U.S. patent application number 16/940419 was filed with the patent office on 2021-01-14 for ablation planning system.
The applicant listed for this patent is KONINKLIJKE PHILIPS N.V.. Invention is credited to SANDEEP DALAL, JOCHEN KRUECKER, XIN LIU.
Application Number | 20210007805 16/940419 |
Document ID | / |
Family ID | 1000005117412 |
Filed Date | 2021-01-14 |
![](/patent/app/20210007805/US20210007805A1-20210114-D00000.png)
![](/patent/app/20210007805/US20210007805A1-20210114-D00001.png)
![](/patent/app/20210007805/US20210007805A1-20210114-D00002.png)
![](/patent/app/20210007805/US20210007805A1-20210114-D00003.png)
![](/patent/app/20210007805/US20210007805A1-20210114-D00004.png)
![](/patent/app/20210007805/US20210007805A1-20210114-D00005.png)
![](/patent/app/20210007805/US20210007805A1-20210114-D00006.png)
![](/patent/app/20210007805/US20210007805A1-20210114-D00007.png)
![](/patent/app/20210007805/US20210007805A1-20210114-D00008.png)
![](/patent/app/20210007805/US20210007805A1-20210114-M00001.png)
United States Patent
Application |
20210007805 |
Kind Code |
A1 |
LIU; XIN ; et al. |
January 14, 2021 |
ABLATION PLANNING SYSTEM
Abstract
An ablation planning system includes a user interface (104)
configured to permit selection of inputs for planning an ablation
procedure. The user interface is further configured to incorporate
selection of ablation probes and one or more combinations of
ablation powers, durations or parameters applicable to selected
probes in the inputs to size the ablation volumes. The user
interface includes a display for rendering internal images of a
patient, the display permitting visualizations of the ablation
volumes for different entry points on the internal images. An
optimization engine (106) is coupled to the user interface to
receive the inputs and is configured to output an optimized therapy
plan which includes spatial ablation locations and temporal
information for ablation so that collateral damage is reduced,
coverage area is maximized and critical structures are avoided in a
planned target volume.
Inventors: |
LIU; XIN; (SCARSDALE,
NY) ; DALAL; SANDEEP; (CORTLANDT MANOR, NY) ;
KRUECKER; JOCHEN; (WASHINGTON DC, DC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KONINKLIJKE PHILIPS N.V. |
EINDHOVEN |
|
NL |
|
|
Family ID: |
1000005117412 |
Appl. No.: |
16/940419 |
Filed: |
July 28, 2020 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
14235140 |
Jan 27, 2014 |
10729499 |
|
|
PCT/IB2012/053860 |
Jul 27, 2012 |
|
|
|
16940419 |
|
|
|
|
61512510 |
Jul 28, 2011 |
|
|
|
61514914 |
Aug 4, 2011 |
|
|
|
61566630 |
Dec 3, 2011 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 2034/104 20160201;
A61B 2034/107 20160201; A61B 34/10 20160201; A61B 18/1815
20130101 |
International
Class: |
A61B 34/10 20060101
A61B034/10; A61B 18/18 20060101 A61B018/18 |
Claims
1. A microwave ablation planning system, comprising: a user
interface configured to permit selection of inputs for planning an
ablation procedure using multiple ablation probes, the user
interface further configured to enable a user to select the
multiple ablation probes for the ablation procedure, a location of
a skin entry point for each of the selected multiple ablation
probes, and one or more combinations of ablation powers, durations,
or parameters applicable to the selected multiple ablation probes,
wherein the selected inputs determine sizes and shapes of ablation
volumes, wherein the user interface further includes a display
configured to render internal images of a patient, wherein the
display is further configured to display visualizations of the
ablation volumes on the internal images; a database configured to
store information related to the multiple ablation probes such that
the information is retrievable by the user interface to select the
multiple ablation probes to be employed as the inputs, wherein the
multiple ablation probes are microwave ablation probes and wherein
the stored information includes power and duration information
corresponding to a plurality of ablation volume sizes and shapes;
and an optimization engine coupled to the user interface and
configured to receive the inputs and configured to output an
optimized microwave ablation therapy plan which includes spatial
ablation locations and power and duration information such that in
a planned microwave ablation target volume collateral damage is
reduced, ablation coverage is maximized, and critical structures
are avoided.
2. The system as recited in claim 1, wherein the optimization
engine computes a cost based on the inputs and minimizes the cost
to determine the output optimized microwave ablation therapy
plan.
3. The system as recited in claim 2, wherein the optimization
engine includes a penalty function to penalize the cost for
unwanted effects.
4. The system as recited in claim 1, wherein the inputs include one
or more of the planned target volume to be covered in the microwave
ablation therapy plan, a margin of error, ablation coverage,
collateral damage, regions to be excluded, ablation power, and
ablation duration.
5. The system as recited in claim 1, wherein the output includes
locations for ablation centers, a minimum number of ablations, a
minimum ablation power or duration, predicted ablation metrics,
collateral damage, unablated planned target volume regions, and
damage to critical structures.
6. The system as recited in claim 7, wherein the plurality of
ablation shapes include ellipses, a major axis of each ellipse
lying along a trajectory between an ablation volume center and a
corresponding skin entry point, radii of each ellipse being
controlled by the ablation power and duration.
7. The system as recited in claim 1, wherein the optimization
engine is configured to interpolate microwave ablation radii from
the power and time data for a plurality of ablation shapes by
assuming the ablation radii grow proportionally with increasing
ablation duration and increasing ablation power.
8. A method for planning a microwave ablation procedure,
comprising: displaying an internal image of a patient on a display
of a user interface, wherein the user interface is configured to
permit selection of inputs for planning an ablation procedure using
multiple ablation probes, the user interface further configured to
input a selection of the multiple ablation probes, input a location
of a skin entry point for each of the selected multiple ablation
probes, and input one or more combinations of ablation power and
duration for the selected ablation probes to size ablation volumes,
the user interface including a display configured to render
internal images of a patient and visualize the ablation volumes,
and the skin entry points on the internal images; wherein the
multiple ablation probes are microwave ablation probes, a size of
the ablation volume of each of the microwave ablation probes being
controlled by application power and duration supplied to each
microwave ablation probe; selecting a plurality of the ablation
probes for performing the ablation procedure using the user
interface; selecting a location of the skin entry point for each of
the multiple ablation probes on the internal image; generating an
optimized microwave ablation plan which includes spatial ablation
locations and ablation power and duration information that reduces
collateral damage, maximizes ablation coverage area, and avoids
critical structures in a planned target volume; and outputting the
optimized therapy plan.
9. The method as recited in claim 8, wherein generating the
optimized microwave plan includes minimizing a cost based on the
selected inputs.
10. The method as recited in claim 9, further including computing a
penalty function to penalize the cost for an unwanted effect.
11. The method as recited in claim 9, wherein the selected inputs
includes one or more of a margin of error, ablation coverage,
collateral damage, regions to be excluded, the ablation power, and
the ablation duration.
12. The method as recited in claim 8, wherein the optimized
microwave ablation plan includes locations for ablation centers, a
minimum number of ablations, a minimum ablation power or duration,
ablation metrics, collateral damage, unablated planned target
volume regions, and damage to critical structures.
13. The method as recited in claim 8, wherein optimizing the
microwave ablation plan includes interpolating microwave ablation
radii from the power and duration for a plurality of ablation
shapes and/or sizes by assuming the ablation radii grow
proportionally with increasing duration and increasing power.
14. The method as recited in claim 8, wherein at least one of the
microwave ablation probes is configured to generate an ellipsoidal
ablation volume, radii of the ellipsoidal ablation volume being
proportional to the ablation power and duration, a major axis of
the ellipsoidal ablation volume being defined by a trajectory
between the ablation volume and the corresponding skin entry point,
and wherein optimizing the therapy plan includes adjusting the
ablation power and duration and the skin entry points.
15. A microwave ablation planning system for planning ablations of
targets with complex shapes comprising: a display configured to
render internal images of an internal region of a patient including
tissue to be ablated, the display further being configured to
visualize a planned target ablation volume to be ablated, ablation
volumes of each of a plurality of microwave ablation probes and
skin entry points, each skin entry point defining a trajectory from
the skin entry point to an ablation center to a corresponding one
of the ablation volumes; a user interface configured to enable
selection of at least two of the plurality of microwave ablation
probes and to retrieve an ablation duration and power to ablation
volume shape relationship for the selected microwave ablation
probes; one or more processors configured to: determine a microwave
ablation plan which maximizes coverage of the planned target volume
and avoids critical structures, the microwave ablation plan
including identifiers of the selected at least two of the microwave
ablation probes, an entry point corresponding to each identified
microwave ablation probe, power applied to each identified
microwave ablation probe, and a duration the power is applied to
each identified microwave ablation probe.
16. The system as recited in claim 15, wherein the one or more
processors are further configured to control the display to render
the internal images of the internal region of the patient,
visualize the planned treatment volume, and visualize the volume
ablated by the two or more selected microwave ablation probes
pursuant to the microwave ablation plan.
17. The system as recited in claim 16, wherein the user interface
is configured to allow a clinician to adjust the entry points, the
ablation powers, and the ablation durations.
18. The system as recited in claim 15, wherein the one or more
processors is configured to determine the microwave ablation plan
using a cost function.
19. The system as recited in claim 18, wherein determining the
microwave ablation plan further includes using a penalty function.
Description
[0001] This application is a continuation of U.S. application Ser
No. 14/235,140, filed Jan. 27, 2014, now U.S. Pat. No. ______ ,
which is a national stage entry of PCT/IB2012/053860 filed Jul. 27,
2012 (WO 2013/014648), which claims priority to provisional
application Ser. No. 61/512,510, filed Jul. 28, 2011, provisional
application Ser. No. 61/514,914, filed Aug. 4, 2011, and
provisional application serial no. 61/566,630, filed Dec. 3, 2011,
all incorporated herein by reference.
[0002] This disclosure relates to medical treatment systems and
methods, and more particularly to ablation planning systems and
methods for patient treatment with improved accuracy.
[0003] Microwave ablation (MWA) is a minimally invasive procedure
used for the treatment of localized tumors most commonly in the
liver, kidney and lung. For large or irregularly shaped lesions,
the treatment requires more than one session, and the physician has
to plan in advance where to place the needle and how many ablations
are needed. MWA has become a recommended treatment modality for
interventional cancer treatment, and has received increasing
attention in recent years. Compared with radiofrequency ablation
(RFA), MWA provides more rapid and larger-volume tissue heating,
and multiple antennae can be used simultaneously with synergistic
effects, e.g., the ablation volume may be increased beyond that
achievable with several sequential single-probe ablations. In
addition, MWA is less susceptible to decreased ablation volumes due
to the heat sink effect (e.g., cooling provided by blood vessels
adjacent to the tumor volume).
[0004] Mental planning of ablations is a daunting task. Physicians
have to picture complete coverage of a three dimensional tumor
volume using overlapping ellipsoidal ablation volumes in different
orientations. Insufficient and imprecise planning leads to
incomplete treatment and potential recurrence of cancer or other
effects. Conventionally, a single ablation probe inserted through a
single entry point is preferred to minimize trauma. However, if
multiple probes are clinically available, large or irregularly
shaped lesions could be treated more effectively than with
conventional single probe units, thus potentially decreasing
procedure time and complications. Mental planning can be an even
more daunting task with multiple entry points. Physicians have to
picture and plan how to completely cover a three dimensional tumor
using an overlapping ellipsoidal ablation volume from different
orientations. Insufficient and imprecise planning leads to
incomplete treatment and potential recurrence of cancer.
[0005] In accordance with the present principles, an ablation
planning system includes a user interface configured to permit
selection of inputs for planning an ablation procedure. The user
interface is further configured to incorporate selection of
ablation probes and one or more combinations of ablation powers,
durations or parameters applicable to selected probes in the inputs
to size the ablation volumes. The user interface includes a display
for rendering internal images of a patient, the display permitting
visualizations of the ablation volumes for different entry points
on the internal images. An optimization engine is coupled to the
user interface to receive the inputs and is configured to output an
optimized therapy plan which includes spatial ablation locations
and temporal information for ablation so that collateral damage is
reduced, coverage area is maximized and critical structures are
avoided in a planned target volume.
[0006] An ablation planning system includes a user interface
configured to permit selection of inputs for planning an ablation
procedure, the user interface further being configured to
incorporate ablation durations in the inputs to size the ablation
volumes. The user interface includes a display for rendering
internal images of a patient. The display permits visualizations of
the ablation volumes for different entry points on the internal
images, and the display is configured to render internal images of
a patient and provide selection controls to enable a user to select
an internal image and a view of the internal image. A database is
configured to store the internal images and information on the
ablation probes to assist in determining sizes and shapes for the
ablation volumes for a given planned target volume by associating
power and time characteristics with the sizes and shapes of the
ablation volumes. An optimization engine is coupled to the user
interface to receive the inputs and is configured to output an
optimized therapy plan which includes spatial ablation locations
and temporal information for minimally needed ablation durations,
so that collateral damage is reduced, coverage area is maximized
and critical structures are avoided in a planned target volume.
[0007] A method for planning an ablation procedure includes
displaying an internal image of a patient on a display of a user
interface; selecting an ablation probe or set of probes for
performing an ablation procedure using the user interface;
selecting a point or points of entry for the ablation probe or set
of probes on the internal image; inputting information to an
optimization engine for a set of inputs including the ablation
probe or set of probes selected, the point or points of entry
selected, time and power information to determine sizes and shapes
of ablation volumes; and outputting from the optimization engine an
optimized therapy plan based on reducing collateral damage,
maximizing coverage area and avoiding critical structures in a
planned target volume.
[0008] These and other objects, features and advantages of the
present disclosure will become apparent from the following detailed
description of illustrative embodiments thereof, which is to be
read in connection with the accompanying drawings.
[0009] This disclosure will present in detail the following
description of preferred embodiments with reference to the
following figures wherein:
[0010] FIG. 1 is a block diagram showing a high-level embodiment of
an ablation therapy system in accordance with the present
principles;
[0011] FIG. 2 is a diagram showing an illustrative graphical user
interface for planning an ablation procedure in accordance with one
illustrative embodiment;
[0012] FIG. 3 is another diagram showing the illustrative graphical
user interface of FIG. 2 showing image details for planning the
ablation procedure in accordance with the illustrative
embodiment;
[0013] FIG. 4 is another diagram showing greater detail on an image
for planning the ablation procedure in accordance with the
illustrative embodiment;
[0014] FIG. 5 is a block/flow diagram showing steps for planning,
executing or training for an ablation procedure in accordance with
an illustrative embodiment;
[0015] FIG. 6 is a block diagram showing a system for planning and
performing an ablation procedure in accordance with the present
principles; and
[0016] FIG. 7-I is a block/flow diagram showing steps for planning,
executing or training for an ablation procedure using the system of
FIG. 6 in accordance with another illustrative embodiment.
[0017] FIG. 7-II is a block/flow diagram showing additional steps
for planning, executing or training for an ablation procedure using
the system of FIG. 6 in accordance with another illustrative
embodiment.
[0018] In accordance with the present principles, to generate a
clinically relevant and reliable result, an automated planning
system is provided that warrants precise locations of probes and
complete coverage of tumor and margin (planned target volume, PTV).
An automatic coverage method is described. The searching for the
best ablation centers is treated as an iterative non-linear
optimization problem where a cost function is formulated as the
weighted sum of un-ablated PTV volume and unwanted collateral
damage to the adjacent health tissue. This is a non-linear
optimization problem which aims to minimize cancerous tissue that
is untreated and the healthy tissue that is damaged. The entire
planning system is implemented with a Graphic User Interface (GUI)
that allows for interactive planning scenarios including proper
probe selection, skin entry localization, ablation number
specifications, etc. The planning system is integrated as a first
step of an electro-magnetically guided navigation system where
planning is executed to permit plans to be transferred to
subsequent navigation working steps in an adaptive manner.
[0019] Focal tumor ablation is an effective alternative to surgical
resection. A microwave ablation (MWA) planning system in accordance
with one embodiment includes a database, an optimization engine and
a user-interface. The system provides optimized ablation parameters
as output to help physicians maximize tumor coverage, minimize
collateral damage to healthy tissue and/or optimize overall
procedure execution in other ways, such as by avoiding critical
structures, such as blood vessels or the like. The system's
user-interface component advantageously provides input/output
specific to microwave ablation, but is also applicable to other
ablation systems that have similar information needs (e.g.,
cryogenic ablation). Such a planning system can assist
interventionists to best plan the ablation procedure using resource
information available from the database and information specified
by the users as input. The output of the system includes but is not
limited to the optimized ablation parameters computed by the
optimization engine.
[0020] To facilitate efficient and accurate execution of ablation
procedures, ablation planning systems have addressed the needs for
radio frequency ablation (RFA) procedures. Such planning systems
generally determine the number and/or location of individual
ablations that together allow complete and efficient eradication of
a tumor. These planning systems, however, do not exploit the
specific advantages of MWA technology which may include, e.g.: 1)
The ability to customize an ablation size by choosing specific
power/time/temperature parameters when running the MWA device; and
2) The ability to insert several probes simultaneously with
synergistic effects, thus increasing the ablated volume further and
decreasing procedure time. As a result of the more rapid
destruction of tissue, MWA procedures are generally more difficult
to control than RFA and may cause harm if not used with care and
confidence. A planning system in accordance with the present
embodiments addresses MWA-specific parameters and workflows and is
highly desirable to help physicians achieve better microwave
ablation results.
[0021] In contrast to RFA, MWA probes can produce ablations in a
range of ablation sizes. The size of the ablation zone is a
function of time and power supplied to the probe. Planning systems
geared towards RFA make no recommendation for specific power/time
settings, nor are they able to take advantage of the variable
ablation sizes in determining the optimal ablation plan.
Furthermore, there may be patient-specific considerations (or
computational complexity and time constraints) that would limit the
choices of power/time settings that the physician is willing to
consider. There may also be patient-specific considerations or
overall time/throughput considerations that would make a particular
treatment approach with multiple simultaneous probe insertions
advantageous.
[0022] MWA manufacturers may provide only limited information on
ablation volume varied with power/time, and if provided, the
ablation information only includes discrete power/time inputs and
their corresponding ablation sizes (e.g., ablation size at 5
minutes, 10 minutes, using power 50 W). It is difficult for users
to extrapolate the size of a necrosis zone using discrete intervals
of the given inputs (e.g., ablation zone at 8 minutes). The present
embodiments address these shortcomings and clinical needs of the
prior art by providing a microwave ablation planning system with a
user interface, optimization engine, and other components that
permit efficient planning and execution of microwave ablation
procedures.
[0023] It should be understood that the present invention will be
described in terms of microwave ablation; however, other ablation
technologies are contemplated. In particular, the present
principles are particularly useful with ablation technologies that
employ time dependent variations for ablation zones. In other
embodiments, in addition to or instead of time dependent ablation
treatment volumes, other dependent variables may be employed, such
as, temperature-dependent variables, power-dependent variables,
etc.
[0024] It also should be understood that the present invention will
be described in terms of medical instruments; however, the
teachings of the present invention are much broader and are
applicable to any instruments employed in treating or analyzing
complex biological or mechanical systems. In particular, the
present principles are applicable to internal tracking and planning
procedures of biological systems, procedures in all areas of the
body such as the lungs, gastro-intestinal tract, excretory organs,
blood vessels, etc. The elements depicted in the FIGS. may be
implemented in various combinations of hardware and software and
provide functions which may be combined in a single element or
multiple elements.
[0025] The functions of the various elements shown in the FIGS. can
be provided through the use of dedicated hardware as well as
hardware capable of executing software in association with
appropriate software. When provided by a processor, the functions
can be provided by a single dedicated processor, by a single shared
processor, or by a plurality of individual processors, some of
which can be shared. Moreover, explicit use of the term "processor"
or "controller" should not be construed to refer exclusively to
hardware capable of executing software, and can implicitly include,
without limitation, digital signal processor ("DSP") hardware,
read-only memory ("ROM") for storing software, random access memory
("RAM"), non-volatile storage, etc.
[0026] Moreover, all statements herein reciting principles,
aspects, and embodiments of the invention, as well as specific
examples thereof, are intended to encompass both structural and
functional equivalents thereof. Additionally, it is intended that
such equivalents include both currently known equivalents as well
as equivalents developed in the future (i.e., any elements
developed that perform the same function, regardless of structure).
Thus, for example, it will be appreciated by those skilled in the
art that the block diagrams presented herein represent conceptual
views of illustrative system components and/or circuitry embodying
the principles of the invention. Similarly, it will be appreciated
that any flow charts, flow diagrams and the like represent various
processes which may be substantially represented in computer
readable storage media and so executed by a computer or processor,
whether or not such computer or processor is explicitly shown.
[0027] Furthermore, embodiments of the present invention can take
the form of a computer program product accessible from a
computer-usable or computer-readable storage medium providing
program code for use by or in connection with a computer or any
instruction execution system. For the purposes of this description,
a computer-usable or computer readable storage medium can be any
apparatus that may include, store, communicate, propagate, or
transport the program for use by or in connection with the
instruction execution system, apparatus, or device. The medium can
be an electronic, magnetic, optical, electromagnetic, infrared, or
semiconductor system (or apparatus or device) or a propagation
medium. Examples of a computer-readable medium include a
semiconductor or solid state memory, magnetic tape, a removable
computer diskette, a random access memory (RAM), a read-only memory
(ROM), a rigid magnetic disk and an optical disk. Current examples
of optical disks include compact disk--read only memory (CD-ROM),
compact disk--read/write (CD-R/W), DVD and Blu-ray.TM..
[0028] Referring now to the drawings in which like numerals
represent the same or similar elements and initially to FIG. 1, a
high level block diagram shows a planning system 100 in accordance
with one illustrative embodiment. The planning system 100 assists
doctors, technicians, etc. in generating a plan on how to ablate a
tumor or other tissue, visualize the ablation plan and evaluate
quantitative metrics associated with the plan. A database or memory
system 102 includes storage for information on a set of ablation
probes and their properties, e.g., power and/or time data versus
ablated volume, ablation shape/size characteristics, etc.
[0029] This information is made available to a user from the
database 102 at a user-interface 104. It should be understood that
an ablation probe can be used interchangeably with ablation needle,
ablation antenna, ablation applicator, etc. An optimization engine
106 optimizes an ablation plan and can read the probe properties of
selected probes from the database 102. The optimization engine 106
also considers user inputs, e.g., selected probe, tumor
segmentation, skin entry points, number of ablations, time/power
preferences, etc. The optimization engine 106 uses the inputs to
create and communicate the ablation plan to the user-interface for
visualization and modification.
[0030] In one embodiment, the planning system 100 includes a
microwave ablation (MWA) planning system. The system 100 addresses
MWA-specific parameters (variable ablation sizes as a function of
power, time and temperature) and workflows that help physicians
achieve better microwave ablation results.
[0031] The ablation probe database 102 includes all relevant
properties for different ablation probes, for example, size of the
ablation zone as a function of different times, power settings for
a given probe, etc. The database 102 provides resource information
of ablation probes and also allows users to refine the probe
properties through the user interface 104. The user interface 104
permits user input and selection of all parameters relevant for
optimizing the ablation plan, and display (and select) results and
choices that become the output of the plan computation. The inputs
may include, e.g., tumor segmentation, one or more skin entry
points, number of ablations either in total or by number of
ablations from each entry point, selection of one or more ablation
probes applicable to all entry points or to specific entry
point(s), a subset of power/time settings to be considered for a
given ablation probe, etc. The displayed plan outputs may include,
e.g., number and location of ablations, shape/sizes and power/time
settings of each ablation, etc. User choices based on plan output
may include, e.g., choosing one of several possible power/time
settings to achieve the planned shape/size of a given ablation.
[0032] The optimization engine 106 optimizes a treatment plan and
may be employed to monitor activities to make suggestions for
future actions based upon the execution of previous events. The
user-interface 104 interacts with the ablation probe database 102
and passes parameters to the optimization engine 106. The
parameters include, for example, a user-specified set of ablation
probes and a user-specified set of power-time characteristics to be
used with those ablation probes. The optimization engine 106
computes an ablation plan based on the inputs from the user
interface 104, and the resource information from the ablation pro
database 102. The optimization engine 106 passes the ablation plan
results back to the user interface 104 for display and, optionally,
additional user choices as input. The ablation plan may be tailored
to achieve a number of objectives, e.g., maximize tumor coverage,
minimize number of ablations, minimize time of ablations, minimize
collateral damage, etc. The optimization engine 106 is however not
restricted to these objectives.
[0033] In one embodiment, a search for the best ablation coverage
can be seen as an iterative optimization problem. The ablation
centers are steered toward the location which minimizes both
un-ablated planned target volume (PTV) (tumor tissue that ought to
be ablated but is not yet ablated) and collateral damage caused to
healthy tissue. The optimization problem can thus be presented
as:
.THETA. ^ = arg min .THETA. C ( V PTV , i V Ai ( .THETA. i , e i )
) ( 1 ) ##EQU00001##
[0034] where V.sub.PTV is the planned target volume (PTV) and
V.sub.Ai is the i.sup.th ablation volume characterized by the
parameter set .THETA..sub.i at given skin entry point e.sub.i. C is
the cost function. .THETA..sub.i is a four dimensional (4D)
parameter defined as:
.THETA..sub.i=[t.sub.xt.sub.yt.sub.zs ].sup.T (2).
[0035] The ablation center (the center of the ellipsoidal ablation
model) is denoted as t.sub.x, t.sub.y, t.sub.zin three dimensions.
s is a scale factor between 0 and 1 that parameterizes the radii
from minimum to maximum.
[0036] Unlike RF ablation where the power and time are fixed and
the ablation size is invariant, microwave ablation manufacturers
may provide an array of ablation sizes and their respective
power/time settings. A model in accordance with the present
principles interpolates microwave ablation radii from available
discrete power/time inputs, assuming radii grow proportionally with
increasing time and increasing power. Other relationships are also
contemplated.
[0037] An iterative search problem may be implemented using, e.g.,
optimization techniques to minimize the following illustrative cost
function C:
C=V.sub.PTV.andgate.(.andgate.V.sub.Ai).mu..sub.u+V.sub.PTV.andgate.(.or-
gate.V.sub.Ai).mu..sub.c+.phi..mu..sub.p (3)
where V.sub.PTV is the PTV volume, V.sub.Ai is the i.sup.th
ablation volume, .mu..sub.u and .mu..sub.c are the weighting
factors for unablated PTV and collateral damage, respectively. The
symbol .andgate. between two volumes represents the count of voxels
that are set in both volumes (intersection of the two volumes),
whereas the symbol U.orgate. represents the count of voxels that
are set in either volume (union of the two volumes). The horizontal
bar above the two volumes, V.sub.PTV and the union of all the
ablation volumes .orgate.V.sub.Ai in the cost function expression,
represent the inverse of the volumes, i.e., voxels that are
"excluded" from the respective volumes. The cost function is
normalized based on these weights which reflect user preferences in
penalizing unwanted results.
[0038] In case of some undesirable situations, a penalty function
.phi. will be introduced. For example, for simultaneous ablation, a
requirement may be provided that adjacent ablations performed
simultaneously are to be kept a minimum distance apart to ensure
that the ablation process is performed optimally. The penalty
function .phi. is then defined as a function of the distance
between adjacent ablation centers. We add a penalty to the cost
function using the third expression .mu..sub.p.phi. to ensure the
adjacent needle ablation centers are not too close. Another example
of a penalty function is when a critical structure is present close
to the PTV. The method may penalize the situation where the
ablation volume overlaps with the critical structure. The method
will successively iterate until convergence, and an optimum
solution for Eq. (1) is achieved. During this process, the
V.sub.PTV (PTV volume) is constant, V.sub.Ai (ith ablation volume)
is changed with positive or negative perturbations of four
independent parameters from set .THETA..sub.i. The probe is
permitted to be repositioned after the first session for sequential
ablation sessions. For single-entry ablation, the probe is allowed
to move anywhere within the PTV (unconstrained search); while for
multi-entry ablation, the probe is allowed to move along the
trajectory between entry point and ablation center (constraint
trajectory search). For example, in sequential multi-ablation
sessions, the probe can be repositioned after each ablation in an
unconstrained way. When using multiple skin entry points for
simultaneous ablations, the probes are only allowed to move along
the trajectory between entry point and ablation center (constraint
trajectory search), in accordance with how ablations are executed
in clinical practice.
[0039] For modeling synergetic effects using simultaneous MWA
applicators, the cost function C could be adjusted such that when
the needles are mostly parallel, the synergetic ablation volume
which is supposed to be larger than the summation of individual
ablations could be extrapolated from the manufacturer's data
brochure. The optimization engine 106 considers the objectives that
provide parallel needles to create a larger ablation zone. In
another embodiment, ablation sizes could be modeled using
principals of thermal physics including, e.g., tissue properties,
thermal coefficients will be integrated into the model and employed
to estimate ablation regions using power and time data.
[0040] Referring to FIG. 2, a planning tool or ablation treatment
planning system 200 includes a graphical user interface of the
user-interface 104 for therapy planning. The ablation treatment
planning system and coverage algorithm 200 provide image
manipulation of pre-operative CT images 220. Quick 3D automatic or
semi-automatic (involving some user interaction) segmentation of
tumors can be performed, and once a tumor is segmented, a margin
which typically ranges from 5-10 mm can be conveniently added to
decide the planned target volume (PTV). The user is then asked to
pick the preferred ablation needle and one or more preferred needle
entry points on the patient's skin. Based on manufacturers' data
brochures and published literature on animal/patient trials using
these probes, an ablation template can be modeled as either a
spherical or ellipsoidal three dimensional object with three known
radii. The method can be easily extended to other geometrical
shapes if necessary.
[0041] In one embodiment, the system 100 prompts users to select an
ablation probe from an ablation probe menu or pane 202 and specify
a preferred power and time combination(s) to be considered for the
given ablation probe in an applicator properties sub-screen 230
that pops up when the probe or applicator is selected in the pane
202. The sub-screen 230 may include a power/time table 232 listing
in a matrix of powers and times and their resulting ablated volume.
For each power/time setting, the table 232 provides information
about a size of the ablation volume modeled as an ellipsoid-shape
3D structure with three distinctive radii in three dimensions
(e.g., Ellips (2,3,0.5). Other shapes may also be employed. The
user may select the modeled shape that is desired and apply the
shape at a particular location in an image screen 225. These user
inputs may be based on user experience and understanding of the
patients' anatomy, and help to confine the search space for the
optimization engine 106.
[0042] The tool 200 may be employed to chart out or plan a complete
procedure, selecting different probes, different shapes, different
power/times, etc. The planning tool 200 may include user-selected
functions to permit planning using different technology, e.g., by
selecting one of fields 204 (RFA or MWA). Other technologies may be
added as well. Such technologies would include at least time/power
dependent ablation volume shapes to provide a highly customizable
and flexible ablation plan. The user may select different patients
208, different scans 210, different views 212, etc. from a memory
or database storing these items. A description pane 206 may be
provided, which includes data on the images, views, patients, etc.
Other useful functions 214 may also be provided, such as export a
plan, print, report, zoom, etc.
[0043] Referring to FIG. 3, a user-interface instance 300 of the
microwave ablation planning system 200 is illustratively shown in
accordance with one embodiment. The instance 300 illustratively
includes an image 302, e.g., a computed tomography scan, magnetic
resonance image, etc. In this example, the image 302 includes a
section 306 of a liver with a segmented tumor 308. Skin entry
points 310, 311 are specified by the user. For each skin entry
point 310, 311, an ablation probe is selected with preferred
power/time settings from the menu/table 232 in pane 230. The
optimization engine 106 provides an ablation plan that includes
planned ablation volumes 312 with the recommended microwave
ablation time and power settings based on pre-defined optimization
objectives. The skin entry points 311 are for parallel needles,
which may be employed to reduce overall ablation time, as one
alternative.
[0044] Using the selected entry point(s) 310 or 311 on the skin, a
single ellipsoidal ablation is overlaid on the PTV to aid in
understanding the size of an ablation. It would be difficult for a
radiologist to arrive at an estimate for the number of ablations
needed to cover this complex, highly irregular-shaped PTV with the
given ablation shape. The present embodiments compute solutions
based on different entry points and result in overlapping
spherical/ellipsoidal ablations that optimally cover the PTV with
minimal collateral damage. With the aid of visualization, the
radiologist can determine if the number of ablations and the
collateral damage are acceptable. Since the computation is quick,
it is easy to modify the entry point or needle to create an
alternative plan. Also, the estimation of tumor coverage is done in
a fully automatic fashion.
[0045] Referring to FIG. 4, an image 400 is illustratively shown to
demonstrate some of the features in accordance with the present
principles. Image 400 includes a scan section having an irregularly
shaped tumor 410. Entry point-1 404 is shown for providing a
planned ablation volume 408, and entry point-2 402 is shown for
providing a planned ablation volume 406. The highly irregular tumor
410 is covered by a PTV which includes two ablations (406 and 408)
using a Covidian-Evidence.TM. MWA probe at 45 W. An estimated
percentage of PTV coverage is 99.86% with 11.13 cm.sup.3 of
collateral damage in this case. As the output of the algorithm,
ablation 408 from the entry point-1 404 is suggested to ablate for
5.3 minutes, whereas the ablation 408 from entry point-2 402 is
suggested to ablate for 9.3 minutes.
[0046] Referring again to FIG. 1 with continued reference to FIGS.
2-4, the system 100 prompts the user to provide the preferred
power/time setting for the selected probes and user-selected entry
points. The optimization engine 106 provides an ablation plan with
a list of power and time combinations that could be employed for
the selected ablation probe(s), to satisfy pre-defined optimization
objectives, e.g., maximize tumor coverage, minimize number of
ablations, minimize time of ablations, minimize collateral damage,
etc. The optimization engine 106 may also consider alternative
entry points, ablation times, probes, etc. to better achieve these
objectives.
[0047] The planning system's input can take a variety of forms in
terms of components to be visualized and presentation style. For
example, user input could include one or more of these components:
tumor segmentation, one or more skin entry points, number of
ablations either in total or by number of ablations from each entry
point, selection of one or more ablation probes, a subset of
power/time settings to be considered for a given ablation probe,
inter-probe distance (applicable to parallel probe insertions),
etc. The user input could be presented in one of multiple graphical
user interface forms e.g.: table, checklist, spreadsheet, drop-down
menu, information window which provides drawing and annotation of
ablation zone in 2D or 3D for a given ablation setting, etc. The
selection of one or more ablation probes may be performed manually
or automatically. For example, ablation probe types could be
manually specified by user-input, or they could be pre-selected in
the user-interface via an automatic detection of probes connected
to the system.
[0048] The planning system's output can also take a variety of
forms in terms of components to be visualized and presentation
style. The planning system's output may include one or more of a
recommended power and time for any selected probe, shape/sizes of
each ablation, recommended entry point locations, recommended probe
types, a recommended number of ablations to be considered for each
skin entry point, etc. The planning system's output could be
presented in one of multiple graphical user interface forms, such
as, e.g., a table, a highlighted list, a marked spreadsheet, a
display and/or an overlay of estimated ablation zone/parameters
onto the original images (e.g., CT) with power/time suggestions,
metrics of tumor coverage (percentage of tumor coverage, collateral
damage), etc.
[0049] In one embodiment, outputs (e.g., power and time for a given
probe) can be a subset of the input selections. Output of the
system may also include error/warning messages. The system could
flag a warning message, indicating the user selection is not
appropriate given the patient anatomy and the tumor size/geometry,
etc. In one example, the selected power and time settings may not
be able to cover the entirety of the tumor. If necessary, the user
can choose to override the recommended settings by discarding the
current plan and running a new instance of the plan using new
combinations of inputs. Where the planning system 100 provides an
output that includes recommended ablation probe types and
power/time settings for the recommended probes, the system 100 may
also be used for other parameter optimization. For example, in one
embodiment, if the users have only a small selection of ablation
probes, the system could specify which probe should be chosen to
treat this specific patient, as a result of the estimation from
optimization engine 106. In another embodiment, the system 100
could specify which skin entry points are beneficial for use in the
procedure based on the objectives included in the optimization
engine 106.
[0050] Preferred embodiments are applied to image-guided microwave
ablation; however, other ablation systems may be employed,
especially where there is high dimensional parameter space for each
insertion and ablation. For example, for other ablation modalities
(e.g., HIFU, Cryo) where variable ablation sizes also vary with
specific input parameters, these parameters can be specified by the
users as the input for the planning system 100, and optimized
through the optimization engine 106, resulting in the output for
optimized parameters. Unlike RF ablation where the power and time
is fixed and the ablation size is invariant, microwave ablation
provides an array of time and power settings, and can vary in their
respective ablation sizes as needed. For a given power, a model can
interpolate microwave ablation radii from a shorest time to a
longest time, assuming three radii grow proportionally with time.
In this way, ablation shapes and sizes may be determined and
implemented using a specific time and power combination. Given the
size and shape needed for an ablation can be provided by applying
an appropriate time of ablation.
[0051] To assess the accuracy of the planning methods disclosed,
the present inventors created, on pre-operative CT images, a series
of lesions with known geometries, i.e., spherical and ellipsoidal
PTVs are synthesized to serve as the ground truth. Estimated
ablation centers, if planned properly, should coincide with the
center of the geometry of these spheres/ellipsoids. In addition,
the estimated ablation radii should circumscribe the boundary of
the PTV with minimal damage to the healthy tissue. Among thirty
runs on three known geometry centers (one sphere, two ellipsoids),
the Mean Location Distance Error (MLDE) which is obtained by
comparing the computed ablation center with the ground truth
ablation center achieves 0.66 mm (STD: 0.22 mm). The Mean Radii
Distance Error (MRDE) which is estimated by comparing the computed
ablation radii with the ground truth radii reaches 0.53 mm (STD:
0.23 mm). These preliminary and illustrative results demonstrate
the accuracy and robustness of the described embodiments. Table 1
shows comparison results for the simulations to demonstrate the
accuracy and feasibility of the disclosed methods.
TABLE-US-00001 TABLE 1 MLDE (mm) and MRDE (mm) are estimated based
on the comparison with the ground truth after ten runs of the
optimization algorithm. Three known geometries on two PTVs are used
for this testing. MLDE_x MLDE_y MLDE_z MLDE MRDE_r (mm) (mm) (mm)
(mm) (mm) PTV1: one 0.71 .+-. 0.43 0.41 .+-. 0.07 0.87 .+-. 0.07
0.66 .+-. 0.14 0.21 .+-. 0.07 ablation PTV2: 1st 1.06 .+-. 0.59
1.42 .+-. 0.83 0.34 .+-. 0.25 0.94 .+-. 0.44 0.99 .+-. 0.54
ablation PTV2: 2nd 0.76 .+-. 0.13 0.11 .+-. 0.09 0.24 .+-. 0.16
0.38 .+-. 0.07 0.41 .+-. 0.08 ablation Mean 0.85 .+-. 0.38 0.65
.+-. 0.33 0.48 .+-. 0.16 0.66 .+-. 0.22 0.53 .+-. 0.23
[0052] Referring to FIG. 5, a method for planning an ablation
procedure is depicted in accordance with illustrative embodiments.
In block 502, an internal image of a patient on a display of a user
interface may be displayed. The image may be a pre-operative image,
a rendering of an image or a model employed for simulation or
practice. The image may be a 2D image or a 3D image and may include
multiple views that can be controlled using the user interface. In
block 504, an ablation probe or set of probes for performing an
ablation procedure using the user interface is/are selected. The
ablation probe may include a microwave ablation probe, and the
information preferably includes power and time data for a plurality
of ablation shapes. The shapes may include spherical or ellipsoidal
shapes, although other shapes may be employed as well. In block
506, a point or points of entry for the ablation probe or set of
probes is/are selected on the internal image. Other input
information may also be selected or provided by a user. In this
way, the experience of the user and the convenience and power of a
computer system can be combined to provide a synergistic and
powerful planning tool. In block 508, information about the
ablation probe or set of probes and the point or points of entry
are input to an optimization engine. Time and power is included in
the input information to determine sizes and shapes of ablation
volumes. The time and power are provided for time dependent
ablation volumes, e.g., the ablation volume is proportional to the
time/ablation duration. Other information may also be included in
the input. In block 509, the set of inputs may include one or more
of a type of ablation probe, a margin of error, ablation coverage,
collateral damage, ablation time, etc.
[0053] In block 510, an optimized therapy plan is output from an
optimization engine based on, e.g., reducing collateral damage and
maximizing coverage area in a planned target volume. Other criteria
may be set as well instead of and/or in addition to the damage and
coverage criteria. In block 512, the optimization of the therapy
plan may include minimizing a cost based on a set of inputs. The
inputs may include at least the point or points of entry and the
information on the ablation probe or set of probes. In block 514,
cost minimization may include computing a penalty function to
penalize the cost for an unwanted effect. The penalty function may
be tailored to account form one or more effects, such as employing
multiple probes, ablation sites that are too close, anatomical
features that are nearby, etc. The cost function and penalty
function may be altered in real-time at the user interface by
selecting different scenarios or physiological conditions in a
patient, e.g., entering blood flow conditions for a nearby blood
vessel, accounting for scar tissue, entering physical properties
measured for a specific patient, etc. The optimized therapy plan
may include one or more types of ablation probes, locations of
entry points, a number of ablation probes used, locations for a
minimum number of ablations, ablation locations to minimize
collateral damage, a minimized ablation time, etc. In block 518,
the recommendations and/or outputs may be automatically input to a
navigation system to carry out the therapy plan. In block 520, the
system may be employed in providing an interface for carrying out
an ablation therapy procedure (or providing training).
[0054] Referring to FIG. 6, a treatment system 600 for ablation
therapy is shown in accordance with one illustrative embodiment.
System 600 may be part of a therapy planning and procedure
monitoring workstation 601 that links optimized plan information,
tissue interaction modeling, dose monitoring, and clinical outcomes
data based on a patient-specific basis for procedure optimization,
reporting, and physician training. System 600 may include memory
storage 604. The database 604 stores images 611, preferably
three-dimensional (3D) images, of a patient 622 on which a
procedure is to be performed. Workstation 601 includes a processor
606 capable of execution of an optimized therapy plan 607 stored in
memory 604.
[0055] An ablation probe navigation system 608 is preferably
controlled by and provides data to the computer 606. The procedure
may be conducted manually as well, without the navigation system
608. The navigation system 608 receives spatial information,
commands from the workstation 601 and carries out the plan 607
created by the planning system 100. The workstation 601 and the
planning system 100 may be integrated together or may be separate
units.
[0056] An ablation probe or a set of probes 630 are selected and
coupled to the system 600. In one embodiment, the database 102 and
optimization engine 106 are stored in memory 604. The probe
information may be referenced from the memory 604 to obtain the
information needed for planning the therapy. In another embodiment,
by connecting the probe or probes 630 to the system 600, the system
senses the types of probes and looks up the probe data from memory
604. Feedback from the ablations on a target 632 in accordance with
the plan 607 may be collected by sensors or by an imaging system
610, which may include fluoroscopy, ultrasound, etc. The feedback
may include PTV coverage area, measured temperatures, etc.
Programming, device control, monitoring of functions and/or any
other interactions with the workstation 601 may be performed using
the user interface 104. A display 619 may also permit a user to
interact with the workstation 601 and its components and functions,
or any other element within the system 600. This is further
facilitated by the interface 104 which may include a keyboard,
mouse, a joystick, a haptic device, or any other peripheral or
control to permit user feedback from and interaction with the
workstation 601 or system 600.
[0057] Referring to FIG. 7-1, a block/flow diagram shows workflow
700 for the system 600 in accordance with one illustrative
embodiment. In block 702, inputs for a therapy plan are
illustratively described. In block 704, a display of 2D and/or 3D
images of a target anatomy in one or more views is provided on the
display (619) of the graphical use interface (104). In block 706,
treatment volume related inputs are provided. Examples of treatment
related inputs include, e.g., an outline of a planned target volume
with margins for treatment coverage inclusion as provided in block
708. In block 710, critical structures are outlined for coverage
exclusion (e.g., tissues that should not be damaged by ablation).
In block 712, another input type includes ablation probe related
inputs. These inputs or at least default inputs can be obtained
from a database. In block 714, an ablation probe or probes are
selected for treatment. In block 716, ablation power/time
characteristics of selected probes are set. The power/time
information is based on the probe selection and is employed to
derive a size and shape of the ablation regions. In other words, an
ablation region of a particular size and shape may be selected
based upon time/power characteristics. The sizes and shapes are
completely customizable based upon temporal data for a given
power.
[0058] Another input type may include entry point data in block
718. In block 720 one or more entry points for the ablation probe
or probes are selected on the image. In block 722, selected
ablation probes are associated with the entry point or points.
Different entry points and associated probe types may provide
different results. So these combinations may be provided as a form
of input. In block 724, a desired number of ablations are also
associated with each entry point. In block 726, criteria,
weightings, margins of error, penalties, etc. are also input for
therapy planning optimization.
[0059] FIG. 7-II is a block/flow diagram showing additional steps
for planning, executing or training for an ablation procedure using
the system of FIG. 6 in accordance with another illustrative
embodiment. In block 728, an optimization engine provides an
optimized therapy plan based upon the inputs provided from block
702. An optimized therapy plan is computed in block 730. In block
732, a cost function or functions are employed on the inputs to
optimize the plan. In block 734, the optimization engine adapts all
inputs (e.g., ablation locations, sizes, shapes, power, time,
inclusion regions, exclusion regions, etc.) to reach an optimal
cost function value as the plan result.
[0060] In block 736, a therapy plan result is output and
visualized. The output may include types and number of ablation
probes, locations of entry points, locations for ablation centers,
minimum number of ablations needed, minimum ablation time needed,
predicted ablation metrics, collateral damage, unablated planned
target volume regions, and damage to critical structures. In block
738, planned ablation volumes for each ablation are visualized on
the display. In block 740, untreated tumor volume is also
visualized on the display. In block 742, planned ablation probe
trajectories are visualized for each entry point and ablation. In
block 744, power, times, ablation size and shape, etc. are
visualized for each ablation. In block 746, quantitative coverage
metrics are computed (e.g., PTV coverage, etc.). In accordance with
the results in block 736, a check is made in block 748 to determine
if the therapy plan is acceptable. Acceptability may be based on
any number of criteria, e.g., coverage, minimum number of
ablations, time of procedure, etc. If unacceptable, the flow path
returns to block 702 and calls for an adjustment or modification of
the inputs. Replanning is performed to achieve updated results
based on the new inputs.
[0061] In interpreting the appended claims, it should be understood
that: [0062] a) the word "comprising" does not exclude the presence
of other elements or acts than those listed in a given claim;
[0063] b) the word "a" or "an" preceding an element does not
exclude the presence of a plurality of such elements; [0064] c) any
reference signs in the claims do not limit their scope; [0065] d)
several "means" may be represented by the same item or hardware or
software implemented structure or function; and [0066] e) no
specific sequence of acts is intended to be required unless
specifically indicated.
[0067] Having described preferred embodiments for an ablation
planning system (which are intended to be illustrative and not
limiting), it is noted that modifications and variations can be
made by persons skilled in the art in light of the above teachings.
It is therefore to be understood that changes may be made in the
particular embodiments of the disclosure disclosed which are within
the scope of the embodiments disclosed herein as outlined by the
appended claims. Having thus described the details and
particularity required by the patent laws, what is claimed and
desired protected by Letters Patent is set forth in the appended
claims.
* * * * *