U.S. patent application number 12/213652 was filed with the patent office on 2008-10-23 for planning and facilitation systems and methods for cryosurgery.
This patent application is currently assigned to Galil Medical Ltd.. Invention is credited to Shaike Schatzberger, Roni Zvuloni.
Application Number | 20080262486 12/213652 |
Document ID | / |
Family ID | 22829844 |
Filed Date | 2008-10-23 |
United States Patent
Application |
20080262486 |
Kind Code |
A1 |
Zvuloni; Roni ; et
al. |
October 23, 2008 |
Planning and facilitation systems and methods for cryosurgery
Abstract
Systems and methods for planning a cryoablation procedure and
for facilitating a cryoablation procedure utilize integrated images
displaying, in a common virtual space, a three-dimensional model of
a surgical intervention site based on digitized preparatory images
of the site from first imaging modalities, simulation images of
cryoprobes used according to an operator-planned cryoablation
procedure at the site, and real-time images provided by second
imaging modalities during cryoablation. The system supplies
recommendations for and evaluations of the planned cryoablation
procedure, feedback to an operator during cryoablation, and
guidance and control signals for operating a cryosurgery tool
during cryoablation. Methods are provided for generating a
nearly-uniform cold field among a plurality of cryoprobes, for
cryoablating a volume with smooth and well-defined borders, thereby
minimizing damage to healthy tissues.
Inventors: |
Zvuloni; Roni; (Haifa,
IL) ; Schatzberger; Shaike; (Haifa, IL) |
Correspondence
Address: |
Martin D. Moynihan;PRTSI, Inc.
P.O. Box 16446
Arlington
VA
22215
US
|
Assignee: |
Galil Medical Ltd.
Yokneam
IL
|
Family ID: |
22829844 |
Appl. No.: |
12/213652 |
Filed: |
June 23, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11219648 |
Sep 7, 2005 |
7399298 |
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12213652 |
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11066294 |
Feb 28, 2005 |
7402160 |
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11219648 |
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09917811 |
Jul 31, 2001 |
6905492 |
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11066294 |
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60221891 |
Jul 31, 2000 |
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Current U.S.
Class: |
606/21 ;
128/898 |
Current CPC
Class: |
A61B 2034/104 20160201;
A61B 2018/00041 20130101; A61B 8/0833 20130101; A61B 2018/00547
20130101; A61B 2018/0262 20130101; A61B 2017/00274 20130101; A61B
18/02 20130101; A61B 90/37 20160201; A61B 2090/374 20160201; A61B
34/10 20160201; A61B 8/445 20130101 |
Class at
Publication: |
606/21 ;
128/898 |
International
Class: |
A61B 18/02 20060101
A61B018/02 |
Claims
1-44. (canceled)
45. A method for planning a cryosurgical ablation procedure,
comprising: (a) utilizing a first imaging modality to create
digitized preparatory images of an intervention site; (b) utilizing
a three-dimensional modeler to create a three-dimensional model of
said intervention site based on said digitized preparatory images;
(c) utilizing a simulator to simulate a cryosurgical intervention,
which simulator comprises a displayer operable to display in a
common virtual space an integrated image comprising a visualization
of said three-dimensional model of said intervention site and a
virtual display of at least one simulated cryoprobe inserted at
least one selected locus; and (d) utilizing a predictor to predict
an effect on body tissues of a patient of operation of said at
least one cryoprobe at said at least one selected locus according
to selected operational parameters, said predictor being operable
to predict size and shape of a prostate two or more weeks after
said operation of said at least one cryoprobe, thereby enabling to
plan said cryoablation procedure in view of said predicted
effect.
46. The method of claim 45, further comprising displaying, in said
integrated image, a visualization of an effect predicted by said
predictor.
47. The method of claim 45, wherein said simulator further
comprises an interface useable by an operator for specifying at
least one operator-specified locus for insertion of said at least
one simulated cryoprobe.
48. The method of claim 45, wherein said simulator further
comprises an interface useable by an operator for specifying
operator-specified parameters for operation of said at least one
simulated cryoprobe.
49. The method of claim 45, wherein said simulator further
comprises a recommender operable to recommend a position for
inserting a cryoprobe into a body of a patient.
50. The method of claim 45, wherein said simulator further
comprises a recommender for recommending operating parameters for a
cryoprobe inserted in a body of a patient.
51. The method of claim 45, further comprising using said predictor
to predictor size and position of an iceball created by operation
of said at least one simulated cryoprobe.
52. The method of claim 45, further comprising using said predictor
to predict size and position of an area of total tissue destruction
created by operation of said simulated cryoprobes.
53. The method of claim 45, further comprising using a recommender
to recommend temperature and duration for cooling of said at least
one simulated cryoprobe.
Description
RELATED APPLICATIONS
[0001] The present application is a Continuation of U.S. patent
application Ser. No. 11/066,294, filed on Feb. 28, 2005, which is a
Divisional of U.S. patent application Ser. No. 09/917,811, filed on
Jul. 31, 2001, now U.S. Pat. No. 6,905,492, issued on Jun. 14,
2005, which claims priority from U.S. Provisional Patent
Application No. 60/221,891, filed on Jul. 31, 2000. The contents of
all of the above-mentioned applications are herein incorporated by
reference.
FIELD AND BACKGROUND OF THE INVENTION
[0002] The present invention relates to cryosurgical systems and
methods useable for planning and for facilitating a cryoablation
procedure. More particularly, the present invention relates to the
use of integrated images displaying, in a common virtual space,
images of a three-dimensional model of a surgical intervention
site, simulation images of a planned cryoablation procedure at the
site, and real-time images of the site during cryoablation. The
present invention further relates to system-supplied
recommendations for, and evaluations of, a planned cryoablation
procedure, and to system-supplied feedback to an operator and
system-supplied control signals to a cryosurgery tool during
cryoablation.
[0003] Cryosurgical procedures involve deep tissue freezing which
results in tissue destruction due to rupture of cells and or cell
organelles within the tissue. Deep tissue freezing is effected by
insertion of a tip of a cryosurgical device into the tissue, either
transperineally, endoscopically or laparoscopically, and a
formation of, what is known in the art as, an ice-ball around the
tip.
[0004] In order to effectively destroy a tissue by such an
ice-ball, the diameter of the ball should be substantially larger
than the region of the tissue to be treated, which constraint
derives from the specific profile of temperature distribution
across the ice-ball.
[0005] Specifically, the temperature required for effectively
destroying a tissue is about -40.degree. C., or cooler. However,
the temperature at the surface of the ice-ball is 0.degree. C. The
temperature declines exponentially towards the center of the ball
such that an isothermal surface of about -40.degree. C. is
typically located within the ice-ball substantially at the half way
between the center of the ball and its surface.
[0006] Thus, in order to effectively destroy a tissue there is a
need to locate the isothermal surface of -40.degree. C. at the
periphery of the treated tissue, thereby exposing adjacent, usually
healthy, tissues to the external portions of the ice-ball. The
application of temperatures of between about -40.degree. C. and
0.degree. C. to such healthy tissues usually causes substantial
damage thereto, which damage may result in temporary or permanent
impairment of functional organs.
[0007] In addition, when the adjacent tissues are present at
opposite borders with respect to the freeze treated tissue, such as
in the case of prostate freeze treatments, as is further detailed
below, and since the growth of the ice-ball is in substantially
similar rate in all directions toward its periphery, if the tip of
the cryosurgical device is not precisely centered, the ice-ball
reaches one of the borders before it reaches the other border, and
decision making of whether to continue the process of freezing,
risking a damage to close healthy tissues, or to halt the process
of freezing, risking a non-complete destruction of the treated
tissue, must be made.
[0008] Although the present invention is applicable to any
cryosurgical treatment, discussion is hereinafter primarily focused
on a cryosurgical treatment of a patient's prostate.
[0009] Thus, when treating a tumor located at a patient's prostate,
there is a trade-of between two options: (a) effectively destroying
the prostatic tissue extending between the prostatic urethra and
the periphery of the prostate and causing unavoidable damage to the
patient's urethra or organs adjacent the prostate such as the
rectum and nerves; (b) avoiding the damaging of the prostatic
urethra and adjacent organs, but exposing the patient to the risk
of malignancy due to ineffective destruction of the prostate tumor.
Treatment of benign prostate hyperplasia (BPH), while not requiring
total destruction of an entire volume of prostate tissue as does
treatment of a malignancy, nevertheless does run the risk of
causing damage to healthy functional tissues and organs adjacent to
the prostate, if care is not taken to limit the scope of
destructive freezing to appropriate locations.
[0010] A classical cryosurgery procedure for treating the prostate
includes the introduction of 5-7 probes into the prostate, the
probes being typically arranged around the prostatic urethra such
that a single probe is located, preferably centered, between the
prostatic urethra and the periphery of the prostate. The dimensions
of such a single probe are usually adapted for effectively treating
the prostatic tissue segment extending from the urethra to the
periphery of the prostate, e.g., a tip of 3 millimeters in
diameter, generating an ice-ball of 3-4 centimeters in diameter,
depending on the size of the prostate. Since a single ice-ball is
used for freezing such a prostatic tissue segment, the volume of
adjacent tissues exposed to damage is substantially greater than
the volume of the treated tissue. For example, if the area of the
ice-ball in cross section is .pi.R.sup.2, and an effective
treatment of at least -40.degree. C. is provided to an area of
.pi.(R/2).sup.2 (in cross section), then the area of adjacent
tissues (in cross section) exposed to between about -40.degree. C.
and about 0.degree. C. is
.pi.R.sup.2-0.25(.pi.R.sup.2)=0.75(.pi.R.sup.2), which is three
times the area of the tissue effectively treated by the
ice-ball.
[0011] A modification of the classic cryosurgery procedure
described in the preceding paragraph, intended to avoid excessive
damage to adjacent tissues, is to use such a single probe of a
smaller diameter producing an ice-ball of smaller size. Such a
modification, however, exposes the patient to the danger of
malignancy because of a possible incomplete destruction of the
tumor.
[0012] The classical cryosurgery procedure herein described,
therefore, does not provide effective resolution of treatment along
the planes perpendicular to the axis of penetration of the
cryosurgical probe into the patient's organ.
[0013] A further limitation of the classical procedure stems from
the fact that anatomical organs such as the prostate usually
feature an asymmetric three-dimensional shape. Consequently,
introduction of a cryosurgical probe along a specific path of
penetration within the organ may provide effective treatment to
specific regions located at specific depths of penetration but at
the same time may severely damage other portions of the organ
located at other depths of penetration.
[0014] U.S. Pat. No. 6,142,991 to Schatzberger teaches a high
resolution cryosurgical method and device for treating a patient's
prostate designed to overcome the described limitations of the
classical cryosurgery procedure described hereinabove.
Schatzberger's "high resolution" method (referred to as the "HR
method" hereinbelow) comprises the steps of (a) introducing a
plurality of cryosurgical probes to the prostate, the probes having
a substantially small diameter and are distributed across the
prostate, so as to form an outer arrangement of probes adjacent the
periphery of the prostate and an inner arrangement of probes
adjacent the prostatic urethra; and (b) producing an ice-ball at
the end of each of said cryosurgical probes, so as to locally
freeze a tissue segment of the prostate. Schatzberger's apparatus
(referred to hereinbelow as the "HR" apparatus) comprises (a) a
plurality of cryosurgical probes of small diameter, the probes
serve for insertion into the patient's organ, the probes being for
producing ice-balls for locally freezing selected portions of the
organ; (b) a guiding element including a net of apertures for
inserting the cryosurgical probes therethrough; and (c) an imaging
device for providing a set of images, the images being for
providing information on specific planes located at specific depths
within the organ, each of said images including a net of marks
being correlated to the net of apertures of the guiding element,
wherein the marks represent the locations of ice-balls which may be
formed by the cryosurgical probes when introduced through said
apertures of the guiding element to said distinct depths within the
organ.
[0015] The HR method and device provide the advantages of high
resolution of treatment along the axis of penetration of the
cryosurgical probe into the patient's organ as well as along the
planes perpendicular to the axis of penetration, thereby enabling
to effectively destroy selective portions of a patient's tissue
while minimizing damage to adjacent tissues and organs, and to
selectively treat various portions of the tissue located at
different depths of the organ, thereby effectively freezing
selected portions of the tissue while avoiding the damaging of
other tissues and organs located at other depth along the axis of
penetration.
[0016] Schatzberger, in U.S. Pat. No. 6,142,991 also teaches the
additional step of three dimensionally mapping an organ of a
patient so as to form a three dimensional grid thereof, and
applying a multi-probe system introduced into the organ according
to the grid, so as to enable systematic high-resolution three
dimensional cryosurgical treatment of the organ and selective
destruction of the treated tissue with minimal damage to
surrounding, healthy, tissues.
[0017] It is, however, a disadvantage of the HR apparatus and
method as taught in U.S. Pat. No. 6,142,991 that the apparatus
enables, and the method requires, a high level of diagnostic
sophistication in the selection and definition of the particular
volume of tissue to be cryoablated. Real-time imaging capabilities
of the HR apparatus provide for imaging of the target organ at a
selected depth of penetration and thereby assist an operator in
deciding where to introduce and utilize a plurality of cryogenic
probes, yet the complex three-dimensional geometry of the
cryoablation target is poorly rendered by the set of two
dimensional images constituting the three dimensional grid as
contemplated by the HR method and apparatus. In this prior art
method, little assistance is provided for an operator in
understanding the three dimensional shape and structure of the
cryoablation target and the surrounding tissues. Information vital
to the operator may be present in the set of images, yet difficult
for the operator to see and appreciate. In a set of images of this
type, the details may be present, yet it may be difficult to
appreciate their significance because of the difficulty of seeing
them in context. A three dimensional "grid" composed of a plurality
of two dimensional images such as ultrasound images contain many
details, yet do not facilitate the understanding of those details
in a three dimensional context.
[0018] Thus there is a widely recognized need for, and it would be
highly advantageous to have, an apparatus for facilitating
cryosurgery which provides real-time imaging of a cryoablation
target site in a manner which is easy for an operator to visualize
and to understand.
[0019] It is an additional limitation of the HR method and
apparatus, and of other prior art systems, that the imaging
capabilities contemplated are not well adapted to assist an
operator in planning a cryoablation procedure. In addition to the
fact that the imaging facilities there provided are poorly adapted
to visualization of the three dimensional space by an operator,
they are also limited in that the apparatus is poorly adapted to
providing images of the target area in advance of the operation,
e.g., for planning purposes. The described HR equipment might, of
course, but used to create the described three dimensional mapping
of the target area well in advance of a surgical intervention, but
no mechanism is provided for facilitating the relating the images
so obtained, and any planned procedures based on those images, to a
subsequent intervention procedure. Moreover, the fact that the
imaging modality of the HR apparatus is physically connected to
parts of the cryosurgery equipment limits its versatility and may
in some cases make it awkward to use for creating preparatory
images of an intervention site.
[0020] Thus there is a widely recognized need for, and it would be
highly advantageous to have, an apparatus for planning and for
facilitating cryosurgery which provides easily understandable
visualization of a cryoablation target site in advance of a
surgical intervention, which further provides facilities for
studying the site and for planning the intervention, and which yet
further provides facilities for applying information gleaned from
prior study of the imaged site, and specific plans for intervening
in the site, to the actual site, in real time, during the planned
cryoablation operation.
[0021] It is a further limitation of the HR method that no means
are provided for facilitating the relating of images obtained in
advance of a surgical intervention to a subsequent intervention.
Yet whereas ultrasound images of a target site can be generated in
real time during an intervention, and MRI techniques may also (if
somewhat less easily) also be obtained during cryosurgery, other
imaging techniques (CT scans, for example) are less well adapted to
being produced during the course of an actual cryosurgery
intervention.
[0022] Thus there is a widely recognized need for, and it would be
highly advantageous to have, an apparatus and method for
facilitating the relating of images obtained prior surgery to
real-time images, from the same or from additional sources,
obtained during cryosurgery.
[0023] Much is now known about the tissue-destructive processes of
cryoablation, and about the subsequent short-term and long-term
consequences to an organ such as a prostate which has undergone
partial cryoablation. The laws of physics relating to the
conduction of heat in a body, reinforced by experimentation and
further reinforced by accumulated clinical experience in
cryosurgery, provide a wealth of information enabling to predict
with some accuracy the effect of a specific planned cryoablation
procedure on target tissues. This information, and this capability
for prediction, is underutilized in current cryosurgery
practice.
[0024] The Seednet Training And Planning Software ("STPS") marketed
by Galil Medical Ltd. of Yokneam, Israel constitutes a set in this
direction, in that it provides a system for displaying, and
allowing an operator to manipulate, a three-dimensional model of a
prostate, and further allows an operator to plan a cryoablation
intervention and to visualize the predicted effect of that planned
intervention on the prostate tissues. STPS, however, is limited in
that it does not provide means for relating a preliminary three
dimensional model of a prostate to the prostate as revealed in
real-time during the course of a surgical procedure. Moreover, the
predictive ability of the STPS system is limited to predicting the
extent of the freezing produced by a given deployment of a
plurality of cryoprobes over a given time. No assistance is
provided to an operator in discerning interactions between the
predicted cryoablation and specific structures desired to be
protected or to be destroyed. No assistance is given in predicting
long-term effects of a given cryoablation procedure. No assistance
is given in recommending procedures, placement of probes,
temperature, or timing of an intervention.
[0025] Thus there is a widely recognized need for, and it would be
highly advantageous to have, apparatus and method for calculating
probable immediate, short-term, and long-term effects of a planned
cryoablation procedure, thereby to facilitate the planning of such
a procedure. There is further a widely recognized need for, and it
would be highly advantageous to have, apparatus and method for
facilitating the implementation of such a planned procedure, in
real time, during execution of a planned cryoablation.
[0026] It is noted that with respect to BPH, the need for such a
planning and facilitation apparatus is particularly strong.
[0027] BPH, which affects a large number of adult men, is a
non-cancerous enlargement of the prostate. BPH frequently results
in a gradual squeezing of the portion of the urethra which
traverses the prostate, also known as the prostatic urethra. This
causes patients to experience a frequent urge to urinate because of
incomplete emptying of the bladder and a burning sensation or
similar discomfort during urination. The obstruction of urinary
flow can also lead to a general lack of control over urination,
including difficulty initiating urination when desired, as well as
difficulty in preventing urinary flow because of the residual
volume of urine in the bladder, a condition known as urinary
incontinence. Left untreated, the obstruction caused by BPH can
lead to acute urinary retention (complete inability to urinate),
serious urinary tract infections and permanent bladder and kidney
damage.
[0028] Most males will eventually suffer from BPH. The incidence of
BPH for men in their fifties is approximately 50% and rises to
approximately 80% by the age of 80. The general aging of the United
States population, as well as increasing life expectancies, is
anticipated to contribute to the continued growth in the number of
BPH sufferers.
[0029] Patients diagnosed with BPH generally have several options
for treatment: watchful waiting, drug therapy, surgical
intervention, including transurethral resection of the prostate
(TURP), laser assisted prostatectomy and new less invasive thermal
therapies.
[0030] Various disadvantages of existing therapies have limited the
number of patients suffering from BPH who are actually treated. In
1999, the number of patients actually treated by surgical
approaches was estimated to be 2% to 3%. Treatment is generally
reserved for patients with intolerable symptoms or those with
significant potential symptoms if treatment is withheld. A large
number of the BPH patients delay discussing their symptoms or elect
"watchful waiting" to see if the condition remains tolerable.
[0031] Thus, development of a less invasive, more convenient, or
more successful treatment for BPH could result in a substantial
increase in the number of BPH patients who elect to receive
interventional therapy.
[0032] Cryoablation is a candidate for being such a popularize
treatment.
[0033] With respect to drug therapies: some drugs are designed to
shrink the prostate by inhibiting or slowing the growth of prostate
cells. Other drugs are designed to relax the muscles in the
prostate and bladder neck to relieve urethral obstruction. Current
drug therapy generally requires daily administration for the
duration of the patient's life.
[0034] With respect to surgical interventions: the most common
surgical procedure, transurethral resection of the prostate (TURP),
involves the removal of the prostate's core in order to reduce
pressure on the urethra. TURP is performed by introducing an
electrosurgical cutting loop through a cystoscope into the urethra
and "chipping out" both the prostatic urethra and surrounding
prostate tissue up to the surgical capsule, thereby completely
clearing the obstruction. It will be appreciated that this
procedure results in a substantial damage inflicted upon the
prostatic urethra.
[0035] With respect to laser ablation of the prostate: laser
assisted prostatectomy includes two similar procedures, visual
laser ablation of the prostate (V-LAP) and contact laser ablation
of the prostate (C-LAP), in which a laser fiber catheter is guided
through a cystoscope and used to ablate and coagulate the prostatic
urethra and prostatic tissue. Typically, the procedure is performed
in the hospital under either general or spinal anesthesia, and an
overnight hospital stay is required. In V-LAP, the burnt prostatic
tissue then necroses, or dies and over four to twelve weeks is
sloughed off during urination. In C-LAP, the prostatic and urethral
tissue is burned on contact and vaporized. Again, it will be
appreciated that these procedures result in a substantial damage
inflicted upon the prostatic urethra.
[0036] With respect to heat ablation therapies: these therapies,
under development or practice, are non-surgical, catheter based
therapies that use thermal energy to preferentially heat diseased
areas of the prostate to a temperature sufficient to cause cell
death. Thermal energy forms being utilized include microwave, radio
frequency (RF) and high frequency ultrasound energy (HIFU). Both
microwave and RF therapy systems are currently being marketed
worldwide. Heat ablation techniques, however, burn the tissue,
causing irreversible damage to peripheral tissue due to protein
denaturation, and destruction of nerves and blood vessels.
Furthermore, heat generation causes secretion of substances from
the tissue which may endanger the surrounding area.
[0037] With respect to transurethral RF therapy: transurethral
needle ablation (TUNA) heats and destroys enlarged prostate tissue
by sending radio waves through needles urethrally positioned in the
prostate gland. The procedures prolongs about 35 to 45 minutes and
may be performed as an outpatient procedure. However TUNA is less
effective than traditional surgery in reducing symptoms and
improving urine flow. TUNA also burn the tissue, causing
irreversible damage to peripheral tissue due to protein
denaturation, and destruction of nerves and blood vessels.
Furthermore, as already discussed above, heat generation causes
secretion of substances from the tissue which may endanger the
surrounding area.
[0038] In contrast to the alternative treatments for BPH listed
above, cryoablation therapy presents significant advantages. The
volume of an enlarged prostate can be reduced, and stricture to the
urethra can be eliminated, by selective destruction of prostate
tissue by cryoablation. Tissues destroyed by cryoablation in
treating BPH are gradually absorbed by the body, rather than being
sloughed off during urination.
[0039] When the tissues to be cryoablated are appropriately
selected and accurately cryoablated, there may be minimal
endangerment of vital healthy functional tissues in proximity to
the prostate. Thus, cryoablation is an important technique for
treating BPH and has potential for becoming an increasingly popular
therapy and enabling treatment of a large population of sufferers
who today receive no effective treatment at all for their
condition.
[0040] Thus, there is a widely recognized need for, and it would be
highly advantageous to have, apparatus and method facilitating the
planning cryoablation for the treatment of BPH by recommending
appropriate number or placement of loci for cryoablation based on a
patient's symptomotology, thereby helping to make this useful
therapy accessible to surgeons not specialized in this specific
method of treatment.
[0041] Particularly for surgeons who are not specialists in the
particular limited field of cryoablation of the prostate, there is
a widely recognized need for, and it would be highly advantageous
to have, apparatus and method which facilitates the execution of a
planned cryoablation treatment of the prostate or of another organ
by providing feedback on the progress of an intervention by
comparing real-time imaging of the intervention site with a
planning model of the site, providing warnings when freezing,
visible in ultrasound, approaches areas designated as needing to be
protected from damage, or when destruction of tissues risks failing
to cover volumes designated as requiring to be destroyed.
Similarly, there is a widely recognized need for, and it would be
highly advantageous to have, mechanisms for guiding movements of an
operator during a cryoablation procedure, or for automatically
managing the movement of cryosurgical tools such as cryoprobes
during a cryoablation intervention, according to information based
on a plan of the intervention and feedback obtained through
real-time imaging of the intervention site.
[0042] In one respect, a system for planning a cryoablation
intervention is particularly useful. Prior art has given little
consideration to the interactive effects of a plurality of closely
placed cryoprobes. Yet tissues which are in proximity to two or
more cryoprobes may be cooled by several sources simultaneously,
and consequently achieve a lower temperature than would be expected
when considering the well-known freezing patterns created by a
single cryoprobe used in isolation.
[0043] Thus there is a widely recognized need for, and it would be
highly advantageous to have, system and method for utilizing a
plurality of cryoprobes that takes into account their
mutually-reinforcing cooling effect to create a near-uniform cold
field within a volume. It would further be advantageous to have a
system and method for defining a volume in which cognizance is take
of the mutually reinforcing cooling effect of a plurality of
closely placed cryoprobes to smoothly and accurately define a
border of a cryoablation volume, thereby ensuring total destruction
of tissues within that volume while minimizing damage to tissues
outside that volume.
SUMMARY OF THE INVENTION
[0044] According to one aspect of the present invention there is
provided a planning system for planning a cryosurgical ablation
procedure, comprising a first imaging modality for creating
digitized preparatory images of an intervention site, a
three-dimensional modeler for creating a three-dimensional model of
the intervention site based on the digitized preparatory images;
and a simulator for simulating a cryosurgical intervention, having
an interface useable by an operator for specifying loci for
insertion of cryoprobes and operational parameters for operation of
the cryoprobes for cryoablating tissues, and a displayer for
displaying in a common virtual space an integrated image comprising
a display of said three-dimensional model of said intervention site
and a virtual display of cryoprobes inserted at said loci.
[0045] According to further features in preferred embodiments of
the invention described below, the planning system further
comprises a memory for storing said specified loci for insertion of
cryoprobes and said operational parameters for operation of said
cryoprobes.
[0046] According to still further features in the described
preferred embodiments the first imaging modality is selected from
the group consisting of magnetic resonance imaging, ultrasound
imaging and computerized tomography imaging, and the
three-dimensional model is expressible in a three-dimensional
Cartesian coordinate system.
[0047] According to still further features in the described
preferred embodiments the interface also serves for highlighting
selected regions within the three-dimensional model, and the
integrated image further comprises a display of an
operator-highlighted regions. The interface is useable by an
operator for identifying tissues to be cryoablated and for
identifying tissues to be protected from damage during
cryoablation, and the integrated image further comprises a display
of said operator-identified tissues to be cryoablated and of said
operator-identified tissues to be protected from damage during said
cryoablation.
[0048] According to still further features in the described
preferred embodiments the system further comprises a predictor for
predicting an effect on tissues of the patient of operation of the
cryoprobes at the loci according to the operational parameters, and
the model displayer additionally displays in the common virtual
space a representation of the predicted effect.
[0049] According to still further features in the described
preferred embodiments, the system further comprises an evaluator
for comparing the predicted effect to an operator-defined goal of
the procedure. The evaluator is for identifying areas of predicted
less-than-total destruction of tissues within a volume of desired
total destruction of tissues as defined by an operator, and for
identifying areas specified as requiring protection during
cryoablation which may be endangered by a specified planned
cryoablation procedure.
[0050] According to still further features in the described
preferred embodiments, the system comprises a recommender for
recommending cryosurgical procedures to an operator, the
recommendation being based on goals of a cryoablation procedure,
the goals being specified by an operator, and further being based
on the three-dimensional model of the site, thereby facilitating
planning the cryoablation procedure. The recommender may recommend
an optimal number of cryoprobes for use in a cryoablation
procedure, or an optimal temperature for a cryoprobe for use in a
cryoablation procedure, or an optimal duration of cooling for a
cryoprobe for use in a cryoablation procedure. The recommendation
may be based on a table of optimal interventions based on expert
recommendations, or on a table of optimal interventions based on
compiled feedback from a plurality of operators, and may comprise
specific locations for insertion of a cryoprobe to affect
cryoablation. The recommended procedures may be for cryoablation of
tissues of a prostate, for treating BPH percutaneously or
transperineally, or for treating a mass or a malignancy. The table
may comprise a measure of volume of a prostate, or a measure of
length of a stricture of a urethra or a measure of symptomatic
severity of a BPH condition such as an AUA questionnaire score.
The recommendation may be of multiple cryoprobes closely placed so
as to ensure a continuous cold field sufficient to ensure complete
destruction of tissues within a target volume, while minimizing
damage to tissues outside said target volume.
[0051] According to another aspect of the present invention there
is provided a surgical facilitation system for facilitating a
cryosurgery ablation procedure, comprising a first imaging
modality, for creating digitized preparatory images of an
intervention site, a three-dimensional modeler for creating a first
three-dimensional model of the intervention site based on the
digitized preparatory images, a second imaging modality, for
creating a digitized real-time image of at least a portion of the
intervention site during a cryosurgery procedure, and an images
integrator for integrating information from the three-dimensional
model of the site and from the real-time image of the site in a
common coordinate system, thereby producing an integrated
image.
[0052] According to further features in preferred embodiments of
the invention described below, the surgical facilitation system
further comprising a planning system as described hereinabove.
[0053] According to still further features in the described
preferred embodiments the surgical facilitation system further
comprises a displayer for displaying the integrated image in a
common virtual space. The displayed integrated image may be a
two-dimensional image or a three-dimensional image.
[0054] According to still further features in the described
preferred embodiments the surgical facilitation system further
comprises a three-dimensional modeler for creating a second
three-dimensional model of at least a portion of the intervention
site based on a plurality of real-time images. The images
integrator may be operable for integrating information from the
first three-dimensional model of the site and from the second
three-dimensional model of at least a portion of the site in a
common coordinate system.
[0055] According to still further features in the described
preferred embodiments the first imaging modality comprises at least
one of a group comprising magnetic resonance imaging, ultrasound
imaging, and computerized tomography imaging, and the second
imaging modality comprises at least one of a group comprising
magnetic resonance imaging, ultrasound imaging, and computerized
tomography imaging.
[0056] According to still further features in the described
preferred embodiments the second imaging modality comprises an
imaging tool operable to report a position of the tool during
creation of the real-time image, thereby providing localizing
information about the real-time image useable by the images
integrator.
[0057] According to still further features in the described
preferred embodiments the imaging tool is an ultrasound probe
inserted in the rectum of a patient and operable to report a
distance of penetration in the rectum of the patient during
creation of ultrasound images of a prostate of the patient.
[0058] According to still further features in the described
preferred embodiments the first three-dimensional model is
expressed in a three-dimensional Cartesian coordinate system.
[0059] According to still further features in the described
preferred embodiments the surgical facilitation system further
comprises an interface useable by an operator for highlighting
selected regions within the first three-dimensional model and the
integrated image further comprises a display of an
operator-highlighted region. The interface is useable by an
operator for identifying tissues to be cryoablated or for
identifying tissues to be protected from damage during
cryoablation, and integrated image further comprises a display of
operator-identified tissues to be cryoablated or of
operator-identified tissues to be protected from damage during said
cryoablation. The interface is also useable by an operator for
labeling topographic features of the first three-dimensional model
and of the real-time images or of the second three-dimensional
model.
[0060] According to still further features in the described
preferred embodiments the images integrator matches
operator-labeled topographic features of the first
three-dimensional model with operator-labeled features of the
real-time images, to orient the first three-dimensional model and
the real-time image with respect to the common coordinate
system.
[0061] According to still further features in the described
preferred embodiments the images integrator matches
operator-labeled topographic features of the first
three-dimensional model with operator-labeled features of the
second three-dimensional model, to orient the first
three-dimensional model and second three-dimensional model with
respect to a common coordinate system.
[0062] According to still further features in the described
preferred embodiments comprises a simulator for simulating a
cryosurgical intervention, the simulator comprising an interface
useable by an operator during a planning phase of the intervention,
for specifying loci for insertion of cryoprobes and operational
parameters for operation of the cryoprobes for cryoablating
tissues, the image integrator being operable to integrate the
operator-specified loci for insertion of cryoprobes into the
integrated image, and the displayer being operable to display the
integrated image.
[0063] According to still further features in the described
preferred embodiments the surgical facilitation system further
comprises a first comparator for comparing the first
three-dimensional model with the real-time image to determine
differences, a representation of the differences being further
displayed by the displayer in the integrated image.
[0064] According to still further features in the described
preferred embodiments the surgical facilitation system further
comprises apparatus for providing feedback to an operator regarding
position of tools being used during a surgical intervention as
compared to the loci for insertion of cryoprobes specified by an
operator during the planning phase of the intervention. The system
further comprises apparatus for providing feedback to an operator
regarding position of tools being used during a surgical
intervention as compared to operator-identified tissues to be
cryoablated, and apparatus for providing feedback to an operator
regarding position of tools being used during a surgical
intervention as compared to operator-identified tissues to be
protected during cryoablation, and apparatus for guiding an
operator in the placement of cryoprobes for affecting cryoablation,
the guiding being according to the loci for insertion of cryoprobes
specified by an operating during the planning phase of the
intervention.
[0065] According to still further features in the described
preferred embodiments the surgical facilitation system further
comprises apparatus for limiting movement of a cryoprobes during a
cryoablation intervention, the limitation being according to the
loci for insertion of cryoprobes specified by an operating during
the planning phase of the intervention.
[0066] According to still further features in the described
preferred embodiments the surgical facilitation system further
comprises a cryoprobe displacement apparatus for moving at least
one cryoprobe to at least one of the loci for insertion of
cryoprobes specified by an operating during the planning phase of
the intervention.
[0067] According to still further features in the described
preferred embodiments the cryoprobe displacement apparatus
comprises a stepper motor and a position sensor, and the surgical
facilitation system is operable to affect cooling of the at least
one cryoprobe, heating of at least one cryoprobe, and is operable
to affect scheduled movement of at least one cryoprobe coordinated
with scheduled alternative heating and cooling of at least one
cryoprobe, to affect cryoablation at a plurality of loci.
[0068] According to yet another aspect of the present invention
there is provided a cryoablation method for ensuring complete
destruction of tissues within a selected target volume while
minimizing destruction of tissues outside the selected target
volume, comprising deploying a plurality of cryoprobes in a dense
array within the target volume, and cooling the cryoprobes to
affect cryoablation, while limiting the cooling to a temperature
only slightly below a temperature ensuring complete destruction of
tissues, thereby limiting destructive range of each cooled
cryoprobe, the plurality of cryoprobes being deployed in an array
sufficiently dense to ensure destruction of tissues within the
target volume.
[0069] According to still further features in the described
preferred embodiments the method further comprises a planner for
planning the dense array, the planner utilizing a three-dimensional
model of the target volume to calculate a required density of the
dense array of deployed cryoprobes operated at a selected
temperature, to affect complete destruction of tissues within the
selected target volume.
[0070] According to still further features in the described
preferred embodiments the method further comprises using a planner
for planning the dense array, the planner utilizing a
three-dimensional model of the target volume to calculate, for a
plurality of cryoprobes deployed to a selected array of freezing
loci, a temperature and duration of cooling for each of the
cryoprobes sufficient to affect complete destruction of tissues
within the selected target volume, while also minimizing cooling of
tissues outside of the selected target volume.
[0071] According to yet another aspect of the present invention
there is provided a cryoablation method ensuring complete
destruction of tissues within a selected target volume while
minimizing destruction of tissues outside the selected target
volume, comprising utilizing cryoprobes to affect cryoablation at a
plurality of freezing loci, the loci being of a first type and of a
second type, the first type being located adjacent to a surface of
the selected target volume and the second type being located at an
interior portion of the selected target volume, and cooling
cryoprobes deployed at loci of the first type to a first degree of
cooling and cooling cryoprobes deployed at loci of the second type
to a second degree of cooling, the first degree of cooling being
less cooling than the second degree of cooling, thereby affecting
wide areas of destruction around each cryoprobe deployed at loci of
the second type and narrow areas of destruction around each
cryoprobe deployed at loci of the first type, thereby ensuring
complete destruction of tissues within a selected target volume
while minimizing destruction of tissues outside the selected target
volume.
[0072] According to still further features in the described
preferred embodiments cryoprobes deployed to freezing loci of the
first type are cooled to a first temperature and cryoprobes
deployed to freezing loci of the second type are cooled to a second
temperature, the second temperature being lower than the first
temperature.
[0073] According to still further features in the described
preferred embodiments cryoprobes deployed to freezing loci of the
first type are cooled for a first length of time, and cryoprobes
deployed to freezing loci of the second type are cooled for a
second length of time, the second length of time being longer than
the first length of time.
[0074] According to still further features in the described
preferred embodiments the method further comprises a planner for
planning the dense array, the planner utilizing a three-dimensional
model of the target volume to calculate, for a given array of
freezing loci, a required temperature and length of cooling time
for loci of the first type and for loci of the second type, to
affect complete destruction of tissues within the selected target
volume while minimizing destruction of issues outside the selected
target volume.
[0075] According to yet another aspect of the present invention
there is provided a method for planning a cryosurgical ablation
procedure, comprising utilizing a first imaging modality to create
digitized preparatory images of an intervention site, utilizing a
three-dimensional modeler to create a three-dimensional model of
the intervention site based on the digitized preparatory images,
and utilizing a simulator having an interface useable by an
operator for specifying loci for insertion of cryoprobes and for
specifying operational parameters for operation of the cryoprobes,
to specify loci for insertion of cryoprobes and operational
parameters for operation of the cryoprobes for cryoablating
tissues, thereby simulating a planned cryosurgical ablation
procedure.
[0076] According to still further features in the described
preferred embodiments, the method further comprises utilizing a
displayer to display in a common virtual space an integrated image
comprising a display of the three-dimensional model of the
intervention site and a virtual display of cryoprobes inserted at
the loci, and utilizing a memory to store the specified loci for
insertion of cryoprobes and the operational parameters for
operation of the cryoprobes. The first imaging modality is selected
from the group consisting of magnetic resonance imaging, ultrasound
imaging and computerized tomography imaging. The three-dimensional
model is expressible in a three-dimensional Cartesian coordinate
system. The method further comprises utilizing the interface to
highlight selected regions within the three-dimensional model.
Highlighting maybe be used to identify tissues to be cryoablated
and to identify tissues to be protected from damage during
cryoablation.
[0077] According to still further features in the described
preferred embodiments the method further comprises utilizing a
predictor to predict an effect on tissues of the patient of
operation of the cryoprobes at the loci according to the
operational parameters, and the model displayer additionally
displays in the common virtual space a representation of the
predicted effect.
[0078] According to still further features in the described
preferred embodiments the method further comprises utilizing an
evaluator to compare the predicted effect to an operator-defined
goal of the procedure.
[0079] According to still further features in the described
preferred embodiments the method further comprising utilizing the
evaluator to identify areas of predicted less-than-total
destruction of tissues within a volume of desired total destruction
of tissues as defined by an operator, and utilizing the evaluator
to identify areas specified as requiring protection during
cryoablation which may be endangered by a specified planned
cryoablation procedure.
[0080] According to still further features in the described
preferred embodiments the method further comprises utilizing a
recommender for recommending cryosurgical procedures, the
recommendation being based on goals of a cryoablation procedure,
the goals being specified by an operator, and further being based
on the three-dimensional model of the site. The recommender
recommends an optimal number of cryoprobes for use in a
cryoablation procedure, an optimal temperature for a cryoprobe for
use in a cryoablation procedure, an optimal duration of cooling for
a cryoprobe for use in a cryoablation procedure. The recommendation
is based on a table of optimal interventions based on expert
recommendations, or on a table of optimal interventions based on
compiled feedback from a plurality of operators.
[0081] According to still further features in the described
preferred embodiments the recommendation comprises specific
locations for insertion of a cryoprobe to affect cryoablation.
[0082] According to still further features in the described
preferred embodiments the recommended procedures are for
cryoablation of tissues of a prostate.
[0083] According to still further features in the described
preferred embodiments the recommended procedures are for treating
BPH, percutaneously or transperineally.
[0084] According to still further features in the described
preferred embodiments the recommended procedures are for treating a
mass.
[0085] According to still further features in the described
preferred embodiments the recommended procedures are for treating a
malignancy.
[0086] According to still further features in the described
preferred embodiments the table comprises a measure of volume of a
prostate.
[0087] According to still further features in the described
preferred embodiments the table comprises a measure of length of a
stricture of a urethra.
[0088] According to still further features in the described
preferred embodiments the table comprises a measure of symptomatic
severity of a BPH condition.
[0089] According to still further features in the described
preferred embodiments the measure of symptomatic severity of a BPH
condition is an AUA score.
[0090] According to still further features in the described
preferred embodiments the recommendation is of multiple cryoprobes
closely placed so as to ensure a continuous cold field sufficient
to ensure complete destruction of tissues within a target volume,
while minimizing damage to tissues outside the target volume.
[0091] According to still another aspect of the present invention
there is provided a method for facilitating a cryosurgery ablation
procedure, comprising utilizing a first imaging modality for
creating digitized preparatory images of an intervention site,
utilizing a three-dimensional modeler for creating a first
three-dimensional model of the intervention site based on the
digitized preparatory images, utilizing a second imaging modality
for creating a digitized real-time image of at least a portion of
the intervention site during a cryosurgery procedure, and utilizing
an images integrator for integrating information from the
three-dimensional model of the site and from the real-time image of
the site in a common coordinate system, thereby producing an
integrated image the site, facilitative to an operator practicing a
cryoablation procedure.
[0092] According to still further features in the described
preferred embodiments the method further comprises utilizing a
planning method.
[0093] According to still further features in the described
preferred embodiments the method further comprises utilizing a
displayer for displaying the integrated image in a common virtual
space.
[0094] According to still further features in the described
preferred embodiments the displayed integrated image is a
two-dimensional image.
[0095] According to still further features in the described
preferred embodiments the displayed integrated image is a
three-dimensional image.
[0096] According to still further features in the described
preferred embodiments the method further comprises utilizing a
three-dimensional modeler for creating a second three-dimensional
model of at least a portion of the intervention site based on a
plurality of real-time images.
[0097] According to still further features in the described
preferred embodiments he method further comprises utilizing the
images integrator to integrate information from the first
three-dimensional model of the site and from the second
three-dimensional model of at least a portion of the site in a
common coordinate system.
[0098] According to still further features in the described
preferred embodiments the first imaging modality comprises at least
one of a group comprising magnetic resonance imaging, ultrasound
imaging, and computerized tomography imaging.
[0099] According to still further features in the described
preferred embodiments the second imaging modality comprises at
least one of a group comprising magnetic resonance imaging,
ultrasound imaging, and computerized tomography imaging.
[0100] According to still further features in the described
preferred embodiments the method further comprises utilizing an
imaging tool to report a position of the tool during creation of
the real-time image, thereby providing localizing information about
the real-time image useable by the images integrator.
[0101] According to still further features in the described
preferred embodiments the imaging tool is an ultrasound probe
inserted in the rectum of a patient operated to report a distance
of penetration of the tool in the rectum of the patient during
creation of ultrasound images of a prostate of the patient.
[0102] According to still further features in the described
preferred embodiments the first three-dimensional model is
expressed in a three-dimensional Cartesian coordinate system.
[0103] According to still further features in the described
preferred embodiments the method further comprises utilizing an
interface to highlight selected regions within the first
three-dimensional model.
[0104] According to still further features in the described
preferred embodiments the integrated image comprises a display of
an operator-highlighted region.
[0105] According to still further features in the described
preferred embodiments the method further comprises utilizing the
interface for identifying tissues to be cryoablated.
[0106] According to still further features in the described
preferred embodiments the integrated image further comprises a
display of the operator-identified tissues to be cryoablated.
[0107] According to still further features in the described
preferred embodiments he method further comprises utilizing the
interface for identifying tissues to be protected from damage
during cryoablation.
[0108] According to still further features in the described
preferred embodiments the integrated image further comprises a
display of the operator-identified tissues to be protected from
damage during the cryoablation.
[0109] According to still further features in the described
preferred embodiments the method further comprises utilizing the
interface for labeling topographic features of the first
three-dimensional model.
[0110] According to still further features in the described
preferred embodiments the method further comprises utilizing the
interface for labeling topographic features of the real-time
images.
[0111] According to still further features in the described
preferred embodiments the method further comprises utilizing the
interface for labeling topographic features of the second
three-dimensional model.
[0112] According to still further features in the described
preferred embodiments the images integrator matches
operator-labeled topographic features of the first
three-dimensional model with operator-labeled features of the
real-time images, to orient the first three-dimensional model and
the real-time image with respect to the common coordinate
system.
[0113] According to still further features in the described
preferred embodiments the images integrator matches
operator-labeled topographic features of the first
three-dimensional model with operator-labeled features of the
second three-dimensional model, to orient the first
three-dimensional model and second three-dimensional model with
respect to the common coordinate system.
[0114] According to still further features in the described
preferred embodiments the method further comprises simulating a
cryosurgical intervention by utilizing a simulator having an
interface, and utilizing the interface during a planning phase of
the intervention to specify loci for insertion of cryoprobes into a
cryoablation site in a patient and to specify operational
parameters for operation of the cryoprobes for cryoablating
tissues, and further utilizing the image integrator to integrate
the specified loci into the integrated image, and utilizing the
displayer to display the integrated image.
[0115] According to still further features in the described
preferred embodiments the method further comprises simulating a
cryosurgical intervention by receiving from an operator during a
planning phase of the intervention specifications of loci for
insertion of cryoprobes into a cryoablation site and operational
parameters for operation of the cryoprobes for cryoablating
tissues, utilizing the image integrator to integrate the
operator-specified loci into the integrated image, and utilizing
the displayer to display the integrated image.
[0116] According to still further features in the described
preferred embodiments the method further comprises utilizing a
first comparator for comparing the first three-dimensional model
with the real-time image to determine differences.
[0117] According to still further features in the described
preferred embodiments the method further comprises utilizing
apparatus for providing feedback to an operator regarding position
of tools being used during a surgical intervention as compared to
the loci for insertion of cryoprobes specified by an operator
during the planning phase of the intervention.
[0118] According to still further features in the described
preferred embodiments the method further comprises providing
feedback to an operator regarding a position of a tool being used
during a surgical intervention as compared to the loci for
insertion of cryoprobes specified by an operator during the
planning phase of the intervention.
[0119] According to still further features in the described
preferred embodiments the method further comprises utilizing
apparatus for providing feedback to an operator regarding a
position of a tool being used during a surgical intervention as
compared to a position of operator-identified tissues to be
cryoablated.
[0120] According to still further features in the described
preferred embodiments the method further comprises utilizing
apparatus for providing feedback to an operator regarding a
position of a tool being used during a surgical intervention as
compared to a position of operator-identified tissues to be
protected during cryoablation.
[0121] According to still further features in the described
preferred embodiments the method further comprises utilizing
apparatus for guiding an operator in the placement of cryoprobes
for affecting cryoablation, the guiding being according to the loci
for insertion of cryoprobes specified by an operating during the
planning phase of the intervention.
[0122] According to still further features in the described
preferred embodiments the method further comprises guiding an
operator in the placement of cryoprobes for affecting cryoablation,
the guiding being according to the loci for insertion of cryoprobes
specified by an operating during the planning phase of the
intervention.
[0123] According to still further features in the described
preferred embodiments the method further comprises utilizing
apparatus for limiting movement of a cryoprobe during a
cryoablation intervention, the limitation being according to the
loci for insertion of cryoprobes specified by an operating during
the planning phase of the intervention.
[0124] According to still further features in the described
preferred embodiments the method further comprises utilizing
cryoprobe displacement apparatus for moving at least one cryoprobe
to at least one of the loci for insertion of cryoprobes specified
by an operator during the planning phase of the intervention.
[0125] According to still further features in the described
preferred embodiments the method further comprises utilizing a
stepper motor to move the cryoprobe.
[0126] According to still further features in the described
preferred embodiments the method further comprises utilizing a
position sensor to sense a position of the cryoprobe.
[0127] According to still further features in the described
preferred embodiments the method further comprises utilizing
control apparatus to control cooling of the at least one
cryoprobe.
[0128] According to still further features in the described
preferred embodiments the method further comprises utilizing
control apparatus to control heating of the at least one
cryoprobe.
[0129] According to still further features in the described
preferred embodiments the method further comprises controlling the
at least one cryoprobe according to a schedule of movements
coordinated with a schedule of alternative heating and cooling of
the at least one cryoprobe, to affect cryoablation at a plurality
of loci.
[0130] The present invention successfully addresses the
shortcomings of the presently known configurations by providing a
system and method for effectively planning a cryoablation procedure
by simulating such a procedure based on preparatory imaging of a
target site in a patient, by simulating the procedure, by
recommending procedural steps and by evaluating procedural steps
specified by a user.
[0131] The present invention further successfully addresses the
shortcomings of the presently known configurations by providing a
system and method for facilitating a cryoablation intervention by
relating preparatory imaging of a site, and plans for intervening
at that site, to real-time images of the site during
cryoablation.
[0132] The present invention further successfully addresses the
shortcomings of the presently known configurations by providing a
system and method for completely destroying target tissues at a
cryoablation site while limiting damage to healthy tissues in close
proximity to that site.
[0133] Implementation of the method and the apparatus of the
present invention involves performing or completing selected tasks
or steps manually, automatically, or a combination thereof.
Moreover, according to actual instrumentation and equipment of
preferred embodiments of the method and apparatus of the present
invention, several selected steps could be implemented by hardware
or by software on any operating system of any firmware or a
combination thereof. For example, as hardware, control of selected
steps of the invention could be implemented as a chip or a circuit.
As software, control of selected steps of the invention could be
implemented as a plurality of software instructions being executed
by a computer using any suitable operating system. In any case,
selected steps of the method of the invention could be described as
being controlled by a data processor, such as a computing platform
for executing a plurality of instructions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0134] The invention is herein described, by way of example only,
with reference to the accompanying drawings. With specific
reference now to the drawings in detail, it is stressed that the
particulars shown are by way of example and for purposes of
illustrative discussion of the preferred embodiments of the present
invention only, and are presented in the cause of providing what is
believed to be the most useful and readily understood description
of the principles and conceptual aspects of the invention. In this
regard, no attempt is made to show structural details of the
invention in more detail than is necessary for a fundamental
understanding of the invention, the description taken with the
drawings making apparent to those skilled in the art how the
several forms of the invention may be embodied in practice.
[0135] In the drawings:
[0136] FIG. 1a is a graph showing the profile of temperature
distribution within an ice-ball formed at the tip of a cryosurgical
probe;
[0137] FIG. 1b is a graph showing the effectiveness of a
cryosurgical treatment, given in percentage of tissue destruction,
as a function of temperature;
[0138] FIGS. 2a-2c are cross sectional views of an ice-ball formed
at the tip of a conventional cryosurgical probe introduced into a
patient's prostate;
[0139] FIGS. 3a-3b are cross sectional views of two ice-balls
formed at the tips of cryosurgical probes introduced into a
patient's prostate, according to methods of the prior art;
[0140] FIG. 4 is a cross sectional view illustrating a method for
treating a patient's prostate, according to methods of the prior
art;
[0141] FIG. 5 is a cross sectional view illustrating a further
method for treating a patient's prostate, according to methods of
the prior art;
[0142] FIG. 6a is a schematic illustration of a multi-probe
cryosurgical device according to methods of the prior art;
[0143] FIG. 6b is a schematic illustration of a pre-cooling element
according to methods of the prior art;
[0144] FIG. 7 is a schematic longitudinal section of a preferred
cryosurgical probe according to methods of the prior art;
[0145] FIG. 8 is a perspective view of a guiding element for
receiving cryosurgical probes, the guiding element being connected
to an ultrasound probe, according to methods of the prior art;
[0146] FIGS. 9 and 10 illustrate a method including the steps of
forming a three-dimensional grid of a patient's prostate and
introducing cryosurgical probes thereto, according to methods of
the prior art;
[0147] FIG. 11 is a simplified block diagram of a planning system
for planning a cryoablation procedure, according to a first
preferred embodiment of the present invention;
[0148] FIGS. 12a-12b are a flow chart showing a method for
automatically generating a recommendation relating to a
cryoablation procedure, according to an embodiment of the present
invention;
[0149] FIG. 13 is a chart showing temperature profiles for several
cryoablation methods, is useful for understanding FIGS. 14 and
15;
[0150] FIG. 14 is a simplified flow chart showing a method for
ensuring total destruction of a selected volume while limiting
damage to tissues outside that selected volume, according to an
embodiment of the present invention;
[0151] FIG. 15 is a simplified flow chart showing another method
for ensuring total destruction of a selected volume while limiting
damage to tissues outside that selected volume, according to an
embodiment of the present invention;
[0152] FIG. 16 is a simplified block diagram of surgical
facilitation system for facilitating a cryosurgery ablation
procedure, according to an embodiment of the present invention;
and
[0153] FIG. 17 is a schematic diagram of mechanisms for control of
cryosurgical tools by a surgical facilitation system, according to
an embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0154] The present invention relates to system and method for
planning a cryoablation procedure and to system and method for
facilitating a cryoablation procedure. More particularly, the
present invention relates to the use of integrated images
displaying, in a common virtual space, a three-dimensional model of
a surgical intervention site based on digitized preparatory images
of the site from first imaging modalities, simulation images of
cryoprobes used according to an operator-planned cryoablation
procedure at the site, and real-time images provided by second
imaging modalities during cryoablation. The present invention
further relates to system-supplied recommendations for and
evaluations of the planned cryoablation procedure, and to
system-supplied feedback to an operator and system-supplied
guidance and control signals for operating a cryosurgery tool
during cryoablation. The present invention still further relates to
methods for generating a nearly-uniform cold field among a
plurality of cryoprobes, for cryoablating a volume with smooth and
well-defined borders.
[0155] For purposes of better understanding the present invention,
reference is first made to the construction and operation of
conventional (i.e., prior art) systems as illustrated in FIGS.
1-10.
[0156] FIG. 1a illustrates the profile of temperature distribution
across an ice-ball formed at the tip of a cryosurgical probe. As
shown, the temperature at a surface 5 of the ice-ball is 0.degree.
C. The temperature declines exponentially towards a center 1 of the
ball where it preferably reaches the value of -170.degree. C., such
that an isothermal surface 7 of about -40.degree. C. is typically
located within the ice-ball at the half way between the center of
the ball and its surface. Thus, if the ice-ball features a radius
R, then the radius of the -40.degree. C. isothermal surface 7 is
about R/2.
[0157] FIG. 1b is a graph showing the effectiveness of a
cryosurgical treatment (given in percentage of tissue destruction)
as a function of temperature. As shown, the temperature required
for effectively destroying a tissue is at least about -40.degree.
C. Accordingly, in order to effectively destroy a tissue, the
isothermal surface of -40.degree. C. (shown in FIG. 1a) should be
placed at the periphery of the treated tissue so that the entire
area of the treated tissue is exposed to at least about -40.degree.
C., thereby exposing adjacent healthy tissues and organs to the
external portion of the ice-ball. The application of temperatures
of between about -40.degree. C. and 0.degree. C. to such healthy
tissues usually causes substantial damage thereto, which damage may
result in temporary or permanent impairment of functional
organs.
[0158] FIGS. 2a-2c illustrate prior-art cryosurgical methods
wherein a single cryosurgical probe of a substantially large
diameter, typically 3-5 millimeters, is introduced between the
patient's prostatic urethra and the periphery of the prostate, so
as to destroy the prostatic tissue extending therebetween.
[0159] Specifically, FIGS. 2a-2c are cross sectional views of an
ice-ball 9 formed at the end of a conventional cryosurgical tip
introduced into a prostate 2 of a patient. The patient's prostatic
urethra, rectum and nerves are designated as 4, 3, and 6
respectively.
[0160] A single ice-ball 9 is formed within the prostatic tissue
segment extending between the prostatic urethra 4 and the periphery
of the prostate 13. The dimensions of a conventional cryosurgical
probe are designed so as to provide an ice-ball 9 having an inner
portion 10 extending through a substantially significant portion of
such a tissue segment, so as to apply temperatures of between about
-170.degree. C. and about -40.degree. C. thereto. The application
of a single probe for producing a single ice-ball 9 imposes a
trade-off between several options.
[0161] FIGS. 2a and 2b illustrate the trade-off between a first
option of avoiding the damaging of the patient's prostatic urethra
4 yet damaging nerves 6 present close to the periphery 13 of the
prostate 2 (FIG. 2a), and a second option of avoiding the damaging
of the patient's nerves 6 yet damaging urethra 4 (FIG. 2b).
[0162] As shown in FIG. 2a, the isothermal surface 7 of -40.degree.
C. is positioned substantially at the periphery 13 of the patient's
prostate 2, such that surface 5 of the ice-ball 9 is positioned
substantially near the patient's urethra 4, so as to avoid damaging
of the patient's urethra 4. Thus, the inner portion 10 of ice-ball
9 effectively freezes the peripheral regions (in cross section) of
the prostate, while outer portion 12 of ice-ball 9 extends through
the patient's nerves 6. The application of temperatures of between
about -40.degree. C. and 0.degree. C. to the patient's nerves 6 may
result in temporary or permanent impairment thereof.
[0163] Similarly, when ice-ball 9 is positioned between the
patient's urethra 4 and rectum 3 in such a manner so as to avoid
the damaging of urethra 4, the application of between about
-40.degree. C. and 0.degree. C. to the patient's rectum may result
in temporary or permanent impairment thereof.
[0164] As shown in FIG. 2b, the isothermal surface 7 of -40.degree.
C. is positioned substantially near the patient's urethra 4 such
that surface 5 of ice-ball 9 is positioned substantially near the
patient's nerves 6 and/or rectum 3 (not shown), so as to avoid
damaging of the patient's nerves 6 and/or rectum 3. Thus, inner
portion 10 of ice-ball 9 effectively freezes the central regions
(in cross section) of prostate 2, while outer portion 12 of
ice-ball 9 extends through the patient's urethra 4. The application
of temperatures of between about -40.degree. C. and 0.degree. C. to
the patient's urethra 4 may result in temporary or permanent
impairment thereof.
[0165] However, none of the alternatives shown in FIGS. 2a and 2b
provides an effective treatment (temperature of at least about
-40.degree. C.) to the entire prostatic tissue segment extending
between urethra 4 and the periphery 13 of the prostate, thereby
exposing the patient to the risk of malignancy.
[0166] FIG. 2c shows another possible alternative wherein a thicker
cryosurgical probe, having a tip diameter of between 4 and 6
millimeters is used for producing a lager ice-ball, of about 4-5
centimeters in diameter, so as to enable effective treatment of the
entire prostatic tissue segment extending between the urethra 4 and
periphery 13 of prostate 2. As shown, inner portion 10 of the
ice-ball 9 extends through the entire tissue segment (in cross
section) between urethra 4 and periphery 13 of the prostate,
thereby exposing urethra 4 and nerves (not shown), as well as the
rectum 3, to outer portion 12 of the ice-ball 9.
[0167] The thickness (in cross section) of tissues exposed to outer
portion 12 of the ice-ball is about R/2, wherein R is the radius of
ice-ball 9. Thus, the volume of adjacent tissues exposed to damage
becomes substantially greater than the volume of the treated
tissue.
[0168] Thus, the conventional cryosurgical probes and methods fail
to provide the necessary resolution of treatment required for
enabling an accurate and effective destruction of a tissue while
preserving other tissues and organs adjacent thereto.
[0169] FIGS. 3a and 3b are schematic illustrations of a
cryosurgical method according to another method of prior art,
wherein a plurality of cryosurgical probes of substantially small
diameters are introduced between the patient's prostatic urethra 4
and periphery 13 of prostate 2, so as to destroy the prostatic
tissue extending therebetween.
[0170] As shown in FIG. 3a, preferably two probes are introduced
into a prostatic tissue segment extending between the patient's
prostatic urethra 4 and periphery 13 of prostate 2, so as to form
two smaller ice-balls, 9a and 9b.
[0171] According to the configuration shown in FIG. 3a, each of
ice-balls 9a and 9b features a radius of R/2, which is half the
radius of ice-ball 9 shown in FIG. 2c. Accordingly, ice-balls 9a
and 9b include respective inner portions, 14a and 14b, each having
a radius of R/4, and respective outer portions, 16a and 16b, each
having a thickness of R/4.
[0172] Therefore, by introducing two probes of a small diameters
rather than a single probe of a larger diameter into the tissue
segment extending between prostatic urethra 4 and periphery 13 of
prostate 2, the thickness of adjacent tissues exposed to damage is
substantially decreased. The specific example of FIG. 3a shows that
the thickness (in cross section) of adjacent tissues exposed to
between about -40.degree. C. and 0.degree. C. is only R/4, which is
half the thickness and respectively much less the volume (e.g., 8
fold less), exposed to damage when using the prior art method
(shown in FIG. 2c).
[0173] By further decreasing the diameter of the cryosurgical
probes and introducing a plurality of probes into the tissue
segment extending between urethra 4 and periphery 13 of prostate 2,
the damage to surrounding tissues may be further minimized, thereby
improving the resolution of the cryosurgical treatment.
[0174] Another prior art embodiment is shown in FIG. 3b, wherein
two probes are introduced into the tissue segment extending between
the patient's urethra 4 and periphery 13 of prostate 2, so as to
form two ice-balls 9a and 9b, such that inner portion 14a of
ice-ball 9a is substantially spaced from inner portion 14b of
ice-ball 9b, and outer portion 16a of ice-ball 9a partially
overlaps outer portion 16b of ice-ball 9b, the overlapping region
being designated as 17. The specific example shown in FIG. 3b is of
two ice-balls each having a radius of R/5, wherein R is the radius
of a conventional ice-ball as shown in FIG. 2c. By using such
configuration, the thickness of adjacent tissues exposed to damage
is decreased to R/5 and the volume thereof is decreased
respectively. It will be appreciated that in the example given
substantial fractions of region 17, from which heat is extracted by
two probes, will become cooler than -40.degree. C.
[0175] The specific examples shown in FIGS. 3a and 3b are of two
ice-balls having tangent and spaced inner portions, respectively.
However, a plurality of probes may be used, each having a distinct
diameter, the inner portions of which being tangent or spaced.
[0176] Referring to FIG. 4, a prior-art cryosurgical method is
shown, illustrating the distribution of a plurality of cryosurgical
probes across a patient's prostate, wherein a single probe is
introduce into a tissue segment extending between prostatic urethra
4 and periphery 13 of prostate 2. According to such a prior art
method, about 5-7 probes are introduced into the patient's
prostate, wherein each of the probes features a diameter of about 3
millimeters. FIG. 4 shows a specific example wherein five probes
are introduced so as to form five ice-balls having inner portions
10a-10e and outer portions 12a-12e. As shown, an effective
treatment is provided by inner portions 10a-10e, and regions
therebetween marked 19, only to limited regions of the prostate,
wherein the damage caused to adjacent tissues such as the patient's
urethra 4, rectum 3 and nerve 6b by outer portions 12a-12e is
considerable.
[0177] FIG. 5 shows a preferred distribution of cryosurgical probes
according to another method of prior art. As shown, at least two
cryosurgical probes of substantially small diameter are introduced
into specific segments of prostatic tissue extending between
urethra 4 and periphery 13 of prostate 2. FIG. 5 shows a specific
example wherein twenty probes are introduced into the patient's
prostate 2, including five pairs of inner and outer cryosurgical
probes located at specific segments of the prostate extending from
the urethra 4 to periphery 13, and additional (five pairs in the
example given) of outer cryosurgical probes are introduced
therebetween. The inner portions of the ice-balls formed by the
pairs of outer and inner probes are designated as 14a and 14b,
respectively, wherein the inner portions of the ice-balls formed
therebetween are designated as 14c.
[0178] The diameter of a single cryosurgical probe according to the
prior art method presented in FIG. 5 is preferably between about
1.2 millimeters and about 1.4 millimeters.
[0179] As shown, such distribution of substantially small diameter
cryosurgical probes enables to provide an effective treatment of at
least -40.degree. C. to a larger area of the prostatic tissue while
substantially minimizing the thickness of healthy adjacent tissues
exposed to damage.
[0180] Thus, the prior art method presented in FIG. 5 substantially
increases the effectiveness and resolution of treatment relative to
the prior art method presented by FIG. 4.
[0181] The pattern of distribution of probes shown in FIG. 5
includes an inner circle and an outer circle of probes, wherein a
portion of the probes is arranged in pairs of an inner probe and an
outer probe. According to another configuration (not shown), the
probes are arranged in an inner circle and an outer circle, but not
necessarily in pairs of an inner probe and an outer probe.
[0182] The probes may be sequentially introduced to and extracted
from the patient's prostate so as to sequentially freeze selected
portions thereof. A method of quick extraction of the probes
without tearing pieces of tissue from the patient, which stick to
the tip of the probe, is disclosed hereinunder.
[0183] The introduction of a plurality of small diameter
cryosurgical probes improves the resolution of treatment along the
planes perpendicular to the axis of penetration of the probes into
the prostate. However, the prostate, as other anatomical organs,
features an asymmetric three dimensional shape. Thus, a specific
pattern of distribution of probes may provide an effective
treatment to a distinct plane located at a specific depth of
penetration, but at the same time may severely damage non-prostatic
tissues located at other depths of penetration. There is need for
cryosurgical method and apparatus which enable high resolution of
treatment along and perpendicular to the axis of penetration of the
probes into a patient's organ. Presented hereinbelow is a
cryosurgical method and apparatus according to prior art which
enable high resolution of treatment along the axis of penetration
of the cryosurgical probe into the patient's organ as well as along
the planes perpendicular to the axis of penetration, wherein these
high resolutions are achieved by forming a three-dimensional grid
of the organ, preferably by using ultrasound imaging, and inserting
each of the cryosurgical probes to a specific depth within the
organ according to the information provided by the grid.
[0184] Referring to FIGS. 6a, 6b and 7, a cryosurgical apparatus
according to methods of prior art includes a plurality of
cryosurgical probes 53, each having an operating tip 52 including a
Joule-Thomson cooler for freezing a patient's tissue and a holding
member 50 for holding by a surgeon. As shown in FIG. 7, operating
tip 52 includes at least one passageway 78 extending therethrough
for providing gas of high pressure to orifice 80 located at the end
of operating tip 52, orifice 80 being for passage of high pressure
gas therethrough, so as to cool operating tip 52 and produce an
ice-ball at its end 90. Gases which may be used for cooling
include, but are not limited to argon, nitrogen, air, krypton,
CO.sub.2, CF.sub.4, xenon, or N.sub.2O.
[0185] When a high pressure gas such as argon expands through
orifice 80 it liquefies, so as to form a cryogenic pool within
chamber 82 of operating tip 52, which cryogenic pool effectively
cools surface 84 of operating tip 52. Surface 84 of operating tip
52 is preferably made of a heat conducting material such as metal
so as to enable the formation of an ice-ball at end 90 thereof.
[0186] Alternatively, a high pressure gas such as helium may be
used for heating operating tip 52 via a reverse Joule-Thomson
process, so as to enable treatment by cycles of cooling-heating,
and further for preventing sticking of the probe to the tissue when
extracted from the patient's body, and to enable fast extraction
when so desired.
[0187] When a high pressure gas such as helium expands through
orifice 80 it heats chamber 82, thereby heating surface 84 of
operating tip 52.
[0188] Operating tip 52 includes at least one evacuating passageway
96 extending therethrough for evacuating gas from operating tip 52
to the atmosphere.
[0189] As shown FIG. 7, holding member 72 may include a heat
exchanger for pre-cooling the gas flowing through passageway 78.
Specifically, the upper portion of passageway 78 may be in the form
of a spiral tube 76 wrapped around evacuating passageway 96, the
spiral tube being accommodated within a chamber 98. Thus, gas
evacuated through passageway 96 may pre-cool the incoming gas
flowing through spiral tube 76.
[0190] As further shown in FIG. 7, holding member 72 may include an
insulating body 92 for thermally insulating the heat exchanger from
the external environment.
[0191] Furthermore, operating tip 52 may include at least one
thermal sensor 87 for sensing the temperature within chamber 82,
the wire 89 of which extending through evacuating passageway 96 or
a dedicated passageway (not shown).
[0192] In addition, holding member 72 may include a plurality of
switches 99 for manually controlling the operation of probe 53 by a
surgeon. Such switches may provide functions such as on/off,
heating, cooling, and predetermined cycles of heating and cooling
by selectively and controllably communicating incoming passageway
70 with an appropriate external gas container including a cooling
or a heating gas.
[0193] As shown in FIG. 6a, each of cryosurgical probes 53 is
connected via a flexible connecting line 54 to a connecting site 56
on a housing element 58, preferably by means of a linking element
51. Cryosurgical probes 53 may be detachably connected to
connecting sites 56.
[0194] Preferably, evacuating passageway 96 extends through
connecting line 54, such that the outgoing gas is evacuated through
an opening located at linking element 51 or at any other suitable
location, e.g., manifold 55, see below. Preferably, line 54 further
includes electrical wires for providing electrical signals to the
thermal sensor and switches (not shown).
[0195] Each of cryosurgical probes 53 is in fluid communication
with a manifold 55 received within a housing 58, manifold 55 being
for distributing the incoming high pressure gas via lines 57 to
cryosurgical probes 53.
[0196] As shown, housing 58 is connected to a connector 62 via a
flexible cable 60 including a gas tube (not shown), connector 62
being for connecting the apparatus to a high pressure gas source
and an electrical source.
[0197] The apparatus further includes electrical wires (not shown)
extending through cable 60 and housing 58 for providing electrical
communication between the electrical source and cryosurgical probes
53.
[0198] Preferably, housing 58 includes a pre-cooling element,
generally designated as 61, for pre-cooling the high pressure gas
flowing to cryosurgical probes 53. Preferably, pre-cooling element
61 is a Joule-Thomson cooler, including a tubular member 48
received within a chamber 49, tubular member 48 including an
orifice 59 for passage of high pressure gas therethrough, so as to
cool chamber 49, thereby cooling the gas flowing through tubular
member 48 into manifold 55.
[0199] Another configuration of a pre-cooling element 61 is shown
in FIG. 6b, wherein tubular member 48 is in the form of a spiral
tube wrapped around a cylindrical element 47, so as to increase the
area of contact between tubular member 48 and the cooling gas in
chamber 49.
[0200] According to yet another configuration (not shown), housing
58 includes a first tubular member for supplying a first high
pressure gas to manifold 55, and a second tubular member for
supplying a second high pressure gas to pre-cooling element 61. Any
combination of gases may be used for cooling and/or heating the
gases flowing through such tubular members.
[0201] Alternatively, a cryogenic fluid such as liquid nitrogen may
be used for pre-cooling the gas flowing through housing 58.
Alternatively, an electrical pre-cooling element may used for
pre-cooling the gas.
[0202] Preferably, thermal sensors (not shown) may be located
within cable 60 and manifold 55 for measuring the temperature of
gas flowing therethrough.
[0203] Referring to FIGS. 8-10, method and apparatus according to
prior art applies an imaging device such as ultrasound, MRI or CT,
so as to form a three-dimensional grid of the patient's treated
organ, e.g., prostate, the three dimensional grid serves for
providing information on the three dimensional shape of the organ.
Each of the cryosurgical probes is then inserted to a specific
depth within the organ according to the information provided by the
grid.
[0204] As shown in FIG. 8, an ultrasound probe 130 is provided for
insertion into the patient's rectum, ultrasound probe 130 being
received within a housing element 128. A guiding element 115 is
connected to housing element 128 by means of a connecting arm 126.
As shown, guiding element 115 is in the form of a plate 110 having
a net of apertures 120, each aperture serves for insertion of a
cryosurgical probe therethrough. Preferably, the distance between
each pair of adjacent apertures 120 is between about 2 millimeters
and about 5 millimeters.
[0205] As shown in FIG. 9, ultrasound probe 130 is introduced to a
specific depth 113 within the patient's rectum 3. A net of marks
112 is provided on the obtained ultrasound image 114, the net of
marks 112 on image 114 being accurately correlated to the net of
apertures 120 on guiding element 115.
[0206] Thus, marks 112 on image 114 sign the exact locations of the
centers of ice-balls which may be formed at the end of the
cryosurgical probes inserted through apertures 120 to the patient's
prostate 2, wherein image 114 relates to a specific depth of
penetration 113 of the cryosurgical probes into the prostate 2.
[0207] As shown in FIG. 9, ultrasound probe 130 is gradually
introduced to various depths 113 of rectum 3, thereby producing a
set of images 114, wherein each image relates to a respective depth
of penetration into the prostate 2. Thus, each of images 114
relates to a specific plane perpendicular to the axis of
penetration of the cryosurgical probes.
[0208] The set of images 114 provides a three dimensional grid of
the prostate. Such three-dimensional grid is then used for planning
the cryosurgical procedure.
[0209] For example, the introduction of a cryosurgical probe along
a given axis of penetration to a first depth may effectively
destroy a prostatic tissue segment, while introduction of the probe
to a second depth may severely damage the prostatic urethra.
[0210] Since the ice-ball is locally formed at the end of the
cryosurgical probe, each probe may be introduced to a specific
depth so as to locally provide an effective treatment to a limited
portion of the prostate while avoiding the damaging of
non-prostatic or prostatic tissues located at other depths of
penetration.
[0211] FIG. 10 shows the insertion of an operating tip 52 of a
cryosurgical probe 50 through an aperture of guiding element 115
into the prostate 2 of a patient.
[0212] Preferably, a plurality of cryosurgical probes are
sequentially inserted through apertures 120 of guiding element 115
into the patient's prostate, wherein each probe is introduced to a
specific depth, thereby providing substantially local effective
treatment to distinct segments of the prostatic tissue while
avoiding the damaging of other prostatic or nonprostatic tissue
segments.
[0213] Preferably, each of the cryosurgical probes includes a scale
for indicating the depth of penetration into the prostate.
[0214] Reference is now made to FIG. 11, which is a simplified
block diagram of a planning system for planning a cryoablation
procedure, according to a first preferred embodiment of the present
invention.
[0215] In FIG. 11, a planning system 240 for planning a
cryoablation procedure comprises a first imaging modality 250 which
serves for creating digitized preparatory images 254 of a
cryoablation intervention site. First imaging modality 250 will
typically be a magnetic resonance imaging system (MRI), an
ultrasound imaging system, a computerized tomography imaging system
(CT), a combination of these systems, or a similar system able to
produce images of the internal tissues and structures of the body
of a patient. First imaging modality 250 is for producing digitized
images of a cryoablation intervention site, which site includes
body tissues whose cryoablation is desired (referred to herein as
"target" tissue), which may be a tumor or other structure, and body
tissues and structures in the immediate neighborhood of the target
tissues, which constitute the target tissue's physical
environment.
[0216] Some types of equipment useable as first imaging modality
250, a CT system for example, typically produce a digitized image
in a computer-readable format. If equipment used as first imaging
modality 250 does not intrinsically produce digitized output, as
might be the case for conventional x-ray imaging, then an optional
digitizer 252 may be used to digitize non-digital images, to
produce digitized preparatory images 254 of the site.
[0217] Digitized images 254 produced by first imaging modality 250
and optional digitizer 252 are passed to a three-dimensional
modeler 256 for creating a three-dimensional model 258 of the
intervention site. Techniques for creating a three dimensional
model based on a set of two dimensional images are well known in
the art. In the case of CT imaging, creation of a three dimensional
model is typically an intrinsic part of the imaging process.
PROVISION, from Algotec Inc.
(http://www.algotec.com/products/provision.htm) is an example of
software designed to make a 2-D to 3-D conversion for images
generated by CT scans. To accomplish the same purpose starting from
ultrasound imaging, SONOReal.TM. software from BIOMEDICOM
(http://www.biomedicom.com/) may be used.
[0218] Three dimensional model 258 is preferably expressible in a
three dimensional Cartesian coordinate system.
[0219] Three dimensional model 258 is useable by a simulator 260
for simulating a cryosurgical intervention. Simulator 260 comprises
a displayer 262 for displaying views of model 258, and an interface
264 useable by an operator for specifying loci for insertion of
simulated cryoprobes 266 and operational parameters for operation
of simulated cryoprobes 266 for cryoablating tissues. Thus, an
operator (i.e., a user) can use simulator 260 to simulate a
cryoablation intervention, by using interface 264 to command
particular views of model 258, and by specifying both where to
insert simulated cryoprobes 266 into an organ imaged by model 258,
and how to operate cryoprobes 266. Typically, an operator may
specify positions for a plurality of simulated cryoprobes 266, and
further specify operating temperatures and durations of cooling for
cryoprobes 266. Display 262 is then useable for displaying in a
common virtual space an integrated image 268 comprising a display
of three dimensional model 258 and a virtual display of simulated
cryoprobes 266 inserted at said operator-specified loci.
[0220] Planning system 240 optionally comprises a memory 270, such
as a computer disk, for storing operator-specified loci for
insertion of cryoprobes and operator-specified parameters for
operation simulated cryoprobes 266.
[0221] Interface 264 comprises a highlighter 280 for highlighting,
under control of an operator, selected regions within three
dimensional model 258. Operator-highlighted selected regions of
model 258 are then optionally displayed as part of an integrated
image 268.
[0222] In particular, highlighter 280 is useable by an operator for
identifying tissues to be cryoablated. Preferably, interface 264
permits an operator to highlight selected regions of three
dimensional model 258 so as to specify therein tissues to be
cryoablated, or alternatively interface 264 permits an operator to
highlight selected regions of digitized preparatory images 254,
specifying therein tissues to be cryoablated. In the latter case,
three-dimensional modeler 256 is then useable to translate regions
highlighted on digitized preparatory images 254 into equivalent
regions of three dimensional model 258. In both cases, tissues
highlighted and selected to be cryoablated can be displayed by
displayer 262 as part of integrated image 268, and can be recorded
by memory 270 for future display or other uses.
[0223] Similarly, highlighter 280 is useable by an operator for
identifying tissues to be protected from damage during
cryoablation. Typically, important functional organs not themselves
involved in pathology may be in close proximity to tumors or other
structures whose destruction is desired. For example, in the case
of cryoablation in a prostate, nerve bundles, the urethra, and the
rectum may be in close proximity to tissues whose cryoablation is
desired. Thus, highlighter 280 is useable by an operator to
identify (i.e., to specify the location of) such tissues and to
mark them as requiring protection from damage during
cryoablation.
[0224] Preferably, interface 264 permits an operator to highlight
selected regions of three dimensional model 258 so as to specify
therein tissues to be protected from damage during cryoablation.
Alternatively, interface 264 permits an operator to highlight
selected regions of digitized preparatory images 254, specifying
therein tissues to be protected during cryoablation. In the latter
case, three-dimensional modeler 256 is then useable to translate
regions highlighted on digitized preparatory images 254 into
equivalent regions of three dimensional model 258. In both cases,
tissues highlighted and selected to be protected from damage during
cryoablation can be displayed by displayer 262 as part of
integrated image 268, and can be recorded by memory 270 for future
display or other uses.
[0225] Planning system 240 further optionally comprises a predictor
290, an evaluator 300, and a recommender 310.
[0226] Predictor 290 serves for predicting the effect on tissues of
a patient, if a planned operation of cryoprobes 266 at the
operator-specified loci is actually carried out according to the
operator-specified operational parameters. Predictions generated by
predictor 290 may optionally be displayed by displayer 262 as part
of integrated image 268, in the common virtual space of image
268.
[0227] In a preferred embodiment, predictions of predictor 290 are
based on several sources. The laws of physics, as pertaining to
transfer of heat, provide one predictive source. Methods of
calculation well known in the art may be used to calculate, with
respect to any selected region within three dimensional model 258,
a predicted temperature, given known locations of cryoprobes 266
which are sources of cooling in proximity to such a region, known
temperatures and cooling capacities of cryoprobes 266, and a
duration of time during which cryoprobes 266 are active in cooling.
Thus, a mathematical model based on known physical laws allows to
calculate a predicted temperature for any selected region within
model 258 under operator-specified conditions.
[0228] Experimentation and empirical observation in some cases
indicate a need for modifications of a simple mathematical model
based on physical laws concerning the transfer of heat, as would be
the case, for example, in a tissue wherein cooling processes were
modified by a high rate of blood flow. However, methods for
adapting such a model to such conditions are also well known in the
art. Such methods take into account heat dissipation in flowing
systems, effected by the flow.
[0229] An additional basis for predictions of predictor 290 is that
of clinical observation over time. Table 1 provides an example of a
predictive basis derived from clinical observation, relating to
medium-term and long-term effects of cryoablation procedures in a
prostate. The example provided in Table 1 relates to treatment of
BPH by cryoablation under a standardized set of cryoprobe operating
parameters.
TABLE-US-00001 TABLE 1 Predicted long-term effects of cryoablation
Distance between 3 week volume 3 months volume probes (mm)
consumption (%) consumption (%) 10 70 100 15 55 85 20 40 70 25 30
50
[0230] As may be seen from Table 1, clinical observation leads to
the conclusion that reduction in the volume of a prostate following
cryoablation is a gradual process which continues progressively for
a number of weeks following a cryoablation procedure. The
clinically derived information of Table 1, and similar clinically
derived information, can also serve as a basis for predictions
generated by predictor 290, and displayed by displayer 262 as part
of integrated image 268 in the common virtual space of image
268.
[0231] Evaluator 300 is useable to compare results predicted by
predictor 290 to goals of a surgical intervention as expressed by
an operator. In particular, evaluator 300 can be used to compare
intervention results predicted by predictor 290 under a given
intervention plan specified by an operator, with that operator's
specification of tissues to be cryoablated. Thus, an operator may
use interface 264 to specify tissues to be cryoablated, plan an
intervention by using interface 264 to specify loci for insertion
of cryoprobes 266 and to specify a mode of operation of cryoprobes
266, and then utilize predictor 290 and evaluator 300 to predict
whether, under his specified intervention plan, his/her goal will
be realized and all tissues desired to be cryoablated will in fact
be destroyed. Similarly, an operator may utilize predictor 290 and
evaluator 300 to predict whether, under his/her specified
intervention plan, tissues which he specified as requiring
protection from damage during cryoablation will in fact be
endangered by his planned intervention.
[0232] Recommender 310 may use predictive capabilities of predictor
290 and evaluator 300, or empirically based summaries of
experimental and clinical data, or both, to produce recommendations
for cryoablation treatment.
[0233] As discussed above, predictor 290 and evaluator 300 can be
used to determine, for a given placement of a given number of
cryoprobes and for a given set of operating parameters, whether a
planned cryoablation procedure can be expected to be successful,
success being defined as destruction of tissues specified as
needing to be destroyed, with no damage or minimal damage to
tissues specified as needing to be protected during cryoablation.
Based on this capability, recommender 310 can utilize a variety of
calculation techniques well known in the art to evaluate a
plurality of competing cryoablation intervention strategies and to
express a preference for that strategy which is most successful
according to these criteria.
[0234] In particular, recommender 310 may consider several
intervention strategies proposed by an operator, and recommend the
most successful among them. Alternatively, an operator might
specify a partial set of operating parameters, and recommender 310
might then vary (progressively or randomly) additional operating
parameters to find a `best fit` solution. For example, an operator
might specify tissues to be destroyed, tissues to be protected, and
a two-dimensional array of cryoprobes such as, for example, the two
dimensional placement array of cryoprobes determined by the use of
guiding element 115 having a net of apertures 120 shown in FIG. 8
hereinabove. Recommender 310 could then test a multitude of options
for displacements of a set of cryoprobes in a third (depth)
dimension to determine the shallowest and deepest penetration
desirable for each cryoprobe. Recommender 310 could further be used
to calculate a temperature and duration of freezing appropriate for
each cryoprobe individually, or for all deployed cryoprobes
controlled in unison, in a manner designed to destroy all tissues
specified to be destroyed, while maximizing protection of tissues
specified to be protected.
[0235] Recommendation activity of recommender 310 may also be based
on empirical data such as experimental results or clinical results.
Table 2 provides an example of a basis for making recommendations
derived from clinical observation.
TABLE-US-00002 TABLE 2 Recommended number of cryoprobes to treat
BPH American Urologists Number of Association cross-sections
Questionnaire with stricture of Prostate Number Score the Urethra
Volume of probes 0-7 1-3 25 2 0-7 1-3 40 2 0-7 2-5 40 2 0-7 1-3 50
2-3 0-7 2-5 50 2-3 0-7 1-3 60 2-3 0-7 2-5 60 3 0-7 2-5 100 4 8-19
1-3 40 2-3 8-19 2-5 40 2-3 8-19 1-3 50 2 8-19 2-5 50 2-3 8-19 1-3
60 3 8-19 2-5 60 3-4 8-19 2-5 100 4 20-35 1-3 40 3 20-35 2-5 40 3
20-35 1-3 50 4 20-35 2-5 50 20-35 1-3 60 4 20-35 2-5 60 5 20-35 2-5
100 6
[0236] Table 2 relates to the treatment of BPH by cryoablation.
Table 2 is essentially a table of expert opinion, wherein three
criterions for describing the symptomatic state of a patient are
related, by experts, to a recommendation for treatment. Table 2 was
in fact compiled by a group of experts in the practice of
cryoablation utilizing a particular tool, specifically a tool
similar to that described in FIG. 8 hereinabove, yet a similar
table may be constructed by other experts and for other tools.
Moreover, feedback from the collective clinical experience of a
population of users of a particular tool may be collected over
time, for example by a company marketing such a tool or by an
independent research establishment, and such collected information
may be fed back into recommender 310 to build a progressively
better informed and increasingly useful and reliable recommendation
system.
[0237] The first column of Table 2, the AUA score, is the score of
a questionnaire in use by the American Urological Association which
may be found in Tanagho E. A., and McAninich J. W., Smith's General
Urology, published by McGraw-Hill, Chapter 23. The AUA score is an
estimate of severity of symptoms as subjectively reported by a
patient, and relates to such urinary problems as incomplete
emptying of the bladder, frequency of urination, intermittency,
urgency, weak stream, straining, nocturia, and the patient's
perceived quality of life as it relates to his urinary
problems.
[0238] The second and third columns of Table 2 relate to diagnostic
criteria discernable from three-dimensional model 258 or from
digitized preparatory images 254 from which model 258 derives. The
second column is a measure of the length of that portion of the
urethra observed to be constricted by pressure from a patient's
prostate. The third column is a measure of the volume of that
patient's prostate. Table 2 constitutes a basis for recommending an
aspect of a cryoablation treatment for BPH, specifically for
recommending, in column four, an appropriate number of cryoprobes
to be used in treating a specific patient, based on three
quantitative evaluations of his condition constituted by the
columns one, two and three of Table 2.
[0239] Reference is now made to FIGS. 12a and 12b, which is a flow
chart showing a method for automatically generating a
recommendation relating to a cryoablation procedure, utilizing the
information of Table 2, or similar information, according to an
embodiment of the present invention. In the specific example of
FIGS. 12a-12b, the generated recommendation is relevant to
cryoablation of tissues of a prostate for treatment of BPH.
[0240] At step 320 of FIG. 12a, first imaging modality 250 is used
to create preparatory images, which are digitized at step 322 to
become digitized preparatory images 254. In the example presented,
images 254 are cross sections of a prostate such as those generated
by a series of ultrasound scans taken at regularly intervals of
progressive penetration into the body of a patient, as might be
produced by the ultrasound equipment described with reference to
FIGS. 8-10 hereinabove.
[0241] At optional step 324, an operator marks or otherwise
indicates, with reference to images 254, locations of tissues to be
cryoablated or to be protected, as explained hereinabove. At step
326 images 254 are input to three-dimensional modeler 256, which
creates three-dimensional model 258 of the intervention site at
step 328. Model 258, along with any operator-highlighted and
classified regions of model 258, are displayed at step 329.
[0242] In a parallel process, raw materials for a recommendation
are gathered. At step 330 clinical input in the form of an AUA
score from a questionnaire of a patient's symptoms is input. At
step 332 a count is made of the number of preparatory images 254
(cross-sections) of the urethra which show constriction to the
urethra caused by pressure from the prostate tissue on the urethra.
A count of cross-sections showing constriction is here taken as an
indication of the length of a stricture. Determination of which
cross-section images show signs of constriction may be made by an
operator, or alternatively may be made by automated analysis of
images 256, using image interpretation techniques well known in the
art. At step 334, information available to three-dimension modeler
256 is used to automatically calculate the volume of the
prostate.
[0243] At step 336, information assembled at steps 330, 332, and
334 is used in a table-lookup operation to retrieve a
recommendation for the appropriate number of probes to be used to
treat the imaged specific case of BPH.
[0244] At step 340, an operator optionally inputs specific boundary
conditions which serve to limit recommendations by the system.
Utilizing model 254 created at step 328, operator-specified
boundary conditions from step 340, operator-specified
identification of locations of specific tissues to be ablated or
protected from step 324, and a calculated recommended number of
probes from step 336, a recommendation for optimal positioning of a
recommended number of probes may be made at step 342. Display of a
recommended intervention is made at step 344.
[0245] Optionally, operator-specified placement of simulated
cryoprobes may modify or replace the recommended intervention, at
step 346.
[0246] Step 344 is optionally iterative. That is, an operator may
repeatedly modify definitions of tissues, boundary conditions, or
manual placement of simulated probes, until the operator is
satisfied with the simulated results. As a part of step 344,
activities of evaluator 300 may be evoked, so as to procure system
feedback based on a simulated intervention. Step 344 is repeated so
long as desired by an operator, and until the operator is satisfied
with the results.
[0247] Referring now to FIG. 12b which is a continuation of the
flowchart of FIG. 12a, at step 348 a final plan is optionally saved
to a computer disk or other memory 270.
[0248] In optional step 350, details of the completed intervention
plan can be used to estimate and display expected long-term results
of the planned intervention, such as an expected future volume and
shape of the prostate. Information from Table 2 or an equivalent is
utilized for step 350, as indicated at step 352. It is noted that
long-term volume of the prostate may also be treated as a boundary
condition of an intervention, at step 340.
[0249] The example presented in FIGS. 12a and 12b refers
specifically to a utilization of planning system 240 for treating a
prostate for BPH. Similar utilizations may be contemplated, for
treating other organs, or for treating other conditions of a
prostate.
[0250] In treating BPH, a desired goal is a reduction in prostate
volume so as to relieve pressure on the urethra of a patient,
because pressure on the urethra from an enlarged prostate
interferes with the process of urination. In treating BPH there is
no need to destroy all of a selected volume, but rather simply to
destroy some desired percentage of that volume.
[0251] In treating, for example, a prostate tumor suspected of
malignancy, goals of the intervention are quite different. To avoid
dangerous proliferation of malignant cells, it is desirable to
ablate a defined volume in its entirety. In such a context, when it
is necessity to destroy all tissues within a selected volume, the
functionality of evaluator 300 of planning system 240 is
particularly useful.
[0252] Evaluator 300 is able to calculate, for each arbitrarily
selected small volume of model 258, the cumulative cooling effect
of all cryoprobes in proximity to said selected small volume.
Consequently evaluator 300 is able to make at least a theoretical
determination of whether, for a given deployment of cryoprobes
utilized under a given set of operating parameters, total
destruction of malignant tissues within a selected volume is to be
expected.
[0253] Reference is now made to FIG. 13, which is a chart showing
temperature profiles for several cryoablation methods, useful for
understanding FIGS. 14 and 15. FIG. 13 contrasts the temperature
profiles for cryoablation used in prior art systems 354 as compared
to the temperature profiles 356 utilized according to the methods
of FIGS. 14 and 15.
[0254] Reference is now made to FIG. 14, which is a simplified flow
chart of a method for ensuring total destruction of a selected
volume while limiting damage to tissues outside that selected
volume, according to an embodiment of the present invention.
[0255] The method presented by FIG. 14 comprises (a) deploying a
plurality of cryoprobes in a dense array within a target volume,
and (b) limiting cooling of the deployed cryoprobes to a
temperature only slightly below a temperature ensuring complete
destruction of tissues. The temperature profile required is shown
in detail in FIG. 13, where it is contrasted to a temperature
profile according to methods of prior art. According to the method
of FIG. 14, limiting cooling of each cryoprobe has the effect of
limiting the destructive range of each cooled cryoprobe. If a
plurality of cryoprobes are deployed in an sufficiently dense array
and cooled to an extent such as that indicated in FIG. 13, a
nearly-uniform cold field is created, the field being uniformly
below a temperature required to ensure destruction of tissues
within the field, yet there is relatively little tendency for
destructive temperature to extend far beyond the deployed cryoprobe
array. Thus, in contrast to methods of the prior art, the method
presented by FIG. 14 relies on making a cryoprobe array more dense,
and less cold. Control of degree of cooling may of course be
accomplished by controlling a temperature of cryoprobes of the
array, either individually or collectively, or by controlling
duration of cooling of cryoprobes of the array, or both.
[0256] Reference is now made to FIG. 15, which is a simplified flow
chart of another method for ensuring total destruction of a
selected volume while limiting damage to tissues outside that
selected volume, according to an embodiment of the present
invention.
[0257] The method of FIG. 15 is similar to that of FIG. 14, in that
it utilizes a dense array of cryoprobes cooled to a lesser extent
than the cooling utilized according to methods of prior art.
According to the method of FIG. 15, however, cryoprobes at the
periphery of a target volume are cooled less than are cryoprobes at
the interior of the target volume. Cryoprobes at the interior of
the target volume are, by definition, relatively distant from
tissues desired to be protected, consequently they can be strongly
cooled with impunity, thereby helping to ensure total destruction
of target tissues. In contrast, cryoprobes near the surface of the
target volume are closer to healthy tissues, consequently it is
desirable to cool them less, so as to limit the damage they cause.
Such lesser cooling of surface cryoprobes is possible, without
sacrificing efficient destruction of target tissues, because a
combination of weak cooling from surface probes together with
strong cooling from interior probes creates a near-uniform cold
field near the surface probes which ensures destruction of tissues
on an interior side of the surface probes, while causing relatively
little destruction of tissues on an exterior side of the surface
probes.
[0258] Planning system 240 can be used effectively to plan dense
arrays of cryoprobes according the methods of FIG. 14 and of FIG.
15. For example, a user might specify a particular density of an
array of probes, then use evaluator 300 to evaluate a range of
possible temperature and duration parameters to find an amount and
duration of cooling which ensures that the specified array will
indeed create a nearly-uniform cold field sufficient to destroy all
target tissues. Alternatively, a user might specify a desired
degree of cooling and use planning system 240 to recommend a
required density of the cryoprobe array.
[0259] Thus, evaluator 300 and recommender 310 can be used to
calculated placement and operational parameters of cryoprobes in a
manner which guarantees a nearly-uniform cold field within a
selected volume. If cryoprobes 266 are sufficiently small and
placed sufficiently close together, cooling effects from a
plurality of probes will influence each selected small volume
within a target volume, and an amount of required cooling can be
calculated which will ensure that all of the target volume is
cooled down to a temperature ensuring total destruction of the
target volume.
[0260] In implementing the method of FIG. 15, control of degree of
cooling may of course be accomplished by controlling temperatures
of cryoprobes of the array, either individually or collectively, or
by controlling duration of cooling of cryoprobes of the array, or
both.
[0261] Reference is now made to FIG. 16, which is a simplified
block diagram of a surgical facilitation system for facilitating a
cryosurgery ablation procedure, according to an embodiment of the
present invention.
[0262] In a preferred embodiment, a surgical facilitation system
350 comprises a first imaging modality 250 and optional digitizer
252, for creating digitized preparatory images 254 of an
intervention site, a first three-dimensional modeler 256 for
creating a first three-dimensional model 258 of the intervention
site based on digitized preparatory images 254, a second imaging
modality 360 with optional second digitizer 362 for creating a
digitized real-time image 370 of at least a portion of the
intervention site during a cryosurgery procedure, and an images
integrator 380 for integrating information from three-dimensional
model 258 of the site and from real-time image 370 of the site in a
common coordinate system 390, thereby producing an integrated image
400 displayable by a display 260. Integrated image 400 may be a two
dimensional image 401 created by abstracting information from a
relevant plane of first three dimensional model 258 for combining
with a real-time image 370 representing a view of that plane of
that portion of the site in real-time. Alternatively, a set of
real-time images 370 may be used by a second three dimensional
modeler 375 to create a second three dimensional model 402,
enabling images integrator 380 to express first three dimensional
model 258 and second three dimensional model 402 in common
coordinate system 390, preferably a Cartesian coordinate system,
thereby combining both images into integrated image 400.
[0263] Various strategies may be used to facilitate combining of
model 258 (based on preparatory images 254) with real-time images
370 (or model 402 based thereupon) by images integrator 380.
Processes of scaling of images to a same scale, and of projection
of a `slice` of a three dimensional image to a chosen plane, are
all well known in the art. Basic techniques for feature analysis of
images are also well known, and can deal with problems of fine
alignment of images from two sources, once common features or
common directions have been identified in both images. Techniques
useful for facilitating aligning of both images by images
integrator 380 include: (a) identification of common features in
both images by an operator, for example by identifying landmark
features such as points of entrance of a urethra into, and points
of exit of a urethra from, a prostate, (b) identification of
constant basic directions, such as by assuring that a patient is in
a similar position (e.g., on his back) during both preparatory
imaging and real-time imaging, (c) operator-guided matching,
through use of interface 264, of a first set of images, (d) use of
proprioceptive tools for imaging, that is, tools capable of
reporting, either mechanically or electronically using an
electronic sensor 364 and digital reporting mechanism 365, their
own positions and movements, and (e) using a same body of imaging
equipment to effect both preparatory imaging, producing preparatory
images 254, and real-time imaging during a cryosurgery procedure,
producing real-time images 370. For example, using ultrasound probe
130 of FIGS. 8-10 and FIG. 16 both for preparatory imaging and for
real-time imaging, and assuring that the patient is in a standard
position during both imaging procedures, greatly facilitates the
task of images integrator 380. Equipping ultrasound probe 130 with
stabilizer 366 and controlling its movements with stepper motor
367, as shown in FIG. 16, yet further simplifies the task of images
integrator 380.
[0264] It will be appreciated that the present invention can
benefit from position tracking of various components thereof so as
to assist either in modeling and/or in actually controlling a
cryoablation procedure. Position tracking systems per se are well
known in the art and may use any one of a plurality of approaches
for the determination of position in a two- or three-dimensional
space as is defined by a system-of-coordinates in two, three and up
to six degrees-of-freedom. Some position tracking systems employ
movable physical connections and appropriate movement monitoring
devices (e.g., potentiometers) to keep track of positional changes.
Thus, such systems, once zeroed, keep track of position changes to
thereby determine actual positions at all times. One example for
such a position tracking system is an articulated arm. Other
position tracking systems can be attached directly to an object in
order to monitor its position in space. An example of such a
position tracking system is an assortment of three triaxially
(e.g., co-orthogonally) oriented accelerometers which may be used
to monitor the positional changes of the object with respect to a
space. A pair of such assortments can be used to determine the
position of the object in six-degrees of freedom.
[0265] Other position tracking systems re-determine a position
irrespective of previous positions, to keep track of positional
changes. Such systems typically employ an array of
receivers/transmitters which are spread in known positions in a
three-dimensional space and transmitter(s)/receiver(s),
respectively, which are in physical connection with the object
whose position being monitored. Time based triangulation and/or
phase shift triangulation are used in such cases to periodically
determine the position of the monitored object. Examples of such a
position tracking systems employed in a variety of contexts using
acoustic (e.g., ultrasound) electromagnetic radiation (e.g.,
infrared, radio frequency) or magnetic field and optical decoding
are disclosed in, for example, U.S. Pat. Nos. 5,412,619; 6,083,170;
6,063,022; 5,954,665; 5,840,025; 5,718,241; 5,713,946; 5,694,945;
5,568,809; 5,546,951; 5,480,422 and 5,391,199, which are
incorporated by reference as if fully set forth herein.
[0266] Position tracking of any of the imaging modalities described
herein and/or other system components, such as the cryoprobes
themselves, and/or the patient, can be employed to facilitate
implementation of the present invention.
[0267] In a preferred embodiment, surgical facilitation system 350
further comprises all functional units of planning system 240 as
described hereinabove. That is, facilitation system 350 optionally
comprises simulator 260 having user interface 264 with highlighter
280, each having parts, functions and capabilities as ascribed to
them hereinabove with reference to FIG. 11 and elsewhere. In
particular, system 350 includes the above-described interface
useable by an operator to specify placements and operational
parameters of simulated cryoprobes 266, and to specify tissues to
be cryoablated or to be protected during cryoablation.
[0268] Similarly, facilitation system 350 further optionally
comprises memory 270, predictor 290, evaluator 300, and recommender
310, each having parts, functions and capabilities as ascribed to
them hereinabove with reference to FIG. 11 and elsewhere.
[0269] Thus, in a preferred embodiment of the present invention,
facilitation system 350 is able to undertake all activities
described hereinabove with respect to planning system 240. In
addition, facilitation system 350 is able to provide a variety of
additional services in displaying and evaluating at least one
real-time image 370, and is further able to compare real-time
images 370 to three dimensional model 258, and also to compare
information from real-time images 370 to stored information such as
that identifying operator-specified tissues to be cryoablated or to
be protected, as is explained more fully hereinbelow.
[0270] In a preferred embodiment, either first imaging modality 250
and/or second imaging modality 360 may each independently be a
magnetic resonance imaging system (MRI), an ultrasound imaging
system, a computerized tomography imaging system (CT), some
combination of these systems, or some similar system able to
produce images of the internal tissues and structures of the body
of a patient, yet in the case of second imaging modality 360,
ultrasound and MRI imaging are more typically used, as being more
conveniently combined with cryosurgery processes.
[0271] Facilitation system 350 further comprises a first comparator
390, for comparing first three-dimensional model 248 with real-time
image 370, particularly to discern differences between both images.
Such differences constitute differences between a status of a
planned intervention and a status of an actual intervention in
real-time. Tools, such as cryoprobes, tissues, such as a urethra,
and ice-balls formed during cryoablation, all figure as elements in
three dimensional model 258, and all may be visualized using second
imaging modality 360. Thus, their expected positions, sizes,
orientations, and behaviors may be compared to their actual
real-time positions, sizes, orientations and behaviors during
cryoablation, by comparator 390.
[0272] Differences thereby revealed, and information concerning
such differences, can be of vital importance to an operator in
guiding his actions during an intervention, particularly if the
operator deviates from a planned intervention without being aware
of doing so. A representation of the revealed differences may be
displayed by displayer 262 and highlighted for greater visibility.
A feedback mechanism 392, for example an auditory feedback
mechanism, may be used to draw attention of an operator to serious
discrepancies between a planned and an actual intervention.
[0273] Similarly, comparator 390 can be used to compare status of
objects visible in real-time images 370 with stored information
about operator-specified tissues to be cryoablated. Comparator 390
can thus provide information about, and displayer 262 can display,
situations in which tissues intended to be cryoablated are in fact
not effectively being cryoablated by a procedure. Similarly,
comparator 390 can be used to check status of objects visible in
real-time images 370, relating them to stored information about
operator-specified tissues which are to be protected during
cryoablation. In the case of discrepancies between an actual
situation and an operator-specified desirable situation, display
262 and feedback mechanism 392 can warn an operator when a
procedure seems to be endangering such tissues.
[0274] The capabilities of facilitation system 350 may extend yet
further, to direct guidance to an operator in the manipulation of
cryoablation tools, and even to partial or complete control of such
tools during a phase of a cryoablation intervention.
[0275] Reference is now made to FIG. 17, which is a schematic
diagram of mechanisms for control of cryosurgical tools by a
surgical facilitation system, according to an embodiment of the
present invention.
[0276] A cryosurgical probe 50 is shown passing through an aperture
120 in a guiding element 115 which is realized in this example as a
plate 110. As described hereinabove in the context of the
discussion of FIGS. 8-10, aperture 120 is for limiting sideways
movement of probe 50, which is however free to move forward and
backwards towards and away from a cryoablation site in a patient.
In the prior art methods presented in FIGS. 8-10, such movement was
conceived as under sole and exclusive control of an operator who
advanced and retracted probe 50 manually.
[0277] As has been noted above, the simulation, evaluation, and
recommendation capacities of planning system 240 and facilitation
system 350, based on preparatory images 254 and three dimensional
model 258, allow system 350 to calculate a recommended maximum and
minimum depth for at which each cryoprobe 50 is to be used for
cryoablation. Further, a cryoablation plan manually entered by an
operator may also determine a maximum and minimum depth at which
each cryoprobe 50 is to be used for cryoablation.
[0278] In a simple implementation of mechanical control based on
information from planning system 240 or facilitation system 350,
planned maximum and minimum depths generated by those systems are
communicated to an operator who adjusts a mechanical blocking
element 430 according to a graduated distance scale 432, in a
manner which limits forward or backward movement of probe 50 so as
to prevent an operator from unintentionally and unknowingly
advancing or retracting probe 50 beyond limits of movement planned
for probe 50. Such an arrangement guides and aids an operator in
use and control of probe 50 for effecting cryoablation according to
a plan.
[0279] In a somewhat more sophisticated implementation, control
signals 438 from system 350 activate a stepper motor 434 to
directly control movement of probe 50. Thus, under control of
system 350 and according to a planned, simulated, examined and
theoretically tested procedure, stepper motor 434 can advance probe
50 to a planned depth for performing cryoablation. System 350 can
also send temperature control signals to heating gas valve 440 and
cooling gas valve 442, thereby controlling a flow of heating gas
from heating gas reservoir 444 and a flow of cooling gas from
cooling gas reservoir 446. Thus, under control of an intervention
plan and utilizing mechanisms presented in FIG. 17, system 350 is
able to directly control some or all of a cryoablation
intervention. Thus, in a typical portion of a cryoablation
procedure, stepper 434 advances probe 50 a planned distance,
cooling gas valve 442 opens to allow passage of a gas which cools
probe 50 to cryoablation temperatures and maintains those
temperatures for a planned length of time, then cooling valve 442
closes to halt cooling. Optionally, heating gas valve 440 then
opens to allow passage of a gas which heats probe 50 so as to melt
tissues in contact with probe 50, thereby restoring to it freedom
of motion, whereupon stepper motor 434 can further advance or
retract probe 50 to a new cryoablation position, at which new
position system 350 can optionally repeat this cryoablation
process.
[0280] To ensure accuracy, movement of cryoprobe 50 may be
monitored by a movement sensor 436. Moreover, all the facilities of
system 350 previously described, for comparing real-time positions
of objects with planned positions of those objects, can be brought
to bear, to monitor this independently controlled cryoablation
process.
[0281] It is appreciated that certain features of the invention,
which are, for clarity, described in the context of separate
embodiments, may also be provided in combination in a single
embodiment. Conversely, various features of the invention, which
are, for brevity, described in the context of a single embodiment,
may also be provided separately or in any suitable
subcombination.
[0282] Although the invention has been described in conjunction
with specific embodiments thereof, it is evident that many
alternatives, modifications and variations will be apparent to
those skilled in the art. Accordingly, it is intended to embrace
all such alternatives, modifications and variations that fall
within the spirit and broad scope of the appended claims.
* * * * *
References