FIG. 5C is a schematic drawing of the inner mechanism of
element 501 of FIGS. 5A and 5B.
[0064] FIGS. 6A through 6C are schematic diagrams showing an
alternative embodiment of the apparatus of the present invention
depicting a side focusing unit in which:
[0065] FIG. 6A shows the unit projecting a depth of focus of a
first depth,
[0066] FIG. 6B shows the unit projecting a depth of focus of a
second depth, and
[0067] FIG. 6C shows the unit projecting a depth of focus of a
third depth.
[0068] FIG. 7 is a schematic diagram showing an alternative
embodiment of the apparatus of the present invention presenting a
front focusing unit.
[0069] FIGS. 8A through 8E are schematic diagrams showing another
alternative embodiment of the apparatus of the present invention
depicting a hand-held unit, in which:
[0070] FIG. 8A shows a top view of the unit,
[0071] FIG. 8B shows a bottom view of the unit,
[0072] FIG. 8C shows the unit being used within a body cavity,
[0073] FIG. 8D shows an alternative set of transducers for the unit
as shown in FIG. 8B, and
[0074] FIG. 8E shows the embodiment of FIG. 8D in use.
[0075] FIG. 9 is a perspective view, schematic drawing of a line
focus transducer adaptable to use in accordance with the present
invention such as shown in FIGS. 1B through 5B.
[0076] FIG. 10 is a block diagram of an electrical controller for a
single channel system in accordance with the present invention.
[0077] FIG. 11 is a block diagram of an electrical controller for a
single channel system in accordance with the present invention
having a focal depth controller as shown in FIGS. 5A-5B.
[0078] FIG. 12 is a block diagram of an electrical controller for a
multi-channel system in accordance with the present invention as
shown in FIG. 8B.
[0079] FIGS. 13A and 13B are schematic drawings in cross section
(elevation) of a telescoping embodiment of a device in accordance
with the present invention in which:
[0080] FIG. 13A depicts the device in a fully retracted position,
and FIG. 13B depicts the device in an extended position.
[0081] FIG. 14 is an exemplary automated drive system for the
apparatus as shown in FIGS. 13A-13B.
[0082] FIGS. 15A through 15C are an alternative transducer mount
and telescoping device for the embodiment as shown in FIGS. 13A and
13B in which:
[0083] FIG. 15A is an elevation view,
[0084] FIG. 15B is a perspective view, and
[0085] FIG. 15C is a perspective view in which part of the device
has been removed.
[0086] FIG. 16 is a graph showing an optimal HIFU Frequency vs.
Tissue Depth plot.
[0087] The drawings referred to in this specification should be
understood as not being drawn to scale except if specifically
noted.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0088] Reference is made now in detail to a specific embodiment of
the present invention, which illustrates the best mode presently
contemplated by the inventors for practicing the invention.
Alternative embodiments are also briefly described as applicable.
In order to describe the various aspects of the present invention
and as several apparatus embodiments are disclosed, the
methodologies of use are presented first. Subtitles provided herein
are for convenience of the reader only and are not intended to
define, describe, or place any limitation on the scope of the
invention; no such intent nor limitation should be implied
therefrom. Presurgical procedures As set forth in the Background
section, ultrasonic energy can be focused to produce
hemo-coagulation and necrosis in living tissue. In FIG. 1A, there
is shown a section of a liver 101, having a tumor 103. While such
tumors are operable, because of the highly vascularized nature of
the liver's pathological constitution (the average blood flow is
about 25% of the resting cardiac output and the liver is a
relatively soft organ that tears easily), liver surgery places the
patient at high risk, making the arresting of rapid liver
hemorrhage or even slow oozing of blood with conventional methods a
time-consuming and difficult task.
[0089] Looking also to FIG. 1B, a simplistically depicted,
high-intensity focused ultrasound ("HIFU" hereinafter) apparatus
105, including an ultrasound transducer device 107 supported by a
top arm 109 is brought into contact with the liver 101 by an
acoustic coupler 111 used to couple acoustic energy to the liver
tissue. The coupler 111 contains an acoustic-transmissive medium
inside a flexible membrane. The membrane is highly elastic to
conform to the anatomy, able to withstand the high ultrasonic
intensities near the acoustic focus, sufficiently tough to survive
in the surgical environment, and bio-compatible. It has been found
that a polyether polyurethane provides a preferred material. The
material is available commercially as PT9300 Dureflex.TM.
polyurethane film, medical grade, 50 microns (0.002 inches) thick,
made by Deerfield Urethane, South Deerfield, Mass. For certain of
the coupling methods, e.g., water-filled cones as described herein,
the elasticity requirements are relaxed, and it may be possible to
use other types of plastic films.
[0090] A bottom arm 113 slips under the tissue and aids in fixing
the distance between the transducer device 107 and the tumor 103.
The transducer device 107 is then activated and used to describe a
shell 115 of coagulated and necrotized tissue around the tumor 103.
In other words, prior to any surgical incision, the tumor is
encapsulated by a shell 115 of tissue that has been thoroughly
cauterized using HIFU energy. The procedure for producing the shell
115 is referred to as "presurgical volume cauterization," the shell
115 comprising a volume of tissue equal to the surface area times
the thickness of the shell.
[0091] Changes in the appearance of the cauterized planes 117, 119,
and the like, of the shell 115 are highly visible after the volume
cauterization process. The tissue is essentially "cooked;" that is,
it hardens and is warm to the touch. The shell 115 then provides a
coagulated surgical pathway. That is, surgical incisions are made
along the coagulated pathway and little to no bleeding results.
Note that while in this exemplary embodiment a box shaped shell 115
has been formed in the liver tissue, depending upon the surgery to
be performed, virtually any shape necrosed surface can be formed as
needed, e.g., flat planar, curved surface, open or closed cubes and
rectangles, inverted wedge shapes, inverted pyramids, open or
closed cylinders, or the like as would provide appropriate necrosed
surgical pathways for the following operation. The goal is to
isolate a region of tissue from the blood supply to it by
surrounding the surgical target with a necrosed surface. The
particular surface chosen is selected to minimize the removal of
viable non-diseased tissue as well as to make it a practical
resection procedure for the surgeon.
[0092] FIGS. 2A-2D depict specific steps of forming a vertical
coagulated and necrotized line or plane during the volume
cauterization process in further detail. In FIG. 2A, the transducer
107 provides a focal region 201 with a dimensional shape having a
depth of field "a" at a depth of focus "b". The aperture
dimensions, frequency, and physics of ultrasound energy propagation
dictate the focal zone 201 dimensions. Note that the FIGURES are
not intended to be to scale; in typical practice, it has been found
that in preferred embodiments the length of the focal region can be
about ten times its lateral width in order to optimize HIFU effects
at the target. Tissue lesions generated by the HIFU beam are
similar in shape to the focal region, but slightly broader nearer
the transducer.
[0093] Appropriate continuous wave or pulsed acoustic energy
(represented by phantom lines) is applied for a predetermined time
(as also will be discussed in detail hereinafter) to necrotize the
tissue of the exemplary liver 101. The depth of focus is then
changed sequentially as depicted in FIGS. 2B-2D, producing a
vertical coagulated and necrosed line, or plane, 203, FIG. 2D.
[0094] The concept of how the position of the focal point of the
transducer can be varied to scan and produce a volume cauterization
is shown in three dimension in FIGS. 3A-3F. FIG. 3A represents a
transducer 107 focusing acoustic energy into a tissue mass 101
through an acoustic coupler 111. The transducer is being moved
laterally in FIGS. 3A and 3B in order for form a burn path in the
tissue approximating a planar surface, such as by cauterizing rows
of adjacent tissue burns. In FIG. 3B, the entire planar surface is
shown which actually forms a contiguous necrotized tissue volume
having a small thickness equal to the depth of field of the
particular transducer 107 in use. This contiguous necrotized tissue
volume might be, for example, a plane beneath a tumor to be removed
surgically. In FIG. 3C, the transducer is moved laterally to scribe
a line defining the perimeter of a complete shell region to be
cauterized, then moved vertically to scribe the next superjacent
perimeter, et seq. as depicted in FIGS. 3D through 3F. In FIG. 3F,
a complete open cubic volume shell has been formed. The shell so
produced provides a surgical pathway where the surgeon may cut
through the tissue with substantially no resultant bleeding.
[0095] It should be noted that in addition to the hyperthermia
effects some cavitation effects may be present in tissue so treated
in accordance with the foregoing procedures. The operative effect
may thus be a combination of hyperthermia and cavitation; thus,
further study is warranted.
[0096] HIFU Apparatus
[0097] A first embodiment of an apparatus 105 for performing
presurgical volume cauterization as shown in FIGS. 2A through 3F is
shown in FIGS. 4A-4E. Again, the liver 101 is used as an exemplary
organ on which an invasive surgical procedure is to be performed. A
bottom arm 113 is provided for resting under the tissue of the
organ to aid in fixing the distance between the transducer device
107 and the focal points within the organ.
[0098] Note also that the bottom arm 113 can carry an acoustic
absorber on the distal side of the tissue from where the ultrasound
energy is applied. The general purpose is to absorb the ultrasound
energy that passes through the tissue beyond the focal point,
thereby insulating subjacent tissues from being insonified. One
characteristic of such an absorber is that acoustic impedance
(density times the speed of sound) should be ideally equal to the
tissue. With such a characteristic most of the energy is absorbed
and there is little reflection of the impinging energy back into
the tissue. A second beneficial characteristic is to have the
absorber have good acoustic absorbing properties at the frequency
of the transducer emission, allowing acoustic energy to be absorbed
rapidly. A third beneficial characteristic is to have the absorber
material have a thickness and thermal properties such that the
surface abutting the tissue does not become hot enough to affect
it.
[0099] Tan gum rubber has a lower impedance, approximately 1.5
Mrayls, but its loss is only about 4.3 dB/cm at 1.0 MHZ. This is
the best material known to date and, though requiring a thicker
layer, such aids in distributing heat caused by energy absorbed and
thus avoids developing a hot surface. An alternative is neoprene,
commercially available (e.g., Gardico Inc., 1107 Elliott W.,
Seattle, Wash.), which has an impedance of 2.4 Mrayls, which
results in only about a five percent reflection. Red SBR rubber has
similar loss characteristics, but a higher impedance. However, red
SBR rubber is adverse to wetting and an air layer between the
rubber and tissue will greatly increase the reflection coefficient.
Hydrophobic materials should be wetted with alcohol before
immersion to minimize such effects.
[0100] In an alternative embodiment, material placed on the bottom
arm 113 could be acoustically reflective. If the coefficient of
reflectivity is high enough, little impinging energy will be
transmitted to tissue or organs beyond, thus the same goal as using
an absorber is achieved. The reflected energy can be used to
enhance the procedure in the tissue of interest. A suitable
reflector should have a characteristic of having an acoustic
impedance much different from the tissue, either lower (such as air
or an air-filled material like Styrofoam.TM.) or much higher (e.g.,
ceramics). For a low impedance reflector, a 180.degree. phase
reversal is produced at the point of reflection. This tends to
cancel the effect of the impinging and reflected wave in the region
proximate to the reflector. For a high impedance reflector, there
is no phase reversal, so the impinging and reflected waves
superimpose, producing an increased heating effect. Thus, a high
impedance reflector should be immediately subjacent the target
region. Furthermore, a mirror-reflection of a diverging beam
impinging on the reflector is further diverging. Therefore, it is
possible to obtain a broader area of effect in the region proximate
the reflector surface. If the focal point is closer to the
transducer than the reflector, it is possible by superimposition to
produce effects with broader beams beyond the maximum depth of
focus.
[0101] The transducer 107 and its acoustic coupler 111--in this
embodiment a simple flexible cuff filled with water--are connected
to a transducer aligning mechanism 401 by a top arm 109. The
transducer aligning mechanism 401 is provided with a thumb trigger
403 adjacent an apparatus handle 405. The transducer aligning
mechanism 401 detail is shown in FIG. 4C. The top arm 113 also
bears electrical cabling 407 connected to an electronic controller
(not shown, but see FIGS. 10-12).
[0102] Turning to FIGS. 4C-4E, the transducer aligning mechanism
401 provides one degree of motion in the Z-axis (FIG. 4B) to lower
or elevate the transducer 107 with respect to the tissue, which
essentially is used to change the depth of focus. The aligning
mechanism 401 has a casing 411 having a hollow through channel 413
(FIG. 4D) and a slide channel 415 (FIGS. 4C and 4D). Arm 109 (FIGS.
4A, 4B, 4C and 4E) fits through the slide channel 415 to have
freedom of motion in the Z-axis. Four ball bearing channels 417
(FIG. 4D) are provided in each interior corner of the casing 411.
An upper end cap 421 and lower end cap 423 close the through
channel 413 of casing 411 at each end. As shown in FIGS. 4D and 4E,
the arm 109 is mounted between an upper bellows 425 and a lower
bellows 427 contained within the through channel 413 by a mount 429
at an end distally located from the transducer 107 (FIGS. 4A and
4B). The bellows-arm mount 429 has a size and exterior shape
conforming to through channel 413 for a sliding fit therein. A ball
bearing 431 mounted for rotation in cavities in each corner of the
bellows-arm mount 429 to fit in respective ball bearing channels
417 of the casing 411 so that the mount rides freely in the Z-axis.
The end caps 421, 423 are provided with bellows pressurizing
apertures 433 (lower cap aperture not shown) for connecting a
suitable pressurizing/depressurizing medium, e.g., an air supply
and tubing (not shown), to each bellows 425, 427. The thumb trigger
403 (FIGS. 4A & 4B) is coupled to the air supply and used to
pneumatically control Z-axis motion of the arm 109 via the bellows
425, 427. Selectively increasing the pressure in one bellows while
decreasing the pressure in the other allows the bellows to expand
and contract respectively, causing the arm 109 to move in the slide
channel 415 and directly translated to the transducer 107. The rate
of flow of pressurized air is set at the pressure source to a
limited value to control the speed that the bellows
inflate-deflate, controlling the speed that the arm 109 is raised
or lowered.
[0103] Motion in directions other than the Z-axis are done
manually. That is, using the handle 405, the surgeon slides the
apparatus 105 towards or away from himself or laterally across the
surface of the organ 101 to move the focal point in a line. If the
transducer is of a semi-cylindrical configuration that is forming a
line of coagulated and necrosed tissue (see FIG. 9 described
hereinafter), moving the apparatus 105 towards or away from himself
describes a horizontal plane; moving the apparatus in the Z-axis
then describes a vertical plane. Thus, as can now be recognized by
a person skilled in the art, a variety of transducer
configurations, described hereinafter, and relative motion will
produce a variety of shapes and sizes of volume cauterization
regions.
[0104] An advanced embodiment is shown in FIGS. 5A-5C in which the
transducer aligning mechanism 401 of FIGS. 4A-4C has been replaced
with an electro-mechanically controlled transducer positioning
assembly for moving the top arm 109, or top and bottom arms 109,
113, in the X-, and Z-axes. Turning to FIG. 5C for details of the
transducer positioning assembly 501, the mechanism 401 (FIG. 4C)
has been modified to add the additional degree of motion control.
The arm 109 is moved in the X-axis by turning the transducer
aligning mechanism 401 to a horizontal orientation. Two pneumatic
bellows 503, 505 are linked together to produce the Z-axis motion.
A top bellows cap 507 and bottom bellows cap 509 are provided with
apertures for receiving air supply tubes 511, 513 in the same
manner as the caps 421, 423 of the transducer aligning mechanism
401, now shown as tubes 435, 437. Left bellows corner struts 515,
517 and right bellows corner struts (not shown) are used as guides
for ball bearings 519 captured in the external corners of
transducer aligning mechanism end caps 421, 423 for mating with the
struts such that inflating and deflating the top bellows 503 and
bottom bellows 505 causes controlled motion in the Z-axis. Thus,
the four corner struts hold the assembly rigid and allow the X-axis
mechanism 401 to move up and down using the external pneumatic
controller (not shown).
[0105] In another embodiment, not shown, a third pair of bellows
can be added to the assembly of FIG. 5C to provide y-axis control
(FIG. 5A). The operator's control can be a joy-stick, foot
controls, or the like, as would be known in the art.
[0106] Depth of focus can be more easily accomplished by an
alternate embodiment as shown in FIGS. 6A-6C. A side-radiating HIFU
unit 601, having a housing which doubles as a handle, 602 uses an
acoustic energy reflector 603 to focus ultrasonic energy,
represented by the phantom lines, transmitted through a suitable
fluid medium 611, out through an acoustic energy window 605 into
the organ 101. The HIFU reflector 603 is at an angle of
approximately 45.degree. to the handle 602 orientation, bending the
ultrasound beam 90.degree.. The depth of focus is varied using a
drive screw 607 powered by a motor, or other linear drive
mechanism, 609 to change the distance between the emitter face of
the transducer 107 and the acoustic energy reflector 603.
Electrical energy for the motor 609 and transducer 107 is provided
using a flexible cable 613. FIGS. 6A-6C again illustrate how a line
or plane of coagulation can be produced by moving the position of
the transducer with respect to the reflector. In a further
refinement, the reflector 603 can be oscillated about its center
line to sweep a point focus precisely in a plane perpendicular to
the axis of the handle 602.
[0107] FIG. 7 demonstrates an even further simplified HIFU tool 701
in the nature of a pencil-like probe 703. The probe 703 has a
transducer 107 with an appropriate electrical connection 705.
Acoustic energy 707 is transmitted through a fluid coupling window
709. The combination of an essentially zero depth of field
characteristic with a short, fixed, focal length 711 provides for
cauterizing tissue immediately in front of the window 709 to the
extent of the depth of field of the transducer 107. Thus, a surgeon
could cauterize a line of tissue, cut the line with a scalpel, then
reapply the probe 703 to cauterize a next line of tissue to be
cut--viz., cauterize, cut, cauterize, cut, etc.--as needed step by
step in the operation. Such an embodiment would be more useful in a
more general exploratory surgery or emergency surgical situations
where an exact surgical target location is undefined.
[0108] Ultrasound is strongly reflected by air and bone interfaces.
Thus, the application of HIFU surgery must be limited to those soft
tissues in which a target region is identified. Intervening bones
and air, viz., in the lungs, must be moved aside. FIGS. 8A-8C
demonstrate yet another embodiment which is a hand-held HIFU
surgical instrument 801, especially suited to emergency situation
use or use within a region of the body cavity where it may be
difficult to reach or see with more complex instruments such as
shown in FIGS. 1A through 6C.
[0109] The imaging transducer 803 is a linear array used for
steering as would be known in the art. An imaging device, such as a
central linear transducer array 803, connected via cabling 804 to
appropriate imaging equipment as would be known in the art, aids
the surgeon in determining where to produce the HIFU cauterization
effects. As the user moves the instrument 801 around within the
patient, they receive an image of the underlying organ to guide
placement of the instrument 801 in order to align HIFU transducer
array elements 805 of a cauterizing transducer array set. Such an
array is advantageous in this embodiment since electronically
controlled depth of focus control can be provided through phase
alignment of the elements 805. The HIFU transducer is a group of
square or rectangular elements 805 located around the imaging
transducer 803. The array is used as the HIFU application
transducer, allowing an electronically controlled change of the
focal depth, depending on the phasing of excitation to each element
805. Thus, the instrument 801 can be steered to some extent as well
as focused at different depths and beam diameters depending on the
phasing of the excitation to each element 805.
[0110] FIGS. 8D and 8E shows an alternative for the transducer
arrangement using an annular array 806. [Some annular array
instruments are known in the art. For example, in U.S. Pat. No.
5,520,188, Hennige et al., assignors to Focus Surgery, Inc.,
describe an annular array transducer for use in a localization and
therapeutic ultrasound system where elements operate together to
focus a continuous wave (CW) ultrasound beam at a focal zone that
is a variable distance from the elements, including a mechanism to
adjust the focal distance via adjusting the phase of the signals
imparted to each element. See also e.g., Intracavity Ultrasound
Phased Arrays for Noninvasive Prostate Surgery, Hutchinson and
Hynynen, IEEE Transactions on Ultrasonics, Ferroelectrics, and
Frequency Control, November 1996, Vol. 43, No. 6 (ISSN 0885-3010),
pages 1032-1042; Ultrasound Surgery: Comparison of Strategies Using
Phased Array Systems, Hong Wan et al., on multiple focal length
designs, id. at pages 1085-1098; and Sparse Random Ultrasound
Phased Array for Focal Surgery, Goss et al., id., pages 1111-1121;
and Design of Focused Ultrasound Surgery Transducers, Rivens et
al., ibid. at pages 1023-1031, discussing a method for
determination of transducer configurations for different fixed
focal lengths.] The annular transducer elements 807 enable an
adjustable focal depth having a wider range than other
configurations. Cutaway region 809 shows a sectional view of dicing
pitch of the transducer elements 807. Providing linear separation
of the elements, in perpendicular axes, also allows beam steering
without the requirement of complex X-, Y-, and Z-axis driving
mechanisms as shown in FIGS. 4A through 5B and equivalents
thereof.
[0111] Other Transducers
[0112] A variety of transducer designs as would be known to a
person skill in the art can be made for use in accordance with the
present invention. For example, current state of the art for
focused bowl transducers is discussed by Rivens et al., Design of
Focused Ultrasound Surgery Transducers, IEEE Transactions, supra.
In commercial therapeutic treatment, Sonic Focus Inc., Fremont,
Calif., manufactures a HIFU system, Sonablate-1.TM., providing a
transrectal probe for prostate hyperthermia treatments.
[0113] An exemplary embodiment for producing a focal line is shown
in FIG. 9. The transducer 901 has an acoustic energy emitting
surface 903 which is a portion of a cylinder 905. This cylindrical
transducer 901 focuses ultrasonic energy (indicated by phantom
lines 907) into a line 911. The distance of this focal line 911
from the transducer face 903 is approximately the radius of
curvature of the cylindrical element 905.
[0114] Controllers
[0115] A variety of means for targeting acoustic transducers are
well known in the art (see e.g., U.S. Pat. Nos. 4,484,569,
4,858,613, 5,520,188; Hynynen et al., Feasibility of Using
Ultrasound Phased Arrays for MRI Monitored Noninvasive Surgery; and
Thomas et al., Ultrasonic Beam Focusing Through Tissue
Inhomogeneities with a Time Reversal Mirror: Application to
Transskull Therapy, IEEE Transactions, supra). Generally, a further
description of specific target acquisition, such as finding a tumor
within the liver, is not necessary to an understanding of the
present invention.
[0116] FIG. 10 is a schematic diagram for a single channel
controller embodiment of the present invention such as exemplified
in FIGS. 6A-6C and 7. A frequency, or function, generator 1001
(such as a Hewlett-Packard.TM. Model 33120 Function Waveform
Generator) is used to generate a waveform for exciting the
transducer 107. The waveform signal is transmitted through an
on/off switching control 1003 that is operator activated (see
broken line arrow labeled "Operator Activation"); alternatively,
preset timer activation can be provided. A power amplifier 1005
(e.g., an Electronic Navigation Industries.TM. Model API 400B)
increases the generator 1001 output and sends it through an
electrical matching network 1007 (having appropriate air or liquid
cooling, if required) to the transducer 107. The matching network
1007 transforms the complex electrical input impedance of the
transducer 107 into a nominally real impedance compatible with the
output stage of the power amplifier 1005. As described above, the
transducer 107 emits ultrasound energy in a pattern and intensity
to produce tissue coagulation at particular intra-tissue sites. The
frequency range useful in accordance with the present is
approximates one-half (0.5) to twenty (20) MHZ. At higher
frequencies, absorption is almost immediate, providing negligible
penetration through living tissue It is intended that the frequency
and amplitude are adjustable to suit a particular implementation or
surgical need. The amplitude of the waveform signal at the output
of the generator has enough amplitude, e.g., one volt RMS, so that
the power amplifier 1005 will increase it to a magnitude whereby
the transducer will have a sufficiently high enough output to
produce tissue coagulation. For example, the electrical power being
transmitted from the power amplifier 1005 may be in the region of
200 watts, which for a 50-ohm load would require 100 volts RMS
output across the load. In turn the transducer 107 may then deliver
intensity at a focal point of 1500 W/cm.sup.2. It is believed that
a spatial peak intensity in the range of 1300 to 3000 W/cm.sup.2
may be applied to obtain appropriate results sought to be achieved
present invention. Note carefully that intensity required to
depends upon the chosen ultrasonic frequency and the
frequency-dependent tissue attenuation rate. The values that are
given may be appropriate in accordance with actual experimental
studies that were performed at 1 to 3 MHZ (further details of which
are not necessary to an understanding of the present invention). At
higher frequencies (e.g., 5 to 10 MHZ) tissue attenuation will be
proportionately higher, and the required focal intensity may be
much lower. In terms of the desired thermal bio-effect, values can
be converted to a specific absorption rate ("SAR") value, in units
of Watts per kilogram. SAR values are commonly used in ultrasound
hyperthermia studies and analysis. The SAR value specifies the
amount of thermal energy that is being deposited per unit weight in
the tissue, and it includes the effect of frequency-dependent
attenuation. To achieve a certain temperature rise within a
specified period, it may be more meaningful to use the SAR value.
Equivalently, one could specify the ultrasonic intensity, the
ultrasonic frequency, and the tissue attenuation rate.
[0117] While temperature elevation by ultrasound has been studied
and reported upon (see e.g., Nyborg et al., Temperature Elevation
in a Beam of Ultrasound, Ultrasound in Med. & Biol., Vol. 9,
No. 6, pp. 611-620, 1983), in addition to specific transducer
instrument operating parameters, various power, frequency, and time
of application combinations are also dependent on a number of
factors. For example, the type of tissue in which coagulation and
necrotization is desired must be taken into consideration as
different tissue will promote different absorption effects.
Absorption of sonic energy are both frequency and tissue dependent.
Another obvious variable is whether the HIFU energy is being
applied in a pulsed or continuous wave form. Moreover, frequency
independent data is an artifact of empirically competing effects of
the absorption of sonic energy increasing with frequency and the
size of the acoustic focal point depth of field decreasing with
increased frequency. In other words, the energy intensity level,
the sonic frequency employed, and the time of exposure, in either a
pulsed or continuous wave modes, is primarily an empirical
function. Each specific implementation may require empirically
determined operational criteria.
[0118] If the ultrasonic frequency that is employed is too low,
most of the energy will propagate past the depth of interest.
Although this can be overcome by increasing the energy input, the
energy that is deposited beyond the depth of interest is likely to
damage tissues beyond the treatment zone. If an acoustic absorber
is used, the waste energy will be converted to heat; this may
protect deeper tissues, but significant heating may occur in the
vicinity of the absorber.
[0119] Similarly, if the ultrasonic frequency that is employed is
too high, most of the energy will be absorbed proximal to the depth
of interest. Although this can be overcome by increasing the energy
input, the energy that is deposited proximal to the depth of
interest is likely to damage tissues.
[0120] In a homogeneous attenuative medium that behaves linearly
with respect to pressure amplitude, it can be shown mathematically
that for a plane wave, optimal energy deposition occurs at a depth
"z" when the ultrasonic intensity at that depth is equal to:
I(z)=I.sub.0/e.congruent.0.368*I.sub.0,
[0121] where:
[0122] I.sub.0=ultrasonic intensity at the surface of the
attenuative region.
[0123] The above formula maximizes the energy deposited at depth
"z" for a given amount of input power. Given the frequency
dependence of the attenuation, one can calculate the optimal
frequency to deposit energy at depth "z" (see attached graph of
FIG. 16). Following this formula, note that only 37% of the input
energy propagates beyond depth "z"; 63% is deposited between the
surface and depth "z".
[0124] Focusing makes this argument more complex, but it does not
alter the basic result. Weak focusing can be used to uniformly
deposit energy from the surface to a depth "z" in a truncated conic
zone; in this case, the beam cross-sectional area at depth "z" must
be equal to:
A(z)=A.sub.0/e.congruent.0.368*A.sub.0,
[0125] where:
[0126] A.sub.0=beam cross-sectional area at the surface of the
attenuative region.
[0127] Thus, to produce high ultrasonic intensity at a depth "z", a
focal intensity gain that is significantly greater than
e.congruent.2.718 is required.
[0128] In HIFU, attenuation is believed to be weakly non-linear
with pressure amplitude in pre- and post-focal regions, and
moderately non-linear near the focus. Nonetheless, the formulas
above can be used to identify initial conditions. In practice, each
specific clinical application will require some experimental
optimization.
[0129] Note that optimal energy deposition requires a system and
transducer capable of delivering energy at higher frequencies at
shallow depths, and lower frequencies at deeper depths.
[0130] A second controller embodiment is shown in FIG. 11. Here the
system is used to control the variation of the depth of focus for
embodiments such as shown in FIGS. 4A-5B. In operation, activation
of the on/off control 1003 causes the system to begin applying
energy at a distal point in the tissue, moving it progressively
closer to the transducer 107 with time. Under programmed control
1101, the circuitry automatically arms itself to position the
transducer to perform a distal to proximal scan and then signals
when ready. The operator turns on the apparatus and a scan is
performed. After the scan, the transducer 107 is repositioned via
transducer positioning assembly 501 to the next line or plane to be
coagulated where a next scan is required.
[0131] Shown in FIG. 12 is an electronic scanning system, useful
with a phased array embodiment such as shown in FIG. 8B, or other
electronically focused transducer. Added to the system are phase
shifters 1201-1201N in order to accommodate each transducer element
107-107N in the annular array 805 (FIG. 8B). Programmed electronic
depth of focus is provided as would be well known in the state of
the art. Note that the controller can be adapted to provide a
pulsed, continuous wave, or combination pulsed and continuous wave
sonic energy emission from the transducer.
[0132] Independent control 1203.sub.1-1203.sub.n over amplitude and
phase is provided. Independent amplitude control is necessary to
produce desired apodization (shading) functions across the array
aperture, which in turn results in control of side lobe levels.
High side lobe levels may cause unwanted tissue damage in adjacent
structures. These levels are easily reduced by the use of
appropriate apodization functions. This is well known in the prior
art. Independent channel gain controls would also be required if
the transducer includes elements with unequal areas. In certain
embodiments, e.g., an annular array with a central rectangular
opening for an imaging array as depicted in FIG. 8D, the array
elements will clearly have different elemental areas, requiring
channel-independent gain.
[0133] Variable Depth of Focus Instrument Embodiments
[0134] As depicted in several drawing heretofore, a flexible bag
111 is provided as an acoustic coupler between the transducer 107
and the organic tissue 111. While adequate for certain uses,
because of its inherent flaccid nature, there can be difficulty in
maintaining both constant contact between the bag and the tissue
and an accurate depth of focus.
[0135] A HIFU tool assembly, having a true variable depth of focus
in accordance with a preferred embodiment of the apparatus of the
present invention is shown in FIGS. 13A and 13B. FIG. 13A depicts a
presurgical device 1301 for preparing an organ of a patient for
surgical incisions using HIFU energy to produce coagulation and
necrosis in the tissue along each predetermined incision pathway,
or using a very shallow depth of focus setting, for producing
localized hemostasis (discussed in further detail hereinafter).
[0136] A transducer mount 1303 holds a transducer, or transducer
array, 1305 in a substantially fixed configuration. A housing 1307,
such as of a molded, clear, plexiglass, forms an internal chamber
1309. The device 1301 is mounted on a suitable handle, such as
handle 109 of FIGS. 3A-4B, having inlet and outlet tubes (not
shown; but see FIGS. 4A-5B, re element 407) allowing a suitable
acoustic energy transmitting medium, such as water to flow into and
out of the chamber 1309. The handle also carries any electrical
wires or cables needed to power the transducer 1305. The housing
1307 has a rotatable collar 1327, having a fixed radial position
relative to the transducer's energy emitting surface 1319 and an
inner wall 1329 of the housing 1307. The housing inner wall 1329 at
least partially forms the sides of the internal chamber 1309. The
rotatable collar 1327 has screw threads 1331 on an interior surface
thereof. A selectively movable focusing cone 1333 is coupled to the
rotatable collar 1327 via focusing cone member screw threads 1335.
When so mated, distally located from the transducer's energy
emitting surface 1319, there is an acoustic window 1321 at a
conical, lower extremity 1333' of the focusing cone 1333. An
acoustically-transmissive, flexible membrane 1323 is stretched
across the window 1321, secured to the housing 1307 by a suitable
mount, such as an o-ring, 1325. Thus, by rotating the collar 1327,
the device 1301 provides a telescoping-type construct. FIG. 13A
shows the construct in an extended position; FIG. 13B shows the
construct in a fully retracted position. In the extended position
of FIG. 13A, the internal chamber 1309 of the housing is
substantially enlarged by the volume of cavity 1309' of the movable
focusing cone 1333. Water is added via the inlet tubes as the
volume of the entire chamber 1309, 1309' increases when the collar
1327 is rotated and withdrawn as the volume decreases when the
collar is counter-rotated. Suitable mounting and sealing o-rings
1311, 1313, 1317 and screw 1315 are provided as necessary to
complete the device 1301.
[0137] As can now be recognized, a telescoping action is produced
between the rotatable collar 1327 and the focusing cone member 1333
when the collar 1327 is rotated about its longitudinal axis of
rotation, "R-R." Rotating collar 1327 changes the gap, "F.sub.n,"
between the transducer's energy emitting surface 1319 and the
acoustic window 1321. As the gap varies, for example from length
F.sub.1 in FIG. 13A to F.sub.2 in FIG. 13B, the depth of focus of
the device 1301 varies; distance F.sub.1 establishing the deepest
focal point or focal zone penetration. As will be recognized by a
person skilled in the art, the device's construct is adaptable to a
variety of transducer types and size implementations.
[0138] The rotating collar may be manually or electro-mechanically
rotated. FIG. 14 depicts a schematic for an automated focus dept
adjustment system. A motor Ml, such as a stepper motor, is coupled
by drive shaft S1 to a gear train G1, G2, G3, gear shaft S2, G4, G5
and G6. The rotating collar 1327 is coupled to gear G6 such that by
activation of the motor, e.g., via a surgeon operated foot switch
(not shown), precise depth of focus can be achieved as focusing
cone 1333 moves with rotation as shown by the arrow labeled "With
Rotation 1333 Moves". Since the mechanism will necessarily be used
under sterile conditions, this configuration allows a single motor
and gear train G1-G4 to be enclosed in a sealed section; gear G5
and the combined unit of gear G6 and the transducer system (FIGS.
13A & 13B) within rotating collar 1327 are removable from the
shaft for cleaning and sterilization.
[0139] An alternative embodiment of a device 1501 having a focusing
mechanism is shown in FIGS. 15A-15C. A base 1503 (similarly, see
also FIG. 13A, element 1303) holds a transducer (not shown)
projecting inwardly through a cavity 1505, FIG. 15C, of the device.
The cavity 1505 is formed by a plurality of telescopic cylinders
1507, 1509, 1511, 1513. The cavity 1505 is adapted for filling with
an acoustic coupling fluid, e.g., degassed water. Again, fluid
couplings not shown, but as would be obvious to a person skilled in
the art, are provided to keep the cavity filled during expansion
and contraction. A spring 1515 is mounted inside the cavity to bias
against an end plate 1517 (FIGS. 15A & 15B only). A bellows
1519 surrounds the telescopic cylinders 1507-1513 and the end plate
1517 is attached thereto in contact with the spring 1515 and the
telescopic cylinders distally from the base 1503. Thus, the device
is in an expanded condition unless compressed by pushing the end
plate against the tissue to a degree to force the spring and
bellows to begin to collapse.
[0140] The end plate 1517 is rigid on its circumference for
connection to the bellows. The inner radial region of the end plate
1517 may be of a different material, but essentially must be
transparent to ultrasonic energy. The purpose of the telescoping
sections is to maintain the axial alignment with the center of the
axis, C--C, running through the aligned base 1503 and the end plate
1517. Thus, the ultrasound energy emitted by the transducer will
not encounter the inner walls of the telescopic cylinders
1507-1513. A flexible bag acoustic coupler 111 lacks this
ability.
[0141] Note that this embodiment can be adapted for use with either
a fixed system as exemplified in FIGS. 1B-5B and 14, or can be hand
held as in FIGS. 8A-8C.
[0142] Hemostasis Procedures
[0143] As another example of the methodology of the present
invention, consider traumatic bleeding. For example, uncontrolled
hemorrhage of the liver is a primary cause of death in hepatic
trauma, occurring in 30% of penetrating and 15-20% of blunt
abdominal trauma, with a mortality rate of 10-15%. Abdominal trauma
patients are often already in hemorrhagic shock prior to arrival at
surgery. Another application is for treating a punctured vessel in
a medical situation where a catheter has been removed from the
artery, resulting in bleeding. Additionally, emergency rescue teams
are often faced with massive bleeding injuries with nothing more
than tourniquets to use to stem the flow of blood.
[0144] In accordance with the present invention, ultrasound having
a frequency in a range of 0.5 MHZ-20 MHz is focused onto the outer
regions of the vessel adjacent to where the puncture or tear
occurred. The energy level and the duration of exposure is
monitored such that the application of HIFU causes the closure of
the fibrous sheath surround a vessel without damaging or
irreversibly damaging the wall tissue of the vessel itself. [But
cf., Potential Adverse Effects of High-Intensity Focused Ultrasound
Exposure on Blood Vessels In Vivo, Hynynen et al., Ultrasound in
Med. & Biol., Vol. 22, No. 2, pp. 193-201, 1996.]
[0145] Particularly suited to this process and portable
implementations are apparatus such as depicted in FIGS. 7 and 8A-8C
since they provide simple, hand-held embodiments. Having a fixed
depth of focus immediately adjacent the front of the instrument,
makes the embodiment of FIG. 7 particularly useful in a roadside,
medical emergency where portability is a factor. Specific
instrument design factors, viz., frequency, transducer size, power,
and the like as discussed heretofore, will determine the duration
of application to cause hemostasis. Again, treatment parameters are
device specific and must be determined empirically. As an example,
a device similar to the embodiments shown in FIGS. 8A-8B was used
for experiments (performed in accordance with the appropriate laws
and guidelines of the U.S. Nation Institute of Health for the use
of laboratory animals). A HIFU, spherically curved transducer had
an aperture of 6.34 cm.sup.2, producing a depth of focus at 4 cm.
It was operated at 3.3 MHZ, CW, by applying 300 V peak-to-peak,
producing an acoustic power of 65W, measured with an absorber-type
radiation force balance and a spatial peak intensity at the focal
region of approximately 3000 W/cm.sup.2. For 94% of incisions in
rabbit liver, major hemostasis was achieved in a time of less than
approximately two minutes of continuous application of HIFU. The
average.+-.standard deviation of the major hemostasis time was
1.4.+-.0.69 minutes. When a large vessel was cut, in approximately
80% of the incisions, complete hemostasis was achieved in a time
less than or equal to 3 minutes of continuous HIFU application.
[0146] Note that occurrence of trauma to a specific tissue or organ
may start bleeding internally. This may produce a hematoma, a shunt
between the arterial and venous system caused by an artery
punctured or ruptured in close proximity to a ruptured or punctured
vein, or bleeding into some non-cardiovascular cavity.
[0147] While shunts can occur substantially anywhere in the
cardiovascular system, yet another medical problem that involves
vascular shunts between the arterial and venous system are
congenital defects known as arterial-venous ("AV") malformations.
AV malformations often occur in the brain and liver. In a shunt,
blood flow may be contained to a local region by reason of the
adjacent tissue remaining normal or intact. An open venous pathway
provides a pressure release and site for blood to flow from the
higher arterial pressure system. Additionally, a shunt can occur
between a vessel with higher pressure to a vessel with a lower
pressure. Whatever the cause, the medical problem is that normal
tissue does not receive proper blood perfusion. Of further
difficulty is that AV malformations themselves have a higher
tendency to hemorrhage. In a similar manner, HIFU energy is applied
to the region where the internal bleeding is detected, that is,
specifically to the vessels with the higher pressure from which the
blood is leaking. In accordance with the present invention, such
shunts or other internal bleeding can be closed without having to
disturb or cut through adjacent tissue, occluding the artery
feeding the shunt, the shunt itself, or the vein receiving the
shunt blood flow. Alternatively, the whole tissue region or
malformation of the vessel feeding the shunt, the shunt, and the
vessel receiving the shunt is coagulated using HIFU energy,
coagulating the specific volume of tissue involved.
[0148] The present invention provides a useful method and apparatus
for a variety of presurgical and traumatic bleeding
applications.
[0149] The foregoing description of the preferred and alternative
embodiments of the present invention has been presented for
purposes of illustration and description. It is not intended to be
exhaustive or to limit the invention to the precise form or to
exemplary embodiments disclosed. Obviously, many modifications and
variations will be apparent to practitioners skilled in this art.
Similarly, any process steps described might be interchangeable
with other steps in order to achieve the same result. While liver
surgery has been discussed at length in an exemplary embodiment,
the volume cauterization procedure is applicable to virtually all
organ surgery. The embodiment was chosen and described in order to
best explain the principles of the invention and its best mode
practical application, thereby to enable others skilled in the art
to understand the invention for various embodiments and with
various modifications as are suited to the particular use or
implementation contemplated. It is intended that the scope of the
invention be defined by the claims appended hereto and their
equivalents.
* * * * *