U.S. patent application number 17/744774 was filed with the patent office on 2022-09-01 for esophagus position detection by electrical mapping.
This patent application is currently assigned to Navix International Limited. The applicant listed for this patent is Navix International Limited. Invention is credited to Yehonatan BEN DAVID, Shlomo BEN-HAIM, Eli DICHTERMAN, Zalman IBRAGIMOV, Yitzhack SCHWARTZ, Yizhaq SHMAYAHU.
Application Number | 20220273219 17/744774 |
Document ID | / |
Family ID | 1000006333064 |
Filed Date | 2022-09-01 |
United States Patent
Application |
20220273219 |
Kind Code |
A1 |
SCHWARTZ; Yitzhack ; et
al. |
September 1, 2022 |
ESOPHAGUS POSITION DETECTION BY ELECTRICAL MAPPING
Abstract
A method of estimating a spatial relationship between at least a
part of a patient esophagus and a heart chamber, including:
measuring at least one electric parameter at one or more positions
within the heart chamber to obtain measured values; and estimating
the spatial relationship based on the measured values.
Inventors: |
SCHWARTZ; Yitzhack; (Haifa,
IL) ; IBRAGIMOV; Zalman; (Rehovot, IL) ; BEN
DAVID; Yehonatan; (Tel-Aviv, IL) ; SHMAYAHU;
Yizhaq; (Ramat-HaSharon, IL) ; DICHTERMAN; Eli;
(Haifa, IL) ; BEN-HAIM; Shlomo; (Geneva,
CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Navix International Limited |
Road Town |
|
VG |
|
|
Assignee: |
Navix International Limited
Road Town
VG
|
Family ID: |
1000006333064 |
Appl. No.: |
17/744774 |
Filed: |
May 16, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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16461010 |
May 15, 2019 |
11331029 |
|
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PCT/IB2017/057185 |
Nov 16, 2017 |
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17744774 |
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62422767 |
Nov 16, 2016 |
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62445433 |
Jan 12, 2017 |
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62546775 |
Aug 17, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 5/0538 20130101;
A61B 5/4233 20130101; A61B 5/742 20130101; A61B 5/1076 20130101;
A61B 5/285 20210101 |
International
Class: |
A61B 5/285 20060101
A61B005/285; A61B 5/0538 20060101 A61B005/0538; A61B 5/107 20060101
A61B005/107; A61B 5/00 20060101 A61B005/00 |
Claims
1. A device for estimating esophagus position, comprising: at least
one body surface electrode connectible to a field generator and
configured to apply an electric field from said field generator to
a heart chamber; measuring circuitry configured to receive signal
measurements of an electric parameter of the electric field applied
by the at least one body surface electrode from an electrode probe
navigating within the heart chamber; and control circuitry,
configured to estimate a position of at least part of an esophagus
adjacent to the heart chamber, based on said signal
measurements.
2. The device of claim 1, further comprising: an interface
circuitry, wherein said interface circuitry generates an indication
of esophagus position based on said estimation of said esophagus
position.
3. The device of claim 1, further comprising: a digital computer
memory; wherein said control circuitry estimates said esophagus
position by comparing a measured map constructed to associate the
signal measurements with positions in the heart chamber to one or
more reference maps, stored in said digital computer memory,
wherein the reference maps associate predicted values of said
electric parameter with the positions in the heart chamber.
4. The device of claim 3, wherein at least one of the reference
maps is a simulated map.
5. The device of claim 4, wherein the simulated map also simulates
effects of an esophagus at a simulated location on measurements of
the reference map.
6. The device of claim 4, wherein the simulated map omits effects
of any esophagus on measurements of the reference map.
7. The device of claim 3, wherein at least one of the reference
maps is a map constructed using a measured map having a known
position of the at least part of the esophagus adjacent to the
heart chamber.
8. The device of claim 1, wherein the control circuitry estimates
said esophagus position by comparing a measured map of the shape of
the heart chamber constructed using the signal measurements to one
or more reference maps of the shape of the heart chamber; wherein
the measured map is constructed using a method that allows
distortions of an electric field due to the presence of an
esophagus to distort a shape of the measured map.
9. The device of claim 8, wherein at least one of the reference
maps is a simulated map.
10. The device of claim 9, wherein the simulated map also simulates
effects of an esophagus at a simulated location on a heart chamber
shape of the reference map.
11. The device of claim 9, wherein the simulated map omits effects
of any esophagus on heart chamber shapes of the reference map.
12. The device of claim 3, wherein at least one of the reference
maps is a map constructed using a measured map having a known
position of the at least part of the esophagus adjacent to the
heart chamber.
13. The device of claim 8, wherein the control circuitry estimates
the esophagus position using a template shape to match a shape of
the measured map of the heart chamber.
14. The device of claim 1, wherein said measuring circuitry is
connected to a catheter system configured to be at least partly
placed within a heart chamber to measure said electric
parameter.
15. The device of claim 1, further comprising: at least one
electrode connectable to said measuring circuitry; wherein said
electrode is shaped and sized to be placed within a heart chamber
to measure said electric parameter.
16. The device of claim 1, comprising: a field generator; wherein
said field generator is configured to deliver an energy field to a
heart chamber through an electrode placed in said heart chamber
based on said esophagus position of said at least part of the
esophagus.
17. The device of claim 1, wherein the control circuitry is further
configured to model the heart chamber based on the signal
measurements.
18. The device of claim 1, wherein the electric parameter of the
electric field is electric potential.
19. The device of claim 1, wherein said estimating comprises
estimating that said esophagus is not within a certain range from a
wall of said heart chamber.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 16/461,010 filed on May 15, 2019 which is a
National Phase of PCT Patent Application No. PCT/IB2017/057185
having International Filing Date of Nov. 16, 2017, which claims the
benefit of priority under 35 USC .sctn. 119(e) of U.S. Provisional
Patent Application No. 62/422,767 filed on Nov. 16, 2016, U.S.
Provisional Patent Application No. 62/546,775 filed on Aug. 17,
2017 and U.S. Provisional Patent Application No. 62/445,433 filed
on Jan. 12, 2017. The contents of the above applications are all
incorporated by reference as if fully set forth herein in their
entirety.
FIELD AND BACKGROUND OF THE INVENTION
[0002] The present invention, in some embodiments thereof, relates
to a method for measuring electric parameters and, more
particularly, but not exclusively, to a method for measuring
electric parameters for estimating esophagus position.
[0003] U.S. Patent Application Publication No. 2008/0177175A1
describes an esophageal mapping catheter that is introduced into
the esophagus and enables a physician to map the location of the
Esophagus so as to avoid damaging the Esophagus during radio
frequency (RF) ablation procedures.
SUMMARY OF THE INVENTION
[0004] There is provided, in accordance with some embodiments of
the present disclosure, a method of estimating a spatial
relationship between at least a part of a patient esophagus and a
heart chamber, comprising: measuring at least one electric
parameter at one or more positions within the heart chamber to
obtain measured values; and estimating the spatial relationship
based on the measured values.
[0005] In some embodiments, the estimating comprises estimating the
spatial relationship between a treatment target site in the heart
chamber and the esophagus.
[0006] In some embodiments, the method further comprises:
generating an electric property map based on the measured
values.
[0007] In some embodiments, the method further comprises:
generating an anatomical map of the heart chamber or a portion
thereof based on the measured values.
[0008] In some embodiments, the estimating further comprises
identifying at least one region within the electric property map
having deviations in the measured values resulted from the
proximity of the esophagus to the heart chamber.
[0009] In some embodiments, the deviations are deviations of the
electric property map from map values corresponding to the absence
of an esophagus in proximity to the at least one region.
[0010] In some embodiments, the deviations are deviations of the
electric property map toward map values corresponding to the
presence of an esophagus in proximity to the at least one
region.
[0011] In some embodiments, the electric property map comprises an
electric potential map.
[0012] In some embodiments, the electric property map comprises an
electric impedance map.
[0013] In some embodiments, the method further comprises:
generating a measured electric property map based on the measured
values; comparing the electric property map to at least one
simulated electric potential map; identifying at least one region
within the electric potential map generated based on the measured
values, the at least one region having deviations resulting from a
proximity of the esophagus to the heart chamber; wherein the
estimating is based on the deviations.
[0014] In some embodiments, the deviations are deviations of the
electric property map from map values corresponding to the absence
of an esophagus in proximity to the at least one region.
[0015] In some embodiments, the deviations are deviations of the
electric property map toward map values corresponding to the
presence of an esophagus in proximity to the at least one
region.
[0016] In some embodiments, the method further comprises:
generating an electric property map based on the measured values;
comparing the electric property map to one or more simulated maps
of the electric property; and identifying one or more simulated
electric property maps similar to the measured electric property
map; wherein the estimating is based on the one or more simulated
electric property maps identified.
[0017] In some embodiments, the identifying one or more similar
maps comprises identifying one or more similar maps with a value
difference aggregate below a threshold.
[0018] In some embodiments, the estimating is based on the
identification of at least two similar maps.
[0019] In some embodiments, the method further comprises:
determining whether the spatial relationship is a targeted spatial
relationship.
[0020] In some embodiments, the method further comprises:
indicating if the spatial relationship is not a targeted spatial
relationship.
[0021] In some embodiments, the method further comprises:
automatically suggesting an alternative target site if the spatial
relationship is not a targeted relationship.
[0022] In some embodiments, the method further comprises:
automatically suggesting at least one modification of an ablation
protocol parameter if the spatial relationship is not a targeted
spatial relationship.
[0023] In some embodiments, the method further comprises: stopping
an ablation procedure unless human overrides, if the spatial
relationship is not a targeted spatial relationship.
[0024] In some embodiments, the method further comprises:
automatically suggesting to move the esophagus to an alternative
position if the spatial relationship is not a targeted spatial
relationship.
[0025] In some embodiments, the method further comprises: applying
at least 3 electric fields to a body of the patient by at least 3
pairs of electrodes placed on the skin of the patient for
determining a position of an electrode within the heart chamber;
wherein the measuring at least one electric parameter comprises
measuring an electric parameter of the fields by an electrode
positioned within the heart chamber.
[0026] In some embodiments, the electrode positioned within the
heart chamber is used both to estimate the position of the
esophagus and for ablation.
[0027] In some embodiments, the measuring at least one electric
parameter comprises measuring electric potential.
[0028] In some embodiments, the estimating comprises estimating
that the esophagus is not within a certain range.
[0029] In some embodiments, the treatment target site comprises an
ablation target site.
[0030] In some embodiments, the heart chamber comprises the left
atrium.
[0031] In some embodiments, the spatial relationship comprises
distance.
[0032] In some embodiments, the method comprises estimating an
effect of a treatment in the heart chamber on the esophagus based
on the spatial relation.
[0033] There is provided, in accordance with some embodiments of
the present disclosure, a method of providing an indication to
spatial relationship between at least a part of a patient esophagus
and a heart chamber, comprising: receiving measurements of at least
one electric parameter at one or more positions within the heart
chamber to obtain measured values; generating a map of the heart
chamber based on the measured values; estimating the spatial
relationship based on the map; and providing an indication of the
spatial relationship estimated.
[0034] In some embodiments, the map is an electrical parameter
map.
[0035] In some embodiments, the map is an anatomical map.
[0036] In some embodiments, providing an indication comprises
providing the map carrying an indication of the spatial
relationship estimated.
[0037] In some embodiments, estimating the spatial relationship
comprises identifying, at a wall of the heart chamber, electrical
field bending indicative of an air-field tube behind the wall of
the heart chamber.
[0038] In some embodiments, estimating the spatial relationship
comprises identifying in the map a deformation indicative of an
air-field tube behind the wall of the heart chamber.
[0039] There is provided, in accordance with some embodiments of
the present disclosure, a method for estimating the position of at
least part of the esophagus from within a heart chamber,
comprising: measuring at least one electric parameter from within
the heart chamber to obtain measured values; and estimating the
position of the at least part of the esophagus based on the
measured values.
[0040] In some embodiments, the method further comprises:
generating an electric potential map based on measured values of
the electric parameter, after the measuring; comparing the electric
potential map to at least one simulated electric potential map;
identifying at least one region within the electric potential map
generated based on the measured values, the at least one region
having variations resulted from a proximity of the esophagus to the
heart chamber, based on the comparing; wherein the estimating is
based on the variations.
[0041] In some embodiments, the method further comprises:
generating an electric potential map based on measured values of
the electric parameter, after the measuring; comparing the electric
potential map to one or more simulated electric potential maps;
identifying one or more similar maps of the simulated electric
potential maps similar to the electric potential map generated
based on measured values; wherein the estimating is based on the at
least one simulated electric potential map identified.
[0042] In some embodiments, the method further comprises:
determining whether the estimated position of the esophagus is a
targeted position.
[0043] In some embodiments, the method further comprises:
indicating if the estimated position is not a targeted
position.
[0044] There is provided, in accordance with some embodiments of
the present disclosure, a method for estimating from within a heart
chamber a probability to affect at least part of the esophagus by
treating the heart chamber, comprising: measuring at least one
electric parameter from within the heart chamber; and estimating
the probability to affect the at least part of the esophagus based
on measured values of the electric parameter.
[0045] In some embodiments, the estimating comprises: estimating
the probability to injure the esophagus.
[0046] In some embodiments, the method further comprises:
generating an electric property map based on measured values of the
electric parameter, after the measuring; wherein the estimating
further comprises identifying at least one region within the map
having variations in the measured values resulted from the
proximity of the esophagus to the heart chamber.
[0047] In some embodiments, the electric property map comprises an
electric potential map.
[0048] In some embodiments, the electric property map comprises an
impedance map calculated from the electric potential map or from
the measured values of the electric parameter.
[0049] In some embodiments, the method further comprises:
generating an electric potential map based on measured values of
the electric parameter, after the measuring; comparing the electric
potential map to at least one simulated electric potential map;
identifying at least one region within the electric potential map
generated based on the measured values, the at least one region
having variations resulted from a proximity of the esophagus to the
heart chamber, based on the comparing; wherein the estimating is
based on the variations.
[0050] In some embodiments, the method further comprises:
generating an electric potential map based on measured values of
the electric parameter, after the measuring; comparing the electric
potential map to one or more simulated electric potential maps;
identifying one or more similar maps of the simulated electric
potential maps similar to the electric potential map generated
based on measured values; wherein the estimating is based on the at
least one simulated electric potential map identified.
[0051] In some embodiments, the method further comprises:
determining whether the probability is higher than a targeted
probability.
[0052] In some embodiments, the method further comprises:
indicating if the probability is higher than a targeted
probability.
[0053] In some embodiments, the method further comprises: stopping
stop a procedure of the treating if the probability is higher than
a targeted probability.
[0054] In some embodiments, the electric parameter comprises
electric potential.
[0055] In some embodiments, the heart chamber comprises the left
atrium.
[0056] In some embodiments, the spatial relationship is between the
at least part of the esophagus and a target site for ablation.
[0057] There is provided, in accordance with some embodiments of
the present disclosure, a device for estimating esophagus position,
comprising: measuring circuitry configured to receive signal
measurements of an electric parameter from an electrode probe
navigating within a heart chamber; and control circuitry,
configured to model the heart chamber based on the signal
measurements, and to estimate a position of at least part of an
esophagus adjacent to the heart chamber, based on the signal
measurements.
[0058] In some embodiments, the device further comprises: an
interface circuitry, wherein the interface circuitry generates an
indication of esophagus position based on the estimation of the
esophagus position.
[0059] In some embodiments, the device further comprises: a digital
computer memory; wherein the control circuitry estimates the
esophagus position by comparing a measured map constructed to
associate the signal measurements with positions in the heart
chamber to one or more reference maps, stored in the digital
computer memory, wherein the reference maps associate predicted
values of the electric parameter with the positions in the heart
chamber.
[0060] In some embodiments, at least one of the reference maps is a
simulated map.
[0061] In some embodiments, the simulated map also simulates
effects of an esophagus at a simulated location on measurements of
the reference map.
[0062] In some embodiments, the simulated map omits effects of any
esophagus on measurements of the reference map.
[0063] In some embodiments, at least one of the reference maps is a
map constructed using a measured map having a known position of the
at least part of the esophagus adjacent to the heart chamber.
[0064] In some embodiments, the control circuitry estimates the
esophagus position by comparing a measured map of the shape of the
heart chamber constructed using the signal measurements to one or
more reference maps of the shape of the heart chamber; wherein the
measured map is constructed using a method that allows distortions
of an electric field due to the presence of an esophagus to distort
a shape of the measured map.
[0065] In some embodiments, at least one of the reference maps is a
simulated map.
[0066] In some embodiments, the simulated map also simulates
effects of an esophagus at a simulated location on a heart chamber
shape of the reference map.
[0067] In some embodiments, the simulated map omits effects of any
esophagus on heart chamber shapes of the reference map.
[0068] In some embodiments, at least one of the reference maps is a
map constructed using a measured map having a known position of the
at least part of the esophagus adjacent to the heart chamber.
[0069] In some embodiments, the control circuitry estimates the
esophagus position using a template shape to match a shape of the
measured map of the heart chamber.
[0070] In some embodiments, the measuring circuitry is connected to
a catheter system configured to be at least partly placed within a
heart chamber to measure the electric parameter.
[0071] In some embodiments, the device further comprises: at least
one electrode connectable to the measuring circuitry; wherein the
electrode is shaped and sized to be placed within a heart chamber
to measure the electric parameter.
[0072] In some embodiments, the device further comprises a field
generator is configured to deliver an energy field to a heart
chamber through an electrode placed in the heart chamber based on
the esophagus position of the at least part of the esophagus.
[0073] Unless otherwise defined, all technical and/or scientific
terms used herein have the same meaning as commonly understood by
one of ordinary skill in the art to which the invention pertains.
Although methods and materials similar or equivalent to those
described herein can be used in the practice or testing of
embodiments of the invention, exemplary methods and/or materials
are described below. In case of conflict, the patent specification,
including definitions, will control. In addition, the materials,
methods, and examples are illustrative only and are not intended to
be necessarily limiting.
[0074] As will be appreciated by one skilled in the art, some
embodiments of the present invention may be embodied as a system,
method or computer program product. Accordingly, some embodiments
of the present invention may take the form of an entirely hardware
embodiment, an entirely software embodiment (including firmware,
resident software, micro-code, etc.) or an embodiment combining
software and hardware aspects that may all generally be referred to
herein as a "circuit," "module" or "system." Furthermore, some
embodiments of the present invention may take the form of a
computer program product embodied in one or more computer readable
medium(s) having computer readable program code embodied thereon.
Implementation of the method and/or system of some embodiments of
the invention can involve performing and/or completing selected
tasks manually, automatically, or a combination thereof. Moreover,
according to actual instrumentation and equipment of some
embodiments of the method and/or system of the invention, several
selected tasks could be implemented by hardware, by software or by
firmware and/or by a combination thereof, e.g., using an operating
system.
[0075] For example, hardware for performing selected tasks
according to some embodiments of the invention could be implemented
as a chip or a circuit. As software, selected tasks according to
some embodiments of the invention could be implemented as a
plurality of software instructions being executed by a computer
using any suitable operating system. In an exemplary embodiment of
the invention, one or more tasks according to some exemplary
embodiments of method and/or system as described herein are
performed by a data processor, such as a computing platform for
executing a plurality of instructions. Optionally, the data
processor includes a volatile memory for storing instructions
and/or data and/or a non-volatile storage, for example, a magnetic
hard-disk and/or removable media, for storing instructions and/or
data. Optionally, a network connection is provided as well. A
display and/or a user input device such as a keyboard or mouse are
optionally provided as well.
[0076] Any combination of one or more computer readable medium(s)
may be utilized for some embodiments of the invention. The computer
readable medium may be a computer readable signal medium or a
computer readable storage medium. A computer readable storage
medium may be, for example, but not limited to, an electronic,
magnetic, optical, electromagnetic, infrared, or semiconductor
system, apparatus, or device, or any suitable combination of the
foregoing. More specific examples (a non-exhaustive list) of the
computer readable storage medium would include the following: an
electrical connection having one or more wires, a portable computer
diskette, a hard disk, a random access memory (RAM), a read-only
memory (ROM), an erasable programmable read-only memory (EPROM or
Flash memory), an optical fiber, a portable compact disc read-only
memory (CD-ROM), an optical storage device, a magnetic storage
device, or any suitable combination of the foregoing. In the
context of this document, a computer readable storage medium may be
any tangible medium that can contain, or store a program for use by
or in connection with an instruction execution system, apparatus,
or device.
[0077] A computer readable signal medium may include a propagated
data signal with computer readable program code embodied therein,
for example, in baseband or as part of a carrier wave. Such a
propagated signal may take any of a variety of forms, including,
but not limited to, electro-magnetic, optical, or any suitable
combination thereof. A computer readable signal medium may be any
computer readable medium that is not a computer readable storage
medium and that can communicate, propagate, or transport a program
for use by or in connection with an instruction execution system,
apparatus, or device.
[0078] Program code embodied on a computer readable medium and/or
data used thereby may be transmitted using any appropriate medium,
including but not limited to wireless, wireline, optical fiber
cable, RF, etc., or any suitable combination of the foregoing.
[0079] Computer program code for carrying out operations for some
embodiments of the present invention may be written in any
combination of one or more programming languages, including an
object oriented programming language such as Java, Smalltalk, C++
or the like and conventional procedural programming languages, such
as the "C" programming language or similar programming languages.
The program code may execute entirely on the user's computer,
partly on the user's computer, as a stand-alone software package,
partly on the user's computer and partly on a remote computer or
entirely on the remote computer or server. In the latter scenario,
the remote computer may be connected to the user's computer through
any type of network, including a local area network (LAN) or a wide
area network (WAN), or the connection may be made to an external
computer (for example, through the Internet using an Internet
Service Provider).
[0080] Some embodiments of the present invention may be described
below with reference to flowchart illustrations and/or block
diagrams of methods, apparatus (systems) and computer program
products according to embodiments of the invention. It will be
understood that each block of the flowchart illustrations and/or
block diagrams, and combinations of blocks in the flowchart
illustrations and/or block diagrams, can be implemented by computer
program instructions. These computer program instructions may be
provided to a processor of a general purpose computer, special
purpose computer, or other programmable data processing apparatus
to produce a machine, such that the instructions, which execute via
the processor of the computer or other programmable data processing
apparatus, create means for implementing the functions/acts
specified in the flowchart and/or block diagram block or
blocks.
[0081] These computer program instructions may also be stored in a
computer readable medium that can direct a computer, other
programmable data processing apparatus, or other devices to
function in a particular manner, such that the instructions stored
in the computer readable medium produce an article of manufacture
including instructions which implement the function/act specified
in the flowchart and/or block diagram block or blocks.
[0082] The computer program instructions may also be loaded onto a
computer, other programmable data processing apparatus, or other
devices to cause a series of operational steps to be performed on
the computer, other programmable apparatus or other devices to
produce a computer implemented process such that the instructions
which execute on the computer or other programmable apparatus
provide processes for implementing the functions/acts specified in
the flowchart and/or block diagram block or blocks.
[0083] Some of the methods described herein are generally designed
only for use by a computer, and may not be feasible or practical
for performing purely manually, by a human expert. A human expert
who wanted to manually perform similar tasks, such as measuring
dielectric properties of a tissue might be expected to use
completely different methods, e.g., making use of expert knowledge
and/or the pattern recognition capabilities of the human brain,
which would be vastly more efficient than manually going through
the steps of the methods described herein.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0084] Some embodiments of the invention are 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 embodiments of the
invention. In this regard, the description taken with the drawings
makes apparent to those skilled in the art how embodiments of the
invention may be practiced.
[0085] In the drawings:
[0086] FIG. 1A is an image describing a typical spatial
relationship between the heart and the esophagus;
[0087] FIG. 1B describes an arrangement of electrodes for
application of electric fields, according to some embodiments of
the invention;
[0088] FIG. 2 is a general flow chart describing a method for
treating the heart based on estimation of esophagus position,
according to some embodiments of the invention;
[0089] FIGS. 3A and 3B are schematic illustrations describing the
positioning of an electrophysiological catheter probe at the left
atrium for measuring electrical properties and/or for treating the
tissue, according to some embodiments of the invention;
[0090] FIG. 4A is a block diagram of a device for measuring
electrical properties from within the heart and for treating the
tissue, according to some embodiments of the invention;
[0091] FIG. 4B is a flow chart of a process for estimating spatial
relationship between the esophagus and the heart in combination
with a treatment, according to some embodiments of the
invention;
[0092] FIG. 5 is a flow chart describing a process for estimating
spatial relationship between the esophagus and the heart combined
with an RF ablation procedure, according to some embodiments of the
invention;
[0093] FIG. 6A is a flow chart describing a process for generating
and updating an electric parameter map, according to some
embodiments of the invention;
[0094] FIG. 6B is a flow chart describing methods for estimating a
position of at least part of the esophagus, according to some
embodiments of the invention;
[0095] FIG. 6C is a flow chart describing estimation of at least
part of the esophagus by comparing measured electric parameter
values to simulated maps, according to some embodiments of the
invention;
[0096] FIGS. 7A-7I are images describing simulated electric
parameter maps of the heart and the LA, according to some
embodiments of the invention; and
[0097] FIGS. 8A-8E, schematically represent views of a phantom left
atrium within which electrode probe voltage mapping measurements
have been performed with and without an adjacent air-filled tube
simulating an esophagus, according to some embodiments of the
present disclosure.
DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION
[0098] The present invention, in some embodiments thereof, relates
to a method for measuring electric parameters and, more
particularly, but not exclusively, to a method for measuring
electric parameters for estimating esophagus position.
[0099] An aspect of some embodiments of the present invention
relates to estimating the position of at least part of the
esophagus from within a heart chamber. In some embodiments, the
position of at least part of the esophagus is estimated prior to a
treatment, when the heart chamber is to be treated in a way (e.g.,
by heart tissue ablation using an ablation probe) that might affect
the esophagus, if the distance between the esophagus and a treated
site is too short. Estimation of the position of the esophagus, or
the distance between the esophagus and a site to be treated, may
allow planning the treatment not to injure the esophagus, and/or
adjusting the treatment once it is estimated during the treatment
that the distance between a site to be treated and the esophagus is
not safe. For example, the treatment may be an ablation treatment
using an ablation probe, and the ablation heat may cause burns in
the esophagus if the latter is too close to an ablated site.
[0100] In some exemplary embodiments of the invention, estimation
of esophagus position is used to guide the placement of an
intra-cardiac treatment probe, e.g., to avoid damage to the
esophagus during a treatment such as tissue ablation using the
probe.
[0101] An aspect of some embodiments includes estimating, from
within a heart chamber, a probability to affect the esophagus when
treating a selected target site within the heart chamber. In some
embodiments, a spatial relationship, for example distance and/or,
angle between esophageal tissue and the treatment target site is
estimated (or existence or lack of existence within a range of
such). In some embodiments, estimating esophagus position and/or
esophageal tissue proximity to a treatment target site allows to
avoid or minimize an adverse effect of the treatment on the
esophageal tissue, for example a site marked as a target for
ablation. The estimation of the esophagus position may take place
prior to the treatment and/or during the treatment,
[0102] In some embodiments, the position of at least part of the
esophagus is estimated by measuring at least one electric
parameter, for example electric potential and/or impedance, from at
least one and preferably from a multiplicity of positions within
the heart chamber. In some embodiments, the position of the
esophagus is estimated based on detected local value deviations,
for example from expected values, and calculating a possible
position of the esophagus that can generate these deviations. In
some embodiments, the expected values are based on multiple
measurements performed in multiple subjects. Alternatively, the
position of the esophagus is determined by comparing a map
generated based on the measured electric parameter values, to a map
expected to have been generated. Herein, uses of the term
"deviation" in conjunction with the indication of an esophagus
position by measurement values should be understood to be deviation
with respect to "expected values" and/or an "expected pattern"
expected in the absence of an esophagus in proximity to the region
from which measurement values are obtained. For example, the
"expected pattern" is pattern expected in the case of the
hypothesis that there is no esophagus in proximity. The deviation
may be understood, for example, as a difference from an expected
pattern. The deviation may more particularly be detected as a
difference between a shape indicated by measurement values used to
map a cardiac chamber and expected shape of the cardiac
chamber.
[0103] Additionally or alternatively, the deviation is recognized
by similarity to one or more patterns of measurement values that do
indicate the proximity of an esophagus, and/or define a
characteristic shape. The characteristic shape may be, for example,
of a portion of a substantially cylindrical shape. The deviation
may be recognized when such a cylindrical (or other characteristic
shape) appears in a region where such a cylindrical shape is not
expected in the absence of an esophagus in proximity.
[0104] In some embodiments, expected values relative to which
deviation is assessed (using values individually, and/or patterns
of values) are derived from multiple measurements performed in
multiple subjects, in regions where the esophagus is not in
proximity. The deviation is optionally assessed relative to a
statistical summary of the expected values (e.g., average and
standard deviation), relative to a collected large population of
expected values (e.g., expressed in terms of an averaged distance
of values from values obtained in individual members of the large
population), and/or using another method, such as a supervised
machine learning method using the expected values as inputs.
Expected values can also be simulated, in some embodiments. In some
embodiments, deviation is additionally assessed with respect to a
large population of measurements at positions wherein the esophagus
is in proximity to the measurement position. For example, such
measurements (and/or simulations thereof) are used as input to a
supervised machine learning algorithm. Accordingly, a deviation
away from expected values or a pattern of values is additionally or
alternatively a deviation toward values or a pattern of values
which is expected in proximity to an esophagus. In this context,
deviating away from expected values means resembling less closely
by a suitable metric and deviating toward expected values means
resembling more closely by a suitable metric. In some embodiments,
a magnitude of difference may be a suitable metric.
[0105] In some embodiments, assessment of deviation of a pattern of
values is based on use of a map generated from measured electric
parameter values. For example, the position of the esophagus is
estimated by comparing similarity of a map generated based on the
measured electric parameter values, to a map having a pattern
expected to have been generated in the absence of an esophagus in
proximity. In some embodiments, the similarity may be compared by
average of magnitude of distance after registration, or other
suitable metric. The comparison allows identifying at least one
pattern that deviates between the two maps and may result from the
proximity of the esophagus. In some embodiments, for example, the
pattern deviations comprise cylindrically-shaped deviations
resulting from the proximity of the cylindrically-shaped esophagus.
The term "cylindrically-shaped" should be understood to refer to a
substantially cylindrical shape or to a portion of such shape.
[0106] In some embodiments, the expected pattern is based on
patterns determined using multiple electrical parameter
measurements performed in many subjects. For example, in some
embodiments, electrical mapping is performed for multiple subjects
as described in relation to FIG. 1B, yielding shapes of heart
chamber walls. Heart wall shapes used to derive one or more
patterns as references for evaluating deviation (away from and/or
toward particular patterns) are based on, for example, which
positions the electrode catheter is able to visit before stopped by
a heart chamber wall, which positions yield measurements indicating
wall contact (e.g., changes in local dielectric properties), and/or
another feature of the electrical measurements. For example U.S.
Provisional Patent No. 62/546,775; filed 17 Aug. 2017, the contents
of which are included herein by reference in their entirety,
relates to a method of electrical mapping using patterns in local
electrical field gradients which may indicate shapes of more remote
chamber surfaces and potentially the existence of features laying
beyond such as the esophagus.
[0107] Optionally, maps used to provide patterns for evaluation of
deviation in a particular case are at least partially simulated. In
some embodiments, the position of the esophagus in a particular
case is estimated by finding similarity between one or more
simulated maps that were generated based on different esophagus
positions, and a map generated based on the measured electric
parameter values. In some embodiments, similarity is detected using
algorithms, for example value difference aggregate algorithms which
summarize the measured values and determine similarity based on a
difference between a value difference aggregate and a threshold. In
addition, statistical calculations and modifications of the
measured electric parameter values are optionally performed, for
example to allow their comparison to simulated maps or simulated
values. Optionally, the esophagus position is estimated by
comparing locally measured dielectric values to predicted
dielectric values that were calculated based on a structural map
(i.e., a map which describes shapes of surfaces) and/or an
anatomical map (i.e., a structural map which additionally includes
representation of tissue volumes, optionally including
representation of tissue type and/or properties) of the measured
region.
[0108] The esophagus 10, for example as shown in FIG. 1A, is a
muscular tube, often partially filled with air, that descends
anteriorly to the vertebral column through the superior and
posterior mediastinum, posteriorly to the heart 20. When the
esophagus 10 passes near the heart 20, at least part of the
esophagus is in close contact or in a close proximity to the
posterior wall 30 of the left atrium (LA). Additionally, the
esophagus 10 moves laterally (as symbolized by the arrows) and can
transiently move to various positions within rectangle 40. The
close proximity to the heart 20 is one of the reasons why
esophageal injury is a potential complication after intraoperative
or percutaneous transcatheter ablation of the posterior aspect of
the LA. To prevent or minimize this complication, it may be
beneficial to estimate the position of at least part of the
esophagus in respect to the posterior wall of the left atrium, and
more particularly, in respect to a site to be ablated. To estimate
an atrium-esophagus distance (A-E distance), an electrode probe,
for example an electrophysiological (EP) catheter probe is
inserted, in some embodiments, into the LA for measuring an
electric parameter. Herein "A-E distance" refers to any estimate of
distance between a particular position on a heart chamber wall
(e.g., left atrial wall) and the esophagus. In some embodiments,
the estimate is qualitative, for example "located behind" or "not
located behind" ("behind" meaning "adjacent to the particular
position at a position exterior to the heart chamber"). In some
embodiments, the estimate is in terms of a functional and/or safety
issue, for example "located too close to safely ablate" or not. In
some embodiments, the distance is estimated as a distance from the
particular position to a position of the atrial wall behind which
the esophagus is estimated to be located, e.g., a position around
which the esophagus is centered, or a position behind which a
nearest side of the esophagus is positioned. Optionally, a distance
(i.e. gap) between the esophagus and the heart wall and/or inner
surface of the heart wall generally is also estimated for positions
of the heart wall behind which the esophagus lies. For example,
deviations may be smaller when the esophagus is spaced from the
heart wall. However, estimation of the esophagus being located
behind a particular region of cardiac wall (or not) generally
provides an A-E distance resolution sufficient for uses such as
avoiding ablation that may put the esophagus at risk for damage, or
limiting ablation energy (i.e. power and/or time of ablation) to
avoid putting the esophagus at risk.
[0109] Alternatively, the electrode probe is inserted into other
heart cavities, for example the right atrium (RA), left ventricle
(LV) or the right ventricle (RV). Optionally, the catheter probe is
inserted into a blood vessel, for example the coronary sinus.
[0110] In some particular embodiments of the invention, the
electric parameter, measurements used to estimate the A-E distance
are measured during application of an electric field to the body.
An electrode optionally measures electric potential and/or another
electric parameter at different locations within the heart chamber
in response to the applied electric field. In some embodiments, the
measured electric potential values reflect dielectric properties of
tissues and organs surrounding the measurement site, for example
cardiac tissue, muscle tissue and esophageal tissue. Esophageal
tissue in particular may create a relatively large deviation in
local dielectric properties (compared to normal conditions in its
absence), because the esophagus often contains one or more pockets
of air, which has a much larger electrical impedance than tissue.
The muscular tissue of the esophagus itself (surrounding the air)
has dielectric properties which are distinguishable from other
tissue types which may be found adjacent to the heart, in
particular lung. Lung also is filled with air, but the structure of
the air pockets is much more finely divided by non-muscular lung
tissue having a lower impedance, making it dielectrically distinct
from the esophagus. Measurements of the electric potential
generated in response to the applied electric field allow, in some
embodiments, estimation of the A-E distance.
[0111] In some embodiments, the electric field is applied by at
least one electrode, or at least one pair of electrodes placed on
the outer surface of the skin, for example 1, 2, 3, 4 pairs of
electrodes. Alternatively or additionally, the electric field is
applied by at least one electrode placed within the body.
Optionally, the electric field is applied by at least one electrode
placed within the heart chamber, for example by at least one
electrode located on the EP probe.
[0112] In some particular embodiments of the invention, the
measured electric parameter values are used to generate a map, for
example an electric property map. In some embodiments, the electric
property map comprises electric potential map, impedance map,
and/or currents map. In some embodiments, the generated map is used
to estimate the position of at least part of the esophagus, for
example by identifying patterns associated with the proximity of
esophageal tissue to the heart. In some embodiments, the identified
patterns comprise deviations in the size, shape or electric
parameter values. Alternatively, the generated map is compared to
one or more simulated electric parameter maps which were prepared
by simulating electric parameter values based on estimated
positions of the esophagus. In some embodiments, results of the
comparison are used to estimate the position of part of the
esophagus and/or a spatial relationship between esophageal tissue
and at least one measurement site or between the esophageal tissue
and the LA.
[0113] In some particular embodiments of the invention, the
position within the heart chamber of the electrode used for
measuring the electric parameter values, is determined using
electric measurements. Additionally or alternatively, the position
of the electrode is determined using another method, for example
using magnetic methods (e.g., sensing from a magnetic coil
positioned within crossing magnetic fields).
[0114] In some embodiments, a magnetic field, rather than or in
addition to the electric field, is applied to the body for
measuring said distance, for example by at least one magnetic
coil.
[0115] In some embodiments, when the electrode position is
determined, the electric parameter is measured, for example to
detect deviations in electric parameter values, for example
compared to expected values.
[0116] In some particular embodiments of the invention, the
simulated map is prepared by simulating predicted electric
potential values, as if they are measured at different locations
within a heart chamber. In some embodiments, at least one simulated
map is prepared based on imaging analysis results which describe
the position of the esophagus and a spatial relationship between
the esophagus and the heart. The imaging may be, for example,
imaging by projection X-ray, CT, MRI, ultrasound, remote electrical
field-based imaging, or another imaging method). The position and
spatial relationship inferred from the imaging analysis are the
position and spatial relation at the time the image was taken.
Additionally, the simulated map is based on estimated dielectric
properties of the tissues surrounding a predicted measurement site
within the heart chamber. In some embodiments, several simulated
maps are prepared which are based on the current position of the
esophagus and on at least one additional predicted location of the
esophagus. In some embodiments, the at least one simulated map is
prepared prior to the insertion of the electrode into the heart
chamber. In some embodiments, by comparing the measured electric
parameter values or the electric potential or impedance map which
are based on these measurements to at least one simulated map, the
position of at least part of the esophagus can be estimated.
[0117] In some particular embodiments of the invention, an ablation
target site is selected based on the estimated location of the
esophagus or based on the estimated spatial relationship between an
optional ablation target site and esophageal tissue. In some
embodiments, if the estimated spatial relationship between an
optional target site and esophageal tissue is not at a desired
spatial relationship (e.g., the A-E distance is too short) then an
indication is delivered to a user, for example to an expert who
navigates the EP probe or the ablation probe. Optionally, an
alternative target site is automatically suggested by the system in
response to a received indication.
[0118] In some embodiments, if the estimated spatial relationship
is not a desired spatial relationship, then the treatment
procedure, for example an ablation procedure is stopped.
Alternatively, if the spatial relationship is not a desired spatial
relationship or if there is a risk that the esophagus will move too
close to the heart chamber, then the esophagus can be moved to a
desired position or to be fixed, for example by insertion of an
object into the esophagus and maneuvering or fixating the esophagus
position. In some embodiments, a desired spatial relationship, for
example a desired distance or a desired
[0119] A-E distance, comprises a spatial relationship between an
ablation target site and at least part of the esophagus that
permits safe ablation at the target site without affecting the
esophagus, or that the effect on the esophagus is an allowed or
safe effect. Optionally, if there are no deviations in the electric
parameter values from expected values in the absence of an
esophagus in proximity, or if the electric parameter map resembles
a simulation run with no esophagus in the vicinity of the heart,
the existence of a targeted spatial relationship (or safe A-E
distance) may be determined.
[0120] In some particular embodiments, the probability to affect
the esophagus when treating a selected target site within the heart
chamber is estimated, for example by measuring an electric
parameter from within the heart chamber. In some embodiments,
estimating the probability to affect the esophagus is based on
detecting deviations in the measured values from expected values in
the absence of an esophagus in proximity to the heart chamber.
Alternatively, estimating the probability to affect the esophagus
is based on finding similarity between the measured values and one
or more simulated maps, for example as described in FIG. 6B. In
some embodiments, if the probability to affect the esophagus is
higher than a maximum allowable probability, then an indication is
delivered to a physician or to an expert. Optionally, if the
probability to affect the esophagus is higher than a maximum
allowable probability then the treatment procedure is stopped. The
maximum allowable probability may be set according to safety
requirements, and in some embodiments may be, for example, 5%, 1%
or lower.
[0121] Before explaining at least one embodiment of the invention
in detail, it is to be understood that the invention is not
necessarily limited in its application to the details of
construction and the arrangement of the components and/or methods
set forth in the following description and/or illustrated in the
drawings and/or the Examples. The invention is capable of other
embodiments or of being practiced or carried out in various
ways.
[0122] Exemplary Method of Estimating the Position of an Electrode
Within the Heart
[0123] Reference is now made to FIG. 1B depicting an arrangement
for electrodes for application of electric fields, according to
some embodiments of the invention.
[0124] In some embodiments, electrical field-guided navigation of a
probe 102 is performed within a region of the body, for example
within heart 20 (FIG. 1A). The navigation comprises assessment of
electrode probe 102 position in space based on electrical field
measurements. The fields as a whole are not necessarily homogenous
or mutually orthogonal, but do include field components falling
along the orthogonal spatial axes. Herein, unless otherwise noted,
the X and Y fields are considered to cross in the transverse plane
of the body. Optionally, a Z field crosses both of these fields
with a component approximately orthogonal to both the X and Y
fields. Optionally, as shown for example in FIG. 1B, the X field
extends across the left and right directions of the body, while the
Y field extends between ventral and dorsal positions.
Optionally--and particularly for sensing in the thoracic and
abdominal cavities--body surface electrode positions are selected
so that fields cross the body in about the cardinal directions,
between electrode positions bracketing the region of interest as
closely as possible.
[0125] In some embodiments, electrode pairs 104, 106 and 108
deliver an electric field 110 to the body, for example by attaching
the electrodes to selected locations on the outer surface of the
skin. In some embodiments, each electrode pair delivers an electric
field with a different frequency. There may also be crossing of
fields between non-paired electrodes; for example, in some
embodiments, at least one electrode of electrode probe 102 measures
electric potential of applied electric field 110 by one or both
electrodes of electrode pair 104. In some embodiments, the measured
electric parameter is a parameter of the applied electric field. In
some embodiments, the position of the electrode probe within the
heart can be determined based on the changes in electric field
generated in different frequencies and the measured electric
potential values.
[0126] In an "ideal" body, having a dielectric constant that is the
same throughout the body, and between electrodes of infinite
separation, the electric field propagates in straight lines between
each two electrodes generating a time-varying electrical field
therebetween, and is attenuated at a constant rate between the
electrodes. Thus, in ideal body there may be a linear relationship
between electrical parameters measured by an electrode, and the
position of the electrode within the ideal body, and a
high-fidelity map may be generated from electrical readings using
linear transformations between the electrical readings and the
positions. However, in a real body with finite electrode
separation, the field is curved, and moreover the dielectric
constant changes in space (at least because different tissues have
different dielectric properties). Linear mapping between electrical
readings and electrode positions results in a low-fidelity map in
this situation. However, non-linear transformations, (for example,
as described in U.S. Provisional Patent No. 62/445,433; filed Jan.
12, 2017) may provide maps with higher fidelity to the actual
spatial arrangement being mapped.
[0127] In some embodiments, the frequencies of the electrical field
used are in the range of 40 kHz to 2 MHz. Optionally, the number of
frequencies used is 10 or fewer frequencies. Optionally, the
frequencies are distributed (for example, distributed evenly)
throughout the full range of frequencies chosen. Optionally,
frequencies chosen are concentrated in some particular frequency
range. Applied voltages are preferably in the safe range for use in
humans, for example, 100-500 millivolts, and/or a current of 1
milliamp or less (a typical body resistance is about 100.OMEGA.).
Resulting field strengths are in the range, for example of a few
millivolts per centimeter; for example, 5 mV/cm, 10 mV/cm, 20
mV/cm, or another larger, smaller, or intermediate value. Based on
requirements for data acquisition, sensing time is optionally about
10 msec per measurement (or a longer or shorter period, for
example, about 100 msec, or 1 second), for embodiments including
fast automated switching of frequencies and/or electrode pairs.
[0128] Exemplary Methods for Estimating Esophagus Position
[0129] Reference is now made to FIG. 6B, depicting methods for
estimating the position of at least part of the esophagus,
according to some embodiments of the invention.
[0130] According to some exemplary embodiments, an electrode probe
is inserted into a heart chamber, for example into the LA and at
least one electrode of the probe measures at least one electric
parameter from at least one and preferably from a multiplicity of
locations within the heart chamber at 614, while moving to map the
heart chamber. Optionally, the electrode measures the electric
parameter, for example electric potential, when contacting the
heart chamber wall.
[0131] According to some exemplary embodiments, the position of at
least part of the esophagus at 618 is estimated by analyzing the
measured values of the electric parameter at 616 and detecting
deviations from measurement values expected in the absence of an
esophagus in proximity. These deviations result from the actual
proximity of at least part of the esophagus to one or more of the
measurement locations. Alternatively, the measured electric
parameter values are compared to a simulated map of electric
potential or impedance values, for example to detect altered
measured electric parameter values compared to the simulated map.
In some embodiments, the position of the esophagus is estimated,
for example by calculating how different positions of the esophagus
would produce the altered electric parameter values compared to the
simulated values. In some embodiments, the measured electric
parameter values are compared to a structural and/or an anatomical
map of the measured region, for example to identify deviations
between the measured values to expected values based on the organ
and tissue types surrounding the one or more measurement
locations.
[0132] According to some exemplary embodiments, the measured
electric parameter values are compared to simulated electric
potential or impedance maps 622 to find a one or more similar maps.
In some embodiments, based on the position of the esophagus in the
one or more similar maps, the position of the esophagus at the time
of measurement can be estimated at 618.
[0133] According to some exemplary embodiments, the position of the
electrode probe within the heart chamber is estimated based on
application of an electric field or a magnetic field to the body,
and then the position of the esophagus is estimated based on
dielectric values of the tissue measured locally by at least two
electrode of the electrode probe. In some embodiments, the measured
dielectric values are analyzed to identify variation caused by
esophageal tissue proximal to the measurement location, for
example, according to the electrode position we expect to measure
dielectric values of a muscle but instead the electrode measured
dielectric properties of a different tissue. Optionally the
measured dielectric values produce a shape which is different for
the expected shape, based on the position of the electrode.
[0134] Exemplary Method for Estimating Esophagus Position
[0135] In some embodiments, the position of the esophagus is
estimated before the ablation treatment to make a determination of
proximity of the esophagus to a targeted treatment location. Such
proximity may be related to a likelihood of esophagus injury from
the treatment, and estimating the proximity in advance may allow
the physician to prevent such esophagus injury, for example, by
changing the ablation plan, or causing the esophagus to move (e.g.,
by asking the patient to swallow several times). Thus, according to
some exemplary embodiments, the position of the esophagus is
estimated before an ablation treatment, in order to prevent
esophagus injury usually caused by the energy used for ablation, if
the esophagus is too close to the ablation sight. Reference is now
made to FIG. 6C depicting a method for estimating esophagus
position by comparing measured electric potential values to
simulated maps, according to some embodiments of the invention.
[0136] According to some exemplary embodiments, a patient undergoes
an imaging procedure, for example CT, MRI or ultrasound of the
whole body or of a selected body region at 624. In some
embodiments, the imaging analysis is used for estimating the
position of tissues and/or organs, for example the position of the
esophagus and/or the position of the heart.
[0137] According to some exemplary embodiments, based on the
results of the imaging procedure, a modeling procedure is performed
at 626. In some embodiments, the modeling procedure comprises
modeling the electrical properties of the body or a selected body
region, for example by assigning tissue specific electrical
properties to tissues and/or organs based on the results of the
imaging procedure. The modeling optionally also includes modeling
of particular conditions of electrode placement (e.g., body surface
electrode placement) and use; for example, electrode position,
electrode size, electrical field frequency, and/or electrical field
voltage.
[0138] According to some exemplary embodiments, several simulated
maps are generated at 628. In some embodiments, each map describes
simulated electric potential that will be measured within at least
part of the heart chamber, for example at least part of the LA when
positioning the esophagus at different locations. In some
embodiments, in each simulated map the esophagus is placed at a
different spatial relationship, for example in a different distance
from the LA. Optionally, at least one simulated map is generated by
simulating electric potential values of the LA when there is no
esophagus, for example to simulate electric potential values of the
LA when there is no effect by the esophagus on the electric
potential values.
[0139] According to some exemplary embodiments, during an ablation
procedure, an electrode probe is inserted into the heart chamber,
for example into the LA at 630. In some embodiments, the electrode
probe includes at least one electrode, for example for application
of an ablating energy and/or for measuring at least one electric
parameter, for example electric potential and/or impedance.
[0140] According to some exemplary embodiments, once the electrode
probe is positioned within the heart chamber, electric fields are
applied to the body at 632. In some embodiments, the electric
fields are applied by at least 3 electrode pairs that are attached
to the outer surface of the skin. In some embodiments, the
electrode pairs are positioned at selected locations on the skin.
Optionally, the selected locations were used during the generation
of the simulated electric potential maps at 628. In some
embodiments, the intensity and/or the duration and/or the frequency
of the applied electric fields were used during the generation of
the simulated electric potential maps at 628.
[0141] According to some exemplary embodiments, during the
application of the electric fields, the at least one electrode
placed within the heart chamber measures electric potential, for
example to map the electric potential of at least part of the heart
chamber at 634. In some embodiments, the electrode measures
electric potential at one or more locations within the heart
chamber. Optionally, the electrode measures electric potential at
one or more locations by contacting the heart chamber wall. In some
embodiments, the measured electric parameter values are converted
into impedance values.
[0142] According to some exemplary embodiments, the measured
electric potential values are compared to the simulated maps at
636. In some embodiments, the measured electric potential values
are compared to the simulated maps for example, to identify one or
more simulated maps that are similar to the measured electric
potential values. In some embodiments, the measured electric
potential values are analyzed to generate a map of at least part of
the heart chamber and then the map is compared to simulated maps,
for example to identify one or more similar regions.
[0143] According to some exemplary embodiments, the position of the
esophagus is estimated at 638. In some embodiments, the relative
position of the esophagus is determined based on the identified
similarity between the measured electric potential values and one
or more of the simulated maps, as discussed at 636. In some
embodiments, since each of the simulated maps is generated based on
an estimated position of the esophagus, and based on the effect of
the estimated position on the simulated electric potential values,
finding similarity between the measured values and one or more
simulated maps allows for example, to estimate the position of the
esophagus. In some embodiments, the relative position of the
esophagus is estimated using the estimated position of the
esophagus that was used in the generation of the similar one or
more simulated maps.
[0144] According to some exemplary embodiments, once the position
of the esophagus is determined, at least one electrode of the
electrode probe delivers treatment energy, for example RF energy to
ablate the cardiac tissue at 640. In some embodiments, before
ablating the tissue the at least one electrode that is used for
ablation is positioned at an ablation target site that is verified
to also be in a spatial relationship, for example larger than a
minimal allowable distance (e.g., minimum safe distance to avoid
damage), from the estimated position of the esophagus. Optionally,
an ablation path which comprises at least two ablation target sites
is selected based on the estimated position of the esophagus,
before initiating the ablation procedure.
[0145] Exemplary Method for Estimating Esophageal Position
[0146] Reference is now made to FIG. 2 depicting a method for
treating the heart based on estimation of esophagus position,
according to some embodiments of the invention. In some
embodiments, the position of the esophagus is estimated prior to
ablation treatment, for example, to minimize or eliminate adverse
effects of the treatment on esophageal tissue.
[0147] According to some exemplary embodiments, the position of the
esophagus is first roughly estimated based on analysis of an image
of at least part of the heart and adjacent organs, at 206. The
image may include both the heart or a portion thereof, and a
portion of the esophagus in vicinity of the heart. This rough
estimate is improved in later stages of the method. The imaging may
be, for example magnetic resonance imaging (MRI), computed
tomography (CT) and/or ultrasound.
[0148] According to some exemplary embodiments, the imaging results
are then used to model the imaged region of the body by assigning
electric properties to different tissues and/or organs demonstrated
in the imaging results, at 208. Additionally, imaging comprises
imaging the insertion of a catheter probe into the heart and
placing at least one electrode pair, used for electric field
application, at selected locations on the skin.
[0149] According to some exemplary embodiments, at least one
simulated electric potential or impedance map is generated at 209.
This simulated map is to be compared with a measured map to improve
the estimation of the esophagus position at 214. In some
embodiments, the simulated map is based on the modeling performed
at 208. In some embodiments, the simulated map is generated by
predicting electric potential or impedance values expected to be
measured by an electrode at different locations within a heart
chamber, for example within the LA of the heart. In some
embodiments, at least one simulated map is generated based on the
estimated position of the esophagus as estimated at 206. In some
embodiments, at least one additional simulated map is generated,
each based on a corresponding position of the esophagus. In some
embodiments, the simulated maps are based on the imaging analysis
results and on estimates of dielectric properties of tissues and/or
organs surrounding the heart, for example dielectric properties
that were assigned at 208.
[0150] According to some exemplary embodiments, at least one
measuring electrode, for example an electrode of an EP catheter
probe is inserted into a cavity of the heart, for example into the
LA at 210, for measuring at least one electric parameter from at
least one and preferably from a multiplicity of locations within
the cavity. In some embodiments, the electrode is placed in contact
with a cardiac tissue, or is found in a close proximity to the
tissue. In some embodiments, the electrode probe is navigated into
the heart chamber or into the blood vessel based on the imaging
analysis used for the position estimation at 208. In some
embodiments, the electrode measures electric potential when an
electric field is applied. Optionally, impedance values are
calculated from the measured electric potential values. In some
embodiments, the electric potential or impedance measured at
different locations inside the LA allows estimating the position of
the esophagus outside the LA due to the effect of the esophagus on
the electrical field developed inside the LA.
[0151] According to some exemplary embodiments, an electric field
is applied by at least one electrode at 211. Alternatively or
additionally, a magnetic field is applied. Alternatively or
additionally, the electrode is in contact with a tissue outside of
the heart chamber, for example with the outer surface of the skin.
In some embodiments, the electric field is applied based on
parameters of an electric field application protocol which includes
for example, the electric field frequency and/or the electric field
intensity.
[0152] According to some exemplary embodiments, at least one
measuring electrode measures an electric parameter, for example
electric potential from within the heart chamber or blood vessel at
212, when an electric field is applied at 211. Optionally,
impedance values are calculated from the measured electric
potential values. In some embodiments, the electrode measures the
electric parameter while moving within the heart chamber or blood
vessel. In some embodiments, the electrode measures the electric
parameter in the whole volume of the chamber, for example the LA.
Optionally, the electrode measures the electric parameter while
contacting the walls of the heart chamber or the blood vessel. In
some embodiments, the electrode measures the electric parameter at
regions that are close to a desired ablation target site, and/or at
regions that are close to at least part of the esophagus. In some
embodiments, if patient is awake and cooperative, swallowing
manipulation can allow an expert performing the procedure to detect
esophagus and assist in verification electrical mapping
diagnostic.
[0153] According to some exemplary embodiments, the measured
electric parameter values are used to estimate the position of at
least part of the esophagus at 214, for example by identifying
deviations in the measured values compared to estimated values,
which reflect an estimated position of the esophagus. In some
embodiments, the measured electric parameter values are analyzed
and optionally used to generate an electric potential or impedance
map. In some embodiments, the generated map is used to estimate the
position of at least part of the esophagus by identifying regions
in the map that demonstrate the effect of a proximal esophageal
tissue.
[0154] In some embodiments, the generated map is compared to at
least one simulated map, for example a simulated map that was
generated at 209, to identify a one or more similar simulated maps.
In some embodiments, since at least one simulated map is based on a
predicted position of the esophagus, finding similarity between a
map which is based on measured values and a simulated map, provides
an indication regarding the position of at least part of the
esophagus in the time of measurement.
[0155] In some embodiments, based on the estimated esophagus
position, at least one treatment target site or a treatment target
path is selected by the system or by an expert performing the
procedure. In some embodiments, selection of a treatment target
site or the treatment target path is guided to avoid delivering
energy within the heart chamber at positions that are close enough
to the esophagus to raise a risk for injuring the esophagus.
[0156] According to some exemplary embodiments, energy for a
treatment, for example RF energy for an ablation, is applied to at
least one selected target site of the cardiac tissue at 216, based
on the estimated esophagus position as described at 214. In some
embodiments, the target site is selected considering its spatial
relationship to the esophagus. Optionally, the target site is
selected based on the probability of the treatment energy to affect
at least part of the esophagus. In some embodiments, the treatment
energy is applied by at least one electrode of the EP catheter
probe.
[0157] According to some embodiments, before each application of
treatment energy, the electric parameter is measured and the
position of the esophagus is estimated, for example as described at
212 to 214, to verify that the esophagus position did not change
during the treatment at 216.
[0158] Example of Finding Relative Probe and Esophagus Positions
from Within the Left Atrium
[0159] Reference is now made to FIGS. 3A and 3B depicting the
positioning of an electrode at different locations in the LA, for
example for measuring electric potential, according to some
embodiments of the invention.
[0160] According to some exemplary embodiments, an electrode probe,
for example electrode probe 302 is inserted into a heart chamber,
for example the LA 30. In some exemplary embodiments, the electrode
probe 302 moves within the LA and/or in contact with the LA 30
wall, for example at target site 306. Optionally, target site 306
is a selected target site for application of a treatment, for
example an RF ablation treatment. In some embodiments, target site
306 is in a close proximity to the pulmonary veins 308. In some
embodiments, target site 306 is selected based on results of an
imaging analysis and/or based on an electric potential or an
impedance map of the region. Optionally, target site 306 is
selected based on an estimated position of at least part of the
esophagus.
[0161] According to some exemplary embodiments, at least one
electrode of the electrode probe 302 measures at least one electric
parameter within the LA 30, for example at a multiplicity of
locations proximal to target site 306, and optionally other
positions near which the esophagus may be positioned. Optionally,
the electric parameter is measured prior to initiation of a
treatment and/or during the treatment and/or after the treatment,
for example application of treatment energy at target site 306.
[0162] According to some exemplary embodiments, application of
treatment energy, for example RF energy to the cardiac tissue may
lead to esophagus injury in cases where the treatment target site
is proximal to esophageal tissue. According to some exemplary
embodiments, the measured electric parameter of the tissue allows,
for example to estimate the proximity of at least part of esophagus
10 to target site 306. Alternatively or additionally, the measured
electric parameter allows, for example to determine whether
application of treatment energy at target site 306 will injure
esophagus 10, or the probability of such injury; or if this
probability is small enough, for example, in reference to a safety
threshold. In some embodiments, if the target site is proximal to
at least part of the esophagus 10, and/or if application of an
electric field at target site 306 is predicted to affect the
esophagus 10, then, optionally, an attempt is made to move the
esophagus, for example, by encouraging swallowing, or manual
manipulation. Additionally or alternatively, an alternative target
site for the treatment, for example target site 307 is selected,
for example, automatically suggested. Target sites are optionally
modified through the modification of a planned line of ablation;
for example, a planned line of ablation is shifted to avoid a
region where it would otherwise pass too close to an estimated
position of the esophagus. Individual sites for ablation along the
line may then be adjusted according to the new line of ablation,
for example, planned so that they create an unbroken transmural
line of ablation. The line of ablation can be shifted, for example,
toward a pulmonary vein being electrically isolated by ablation. In
some embodiments, at least one protocol parameter of the treatment
energy application is modified, as part of the modification of an
ablation site and/or line of ablation; for example the intensity
(e.g., power and/or duration) of the treatment energy or the
duration of the treatment is optionally modified.
[0163] In some embodiments, an electrode probe in the LA, measures
electric potential or impedance, for example to determine the
position of the electrode probe within the LA based on measured
electric potential and/or impedance values and produces a map of
corresponding electrode positions and measured values. Optionally,
the determined correspondences of electrode positions with measured
values are used to determine the position of the same or a
different electrode probe which measures electric potential for
estimating esophagus position as described herein. In some
embodiments, an ablation probe is also an electrode probe which
uses the determined correspondences of electrode positions with
measured values to locate, e.g., ablation sites. The same electrode
probe may be used for all three functions (map production,
esophagus position estimation, and ablation), all three functions
may be performed by separate probes, or the functions may be
performed in any suitable combination by another plurality of
probes.
[0164] Exemplary System for Estimating the Presence of the
Esophagus
[0165] Reference is now made to FIG. 4A depicting a block diagram
of a system for estimating the presence of at least part of the
esophagus, according to some embodiments of the invention.
[0166] According to some exemplary embodiments, an electrode probe,
for example catheter probe 402, is inserted into a heart chamber
404 (depicted body parts such as heart chamber 404 and esophagus 10
are not part of the system itself, but rather illustrated to help
in an understanding of how the system components relate to one
another and to functioning of the system). In some embodiments,
catheter probe 402 comprises electrodes 406 with electrode contacts
on the outer surface of catheter probe 402. In some embodiments,
catheter probe electrodes 406 measure electrical parameters of one
or more electrical fields generated within heart chamber 404, for
example, parameters of electric potential and/or impedance at one
or more frequencies.
[0167] According to some exemplary embodiments, at least one
electrode of electrodes 406 is configured to apply treatment
energy, for example to target site 405. In some embodiments, the
treatment energy is delivered using an electric field, a thermal
device, and/or radio-frequency transmission. Optionally the
electrode is configured to ablate the tissue, for example by RF
ablation.
[0168] According to some exemplary embodiments, the catheter probe
402 and/or electrodes 406 are connected by wiring 408 to an
electric parameter measurer 410 component of device 400.
Optionally, electric parameter measurer is configured to measure
electric potential. In some embodiments, electric parameter
measurer 410 receives the measured electrical signal from at least
one electrode of electrodes 406, and optionally modifies the
received signal for example, by amplifying and/or filtering the
received signal.
[0169] According to some exemplary embodiments, electric parameter
measurer 410 is connected to at least one additional electrode, for
example skin electrode 413. In some embodiments, at least one skin
electrode 413 comprises 1, 2, 3, 4, 5, 6, or 8 electrodes.
Optionally, skin electrode 413 comprises at least one pair of
electrodes, for example 2 pairs, 3 pairs, or 4 pairs.
[0170] According to some exemplary embodiments, electric parameter
measurer 410 is connected to control circuitry 414. In some
embodiments, control circuitry 414 is connected to treatment energy
generator 412, which is configured to generate treatment energy,
for example an electric, thermal or acoustic field. In some
embodiments, the field generator is connected to electrodes 406
and/or to skin electrodes 413, for example to deliver the generated
treatment energy to the tissue.
[0171] According to some exemplary embodiments, at least one
electrode of electrodes 406 is positioned in close contact or
adjacent to a cardiac tissue and measures at least one electric
parameter of the tissue and/or surrounding tissues. The probe is
preferably moved to measure at a multiplicity of locations, in
order to build up a map of the region, optionally while measuring
at a rate, e.g., of about 100 Hz. In some embodiments, the field
generator 412 generates an electric field and delivers the electric
field through at least one skin electrode 413 to the skin. In some
embodiments, at least one electrode of electrodes 406 measures the
electric parameter after the electric field is delivered by skin
electrode 413.
[0172] According to some embodiments, control circuitry 414
estimates the position of at least part of the esophagus based on
electric parameter values, for example electric potential values
that were measured by electrodes 406 and/or skin electrode 413.
Optionally, the presence of the esophagus is estimated based on
analysis of the measured electric parameters results of MRI, CT, or
ultrasound imaging analysis procedures.
[0173] According to some exemplary embodiments, control circuitry
414 estimates the position of at least part of the esophagus by
generating a measured map based on the measured values of the
electric parameter, and comparing this measured map to one or more
reference maps that map expectations related to the esophagus in
different places (including, optionally, in a place where it does
not affect the measurements). Two main groups of embodiments of
these two types of map will now be discussed in turn.
[0174] The embodiments of the first group rely on an assumption
that all maps (measured and reference) assign values of the
electrical parameter (e.g., voltage and/or impedance) to a common
underlying anatomy, and if different values of the electrical
parameter are associated to same anatomical places in different
maps, this difference may be indicative of difference in the
location of the esophagus. Thus, identifying the esophagus uses
knowledge regarding which values were measured at different
locations in heart chamber 404.
[0175] The embodiments of the second group rely on an assumption
that all maps (measured and reference) result from a given mapping
transformation transforming electrical values into anatomical
structures; and differences between anatomies represented by the
maps are indicative to where the esophagus is. Thus, identifying
the esophagus requires comparing shapes of anatomical maps of heart
chamber 404.
[0176] In the first group of embodiments, the measured map
comprises measured values of one or more electrical field
properties (for example, electric potential and/or impedance at one
or more frequencies of one or more electrical fields induced
through a mapped region of tissue), stored in correspondence with
respective positions within the mapped region of tissue. The
positions may be determined, for example, as described in relation
to the second group of embodiments described below, or by another
method; for example, magnetic sensing; or medical imaging using
ultrasound and/or X-ray. In one such embodiment, the measured map
may be generated by registering measured values of an electrical
parameter to a pre-acquired image of the heart chamber. For
example, measured voltage values may be registered to the
pre-acquired image, and impedance values associated with the
voltage values may be assigned to locations in the pre-acquired
image based on the registration between voltages and locations.
[0177] The reference maps, in the first group of embodiments,
comprise values of simulated and/or previously recorded electrical
field properties (for example, electric potential and/or impedance
at one or more frequencies of one or more electrical fields induced
through a mapped region of tissue) stored in a digital computer
memory 418 in association with respective positions at which the
values occur. Optionally, each of the reference maps are generated
by simulating values expected for the electrical parameter (e.g.,
for the impedance) based on the pre-acquired image used in
determining positions for the reference maps, and an assumption of
an esophagus missing, or located in a certain location in respect
to the pre-acquired image.
[0178] The reference maps stored in memory 418 optionally include
association between some portions of heart chamber 404 and
different positions of the esophagus in the different maps
(optionally no esophagus at all, which is explained separately
further below). Simulated maps are generated, for example, as
described in relation to block 209, herein. Additionally or
alternatively, reference maps are generated from previously
recorded data (e.g., in other subjects, where the position of the
esophagus was known).
[0179] Comparison of the measured map to the reference map, in the
first group of embodiments, optionally comprises identifying to
what reference map the simulated map is most similar. For example,
position-to-position (and optionally throughout the mapped volume,
not necessarily just near the chamber wall), map values are
compared, and the comparison that results in the smallest
cumulative difference (or other metric of similarity) in a relevant
portion of the maps indicates the most similar reference map. The
esophagus position in the most similar reference map is then used
as the estimated position of the esophagus. The "deviation" caused
by the esophagus in this case may be understood as the portion of
the most-similar reference map which is different from the way it
is shown in reference maps with the esophagus missing, or located
sufficiently distant not to affect the measurements.
[0180] Additionally or alternatively, a reference map used in a
comparison is a map generated without any esophagus at all, for
example by simulation, by the combination of suitable non-esophagus
portions of a pool of maps obtained from previously recorded data
(e.g., in other subjects), by the combination of enough maps with
the esophagus in different positions that the esophagus "averages
out", or another suitable method. The reference map should be
well-registered to the measured map, for example by suitable
distortions to align landmark features such as major apertures
(blood vessels) and the like. A simulation based on the patient's
own anatomy (for example, as determined using an MRI image) is
preferable; however reference map data from other patients is
optionally used by registering suitable portions of the reference
maps data to a scaffold provided by imaging of the patient's own
anatomy. Since the position of the esophagus is generally
constrained, e.g., to a particular side of a heart chamber, the
registration may be somewhat simplified to a matter of registering
just the wall on that side. Then a difference between the reference
map and the measured map is determined, for example, by subtraction
of corresponding values. A region of the map showing large
differences from similarity is then a candidate for the estimated
position of the esophagus.
[0181] In the second group of embodiments, the measurement map is
used in a form that defines an inner surface of heart chamber 404,
and/or the boundaries of a cluster of measurement positions
constrained by the inner surface so that they delimit an interior
volume of heart chamber 404. For example, the measurement map may
be generated by transforming the measurements using a given mapping
transformation into anatomical structures. The reference map may be
generated by transforming reference data by the same given mapping
transformation. More generally, a measurement map in the form of a
surface shape can be generated by several different methods.
[0182] One method uses impedance measurements of three crossed
electrical fields having different frequencies, with each
electrical field effectively establishing a spatial axis. Then
measurements of a particular set of three voltage values correspond
to a particular position in 3-D space. The surface shape of the
heart chamber 404 may then be determined from the limits of the
positions which can be visited within a well-explored heart chamber
404. The surface shape may additionally or alternatively be
determined by measurements that indicate contact with a wall of the
heart chamber, for example a change in impedance and/or force which
is measured upon contact and/or near contact. Optionally,
corrections for non-orthogonality and/or non-linearities help to
improve the correspondence between the actual heart chamber 404
shape, and a shape determined from the three-field mapping values.
However, if corrections for the effects of esophagus position are
not explicitly provided, this mapping method may lead to errors in
shape determination, due to distortion of the electrical field in
the vicinity of the esophagus (particularly if the esophagus is gas
filled). That error may be used as one source of a basis for
esophagus position estimation.
[0183] Another method of determining surface shape uses an
electrode probe which carries a plurality of sensing electrodes,
each at known relative distances from the others. Then the known
distances serve as a kind of ruler, allowing electrical
measurements to be constrained in their relative spatial positions
to occur at certain distances from one another, which are
consistent with the distances between the sensing electrodes.
Optionally, other constraints, are used as well; for example, a
constraint that nearby points in the heart chamber should also be
correspondingly nearby in their respective electrical field
properties (e.g., but not only, lacking sharp discontinuities). The
potential advantage of this method is that the electrical
parameters being measured are not necessarily organized to a
special arrangement of approximately linear crossing axes. This
allows a wider range of electrical field configurations to be used,
for example, configurations using transmitting electrodes
positioned within the body space (optionally, electrodes of the
mapping probe itself may be used as transmitting electrodes, albeit
with some potential tradeoffs in utility, since the fields
generated would then no longer be fixed). Intrabody transmitting
electrodes in turn have potential advantages for removing sources
of measurement variability such as the properties of extraneous
tissue, and electrical contact of electrodes with skin; and for
allowing an increased gradient of voltage with potentially
increased signal to noise ratio.
[0184] The self-ruler method of measurement helps to constrain a
measured map of surface position to something like its actual 3-D
shape. It also becomes apparent from the position data that some
regions have a different voltage gradient than others. That
gradient difference can be affected by proximity of an esophagus.
If the mapped distribution of gradients is relied on, the map may
be used in comparisons as described for the first group of
embodiments. Alternatively, the voltage gradient can be adjusted so
that it matches some reference gradient in a region--but in order
to accommodate this, the ruler length has to be adjusted
accordingly. The distortion of the ruler distorts the mapped shape
of the chamber. Additionally or alternatively, the ruler constraint
is optionally not applied absolutely during reconstruction, but
rather provided a weighting that allows the virtual ruler to shrink
or expand slightly in order to improve, for example, a level of
local electrical field self-correlation. In either instance, the
error in the distorted shape can be used to estimate the position
of the esophagus.
[0185] Another method of determining surface shape is to measure
the magnitudes and directions of electrical field gradients in
several different positions, and from this reconstruct an estimate
of the overall shape of the heart chamber 404. For example, a
simplifying assumption may be made that small gradient differences
as a function of solid angle are due to differences in the distance
in that direction of a substantially electrically uniform
surrounding medium such as the cardiac wall. Blood vessels, being
filled with relatively low-impedance blood, may be modeled to be
"far away", for example (that is, located beyond open apertures),
while expanses of heart chamber wall, with a higher impedance, are
modeled to appear closer. However, the presence of the esophagus
disturbs the simplifying assumption. A high impedance air pocket in
an esophagus can make the heart chamber wall appear closer still,
resulting in a bulge that may approximate a portion of a cylinder
along the extent of the esophagus. Again, this type of error may be
turned to advantage in estimating a position of the esophagus.
[0186] For any of the above-described methods of producing a
measured map of a surface shape, similar methods of comparison to a
reference map are available as were described for the first group
of embodiments; but in the second group of embodiments using shapes
of a surface in space as a basis of comparison. The reference map
may be, for example, a map of a "true" shape of a heart chamber 404
(similar to a "non-esophagus" type reference map), or it may be a
map that gives a shape distorted by a simulated and/or previously
measured esophagus. It should also be noted that the partial
cylinder shape also gives a method of finding and/or verifying an
estimated esophagus position; for example, by matching a partial
cylinder (or other suitable template shape, for example, a surface
of a spheroid, ellipsoid, 3-D mesh, or other 3-D structure) to a
bulge or indentation that comprises the deviation from the actual
shape of the wall of the heart chamber 404.
[0187] It is noted that reference maps of surface shapes are
optionally used as training tools for a physician, for example to
train the physician to recognize esophagus shape on measured maps
of surface shape.
[0188] According to some exemplary embodiments, the anatomical
imaging component 416 comprises computer circuitry configured to
analyze the received electric signals, for example, by combining
the received signal with additional information, for example
anatomical maps and/or imaging analysis results which are stored in
memory 418. The result of the analysis, in some embodiments, is a
measured map, which may be of the type that assigns electric field
properties to positions, and/or of the type that explicitly
determines an anatomical shape such as a lumen shape of a heart
chamber, based on measured electric field properties. In some
embodiments, the memory 418 stores programs and/or algorithms which
can be used by control circuitry 414 to estimate the position of
the esophagus, using the measured map and the reference maps(s). In
some embodiments, memory 418 stores measured electric parameter
values that were previously measured at different sites within a
heart chamber (e.g., available for use by anatomical imaging
component 416). In some embodiments, memory 418 comprises
anatomical and/or electrical information of body tissues for
example cardiac tissue and/or esophageal tissue.
[0189] According to some embodiments, control circuitry 414
estimates whether at least part of the esophagus 10 is present in
an adverse location and/or whether the presence of the esophagus
affects at least one outcome of a treatment. Alternatively or
optionally, control circuitry 414 determines whether positioning at
least one electrode at a specific target site for treating the
cardiac tissue, for example by RF ablation will have an adverse
effect on the esophageal tissue. In some embodiments, if
application of treatment energy at the target site has no effect on
the esophagus or that the effect on the esophagus is an allowed
effect, then control circuitry 414 signals the field generator 412
to generate the treatment energy. Alternatively, if application of
treatment energy at the target site is expected to have an adverse
effect on the esophagus, then control circuitry 414 selects an
alternative target site for the treatment, and/or modifies the
treatment path and/or modifies at least one parameter of the
treatment protocol. In some embodiments, the treatment protocol
parameters comprise the intensity of the treatment energy and/or
the duration of the treatment session and/or the interval between
two consecutive treatment sessions. In some embodiments, the
modified treatment protocol parameters allows for example, to avoid
or to minimize the adverse effect of the treatment on the esophagus
10. In some embodiments, the treatment energy is delivered to the
tissue by at least one electrode of electrodes 406.
[0190] According to some exemplary embodiments, if at least part of
the Esophagus 10 is estimated to be present in an adverse location
in relation to a selected treatment target site, then the control
circuitry signals interface 420 to generate a human detectable
indication, for example an alert signal, a light and/or a sound
signal. Alternatively or additionally, the control circuitry 414
prevents the application of the treatment at the measured site.
Optionally, control circuitry 414 selects an alternative target
site for application of the treatment.
[0191] According to some exemplary embodiments, control circuitry
414 estimates the probability that application of treatment energy,
for example RF energy at a selected treatment target site will
cause esophagus injury, based on the estimated location of the
esophagus, for example by simulating a treatment using the
treatment parameters and the measured electric parameters of the
tissue. In some embodiments, the simulation results are stored in
memory 418. In some embodiments, device 400 comprises casing
422.
[0192] Exemplary Process for Estimating Esophagus Position Combined
with a Treatment
[0193] Reference is now made to FIG. 4B, depicting a flow chart for
estimating the position of at least part of the esophagus prior to
a treatment procedure, for example in order to avoid or to minimize
the effect of the treatment on the esophagus, according to some
embodiments of the invention.
[0194] According to some exemplary embodiments, a patient is
diagnosed, for example a patient with atrial fibrillation, and a
treatment procedure is selected. In some embodiments, the treatment
procedure comprises ablating a selected region of the cardiac
tissue. Optionally, a treatment site is selected at 430 based on at
least one clinical parameter and/or based on the results of an
imaging procedure, for example MRI, CT or ultrasound procedure. In
some embodiments, the selected treatment procedure comprises RF
ablation.
[0195] According to some exemplary embodiments, the position of the
esophagus is estimated, as previously described at 208. In some
embodiments, estimating the position of the esophagus allows for
example, to select at least one target site or target region or a
path for the treatment and/or to determine which regions of the
cardiac tissue to avoid during the treatment in order to minimize
an adverse effect of the tissue, for example esophagus injury.
[0196] According to some exemplary embodiments, an electrode probe,
which includes at least one electrode, is inserted into a heart
chamber, for example the LA at 432. In some embodiments the
electrode probe is inserted, for example to measure at least one
electric parameter, for example electric potential and/or
impedance; and/or to apply the treatment energy, for example RF
energy to the cardiac tissue. Optionally the electrode is placed at
the treatment target site or at the treatment path that was
previously selected at 430.
[0197] According to some exemplary embodiments, the electrode
measures at least one electric parameter of the tissue at 434. In
some embodiments, the electric parameter is measured (e.g., while
moving the electrode and recording, for example, about 100
measurement recordings per second) at different locations within
the LA and/or at the selected treatment target site or adjacent to
the selected treatment target site. In some embodiments, the at
least one electric parameter comprises electric potential and/or
impedance.
[0198] In some embodiments, the electrode measures the electric
parameter at 434 during application of an electric field to the
tissue, for example by at least one additional electrode or at
least one additional pair of electrodes, for example 2 pairs, 3
pairs, or 4 pairs. In some embodiments, the additional electrode or
electrode pair is located on the electrode probe that was inserted
into the heart chamber. Alternatively, the additional electrode or
electrode pair is attached to the outer surface of the body, for
example to the skin of the patient, optionally at selected
locations on the skin.
[0199] According to some exemplary embodiments, the measured values
of the electric parameter, for example electric potential, are
analyzed at 436. In some embodiments, the analysis comprises
generating an electric potential map or an impedance map based on
the measured values of the electric parameter. In some embodiments,
an additional parameter is used to help determine a measured map
derived from the electric parameter: it may be a clinical
parameter, for example an electrophysiological parameter.
Alternatively or additionally, the additional parameter comprises
an anatomical parameter of the tissue. Optionally, the additional
parameter comprises the results of an imaging analysis procedure
for example MRI, CT or ultrasound imaging analysis.
[0200] According to some exemplary embodiments, the analysis at 436
comprises comparing measured electric potential values with
simulated values. The comparison may reveal differences which are
due to disturbances in the electrical field due to the nearby
presence of the esophagus.
[0201] In some embodiments, the comparison is of an electric
potential map constructed based on measured values with a simulated
electric potential map of the tissue. The simulated map may be
understood as converting positions in a simulation into expected
electric potentials or other electric field parameter values
(without an esophagus), and the deviations are deviations from
this. Additionally or alternatively, a simulation which includes
simulation of an esophagus is considered to already include a
deviation from the non-esophagus state, and to the extent that
measured values match that simulation, the measured electric
potential map shares the same deviation. Deviations in electric
potential map may be understood to have a "shape", e.g., insofar as
electrical potential magnitude varies to different values
("heights" or "distance", if was graphed) as a function of
positions along an extent following the heart chamber wall.
[0202] Additionally or alternatively, in some embodiments, the
measured map is a map of tissue positions (also referred to herein
as a measured map of surface shape), wherein measured electrical
potentials are used to determine positions of the tissue wall that
comprise the map (a "wall shape"), without a prior assumption that
there is a deviation of indicated tissue wall positions from actual
wall positions due to the presence of an esophagus. Then the map
being compared to is a map of actual heart chamber wall positions,
and the deviation is described in terms of a deviation in physical
shape.
[0203] In some embodiments (without prior assumption of esophagus
effects, so that a true wall position measurement is what is
"expected"), the electrical potential map may result in
measurements which indicate an atrial wall which somewhat indents
from its actual position. This may be due to effects within a
region on local impedance measurements, that result from an
inhomogeneity in dielectric properties that the esophageal tissue
and/or air within the esophagus introduce to the region.
[0204] In some embodiments, the simulated electric potential map is
generated as previously described at 209. Alternatively, the
measured electric potential map is analyzed to identify specific
regions which might indicate the presence of esophageal tissue
proximal to the LA, for example by identifying shapes (e.g.,
plotting a magnitude as a function of position along the wall
surface) substantially corresponding to a portion of a cylinder
(e.g., an elliptical right cylinder) wherein the cylinder height
extends generally along a rostro-caudal anatomical axis. In some
embodiments, an axis of the cylinder cross-section extends
substantially parallel to the LA wall having a length of about 5-15
mm, 10-20 mm, or another length. In some embodiments, deviations in
measured "wall shape" from actual wall shape are distinguished by
another pattern which superimposes on the position map of the LA
wall.
[0205] In some embodiments, the measured electric potential map is
compared to simulated electric potential maps which were generated
based on estimated positions of the esophagus. In some embodiments,
identifying a simulated map which is similar to the measured map
allows for example, to estimate the position of the esophagus.
[0206] According to some exemplary embodiments, the position of at
least part of the esophagus is estimated at 438, optionally based
on the analysis of the measured electric parameter values as
described at 436. In some embodiments, estimating the position of
at least part of the esophagus comprises estimating a spatial
relation between at least part of the esophagus and the LA or a
treatment target site within the LA. Optionally, estimating the
esophagus position comprises predicting whether application of
treatment energy, for example RF energy at a selected target site
within the LA will have an adverse effect on at least part of the
esophagus.
[0207] According to some exemplary embodiments, if application of
treatment energy at the selected treatment target site is predicted
to have an adverse effect on the esophagus, for example to injure
at least part of the esophageal tissue, then an indication, for
example a human-detectable indication is delivered at 442. In some
embodiments, the indication is delivered to a user of the device,
for example a physician or a technician performing the procedure.
Optionally, the indication comprises an alert signal. In some
embodiments, the indication comprises information regarding an
alternative treatment site, optionally based on the estimated
esophagus position.
[0208] According to some exemplary embodiments, if application of
treatment energy at a selected target site is predicted to have an
adverse effect on the esophagus, then the electrode probe or at
least one electrode of the electrode probe is re-positioned at 444.
In some embodiments, the electrode is positioned at an alternative
treatment site, optionally based on the estimated Esophagus
position. In some embodiments, once the electrode is re-positioned,
the electric parameter is measured at the new treatment target
site, for example as described at 434.
[0209] According to some exemplary embodiments, if application of
treatment energy at a selected target site is predicted to have an
adverse effect on the esophagus, then at least one parameter of the
treatment is modified or adjusted at 446, optionally based on the
estimated esophagus position and/or based on a spatial relationship
between the target site and the esophagus. In some embodiments, the
at least one parameter comprises the duration of the treatment, the
intensity of the treatment and/or an alternative treatment path,
for example an alternative ablation path, which comprises at least
one alternative treatment target site. Optionally, the at least one
parameter comprises the number of treatment sessions, the duration
of each treatment session or the interval between sequential
treatment session.
[0210] According to some embodiments, once the at least one
treatment parameter is modified or adjusted, a treatment is applied
at 448. In some embodiments, the treatment is applied by at least
one electrode or set of electrodes located on the electrode probe.
Optionally, the treatment is applied by at least one electrode
positioned inside the body or outside the body of the patient, for
example by a skin electrode.
[0211] According to some exemplary embodiments, if application of
treatment energy at a selected target site is not predicted to have
an adverse effect on the esophagus, then an indication is provided
to a user at 450.In some embodiments, the indication is delivered
to a user of the device, for example a physician or a technician
performing the procedure. In some embodiments, the delivered
indication comprises a human detectable indication, for example a
light or a sound indication. In some embodiments, a treatment is
applied at 448, as previously described.
[0212] Exemplary Estimation of the Position of the Esophagus in
combination with an Ablation Process
[0213] Reference is now made to FIG. 5 depicting a process for
estimating the presence and/or position of at least part of the
esophagus in combination with an ablation procedure, according to
some embodiments of the invention.
[0214] According to some exemplary embodiments, the position of at
least part of the esophagus is estimated at 501. In some
embodiments, the esophagus position is estimated based on an
imaging analysis, for example a CT, MRI or ultrasound imaging
analysis. It should be noted that the esophagus is capable of
moving relative to the heart (e.g., due to swallowing movements)
over a period of time, so imaging-based estimation of esophagus
position is preferably performed using an image taken very close in
time to a treatment procedure that uses the position estimate.
[0215] In some embodiments, a map, for example an electric
potential or an impedance map, is generated based on simulated
electric potential or impedance values, and optionally based on the
results of the imaging analysis. In some embodiments, the simulated
map comprises electric potential or impedance values that are
expected to be measured by an electrode placed within the heart
cavity, for example the LA. In some embodiments, the estimated
position of the esophagus at 501 comprises possible locations of
the esophagus, optionally due to predicted movement of the
esophagus, for example lateral movement of the esophagus relative
to the heart. In some embodiments, each simulated map is generated
based on a different estimated position of the esophagus,
optionally in relationship to the heart. In some embodiments, at
least one simulated map and/or the information regarding the
estimated position of the esophagus are presented on a display, for
example prior to or during the treatment.
[0216] According to some exemplary embodiments, at least one
ablation treatment target site and/or an ablation path are planned
at 502. In some embodiments, the ablation target site and/or the
ablation path are selected based on at least one clinical
parameter, for example an electrophysiological parameter.
Additionally or optionally, the target site is selected based on
anatomical information, for example an anatomical map and/or based
on the results of at least one imaging analysis, for example CT,
MRI or ultrasound analysis. In some embodiments, the ablation
target site and/or the ablation path are selected based on at least
one simulated map, for example at least one simulated map that was
generated at 501.
[0217] According to some exemplary embodiments, at least one
electrode is positioned within a heart chamber and/or at the
planned treatment target site or treatment path, for example the
planned target site or path, at 504. In some embodiments, the
target site or path is located at the LA, for example at the
cardiac tissue of the LA. In some embodiments, the electrode is
positioned based on the simulated map.
[0218] According to some exemplary embodiments, the electrode
measures at least one electric parameter, for example electric
potential within the LA, optionally at the target site or adjacent
to the target site at 506, and/or at a multiplicity of other sites.
In some embodiments, the electric parameter is measured during
application of an electric field to the body, optionally to the
skin. In some embodiments, the simulated map is modified based on
the measured electric parameter values that are measured from
within the LA. Alternatively, the measured electric parameter
values are compared to simulated values. In some embodiments, the
measured electric parameter values are used to generate an electric
potential map or and impedance map.
[0219] According to some exemplary embodiments, the position of the
esophagus or a spatial relationship between the LA and at least
part of the esophagus is estimated at 508. Optionally, esophageal
tissue proximity to a selected target site or to the selected
treatment path is estimated.
[0220] According to some exemplary embodiments, the position of the
esophagus is estimated by identifying, in the maps regions that
exhibit deviations in the measured electric parameter values
compared to estimated values, which are related to the effect of a
proximal esophageal tissue on the measured values. In some
embodiments, the estimated values are based on multiple electric
parameter measurements in many subjects. Alternatively, the
esophagus position is estimated by comparing the map based on the
measured values to the simulated maps, to identify the simulated
map that is most similar to the map of measured values. In some
embodiments, the esophagus position is estimated by comparing the
measured values to simulated values that reflect different
predicted positions of the esophagus. In some embodiments, if
patient is awake and cooperative, swallowing manipulation can allow
an expert performing the procedure to detect esophagus and assist
in verification electrical mapping diagnostic.
[0221] In some embodiments, the measured electric parameter values,
for example electric potential values are used to indicate a
spatial relationship, for example distance between the measurement
site and/or the electrode probe and esophageal tissue. In some
embodiments, the measured electric parameter values are used to
estimate a spatial relationship, for example distance between an
ablation target site and/or an ablation path to esophageal tissue,
without the need to generate a map based on these measured values.
In some embodiments, the measured electric parameter values are
used to determine whether the estimated spatial relationship is a
targeted or an allowed spatial relationship before the ablation. In
some embodiments, a targeted or an allowed spatial relationship
comprises a spatial relationship between at least part of the
esophagus and a selected ablation target site that allows, for
example to deliver RF energy to the tissue at the target site
without affecting the at least part of the esophagus, or that the
effect on the esophagus is an allowed effect, for example an effect
that does not lead to esophagus injury. Optionally, a targeted
spatial relationship comprises that the esophagus is not detected
at the measurement site of the electric parameter values.
[0222] According to some exemplary embodiments, if ablating the
target site or along the target path is predicted to have no
adverse effects on the esophagus or that the effect on the
esophagus is predicted to be an allowed effect, then an ablation
procedure is initiated at 516. Optionally, the ablation procedure
is initiated if the ablation target site is in a targeted or an
allowed spatial relation, for example a targeted or an allowed
distance from the esophagus, based on the measured electric
parameter values. In some embodiments, if ablation at the target
site or along the target path is allowed, then an indication is
provided.
[0223] According to some exemplary embodiments, if ablating the
target site or along the target path is predicted to have adverse
effect on the esophagus, for example to injure the esophagus, based
on the measured electric parameter values, then an indication is
provided. Additionally, alternative ablation sites and/or an
alternative ablation path are selected at 510. Alternatively, at
least one parameter of the ablation treatment is modified, for
example to minimize or to avoid the adverse effect, at 512. In some
embodiments, the modified ablation parameter is automatically
selected from a list comprising the intensity of the ablation, the
duration of each ablation pulse, the ablation frequency, and/or the
time interval between at least two consecutive ablation
sessions.
[0224] According to some exemplary embodiments, if ablating the
target site or along the target path is predicted to have adverse
effect on the esophagus, then the esophagus is moved to a targeted
location at 513. Optionally, movement of the esophagus is
accomplished by encouraging the subject (if conscious) to swallow;
this can result in esophagus movement away from the target site.
The movement can be monitored and verified as for the original
estimate of esophagus position. In some embodiments, the esophagus
is moved, for example by insertion of a device into the esophagus
that allows to safely move the esophagus and optionally to fix the
esophagus at a targeted position.
[0225] According to some exemplary embodiments, if the electrode is
placed at an alternative target site for ablation, the verification
is performed at 514. In some embodiments, verification comprises
measuring at least one electric parameter at the alternative target
site, and estimating a spatial relationship between the alternative
target site and at least part of the esophagus, before
ablating.
[0226] According to some exemplary embodiments, an ablation
procedure is applied at 516. In some embodiments, during the
ablation procedure an electric potential map or a map which is
based on measured and/or simulated electric potential values is
displayed. In some embodiments, the displayed map is used to
position the ablation probe within the heart chamber at locations
that are in an allowed spatial relationship, for example distance
from at least part of the esophagus.
[0227] According to some exemplary embodiments, after each ablation
session, additional measurements of the electric potential are
performed. In some embodiments, the additional measurements are
used to update an existing electric potential or impedance map,
optionally to identify movements of the esophagus during or after
the ablation session.
[0228] Exemplary Process for Simulating an Electric Potential or
Impedance Map
[0229] Reference is now made to FIG. 6A depicting a process for
generating an electric potential or impedance map, according to
some embodiments of the invention.
[0230] According to some exemplary embodiments, an imaging analysis
is performed at 602, for example to estimate the position of the
esophagus, the heart and other tissues or organs. In some
embodiments, the imaging analysis comprises CT, MRI or ultrasound
imaging analysis.
[0231] According to some exemplary embodiments, a simulation of
electric parameter values is performed at 604. In some embodiments,
electric potential and/or impedance values are simulated as they
would be measured by at least one electrode from within the heart
chamber, for example the LA. In some embodiments, the simulation is
based on the position and the number of the electrodes that will be
used to generate the electric field, the electric field frequency
that will be applied to the body by each electrode or pair of
electrodes, and on the tissue types surrounding the LA and their
respective dielectric properties.
[0232] According to some exemplary embodiments, based on the
simulated values, a simulated map is generated at 606, for example
a simulated electric potential or impedance map. Optionally, the
map is generated by combining the simulated electric parameters
values with anatomical data, for example anatomical data that was
obtained in imaging analysis 602.
[0233] According to some exemplary embodiments, at least one
electrode is inserted into a heart chamber or into a blood vessel
to measure at least one electric parameter of the tissue from at
least one and preferably from a multiplicity of locations, for
example at 610. Optionally, impedance values are calculated from
the measured electric potential values. In some embodiments, the
electric potential or impedance values are used to generate a map,
for example an electric potential or an impedance map.
[0234] In some embodiments, the measured electric potential or
impedance values are used to update the simulated map at 612.
Alternatively the generated electric potential or impedance map is
used to update the simulated map. In some embodiments, the updated
map which describes the updated position of the esophagus and/or
the proximity of esophageal tissue to the LA is displayed to an
expert before and/or during and/or after a treatment, for example
an RF ablation treatment. In some embodiments, the updated map
allows the expert for example, to place the ablation electrode at a
location or to plan an ablation path that will not result with
esophagus injury once the treatment energy is applied.
[0235] Exemplary Simulated Maps
[0236] According to some exemplary embodiments, simulation results
are obtained by modeling electric field propagation in an area
modeled to contain material having the dielectric properties
associated with the tissues imaged in the CT scan (or other
anatomical data). In some embodiments, tissue type identity is
assigned based on automatic segmentation of the CT scan imaging
results. It is a potential advantage to use a high-resolution scan.
Example of high resolution scan is a CT scan with slices of between
1 mm-3 mm. Higher resolution, should it be available, is
preferable. In some embodiments, the scan is optionally used as a
basis of the segmentation, as this sets the conditions of the field
simulation more nearly to the actual situation. In some
embodiments, post-processing, optionally manually guided, is
performed to remove segmentation artifacts.
[0237] Optionally, post-processing, e.g., for cleaning up
segmentation, uses capabilities of commercially available imaging
system, such as a Carto.TM. or Insight.TM. system. In some
embodiments, post-processing is performed under the guidance of an
imaging technician experienced in tasks of anatomical segmentation.
In general, results of the electromagnetic simulation are dependent
on the degree of care devoted to obtaining accurate,
high-resolution anatomical data. The higher resolution of the
scanned tissues should also be preserved in the simulation modeling
itself.
[0238] Reference is now made to FIGS. 7A-7I depicting simulated
electric potential maps of the LA, according to some exemplary
embodiments of the invention.
[0239] According to some exemplary embodiments, simulated electric
potential maps are generated by simulation of electric potential
values as if they are measured from within at least part of the
heart, for example from within the LA. In some embodiments, the
simulation is based on the dielectric properties of cardiac tissues
and other tissue types surrounding the LA. In addition, simulation
of LA electric potential values is based on a simulated position of
an electrode probe within the LA, position of electrodes on the
skin for application of electric fields, and on other parameters of
the applied electric fields for example frequencies and intensity.
In some embodiments, each of the simulated maps is generated based
on a different estimated position of the esophagus, and represents
the effect of the esophagus at this estimated position on the
simulated electric potential values. Alternatively, the simulated
maps are prepared based on a different spatial relationship between
a simulated measurement site and at least part of the
esophagus.
[0240] According to some exemplary embodiments, for example as
shown in FIGS. 7A and 7B the white electric potential simulated map
shown in FIG. 7B is a simulated electric potential map that was
generated based on an assumption that the esophagus is not
affecting the electric field inside the heart 20. In some
embodiments, for example as shown in FIGS. 7D-7F, the simulated
electric potential maps are generated based on the assumption that
the esophagus 10 is positioned at different spatial relationships,
for example in a different distance, from the heart 20. In some
embodiments, based on the different positions of the esophagus
different simulated electric potential maps are generated. In some
embodiments, for example as shown in FIG. 7G each colored simulated
map reflects a different spatial relationship between the esophagus
and the heart. For example, the red simulation map is generated
based on the assumption that the esophagus 10 is positioned in
distance 720 from the heart 20. Additionally, the green and the
black colored simulation maps are generated based on the assumption
that the esophagus 10 is positioned in distances 722 and 724,
respectively. In some embodiments, a minimal spatial difference of
2% between the white, red, green and black colored electric
potential maps shown for example in FIG. 7G, allows to identify
possible positions of the esophagus.
[0241] According to some exemplary embodiments, the position of the
LA is determined based for example, on CT scanning results and
different simulated electric potential maps are generated based on
the assumption that the esophagus is placed in different distances
from the LA, as shown for example in FIGS. 7H and 71. In some
embodiments, FIG. 71 is an overlay of simulated maps that were
prepared based on estimated positions of the esophagus related to
LA 30, shown in FIG. 7H.
[0242] Exemplary Simulated Maps
[0243] Reference is now made to FIGS. 8A-8E, which schematically
represent views of a phantom left atrium within which electrode
probe voltage mapping measurements have been performed with and
without an adjacent air-filled tube simulating an esophagus,
according to some embodiments of the present disclosure.
[0244] FIGS. 8A and 8B each show a point cloud of voltage
measurements, wherein the measurement position has been determined
using an electrode probe which carries a plurality of sensing
electrodes, each at known relative positions (at least known
distance) with respect to one another. The known relative positions
were used as a constraint in finding the positions of the
measurement points with respect to one another. In some
embodiments, the constraint may be soft, that is, a mapping that
keeps the distance between the electrodes equal to the distance in
reality is preferred over a mapping that does not keep these
distances equal, but the latter is not absolutely prevented. During
the measurements of FIG. 8B, but not FIG. 8A, a tube filled with
air was submerged adjacent to the phantom at position 803. The
resulting indentation (deviation) at 803 of FIG. 8B can be observed
relative to the shape of region 801 in FIG. 8A. FIG. 8C is a
differential image, with the point cloud of FIG. 8B dark and the
point cloud of FIG. 8A light. The difference between the two point
clouds is seen as the lighter points of region 801 showing through
the gap left in region 803.
[0245] FIG. 8D and 8E represent rolling marble reconstructions 810,
812 based on point clouds acquired as described for FIGS. 8A and
8B, respectively. Rolling marble reconstruction rolls a virtual
sphere of a certain diameter over the body of a point cloud with a
controlled degree of intrusion, defining a surface that contains
the measurements of the point cloud within it. In FIG. 8E, a
deviation (indentation) at 813 appears due to the influence of the
air-filled tube, which is absent at 811.
[0246] General
[0247] As used herein with reference to quantity or value, the term
"about" means "within .+-.10% of".
[0248] The terms "comprises", "comprising", "includes",
"including", "has", "having" and their conjugates mean "including
but not limited to".
[0249] The term "consisting of" means "including and limited
to".
[0250] The term "consisting essentially of" means that the
composition, method or structure may include additional
ingredients, steps and/or parts, but only if the additional
ingredients, steps and/or parts do not materially alter the basic
and novel characteristics of the claimed composition, method or
structure.
[0251] As used herein, the singular forms "a", "an" and "the"
include plural references unless the context clearly dictates
otherwise. For example, the term "a compound" or "at least one
compound" may include a plurality of compounds, including mixtures
thereof.
[0252] Throughout this application, embodiments of this invention
may be presented with reference to a range format. It should be
understood that the description in range format is merely for
convenience and brevity and should not be construed as an
inflexible limitation on the scope of the invention. Accordingly,
the description of a range should be considered to have
specifically disclosed all the possible subranges as well as
individual numerical values within that range. For example,
description of a range such as "from 1 to 6" should be considered
to have specifically disclosed subranges such as "from 1 to 3",
"from 1 to 4", "from 1 to 5", "from 2 to 4", "from 2 to 6", "from 3
to 6", etc.; as well as individual numbers within that range, for
example, 1, 2, 3, 4, 5, and 6. This applies regardless of the
breadth of the range.
[0253] Whenever a numerical range is indicated herein (for example
"10-15", "10 to 15", or any pair of numbers linked by these another
such range indication), it is meant to include any number
(fractional or integral) within the indicated range limits,
including the range limits, unless the context clearly dictates
otherwise. The phrases "range/ranging/ranges between" a first
indicate number and a second indicate number and
"range/ranging/ranges from" a first indicate number "to", "up to",
"until" or "through" (or another such range-indicating term) a
second indicate number are used herein interchangeably and are
meant to include the first and second indicated numbers and all the
fractional and integral numbers therebetween.
[0254] Unless otherwise indicated, numbers used herein and any
number ranges based thereon are approximations within the accuracy
of reasonable measurement and rounding errors as understood by
persons skilled in the art.
[0255] 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
or as suitable in any other described embodiment of the invention.
Certain features described in the context of various embodiments
are not to be considered essential features of those embodiments,
unless the embodiment is inoperative without those elements.
[0256] 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.
[0257] All publications, patents and patent applications mentioned
in this specification are herein incorporated in their entirety by
reference into the specification, to the same extent as if each
individual publication, patent or patent application was
specifically and individually indicated to be incorporated herein
by reference. In addition, citation or identification of any
reference in this application shall not be construed as an
admission that such reference is available as prior art to the
present invention. To the extent that section headings are used,
they should not be construed as necessarily limiting.
[0258] It is the intent of the applicant(s) that all publications,
patents and patent applications referred to in this specification
are to be incorporated in their entirety by reference into the
specification, as if each individual publication, patent or patent
application was specifically and individually noted when referenced
that it is to be incorporated herein by reference. In addition,
citation or identification of any reference in this application
shall not be construed as an admission that such reference is
available as prior art to the present invention. To the extent that
section headings are used, they should not be construed as
necessarily limiting. In addition, any priority document(s) of this
application is/are hereby incorporated herein by reference in
its/their entirety.
* * * * *