U.S. patent application number 11/953615 was filed with the patent office on 2008-04-17 for irrigated ablation catheter having magnetic tip for magnetic field control and guidance.
Invention is credited to Jeremy D. Dando, James Kauphusman, Harry Puryear, Huisun Wang.
Application Number | 20080091193 11/953615 |
Document ID | / |
Family ID | 39303947 |
Filed Date | 2008-04-17 |
United States Patent
Application |
20080091193 |
Kind Code |
A1 |
Kauphusman; James ; et
al. |
April 17, 2008 |
Irrigated ablation catheter having magnetic tip for magnetic field
control and guidance
Abstract
Embodiments of the present invention provide an irrigated
ablation electrode assembly for use with an irrigated catheter
device comprises at least one passageway for a fluid with an outlet
disposed at an external surface of the electrode assembly; a
permanent magnet; a shield separating the permanent magnet from the
at least one passageway and from an exterior, the shield being
substantially less oxidizable than the permanent magnet; and an
electrode having an external electrode surface. A catheter guidance
control and imaging system drives the permanent magnet to guide and
control the catheter tip. In specific embodiments, the irrigation
fluid flow paths through the electrode assembly are thermally
insulated from the electrode and temperature sensor. The irrigation
fluid is directed at target areas where coagulation is more likely
to occur. One or more monitoring electrodes are provided for
mapping or other monitoring functions.
Inventors: |
Kauphusman; James;
(Champlin, MN) ; Wang; Huisun; (Maple Grove,
MN) ; Dando; Jeremy D.; (Plymouth, MN) ;
Puryear; Harry; (Shoreview, MN) |
Correspondence
Address: |
ST. JUDE MEDICAL, ATRIAL FIBRILLATION DIVISION
14901 DEVEAU PLACE
MINNETONKA
MN
55345-2126
US
|
Family ID: |
39303947 |
Appl. No.: |
11/953615 |
Filed: |
December 10, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11948362 |
Nov 30, 2007 |
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11953615 |
Dec 10, 2007 |
|
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11434200 |
May 16, 2006 |
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11948362 |
Nov 30, 2007 |
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Current U.S.
Class: |
606/41 |
Current CPC
Class: |
A61B 2034/2051 20160201;
A61B 2018/00577 20130101; A61B 18/1492 20130101; A61B 2218/002
20130101; A61B 2018/00791 20130101 |
Class at
Publication: |
606/041 |
International
Class: |
A61B 18/14 20060101
A61B018/14 |
Foreign Application Data
Date |
Code |
Application Number |
May 16, 2005 |
JP |
2005-142690 |
Claims
1. An irrigated ablation electrode assembly for use with an
irrigated catheter device, the irrigated ablation electrode
assembly comprising: at least one passageway for a fluid with an
outlet disposed at an external surface of the electrode assembly; a
permanent magnet; a shield separating the permanent magnet from the
at least one passageway and from an exterior, the shield being
substantially less oxidizable than the permanent magnet; and an
electrode having an external electrode surface.
2. The irrigated ablation electrode assembly of claim 1, wherein
the electrode forms at least a portion of the shield, and wherein
the electrode comprises an electrically conductive material that is
substantially less oxidizable than the permanent magnet.
3. The irrigated ablation electrode assembly of claim 2 wherein the
electrically conductive material is selected from the group
consisting of platinum, gold, tantalum, iridium, stainless steel,
palladium, and mixtures thereof, and wherein the electrically
conductive material is plated onto a substrate made of a
biocompatible material that is substantially less oxidizable than
the permanent magnet.
4. The irrigated ablation electrode assembly of claim 1 wherein the
shield comprises one or more materials selected from the group
consisting of silicone, polyimide, platinum, gold, tantalum,
iridium, stainless steel, palladium, and mixtures thereof.
5. The irrigated ablation electrode assembly of claim 1 wherein the
permanent magnet comprises NdFeB.
6. The irrigated ablation electrode assembly of claim 1 further
comprising at least one mapping electrode spaced proximally from
the electrode which is a distal electrode capable of ablation.
7. The irrigated ablation electrode assembly of claim 1 wherein the
electrode is disposed at a distal portion of the electrode
assembly, and wherein the electrode assembly further comprises a
proximal portion which includes at least one proximal passageway
for a fluid with an outlet disposed at an external surface of the
proximal portion.
8. The irrigated ablation electrode assembly of claim 7 wherein the
proximal portion comprises a material which is electrically
nonconductive and has a lower thermal conductivity than a material
of the electrode.
9. The irrigated ablation electrode assembly of claim 7 wherein the
at least one proximal passageway extends toward the electrode at an
acute angle with respect to the longitudinal axis of the proximal
portion.
10. The irrigated ablation electrode assembly of claim 7 wherein
the proximal portion comprises a material which is electrically
nonconductive, and wherein the external surface of the proximal
portion and the external electrode surface of the electrode at the
distal portion meet at an intersection, and wherein the at least
one proximal passageway is configured to direct a fluid flow
through the outlet toward a region adjacent the intersection.
11. The irrigated ablation electrode assembly of claim 7 wherein
the permanent magnet is disposed in the distal portion, and wherein
the electrode assembly further comprises at least one temperature
sensor disposed in the permanent magnet.
12. The irrigated ablation electrode assembly of claim 1 wherein
the electrode includes at least one electrode passageway for a
fluid with an outlet disposed at the external electrode
surface.
13. The irrigated ablation electrode assembly of claim 12 wherein
the at least one electrode passageway is thermally insulated from
the distal member by a poor thermal conductive material which is
lower in thermal conductivity than a material of the electrode.
14. The irrigated ablation electrode assembly of claim 12 wherein
the permanent magnet comprises an annular permanent magnet with an
axial opening to permit fluid flow to the at least one electrode
passageway, and wherein the electrode assembly further comprises a
fluid lumen extending through the axial opening of the annular
permanent magnet to the at least one electrode passageway.
15. The irrigated ablation electrode assembly of claim 14 wherein
the fluid lumen comprises stainless steel braided polyimide forming
a portion of the shield, and wherein the electrode forms another
portion of the shield.
16. The irrigated ablation electrode assembly of claim 15 wherein
the shield includes a silicone seal to prevent fluid from reaching
the annular permanent magnet via a junction between the electrode
and the fluid lumen.
17. The irrigated ablation electrode assembly of claim 12 wherein
the electrode is disposed at a distal portion of the electrode
assembly, and wherein the electrode assembly further comprises a
proximal portion which includes at least one proximal passageway
for a fluid with an outlet disposed at an external surface of the
proximal portion, wherein the proximal portion comprises a material
which is electrically nonconductive, wherein the external surface
of the proximal portion and the external electrode surface of the
electrode at the distal portion meet at an intersection, and
wherein the at least one proximal passageway is configured to
direct a fluid flow through the outlet toward a region adjacent the
intersection.
18. An irrigated ablation electrode assembly for use with an
irrigated catheter device, the irrigated ablation electrode
assembly comprising: a permanent magnet, at least one passageway
for a fluid with an outlet disposed at an external surface of the
electrode assembly, the at least one passageway extending through
the permanent magnet; an inner shield separating the permanent
magnet from the at least one passageway, the inner shield being
substantially less oxidizable than the permanent magnet; and an
outer shield separating the permanent magnet from an exterior, the
outer shield being substantially less oxidizable than the permanent
magnet.
19. The irrigated ablation electrode assembly of claim 18 wherein
the inner shield comprises a fluid lumen supplying fluid to the at
least one passageway.
20. The irrigated ablation electrode assembly of claim 18 further
comprising an electrode having an external electrode surface, and
wherein the electrode forms at least a portion of the outer
shield.
21. The irrigated ablation electrode assembly of claim 20 wherein
the electrode is disposed at a distal portion of the electrode
assembly, wherein the electrode assembly further comprises a
proximal portion having a material which is electrically
nonconductive, and wherein the proximal portion forms at least a
portion of the inner shield.
22. A catheter comprising: a shaft; and an irrigated ablation
electrode assembly coupled to a distal end of the shaft, the
irrigated ablation electrode assembly having at least one
passageway for a fluid with an outlet disposed at an external
surface of the electrode assembly; a permanent magnet; a shield
separating the permanent magnet from the at least one passageway
and from an exterior, the shield being substantially less
oxidizable than the permanent magnet; and an electrode having an
external electrode surface.
23. The catheter of claim 22 wherein the electrode is disposed at a
distal portion of the electrode assembly, and wherein the electrode
assembly further comprises a proximal portion which includes at
least one proximal passageway for a fluid with an outlet disposed
at an external surface of the proximal portion.
24. The catheter of claim 22 wherein the electrode includes at
least one electrode passageway for a fluid with an outlet disposed
at the external electrode surface, wherein the permanent magnet
comprises an annular permanent magnet with an axial opening to
permit fluid flow to the at least one electrode passageway, and
wherein the catheter further comprises a fluid lumen extending
through the axial opening of the annular permanent magnet to the at
least one electrode passageway.
25. The catheter of claim 22 further comprising a second permanent
magnet disposed near the distal end of the shaft and spaced from
the permanent magnet in the irrigated ablation electrode assembly.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 11/948,362, filed on Nov. 30, 2007, which is a
continuation-in-part of U.S. patent application Ser. No.
11/434,200, filed May 16, 2006, the entire disclosures of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] a. Field of the Invention
[0003] The present invention pertains generally to ablation
catheters and electrode assemblies. More particularly, the present
invention is directed toward ablation electrode assemblies for use
in the human body having a magnetic tip for magnetic field control
and guidance, a mechanism for irrigating targeted areas, and
mapping characteristics.
[0004] b. Background Art
[0005] Electrophysiology catheters are used for an ever-growing
number of procedures. For example, catheters are used for
diagnostic, therapeutic, and ablative procedures, to name just a
few examples. Typically, the catheter is manipulated through the
patient's vasculature and to the intended site, for example, a site
within the patient's heart.
[0006] The catheter typically carries one or more electrodes, which
may be used for ablation, diagnosis, or the like. There are a
number of methods used for ablation of desired areas, including for
example, radiofrequency (RF) ablation. RF ablation is accomplished
by transmission of radiofrequency energy to a desired target area
through an electrode assembly to ablate tissue at the target
site.
[0007] Because RF ablation may generate significant heat, which if
not carefully monitored and/or controlled can result in protein
denaturation, blood coagulation, excess tissue damage, such as
steam pop, tissue charring, and the like, it is desirable to
monitor the temperature of the ablation assembly. It is further
desirable to include a mechanism to irrigate certain target areas
with biocompatible fluids, such as saline solution. This irrigation
reduces or avoids excess, unwanted tissue damage, as well as blood
coagulation and problems associated therewith. However,
introduction of this irrigation solution may inhibit the ability to
accurately monitor and/or control the temperature of the ablation
assembly during use.
[0008] There are typically two classes of irrigated electrode
catheters, open and closed irrigation catheters. Closed ablation
catheters typically circulate a cooling fluid within the inner
cavity of the electrode. Open ablation catheters, on the other
hand, typically deliver the cooling fluid through open orifices on
the electrode. Examples of these known catheters include the
THERMOCOOL brand of catheters marketed and sold by
Biosense-Webster. The current open irrigated ablation catheters use
the inner cavity of the electrode, or distal member, as a manifold
to distribute saline solution. The saline thus flows directly
through the open orifices of the distal electrode member. This
direct flow through the distal electrode tip lowers the temperature
of the distal tip during operation, rendering accurate monitoring
and control of the ablative process more difficult.
[0009] In these open electrode irrigated catheters, it has been
determined that insulating the irrigation channels from the
ablation electrode is beneficial. One such example was published on
or around March 2005 in an article entitled "Saline-Irrigated
Radiofrequency Ablation Electrode with Electrode Cooling," by Drs.
Wittkampf and Nakagawa et al., the content of which is hereby
incorporated by reference in its entirety. Similarly, the content
of PCT International Publication No. WO 05/048858, published on
Jun. 2, 2005, is hereby incorporated by reference in its
entirety.
[0010] Recently, magnetic systems have been proposed, wherein
magnetic fields produced by one or more electromagnets are used to
guide and advance a magnetically tipped catheter. For example, U.S.
Patent Application Publication No. 2007/0016006 discloses an
apparatus and a method for guiding, steering, and advancing
invasive devices and for accurately controlling their positions for
providing positioning of magnetic fields and field gradient, for
providing fields configured to push/pull, bend/rotate, and by
further enabling apparatus to align the distal end of the catheter
tip so as to achieve controlled movement in 3D space and ability of
apparatus to control the magnetic field characteristics, preferably
without excessively large power and field intensities that are
potentially dangerous to medical personnel and that can be
disruptive to other equipment. The entire disclosure of US
2007/0016006 is incorporated herein by reference.
BRIEF SUMMARY OF THE INVENTION
[0011] Embodiments of the present invention provide an irrigated
catheter configured to provide better electrode surface cooling and
more accurate electrode tip temperature measurement, and having a
magnetic tip that can be magnetically guided and controlled. The
irrigated catheter may further include one or more monitoring or
measuring electrodes for mapping or the like. The irrigation fluid
is directed at target areas where coagulation is more likely to
occur so as to minimize blood coagulation and the associated
problems. In some embodiments, the invention further provides for
significant improvements over known irrigation catheters, including
those disclosed by Wittkampf and Nakagawa et al., by providing a
multiple piece irrigated ablation electrode assembly that has the
advantages of irrigating the target area while simultaneously
improving the operation, temperature response, temperature
monitoring and/or control mechanisms of the ablation assembly, so
as to prevent unwanted, unnecessary tissue damage and blood
coagulation.
[0012] The present invention is directed to improved irrigated
ablation electrode assemblies and methods useful in conjunction
with irrigated catheter and pump assemblies and RF generator
assemblies designed to monitor and control the ablation process
while minimizing blood coagulation and unnecessary tissue damage,
and with catheter guidance control and imaging systems designed to
guide and control the magnetic tips of the electrode assemblies and
perform mapping and other imaging functions.
[0013] In accordance with an aspect of the present invention, an
irrigated ablation electrode assembly for use with an irrigated
catheter device comprises at least one passageway for a fluid with
an outlet disposed at an external surface of the electrode
assembly; a permanent magnet; a shield separating the permanent
magnet from the at least one passageway and from an exterior, the
shield being substantially less oxidizable than the permanent
magnet; and an electrode having an external electrode surface.
[0014] In some embodiments, the electrode forms at least a portion
of the shield, and comprises an electrically conductive material
that is substantially less oxidizable than the permanent magnet.
The electrically conductive material is selected from the group
consisting of platinum, gold, tantalum, iridium, stainless steel,
palladium, and mixtures thereof, and the electrically conductive
material is plated onto a substrate made of a biocompatible
material that is substantially less oxidizable than the permanent
magnet. The shield comprises one or more materials selected from
the group consisting of silicone, polyimide, platinum, gold,
tantalum, iridium, stainless steel, palladium, and mixtures
thereof. In one example, the permanent magnet comprises NdFeB. At
least one mapping electrode is spaced proximally from the electrode
which is a distal electrode capable of ablation.
[0015] In specific embodiments, the electrode is disposed at a
distal portion of the electrode assembly and includes an external
electrode surface, and the electrode assembly further comprises a
proximal portion which includes at least one proximal passageway
for a fluid with an outlet disposed at an external surface of the
proximal portion. The proximal portion comprises a material which
is electrically nonconductive and has a lower thermal conductivity
than a material of the electrode. The at least one proximal
passageway extends toward the electrode at an acute angle with
respect to the longitudinal axis of the proximal portion. The
proximal portion comprises a material which is electrically
nonconductive; the external surface of the proximal portion and the
external electrode surface of the electrode at the distal portion
meet at an intersection; and the at least one proximal passageway
is configured to direct a fluid flow through the outlet toward a
region adjacent the intersection. The permanent magnet is disposed
in the distal portion, and the electrode assembly further comprises
at least one temperature sensor disposed in the permanent magnet.
The electrode includes an external electrode surface, and the
electrode includes at least one electrode passageway for a fluid
with an outlet disposed at the external electrode surface. The at
least one electrode passageway is thermally insulated from the
distal member by a poor thermal conductive material which is lower
in thermal conductivity than a material of the electrode.
[0016] In some embodiments, the permanent magnet comprises an
annular permanent magnet with an axial opening to permit fluid flow
to the at least one electrode passageway, and the electrode
assembly further comprises a fluid lumen extending through the
axial opening of the annular permanent magnet to the at least one
electrode passageway. The fluid lumen comprises stainless steel
braided polyimide forming a portion of the shield, and the
electrode forms another portion of the shield. The shield includes
a silicone seal to prevent fluid from reaching the annular
permanent magnet via a junction between the electrode and the fluid
lumen. The electrode is disposed at a distal portion of the
electrode assembly, and the electrode assembly further comprises a
proximal portion which includes at least one proximal passageway
for a fluid with an outlet disposed at an external surface of the
proximal portion. The proximal portion comprises a material which
is electrically nonconductive. The external surface of the proximal
portion and the external electrode surface of the electrode at the
distal portion meet at an intersection. The at least one proximal
passageway is configured to direct a fluid flow through the outlet
toward a region adjacent the intersection.
[0017] In accordance with another aspect of the invention, an
irrigated ablation electrode assembly for use with an irrigated
catheter device comprises a permanent magnet, at least one
passageway for a fluid with an outlet disposed at an external
surface of the electrode assembly, the at least one passageway
extending through the permanent magnet; an inner shield separating
the permanent magnet from the at least one passageway, the inner
shield being substantially less oxidizable than the permanent
magnet; and an outer shield separating the permanent magnet from an
exterior, the inner shield being substantially less oxidizable than
the permanent magnet.
[0018] In some embodiments, the inner shield comprises a fluid
lumen supplying fluid to the at least one passageway. The electrode
assembly includes an electrode that has an external electrode
surface and forms at least a portion of the outer shield. The
electrode is disposed at a distal portion of the electrode
assembly; the electrode assembly further comprises a proximal
portion having a material which is electrically nonconductive; and
the proximal portion forms at least a portion of the inner
shield.
[0019] In accordance with another aspect of this invention, a
catheter comprises a shaft; and an irrigated ablation electrode
assembly coupled to a distal end of the shaft. The irrigated
ablation electrode assembly has at least one passageway for a fluid
with an outlet disposed at an external surface of the electrode
assembly; a permanent magnet; a shield separating the permanent
magnet from the at least one passageway and from an exterior, the
shield being substantially less oxidizable than the permanent
magnet; and an electrode having an external electrode surface.
[0020] In some embodiments, the catheter further comprises a second
permanent magnet disposed near the distal end of the shaft and
spaced from the permanent magnet in the irrigated ablation
electrode assembly.
[0021] The foregoing and other aspects, features, details,
utilities, and advantages of the present invention will be apparent
from reading the following description and claims, and from
reviewing the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is an isometric view of an ablation electrode
assembly according to an embodiment of the present invention in
conjunction with an irrigated catheter assembly operably connected
to an RF generator assembly and a pump assembly.
[0023] FIG. 2 is an enlarged, isometric view of the ablation
electrode assembly according to an embodiment of the present
invention operably connected to an irrigated catheter assembly.
[0024] FIG. 3 is a cross-sectional view of the ablation electrode
assembly of FIG. 2 taken along line 4-4 of FIG. 2.
[0025] FIG. 4 is a cross-sectional view of an ablation electrode
assembly according to another embodiment of the present
invention.
[0026] FIG. 4A is a cross-sectional view of an ablation electrode
assembly according to another embodiment of the present
invention.
[0027] FIG. 5 is a cross-sectional view of an ablation electrode
assembly according to another embodiment of the present
invention.
[0028] FIG. 6 is a perspective view of the magnet structure of the
Catheter Guidance Control and Imaging (CGCI) system.
[0029] FIG. 7A is a perspective view of the CGCI right section
showing the hydraulically actuated core extended.
[0030] FIG. 7B is a perspective view of the CGCI right section
showing the hydraulically actuated core extracted.
[0031] FIG. 7C is a system block diagram for a surgery system that
includes an operator interface, a catheter guidance system, and
surgical equipment.
[0032] FIG. 7D is a block diagram of the imaging module for use in
a CGCI surgery procedure that includes the catheter guidance
system, a radar system, Hall Effect sensors, and a hydraulically
actuating core extension mechanism.
[0033] FIG. 8A is a first perspective view of a catheter
assembly.
[0034] FIG. 8B is a second perspective view of the catheter
assembly.
[0035] FIG. 9A is a side view of the apparatus of FIG. 6.
[0036] FIG. 9B is an underside view of the apparatus of FIG. 6.
[0037] FIG. 10 is an isometric view showing the apparatus of FIG. 6
in an open mode where the left and right clusters are
separated.
[0038] FIG. 11 is a side view of the configuration shown in FIG.
10.
[0039] FIG. 12 is an underside view of the configuration shown in
FIG. 10.
[0040] FIG. 13 is an end view of the configuration shown in FIG.
10.
[0041] FIG. 14 is a block diagram of one embodiment of the CGCI
apparatus with magnetic sensors.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
Irrigated Catheter with Magnetic Tip
[0042] In general, the instant invention relates to irrigated
ablation electrode assemblies, and to methods of manufacturing and
using such irrigated ablation electrode assemblies. For purposes of
this description, similar aspects among the various embodiments
described herein will be referred to by the same reference number.
As will be appreciated, however, the structure of the various
aspects may be different among the various embodiments.
[0043] As seen in FIG. 1, the ablation electrode assembly may
comprise part of an irrigated ablation catheter assembly 12,
operably connected to a pump assembly 15 and an RF generator
assembly 14 which serves to facilitate the operation of ablation
procedures through monitoring any number of chosen variables (e.g.,
temperature of the ablation electrode, ablation energy, and
position of the assembly), assist in manipulation of the assembly
during use, and provide the requisite energy source delivered to
the electrode assembly 10. The present embodiments describe RF
ablation electrode assemblies and methods, but it is contemplated
that the present invention is equally applicable to any number of
other ablation electrode assemblies where the temperature of the
device and the targeted tissue areas is a factor during the
procedure.
[0044] FIG. 1 is a general perspective view of an irrigated
ablation catheter assembly having an RF generator assembly 14 and a
fluid pump assembly 15 operably connected to an irrigated catheter
assembly 12 having an irrigated electrode assembly 10 according to
the present invention operably attached thereto. The structural and
functional features of the catheter assembly 12 and the RF
generator assembly 14 and pump assembly 15 are well-known to those
of skill in the art. For example, the RF generator assembly could
be an IBI-1500T RF Cardiac Ablation Generator available from Irvine
Biomedical, Inc. in Irvine, Calif. 92614. The RF generator assembly
could also be any other known assembly, including, for example, a
Stockert RF generator available from Biosense, or one of the
Atakr.RTM. series of RF generators available from Medtronic. The
pump assembly can be any known assembly, including fixed volume
rolling pumps, variable volume syringe pumps, and any other pump
assembly known to those of skill in the art. FIGS. 2-5, discussed
in more detail below, exemplify various embodiments of the
irrigated ablation electrode assembly 10 according to the present
invention.
[0045] FIG. 2 is an isometric view of an ablation electrode
assembly 11 connected to an irrigated ablation catheter assembly 12
having a fluid delivery tube 16 therein. The ablation electrode
assembly 11 generally comprises an irrigation member 20 and an
ablation electrode member 18. The orientation of the members 18, 20
are generally such that the ablation electrode assembly 18 is
situated at the distal end of the assembly with the irrigation
member 20 located at the proximal end of the assembly, although it
is conceivable the orientation could be reversed. The proximal
member 20 has at least one passageway 24 (see FIG. 3) and at least
one outlet 22 for delivery of a fluid to targeted tissue areas and
the outside of the electrode assembly 11. The distal member 18
further comprises at least one temperature sensing mechanism 26
(see FIG. 3) disposed therein and operably connected to the RF
generator assembly 14. The distal member 18 is comprised of any
electrically, and potentially thermally, conductive material known
to those of ordinary skill in the art for delivery of ablative
energy to target tissue areas. Examples of the electrically
conductive material include gold, platinum, iridium, palladium,
tantalum, stainless steel, and any mixtures thereof. Moreover,
there are a number of electrode designs contemplated within the
scope of the present invention including tip electrodes, ring
electrodes, and any combination thereof.
[0046] In general accordance with the embodiments described herein,
the fluid passageway(s) 24 and outlet(s) 22 are separated from the
distal member 18, and accordingly the temperature sensing mechanism
26, by at least one poor thermally conductive material. A poor
thermally conductive material is one with physical attributes that
decrease heat transfer between the passageway(s) 24 and the distal
member 18 by about 10% or more, and more preferably by about 25% or
more measured by known methods to one of ordinary skill in the art.
In particular embodiments, materials that decreased heat transfer
by more than approximately 75% performed favorably. It is further
contemplated that a poor thermally conductive material could have
physical attributes that decrease heat transfer less than about
10%, provided that the remaining structural components are selected
with the appropriate characteristics and sensitivities to maintain
adequate monitoring and control of the process. Thus, while these
properties are preferred, the poor thermally conductive material
may be any material known to one of skill in the art consistent
with the spirit of the invention. Examples of poor thermally
conductive materials useful in conjunction with the present
invention include, but are not limited to, high-density
polyethylene (HDPE), polyimides, polyaryletherketones,
polyetheretherketones, polyurethane, polypropylene, oriented
polypropylene, polyethylene, crystallized polyethylene
terephthalate, polyethylene terephthalate, polyester, ceramics, and
plastics such as acetal, and mixtures thereof.
[0047] As shown in more detail with respect to specific embodiments
below, the poor thermally conductive material may be the material
comprising the proximal member 20, or the distal member 18, a
separate material from the proximal member 20 and the distal member
18, or any combination thereof. Additionally, the passageway(s) 24
and outlet(s) 22 defined by the proximal member 18 may also be
separated longitudinally from the end 46 (see FIG. 3) of the distal
member 18 thereby providing the benefit of insulating the
passageway(s) 24 from the temperature sensor(s) 26 for improved
temperature monitoring of the ablated target area during operation.
The poor thermally conductive material, and the separation from the
temperature sensing mechanism 26 disposed near the end 46 of the
distal member 18, serve individually, and cooperatively, to
minimize the effect of the lower temperature of the fluid delivered
through the passageway(s) 24 and outlet(s) 22 from the temperature
sensing mechanism(s) 26 within the distal member 18. The separation
of the passageway(s) 24 and outlet(s) 22 from the distal member 18,
and more particularly the temperature sensing mechanism 26,
facilitates the dual purposes of (1) effectively irrigating the
electrode assembly 11 and the targeted tissue area to minimize
coagulation and unwanted tissue damage and (2) effectively
controlling the operation of the ablation electrode assembly 11 in
accordance with objects of the present invention.
[0048] FIG. 3 is a cross-sectional view of an embodiment of the
ablation electrode assembly 11. An ablation electrode assembly 11
is connected to an irrigated catheter assembly 12 having a fluid
delivery tube 16 and a catheter shaft 17. The ablation electrode
assembly 11 comprises a proximal member or manifold 20, a distal
member 18, and a temperature sensing mechanism 26 operably
connected to the RF generator assembly 14 (see FIG. 1). In this
embodiment, the proximal member 20 itself is comprised of a poor
thermally conducting material that serves to insulate the
irrigation fluid from the remaining portions of the assembly 11.
Preferably the proximal member 20 is made from a poor thermally
conductive polymer, more preferably from a polyether ether ketone
("PEEK") because of this material's combination of thermal and
physical properties. Another possible material is Ultem.RTM.
polyetherimide. The proximal member 20 is configured to receive the
fluid tube 16 of the catheter assembly 12 and comprises a plurality
of passageways 24 (e.g., 4-8 passageways) extending from a central
axis 28 of the assembly 11 axially toward the outer portion of the
proximal member 20 terminating in corresponding outlets 22.
Preferably, the plurality of passageways 24 are equally distributed
around the proximal member 20 so as to provide equal distribution
of fluid to the targeted tissue area and the outside of the
assembly 11. The passageway 24 may be a single, annular passageway,
or a number of individual passageways equally distributed around
the proximal member 20. In this embodiment, the passageways 24 are
at an acute angle with respect to the longitudinal axis 28 of the
assembly 11. In operation, fluid is pumped through the delivery
tube 16 and passes through the passageways 24 and through the
outlets 22 where it contacts with targeted tissue areas and the
outside portion of the ablation electrode assembly 11.
[0049] In this embodiment, the fluid delivery conduits or
passageways 24 extend at an angle substantially less than
perpendicular to the longitudinal axis 28. Angling of the
passageways 24 away from perpendicular, but less than parallel,
further assists in the delivery of the fluid to the targeted tissue
areas, further decreases the risk of coagulation of the bodily
fluids during ablation procedures, and allows for improved
measurement and control of the ablation assembly 11 during
operation. More specifically, the passageways 24 are oriented to
direct irrigation fluid flow at the target area adjacent,
preferably immediately adjacent, the intersection between the
proximal member 20 and the distal member 18. Blood coagulation is
more likely to occur in the target area due to a sharp rise in RF
intensity, material discontinuity, and potentially geometric
discontinuity caused by manufacturing imperfection in joining the
proximal member 20 and the distal member 18. In specific
embodiments, the passageways 24 extend at an angle between
approximately 20 and 70 degrees, preferably at an angle between
approximately 30 and 60 degrees, and more preferably at an angle of
approximately 30 degrees. It is also contemplated that the
passageways may be further angled in a second dimension, such that
the passageways and orifices are configured to provide fluid to the
external portion of the assembly in a swirling, or helical fashion.
This configuration also serves to keep the fluid in closer
proximity to the electrode assembly, thereby further preventing
against coagulation during operation.
[0050] The distal member 18 of the ablation electrode assembly 11
has a generally cylindrical shape terminating in a rounded end
which may be a hemispherical end or an end that is non-spherical.
The distal member 18 includes a permanent magnet 48 at least
partially encased in a distal electrode shell 50 and an electrode
anchor 52. The permanent magnet 48 is desirably made of NdFeB which
has a strong magnetic field so that only one such permanent magnet
is needed for magnetic field control and guidance of the catheter
tip (instead of a plurality of magnets spaced apart from each
other). Other rare earth permanent magnets with similar
characteristics may be used in other embodiments. If two or more
permanent magnets are used, additional materials may be considered.
The permanent magnet 48 typically has a length of about 2-6 mm,
typically about 4 mm, in the longitudinal direction. The distal
electrode shell 50 provides most of the external surface of the
distal electrode. The electrode anchor 52 is coupled to the
proximal member 20 and connected to a power line or cable such as
an RF wire 54. The electrode anchor 52 may be connected to the
proximal member 20 by any known mechanism including adhesives,
press-fit configurations, snap-fit configurations, or the like. An
inner tube 56 is connected to the electrode anchor 52 and/or the
proximal member 20 to accommodate the power line 54 and the
temperature sensor conductor for the temperature sensor 26. Because
the temperature sensor 26 is embedded in the permanent magnet 48,
the permanent magnet material preferably is a good thermal
conductor (e.g., NdFeB) so that the temperature sensor 26 can
measure the temperature of the distal electrode accurately.
[0051] In the embodiment shown, the distal electrode shell 50, the
electrode anchor 52, and the inner tube 56 form a shield that keeps
the permanent magnet 48 from exposure to irrigation and/or bodily
fluids, comprising an inner shield that separates the permanent
magnet 48 from the irrigation fluid including the passageways 24
and an outer shield that separates the permanent magnet 48 from the
exterior. Because the permanent magnet 48 is highly oxidizable, any
contact between the permanent magnet and liquid is undesirable
since oxidation of the permanent magnet 48 can lead to corrosion
problems. The shield prevents such contact from occurring. The
materials for the shield are less oxidizable, preferably
substantially less oxidizable, than the permanent magnet 48. For
instance, the oxidization rate of a shield material is less than
about 50%, more preferably less than about 20%, most preferably
less than about 5%, of the oxidation rate of the permanent magnet
48. The distal electrode shell 50 and the electrode anchor 52 are
made of an electrically conductive material such as platinum, gold,
tantalum, iridium, stainless steel, palladium, tantalum, and
mixtures thereof. The electrically conductive material selected is
preferably biocompatible. In some embodiments, the biocompatible
electrically conductive material is plated onto a substrate made of
copper or beryllium copper to improve the biocompatibility of the
distal electrode shell 50 and the electrode anchor 52. The
electrode anchor 52 may be laser welded to the distal electrode
shell 50. The inner tube 56 may be made of silicone, polyimide,
stainless steel braided polyimide, or the like. The inner tube 56
may be thermally bonded or molded onto the platinum anchor 52. In
alternate embodiments, the distal electrode shell 50 and the
electrode anchor 52 form a complete shield around the permanent
magnet 48 without the need for the inner tube 56 for separating the
permanent magnet 48 from irrigation fluid flow.
[0052] The proximal member 20 preferably is made of a poor
thermally conductive material (as discussed above) having a thermal
conductivity that is lower, more preferably substantially lower,
than the thermal conductivity of the material of the distal member
18. The proximal passageways 24 do not come into contact with any
interior portion of the distal member 18. In this way, the
irrigation fluid flowing through the proximal passageways 24 is
substantially insulated from the electrode and the temperature
sensor of the distal member 18 by distance and material of poor
conductivity, so that the temperature sensor 26 can more accurately
measure the temperature of the distal electrode. The proximal
members may be made of a variety of materials that have insulating
properties such as, for example, acetal, polyetheretherketone
(PEEK), and high-density polyethylene (HDPE), as well as other
materials of poor thermal conductivity mentioned above.
[0053] One or more monitoring or measuring electrodes may be
provided in the catheter assembly 12 for mapping or other
monitoring or measuring functions. FIG. 3 shows two monitoring
electrodes 58, 59 that are ring electrodes spaced from the distal
electrode 18. To facilitate catheter tip positioning and location
in a mapping system, the position of each electrode is determined.
Calibration of the positioning system is achieved by the two
monitoring electrodes 58, 59 separated by a known interelectrode
distance, or by the distal electrode 18 and one monitoring
electrode (58 or 59) that are separated by a predetermined
distance. In use, a voltage is sensed between one electrode on the
catheter assembly 12 (typically the distal electrode 18) and a
reference electrode on the patient's body (suitably a surface
electrode on the patient's skin). For a catheterization procedure
which is to lead to ablation, sensing is performed to gather data
relating to the heart, such as the location of an arrhythmia focus.
Such data gathering techniques are well known in the art. The
location information is determined based on the calibration (see,
e.g., U.S. Pat. Nos. 5,697,377 and 5,983,126, the entire
disclosures of which are incorporated herein by reference), and the
sensed information and location are stored and/or mapped.
[0054] FIG. 4 is a cross-sectional view of another embodiment of
the ablation electrode assembly 61. The ablation electrode assembly
61 is connected to an irrigated catheter assembly 62 having a fluid
delivery tube or lumen 64 and a catheter shaft 66. The ablation
electrode assembly 61 comprises a distal member 68, a permanent
magnet 70 disposed proximal to the distal member 68, and a shell 72
surrounding the outer surface and the proximal surface of the
permanent magnet 70. The distal member 68 has a generally
cylindrical shape terminating in a rounded end which may be a
hemispherical end or an end that is non-spherical. The permanent
magnet 70 is an annular member having an inner surface covered by a
portion of the fluid delivery tube 64. The permanent magnet 70 is
desirably made of NdFeB which has a strong magnetic field so that
only one such permanent magnet is needed for magnetic field control
and guidance of the catheter tip (instead of a plurality of magnets
spaced apart from each other). The permanent magnet 48 typically
has a length of about 2-6 mm, typically about 4 mm in the
longitudinal direction. The distal member 68, shell 72, and fluid
delivery tube 64 form a shield that keeps the permanent magnet 70
from exposure to liquid, comprising an inner shield that separates
the permanent magnet 70 from the irrigation fluid flowing through
the catheter assembly 62 and an outer shield that separates the
permanent magnet 70 from the exterior. A sealant 74 is preferably
provided between the proximal surface of the distal member 68 and
the distal surface of the permanent magnet 70 to further ensure no
liquid reaches the permanent magnet 70 via the junction between the
distal member 68 and the fluid delivery tube 64.
[0055] The distal member 68 provides the external surface of the
distal electrode. The shell 72 may also be an electrically
conductive surface to provide additional external surface of the
distal electrode. In that case, the electrode shell 72 is connected
to a power cable or line such as an RF wire 76. One or more
temperature sensors 77 may be provided in the distal member 68 and
the temperature sensor conductor 78 for the temperature sensor 77
extends proximally through the catheter shaft 66.
[0056] Because the permanent magnet 70 is highly oxidizable, any
contact between the permanent magnet and liquid is undesirable. The
shield prevents such contact from occurring. The materials for the
shield are less oxidizable, preferably substantially less
oxidizable, than the permanent magnet 70. The distal member 68 and
the electrode shell 72 are made of an electrically conductive
material such as platinum, gold, tantalum, iridium, stainless
steel, palladium, tantalum, and mixtures thereof. The electrically
conductive material selected is preferably biocompatible. In some
embodiments, the biocompatible electrically conductive material is
plated onto a substrate made of copper or beryllium copper to
improve the biocompatibility of the distal member 68 and the
electrode shell 72. The fluid delivery tube 64 is electrically
nonconductive, and may be made of silicone, polyimide, stainless
steel braided polyimide, or the like. The electrode shell 72 is
connected to the distal member 68 by laser weld or the like. The
distal member 68 and the electrode shell 72 form the distal
electrode. The shell 72 may be connected to the catheter shaft 66
using adhesives or the like. The fluid delivery tube 64 may be
connected to the shell 72, permanent magnet 70, and distal member
68 by thermal bonding, molding, adhesives, or the like.
[0057] The fluid delivery tube 64 flows fluid through one or more
distal passageways 79 in the distal member 68 to their external
outlets. There is preferably a central passageway along the
longitudinal axis of the distal member 68 and, optionally,
additional passageways distributed around the central passageway.
The passageways 79 are preferably lined with a poor thermally
conducting material 75 such as a polyether ether ketone ("PEEK")
that serves to insulate the fluid from the material of the distal
member 68 and from the temperature sensor 77. In this way, the
fluid flow through the passageways 79 does not influence the
measurement of the temperature sensor 77, so that the temperature
sensor 77 can more accurately measure the temperature of the distal
electrode. Preferably, the additional passageways are equally
distributed around the central passageway so as to provide equal
distribution of fluid to the targeted tissue area and the outside
of the assembly 61.
[0058] One or more monitoring or measuring electrodes may be
provided in the catheter assembly 62 for mapping or other
monitoring or measuring functions. FIG. 4 shows one monitoring
electrode 80 that is a ring electrode spaced from the distal
electrode (formed by the distal member 68 and the electrode shell
72) by a known interelectrode distance for calibration. In use, a
voltage is sensed between the distal electrode (68 and 72) and a
reference electrode on the patient's body (suitably a surface
electrode on the patient's skin). The location information is
determined based on the calibration, and the sensed information and
location are stored and/or mapped.
[0059] FIG. 4A shows an irrigated catheter assembly 62A that is
virtually identical to the irrigated catheter assembly 62 of FIG.
4. The assembly 62A includes a second permanent magnet 70A disposed
near the distal end of the shaft 66 and spaced from the first
permanent magnet 70. In the embodiment shown, the second permanent
magnet 70A is an annular magnet and is smaller in size and
thickness than the first permanent magnet 70. The second permanent
magnet 70A does not require an additional shield because it is
disposed in a space between the catheter shaft 66 and the fluid
delivery tube 64 which is free from exposure to liquid. Of course,
the second permanent magnet may have other configurations in
different embodiments, and may be formed in the irrigated ablation
electrode assembly 61 instead of being inside the catheter shaft 66
and spaced proximally from the electrode assembly 61. Additional
permanent magnets in the assembly may provide additional options
for magnetically controlling and guiding the catheter tip.
[0060] FIG. 5 is a cross-sectional view of another embodiment of
the ablation electrode assembly 81 which is connected to an
irrigated catheter assembly 82. The electrode assembly 81 of FIG. 5
is similar to the electrode assembly 61 of FIG. 4, in that it also
includes a distal member 68, a permanent magnet 70, a shell 72
connected to an RF wire 76, a sealant 74, and a temperature sensor
77 connected to a temperature sensor conductor 78. In this
embodiment, the distal member 68 has a central passageway 79 that
is preferably lined with a poor thermally conducting material 75
such as a polyether ether ketone ("PEEK"). A fluid delivery tube 64
extends through a catheter shaft 66 to the electrode assembly 81.
One or more monitoring or measuring electrodes 80 may be provided
in the catheter assembly 62 for mapping or other monitoring or
measuring functions.
[0061] In FIG. 5, the ablation electrode assembly 81 includes a
proximal member 84 located on the proximal side of the permanent
magnet 70 and electrode shell 72. The proximal member 84 has at
least one proximal passageway 86 with at least one outlet 88 for
delivery of a fluid to targeted tissue areas and the outside of the
electrode assembly 81. The proximal passageway(s) 86 and outlet(s)
88 are separated from the distal member 68 and electrode shell 72,
and accordingly the temperature sensing mechanism 77, by at least
one poor thermally conductive material. The poor thermally
conductive material may be the material comprising the proximal
member 84, or the distal member 68, a separate material from the
proximal member 84 and the distal member 68, or any combination
thereof. In this embodiment, the proximal member 84 is comprised of
a poor thermally conducting material that serves to insulate the
fluid from the remaining portions of the assembly 81. The proximal
member 84 is configured to receive the fluid tube 64 of the
catheter assembly 82 and comprises a plurality of proximal
passageways 86 (e.g., 4-8 passageways) extending from a central
axis of the assembly 81 axially toward the outer portion of the
proximal member 84 terminating in corresponding outlets 88.
Preferably, the plurality of proximal passageways 86 are equally
distributed around the proximal member 84 so as to provide equal
distribution of fluid to the targeted tissue area and the outside
of the assembly 81. The proximal passageway 86 may be a single,
annular passageway, or a number of individual passageways equally
distributed around the proximal member 84. In this embodiment, the
proximal passageways 86 are at an acute angle with respect to the
longitudinal axis of the assembly 81. In operation, fluid is pumped
through the delivery tube 64 and passes through the proximal
passageways 86 and through the outlets 88 where it contacts with
targeted tissue areas and the outside portion of the ablation
electrode assembly 81.
[0062] In this embodiment, the proximal passageways 86 extend at an
angle substantially less than perpendicular to the longitudinal
axis. Angling of the passageways 86 away from perpendicular, but
less than parallel, further assists in the delivery of the fluid to
the targeted tissue areas, further decreases the risk of
coagulation of the bodily fluids during ablation procedures, and
allows for improved measurement and control of the ablation
assembly 81 during operation. More specifically, the proximal
passageways 86 are oriented to direct irrigation fluid flow at the
target area adjacent, preferably immediately adjacent, the
intersection between the proximal member 84 and the electrode shell
72. Blood coagulation is more likely to occur in the target area
due to a sharp rise in RF intensity, material discontinuity, and
potentially geometric discontinuity caused by manufacturing
imperfection in joining the proximal member 84 and the electrode
shell 72. In specific embodiments, the proximal passageways 24
extend at an angle between approximately 20 and 70 degrees,
preferably at an angle between approximately 30 and 60 degrees, and
more preferably at an angle of approximately 30 degrees. It is also
contemplated that the proximal passageways may be further angled in
a second dimension, such that the proximal passageways and orifices
are configured to provide fluid to the external portion of the
assembly in a swirling, or helical fashion. This configuration also
serves to keep the fluid in closer proximity to the electrode
assembly, thereby further preventing against coagulation during
operation.
[0063] The proximal member 84 further includes a longitudinal
outlet that transfers fluid through a central conduit 90 to the
central passageway 79 of the distal member 68. The central conduit
90 is electrically nonconductive, and may be made of silicone,
polyimide, stainless steel braided polyimide, or the like. The
central conduit 90 may be connected to the electrode shell 72,
permanent magnet 70, and distal member 68 by thermal bonding,
molding, adhesives, or the like. The distal member 68, electrode
shell 72, and central conduit 90 form a shield that separates the
permanent magnet 70 from the irrigation fluid and the exterior.
Catheter Guidance Control and Imaging (CGCI)
[0064] One example of a system for magnetically guiding and
controlling a catheter having a magnetic tip is found in U.S.
Patent Application Publication No. 2007/0016006, the entire
disclosure of which is incorporated herein by reference. FIGS. 6,
7A, and 7B are isometric drawings of a Catheter Guidance Control
and Imaging (CGCI) system 1500 (FIG. 7C), having a left coil
cluster 100 and a right coil cluster 101 provided to rails 102. The
rails 102 act as guide alignment devices. The CGCI system
workstation 1500 includes a structural support assembly 120, a
hydraulic system 140, and a propulsion system 150.
[0065] A central arc 106 supports an upper cylindrical coil 110 and
two shorter arcs 107, 108 support two conical shaped coils 115,
116. The two shorter arcs 107, 108 are displaced from the central
arc 106 by approximately 35 degrees. The angle of separation
between the two smaller arcs is approximately 70 degrees. At the
end of each arc 106, 107 and 108 is a machined block of 1010 steel
with a connection that provides for attachment of the coil
assemblies 115, 116, 110.
[0066] Two curved shield plates 105 form a shield to at least
partially contain and shape the magnetic fields. The shields 105
also provide lateral strength to the assembly. A base 117 houses
the propulsion system 150 and locking mechanism 118. In one
embodiment, the plates 105 are made from steel, nickel, or other
magnetic material.
[0067] In addition to FIG. 6, FIGS. 7A and 7B further show various
mechanical details which form the CGCI cluster half section (right
electromagnetic cluster 101). A locking hole 103, a spur-drive rail
104, cam rollers 118, and the solenoid locking pin 119, are
configured to allow portions of the CGCI to move along the tracks
102. The cluster 101 includes three electromagnets forming a
magnetic circuit. The left coil 116 and right coil 115 are mounted
as shown and are supported by C-Arms 107 and 108. The coil 110
includes a hydraulically actuated core 111, supported by a coil
clamping disc 127 made of stainless steel. A coil stress relief
disc 113 is made of Teflon. The coil cylinder 110, is enclosed by a
coil base disc 114 made of stainless steel. The coil core 111 is
actuated (extended and retracted) by a hydraulic system 109. FIG.
7B shows the right coil cluster 101 with the hydraulically actuated
core 111 retracted by the use of the hydraulic system 109 which
allows the CGCI to shape the magnetic field.
[0068] FIG. 7C is a system block diagram for a surgery system 800
that includes an operator interface 500, the CGCI system 1500,
surgical equipment 502 (e.g., a catheter tip 11 in FIG. 3, a
catheter tip 61 in FIG. 4, a catheter tip 81 in FIG. 5, or a
catheter tip 377 in FIG. 8A, etc.), one or more user input devices
900, and a patient 390. The user input devices 900 can include one
or more of a joystick, a mouse, a keyboard, a virtual tip 905, and
other devices to allow the surgeon to provide command inputs to
control the motion and orientation of the catheter tip 377 (or tip
11, 61, 81).
[0069] In one embodiment, the CGCI system 1500 includes a
controller 501 and an imaging synchronization module 701. FIG. 7C
shows the overall relationship between the various functional units
and the operator interface 500, auxiliary equipment 502, and the
patient 390. In one embodiment, the CGCI system controller 501
calculates the Actual Tip (AT) position of the distal end of a
catheter. Using data from the Virtual Tip (VT) 905 and the imaging
and synchronization module 701, the CGCI system controller 501
determines the position error, which is the difference between
actual tip position (AP) and the desired tip position (DP). In one
embodiment, the controller 501 controls electromagnets to move the
catheter tip in a direction selected to minimize the position error
(PE). In one embodiment, the CGCI system controller 501 provides
tactile feedback to the operator by providing force-feedback to the
VT 905.
[0070] FIG. 7D is a block diagram of a surgery system 503 that
represents one embodiment of the CGCI system 1500. The system 503
includes the controller 501, a radar system 1000, a Hall effect
sensor array 350, and the hydraulically actuated mechanism 140. In
one embodiment, the sensor 350 includes one or more Hall effect
magnetic sensors. The radar system 1000 can be configured as an
ultra-wideband radar, an impulse radar, a Continuous-Wave (CW)
radar, a Frequency-Modulated CW (FM-CW) radar, a pulse-Doppler
radar, etc. In one embodiment, the radar system 1000 uses Synthetic
Aperture Radar (SAR) processing to produce a radar image. In one
embodiment, the radar system 1000 includes an ultra-wideband radar
such as described, for example, in U.S. Pat. No. 5,774,091, hereby
incorporated by reference in its entirety.
[0071] In one embodiment, the radar 1000 is configured as a radar
range finder to identify the location of the catheter tip 377. The
radar 1000 is configured to locate reference markers (fiduciary
markers) placed on the patient 390. Data regarding location of the
reference markers can be used, for example, for image capture
synchronization 701. The motorized hydraulically and actuated
motion control mechanism 140 allows the electromagnets of the
cylindrical coils 51AT and 51DT (see FIG. 14) to be moved relative
to the patient 390.
[0072] In one embodiment, the use of the radar for identifying the
position of the catheter tip 377 has advantages over the use of
Fluoroscopy, Ultrasound, Magnetostrictive sensors, or SQUID. Radar
can provide accurate dynamic position information, which provides
for real-time, relatively high resolution, relatively high fidelity
compatibility in the presence of strong magnetic fields.
Self-calibration of the range measurement can be based on
time-of-flight and/or Doppler processing. Radar further provides
for measurement of catheter position while ignoring "Hard" surfaces
such as a rib cage, bone structure, etc., as these do not interfere
with measurement or hamper accuracy of the measurement. In
addition, movement and displacement of organs (e.g., pulmonary
expansion and rib cage displacement as well as cardio output during
diastole or systole) do not require an adjustment or correction of
the radar signal. Radar can be used in the presence of movement
since radar burst emission above 1 GHz can be used with sampling
rates of 50 Hz or more, while heart movement and catheter dynamics
occur at 0.1 Hz to 2 Hz.
[0073] In one embodiment, the use of the radar 1000 reduces the
need for complex image capture techniques normally associated with
expensive modalities such as fluoroscopy, ultrasound,
Magnetostrictive technology, or SQUID which require computationally
intensive processing in order to translate the pictorial view and
reduce it to a coordinate data set. Position data synchronization
of the catheter tip 377 and the organ in motion is readily
available through the use of the radar 1000. The radar 1000 can be
used with phased-array or Synthetic Aperture processing to develop
detailed images of the catheter location in the body and the
structures of the body. In one embodiment, the radar system
includes an Ultra Wide Band (UWB) radar with a relatively high
resolution swept range gate. In one embodiment, a differential
sampling receiver is used to effectively reduce ringing and other
aberrations included in the receiver by the near proximity of the
transmit antenna. As with X-ray systems, the radar system can
detect the presence of obstacles or objects located behind barriers
such as bone structures. The presence of different substances with
different dielectric constants such as fat tissue, muscle tissue,
water, etc., can be detected and discerned. The outputs from the
radar can be correlated with similar units such as multiple
catheters used in electrophysiology (EP) studies while detecting
spatial location of other catheters present in the heart lumen. The
radar system 1000 can use a phased array antenna and/or SAR to
produce 3D synthetic radar images of the body structures, catheter
tip and organs.
[0074] In one embodiment, the location of the patient relative to
the CGCI system (including the radar system 1000) can be determined
by using the radar 1000 to locate a plurality of fiduciary markers.
In one embodiment, the data from the radar 1000 is used to locate
the body with respect to an imaging system. The catheter position
data from the radar 1000 can be superimposed (synchronized) with
the images produced by the imaging system. The ability of the radar
and the optional Hall effect sensors 350 to accurately position the
catheter tip 377 relative to the stereotactic frame allows the pole
pieces to be moved by the actuators 109, 140 to optimize the
location of the magnet poles with respect to the patient 390 and
thus reduce the power needed to manipulate the catheter tip.
[0075] FIGS. 8A and 8B shows one embodiment of a catheter assembly
375 and guidewire assembly 379 to be used with the CGCI apparatus
1500. The catheter assembly 375 is a tubular tool that includes a
catheter body 376 which extends into a flexible section 378 that
possesses sufficient flexibility for allowing a relatively more
rigid responsive tip 377 to be steered through the patient. The tip
377 can be replaced by the tip 21 of FIG. 3, the tip 61 of FIG. 4,
or the tip 81 of FIG. 5.
[0076] In one embodiment, the magnetic catheter assembly 375 in
combination with the CGCI apparatus 1500 reduces or eliminates the
need for the plethora of shapes normally needed to perform
diagnostic and therapeutic procedures. During a conventional
catheterization procedure, the surgeon often encounters difficulty
in guiding the conventional catheter to the desired position, since
the process is manual and relies on manual dexterity to maneuver
the catheter through a tortuous path of, for example, the
cardiovascular system. Thus, a plethora of catheters in varying
sizes and shapes are to be made available to the surgeon in order
to assist him/her in the task, since such, tasks require different
bends in different situations due to natural anatomical variations
within and between patients.
[0077] By using the CGCI apparatus 1500, only a single catheter is
needed for most, if not all patients. The catheterization procedure
is now achieved with the help of the CGCI system 1500 that guides
the magnetic catheter and guidewire assembly 375 and 379 to the
desired position within the patient's body 390 as dictated by the
surgeon's manipulation of the virtual tip 905. The magnetic
catheter and guidewire assembly 375, 379 (i.e. the magnetic tip 377
can be attracted or repelled by the electromagnets of the CGCI
apparatus 1500) provides the flexibility needed to overcome
tortuous paths, since the CGCI apparatus 1500 overcomes most, if
not all the physical limitations faced by the surgeon while
attempting to manually advance the catheter tip 377 through the
patient's body.
[0078] In one embodiment, the catheter tip 377 includes a guidewire
assembly 379, a guidewire body 380 and a tip 381 response to
magnetic fields. The tip 377 is steered around sharp bends so as to
navigate a torturous path. The responsive tips 377 and 381 of both
the catheter assembly 375 and the guidewire assembly 379,
respectively, include magnetic elements such as permanent magnets.
The tips 377 and 381 include permanent magnets that respond to the
external flux generated by the electromagnets 110, 115, 116 and its
symmetric counterpart 100.
[0079] In one embodiment, the responsive tip 377 of the catheter
assembly 375 is tubular, and the responsive tip 381 of the
guidewire assembly 379 is a solid cylinder. The responsive tip 377
of the catheter assembly 375 is a dipole with longitudinal polar
orientation created by the two ends of the magnetic element
positioned longitudinally within it. The responsive tip 381 of the
guidewire assembly 379 is a dipole with longitudinal polar
orientation created by two ends of the magnetic element 377
positioned longitudinally within it. These longitudinal dipoles
allow the manipulation of both responsive tip 377 and 381 with the
CGCI apparatus 1500, as the electromagnet assemblies 100, 101, and
will act on the tips 377 and 381 and "drag" them in unison to a
desired position as dictated by the operator.
[0080] FIGS. 9A and 9B show additional views of the CGCI structural
support assembly 120. The structural support assembly 120 is
configured so as to facilitate the use of X-Ray and/or other
surgical medical equipment 502 in and around the patient during
operation. The two symmetrical left 100 and right 101
electromagnetic clusters are mounted on the stainless steel guide
rails 102, allowing the two sections 100 and 101 to move away from
each other as shown in FIGS. 10-12. The rails 102 are bolted to a
floor or mounting pad. The cluster on the CGCI structure 120 rolls
inside the rails 102, under relatively tight tolerance to prevent
lateral or vertical movement during a seismic event. In one
embodiment, the rails 102 are designed to withstand the forces of a
Zone 4 seismic event without allowing the CGCI structure to escape
containment.
[0081] A stainless steel spur toothed rail 104 is bolted to the
floor or mounting pad under the CGCI structure 120. A Servo Dynamic
model HJ96 C-44 brushless servomotor 128 (max 27 lb.-in torque)
with its associated servomotor amplifier model 815-BL 129 are
provided to move the clusters 101, 100. The motor has a reduction
gearbox with a ratio of 100:1. A stainless steel spur gear attached
to the reduction gear shaft meshes with the spur toothed rail 104.
The propulsion system 150 is configured to exert up to 2700 lbs. of
force to move the CGCI sections 100 and 101.
[0082] FIGS. 9A and 9B further show the CGCI assembly 120 when the
system is set in the "operational mode." The two symmetrical
clusters 100 and 101 are engaged as described above. FIGS. 9A and
9B show the location of the spur toothed rail 104 and the brushless
servo motor 128.
[0083] FIGS. 10-13 are isometric views of the CGCI assembly 120
when its main two symmetric left 100 and right 101 coil clusters
are in a fully open mode (non operational) and the magnetic cores
are retracted. The rear view of the symmetrical one half of the
CGCI shows the parabolic flux collector shields 105 with the C-Arm
upper cylinder coil support 106. In one embodiment, the CGCI
assembly 120 is configured to meet the structural as well as safety
considerations associated with the generation of a magnetic field
of 2 Tesla.
[0084] FIG. 14 depicts the CGCI system 1500 top architecture
showing the major elements comprising the controller 501 of the
magnetic circuit. The controller 501 includes a system memory, a
torque/force matrix algorithm residing in 528 and a CPU/computer
527. The CPU/computer such as PC 527 provides computation and
regulation tasks. FIG. 14 further shows the six-coil
electromagnetic circuit formed out of coils 51A, 51B, 51C, 51D,
51AT and 51DT and the magnetic field sensors (MFS) 351, 352, 353,
354, 355 and 356 such as Hall sensor ring 350 mounted on an
assembly forming the X, Y, and Z axis controls. A D/A converter 550
and an I/O block 551 provide communication between the controller
501 and the coils 51A and the hydraulic systems 140. The six
channel DC amplifier 525 provides current to the coils.
[0085] FIG. 14 shows the relationship and command structure between
the joystick 900, the virtual tip 905, and the CPU 701. The CPU 701
displays control conveying real time images generated by the X-ray,
radar 1000, or other medical imaging technologies such as
fluoroscopy, MRI, PET SCAN, CAT SCAN, etc., on a display 730. A
flow diagram of the command structure of the control scheme is
shown by the use of the 2D virtual plane coil polarity matrixes. By
assigning the coil position and polarity elements to the directions
of torque rotation and force field gradient on each 2D plane of a
six coil cluster 414, a computer program such as MathLab or Math
Cad is able to sift through the combination matrixes and compute
the proper combination for the six coil current polarities and
amplitudes. In one embodiment, a boundary condition controller is
used for regulating the field strength 405 and field gradient 406
in the effective region. The controller 501 computes the fields in
the neighborhood of the catheter tip 377 and as defined by the
fields on the 2D planes in the effective area. Rules for computing
the fields with rotated coil on the surface of the sphere are set
forth in US 2007/0016066.
[0086] In one embodiment, look-up tables are used as a reference
library for use by the controller 501. Lookup tables of the setting
of various scenarios of force as well as torque position and
magnitude allow the controller 501 to use a learning algorithm for
the control computations. The look-up tables shorten the
computational process for optimal configuration and setting of the
coil currents and pole positions. The D/A and A/D system 550 allows
the connection of voltage and current measuring instruments as well
as input from the magnetic field sensor (MFS) 350 array, the MFS
351, 352, 353, 354, 355 and 356. The magnetic field sensor
measuring the boundary plane field strength allows the CGCI to use
a low-level logic algorithm to compute the positions, settings,
coil currents, etc. The low-level simulation is performed prior to
activating the power section of the CGCI apparatus 1500, thus
providing a "soft" level check prior to action performed by actual
machine. The two-level control architecture that starts with
low-level simulation architecture of low-level simulation allows
the surgeon or operator of the CGCI apparatus 1500 to test each
movement prior to actually performing the move. US 2007/0016066
describes the field regulator loop outlined in FIG. 14 using the
Hall effect ring 350.
[0087] Instead of using the radar system to identify the position
of the catheter tip 377, the present invention may rely on the use
of the monitoring or measuring electrodes (58, 59 in FIG. 3; 80 in
FIGS. 4 and 5), optionally in conjunction with a visualization and
mapping tool such as the EnSite NavX.TM. technology available from
St. Jude Medical, Inc. See, e.g., U.S. Pat. Nos. 6,990,370 and
6,939,309, the entire disclosures of which are incorporated herein
by reference.
[0088] All directional references (e.g., upper, lower, upward,
downward, left, right, leftward, rightward, top, bottom, above,
below, vertical, horizontal, clockwise, and counterclockwise) are
only used for identification purposes to aid the reader's
understanding of the present invention, and do not create
limitations, particularly as to the position, orientation, or use
of the invention. Joinder references (e.g., attached, coupled,
connected, and the like) are to be construed broadly and may
include intermediate members between a connection of elements and
relative movement between elements. As such, joinder references do
not necessarily infer that two elements are directly connected and
in fixed relation to each other. It is intended that all matter
contained in the above description or shown in the accompanying
drawings shall be interpreted as illustrative only and not
limiting. Changes in detail or structure may be made without
departing from the spirit of the invention as defined in the
appended claims.
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