U.S. patent application number 10/775747 was filed with the patent office on 2004-12-23 for multiple antenna ablation apparatus and method with multiple sensor feedback.
This patent application is currently assigned to RITA Medical Systems, Inc.. Invention is credited to Gough, Edward J., Stein, Alan A..
Application Number | 20040260282 10/775747 |
Document ID | / |
Family ID | 33519545 |
Filed Date | 2004-12-23 |
United States Patent
Application |
20040260282 |
Kind Code |
A1 |
Gough, Edward J. ; et
al. |
December 23, 2004 |
Multiple antenna ablation apparatus and method with multiple sensor
feedback
Abstract
An ablation apparatus includes an ablation energy source
producing an electromagnetic energy output. A monopolar multiple
antenna device is included and has a primary antenna with a
longitudinal axis, a central lumen and a distal end, and a
secondary antenna with a distal end. The secondary antenna is
deployed from the primary antenna central lumen in a lateral
direction relative to the longitudinal axis. The primary antenna
and secondary antennas are each electromagnetically coupled to the
electromagnetic energy source.
Inventors: |
Gough, Edward J.; (Menlo
Park, CA) ; Stein, Alan A.; (Moss Beach, CA) |
Correspondence
Address: |
PERKINS COIE LLP
P.O. BOX 2168
MENLO PARK
CA
94026
US
|
Assignee: |
RITA Medical Systems, Inc.
|
Family ID: |
33519545 |
Appl. No.: |
10/775747 |
Filed: |
February 9, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10775747 |
Feb 9, 2004 |
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08577208 |
Dec 22, 1995 |
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6689127 |
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08577208 |
Dec 22, 1995 |
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08515379 |
Aug 15, 1995 |
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5683384 |
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Current U.S.
Class: |
606/41 |
Current CPC
Class: |
A61B 2018/00726
20130101; A61B 2018/00273 20130101; A61B 2018/124 20130101; A61N
1/06 20130101; A61B 2018/00666 20130101; A61B 2018/00892 20130101;
A61B 2018/00827 20130101; A61B 18/18 20130101; A61B 2018/00452
20130101; A61B 18/1492 20130101; A61B 2018/00875 20130101; A61B
18/1482 20130101; A61B 2018/00577 20130101; A61B 18/1206 20130101;
A61B 18/1485 20130101; A61B 2018/00761 20130101; A61B 2018/1472
20130101; A61B 2018/00279 20130101; A61B 2018/00791 20130101; A61B
2018/00797 20130101; A61B 2018/00196 20130101; A61B 2018/1432
20130101; A61B 2017/00101 20130101; A61B 2018/162 20130101; A61N
5/04 20130101; A61B 2018/143 20130101; A61B 2018/1435 20130101;
A61M 25/007 20130101; A61B 18/1477 20130101; A61B 18/14 20130101;
A61B 2218/002 20130101; A61B 18/1402 20130101; A61B 2017/00022
20130101; A61B 2018/126 20130101; A61B 2018/1425 20130101; A61B
2018/00779 20130101; A61B 2018/00702 20130101; A61M 3/0279
20130101; A61B 2018/00011 20130101; A61B 2018/1253 20130101; A61N
1/403 20130101; A61B 2018/183 20130101; A61B 2018/00678 20130101;
A61B 18/1815 20130101; A61B 2018/00744 20130101; A61B 2018/00023
20130101; A61B 2018/00476 20130101; A61B 2018/00708 20130101 |
Class at
Publication: |
606/041 |
International
Class: |
A61B 018/14 |
Claims
What is claimed is:
1. An ablation treatment apparatus, comprising: an introducer
having a distal portion and a proximal portion: and at least one
antenna positioned in the introducer as the introducer is
introduced through tissue and exhibiting a changing direction of
travel when deployed from the introducer at a selected tissue mass,
said at least one antenna being operatively coupled to a microwave
energy source; and at least one thermal sensor coupled to at least
one of (i) the introducer. or (ii) at least one of the at least one
antennas.
2. The apparatus of claim 1, wherein at least a portion of a distal
end of the at least one antenna is constructed to be structurally
less rigid than the introducer, and the introducer is constructed
to be rigid enough to be introduced through tissue.
3. The apparatus of claim 1, further comprising: a feedback control
system operatively coupled to the at least one sensor and the
microwave energy source.
4-6. (canceled)
7. The apparatus of claim 1, wherein said at least one antenna
comprises at least two antennas, each of the antennas having an
energy delivery surface to create an ablation volume between the
energy delivery surfaces.
8. The apparatus of claim 1, wherein each antenna includes at least
one thermal sensor to measure temperature.
9. The apparatus of claim 1, wherein said at least one antenna
comprises at least three antennas, each of the antennas having an
energy delivery surface to create an ablation volume between the
energy delivery surfaces.
10. (canceled)
11. The apparatus of claim 1, further comprising: an insulation
sleeve positioned in a surrounding relationship around at least a
portion of at least one of (i) the introducer, or (ii) the at least
one antenna.
12. The apparatus of claim 11, wherein the insulation sleeve is
adjustably moveable along an exterior of the introducer or the at
least one antenna.
13-14. (canceled)
15. The apparatus of claim 1, further including a ground pad
electrode.
16-17. (canceled)
18. The apparatus of claim 1, wherein the introducer is hollow and
coupled to an infusion medium source to receive an infusion
medium.
19. The apparatus of claim 1, further comprising: a cooling element
coupled to the introducer.
20. A method for creating an ablation volume in a selected tissue
mass, comprising: providing an ablation device with an introducer
at least one antenna with a distal end and being operatively
coupled to a microwave energy source, and at least one thermal
sensor coupled to at least one of (i) the introducer, or (ii) at
least one of the at least one antennas; inserting the introducer
into the selected tissue mass with the at least one antenna distal
end positioned in the introducer lumen; advancing the at least one
antenna distal end out of the introducer lumen and into the
selected tissue mass; delivering electromagnetic energy from the
microwave energy source to the at least one antenna; and creating
an ablation volume in the selected tissue mass.
21. The method of claim 20, wherein said at least one antenna
comprises at least two antennas, each having an energy delivery
surface, are advanced from the primary antenna, and an ablation
volume is created between the two antennas energy delivery
surfaces.
23. The method of claim 21, wherein the at least two antennas are
advanced out of a distal end of the introducer
24. The method of claim 21, wherein the at least two antennas are
advanced out of separate ports formed in the introducer.
25-29. (canceled)
30. The method of claim 20, wherein the introducer is operatively
coupled to an energy source and has an energy delivery surface.
31. The apparatus of claim 3, wherein the feedback control adjusts
at least one of (i) a power level, (ii) a duty cycle, and (iii) an
energy delivery in response to the temperature measured at the at
least one sensor.
32. The apparatus of claim 1, further comprising: a display for
displaying temperature values measured at the at least one
sensor.
33. The apparatus of claim 1, wherein said introducer is an antenna
operatively coupled to an energy source.
34. The apparatus of claim 33, wherein said introducer is coupled
to a RF energy source.
35. The apparatus of claim 1, wherein the introducer includes a
tissue piercing distal end.
36. The apparatus of claim 3, further comprising: a controller
coupled to the energy source and at least one of (i) the at least
one thermal sensor and (ii) the feedback control to adjust the
energy supplied to the antennas in response to the temperature
measured at the at least one sensor.
37. The apparatus of claim 20, further comprising: adjusting the
energy supplied to the at least one antenna in response to a
temperature measured at the at least one sensor.
Description
REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 08/515,379, filed Aug. 15, 1995, entitled
"Multiple Antenna Ablation Apparatus", incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates generally to a treatment and ablation
apparatus that includes a primary antenna inserted into or adjacent
to a selected body mass, such as a tumor, with one or more side
deployed secondary antennas which are actively coupled to the
primary antenna, and more particularly to a multiple antenna RF
treatment and ablation apparatus with one or more secondary
antennas actively coupled to the primary antenna, with the primary
antenna coupled to a feedback control device and energy source.
[0004] 2. Description of the Related Art
[0005] Current open procedures for treatment of tumors are
extremely disruptive and cause a great deal of damage to healthy
tissue. During the surgical procedure, the physician must exercise
care in not cutting the tumor in a manner that creates seeding of
the tumor, resulting in metastasis. In recent years, development of
products has been directed with an emphasis on minimizing the
traumatic nature of traditional surgical procedures.
[0006] There has been a relatively significant amount of activity
in the area of hyperthermia as a tool for treatment of tumors. It
is known that elevating the temperature of tumors is helpful in the
treatment and management of cancerous tissues. The mechanisms of
selective treatment are not completely understood. However, four
cellular effects of hyperthermia on cancerous tissue have been
proposed, (i) changes in cell or nuclear membrane permeability or
fluidity, (ii) cytoplasmic lysomal disintegration, causing release
of digestive enzymes, (iii) protein thermal damage affecting cell
respiration and the synthesis of DNA or RNA and (iv) potential
excitation of immunologic systems. Treatment methods for applying
heat to tumors include the use of direct contact radio-frequency
(RF) applicators, microwave radiation, inductively coupled RF
fields, ultrasound, and a variety of simple thermal conduction
techniques.
[0007] Among the problems associated with all of these procedures
is the requirement that highly localized heat be produced at depths
of several centimeters beneath the surface of the skin. RF
applications may be used at depth during surgery. However, the
extent of localization is generally poor, with the result that
healthy tissue may be harmed.
[0008] With RF lesion making, a high frequency alternating current
flows from the electrode into the tissue. Ionic agitation is
produced in the region of tissue about the electrode tip as the
ions attempt to follow the directional variations of the
alternating current. This agitation results in frictional heating
so that the tissue about the electrode, rather than the electrode
itself, is the primary source of heat. Tissue heat generated is
produced by the flow of current through the electrical resistance
offered by the tissue. The greater this resistance, the greater the
heat generated.
[0009] Lesion size ultimately is governed by tissue temperature.
Some idea of tissue temperature can be obtained by monitoring the
temperature at an electrode or probe tip, usually with a
thermistor. RF lesion heat is generated within the tissue, the
temperature monitored will be the resultant heating of the
electrode by the lesion. RF lesion heat is generated within the
tissue, the temperature monitored is the resultant heating of the
probe by the lesion. A temperature gradient extends from the lesion
to the probe tip, so that the probe tip is slightly cooler than the
tissue immediately surrounding it, but substantially hotter than
the periphery of the lesion because of the rapid attenuation of
heating effect with distance.
[0010] Current spreads out radially from the electrode tip, so that
current density is greatest next to the tip, and decreases
progressively at distances from it. The frictional heat produced
from ionic agitation is proportional to current, i.e., ionic
density. Therefore, the heating effect is greatest next to the
electrode and decreases with distance from it. One consequence of
this is that lesions can inadvertently be made smaller than
anticipated for a given electrode size if the RF current level is
too high. There must be time for equilibrium heating of tissue to
be reached, especially at the center of the desired lesion volume.
If the current density is too high, the tissue temperature next to
the electrode rapidly exceeds desired levels and carbonization and
boiling occurs in a thin tissue shell surrounding the electrode
tip.
[0011] A need exists for an ablation apparatus with an
electromagnetic energy source and a monopolar multiple antenna
device. There is a further need for a monopolar multiple antenna
device with a primary antenna, and one or more secondary antennas
that are positioned in a lumen of the primary antenna, laterally
deployable from the primary antenna into a selected tissue mass,
with both antennas electromagnetically coupled to an
electromagnetic energy source. It would be desirable to provide a
monopolar method to ablate a selected tissue mass by introducing
the primary antenna into the selected mass, deploying a distal end
of the secondary antenna into the selected mass, and applying
electromagnetic energy to the primary and secondary antennas.
SUMMARY OF THE INVENTION
[0012] Accordingly, it is an object of the invention to provide an
ablation device which includes a monopolar multiple antenna.
[0013] Another object of the invention is to provide an ablation
apparatus with a monopolar multiple antenna device including a
primary antenna that pierces and advances through tissue, a
secondary electrode positioned in a primary antenna lumen that is
laterally deployable from the primary antenna into a selected
tissue mass.
[0014] Yet another object of the invention is to provide an
ablation apparatus with a monopolar multiple antenna device,
including primary and secondary antennas that are each
electromagnetically coupled to an electromagnetic energy
source.
[0015] A further object of the invention is to provide a method for
ablating a selected tissue mass utilizing a monopolar multiple
antenna device.
[0016] These and other objectives are achieved in an ablation
treatment apparatus. The apparatus includes an ablation energy
source producing an electromagnetic energy output. A monopolar
multiple antenna device is included and has a primary antenna with
a longitudinal axis, a central lumen and a distal end, and a
secondary antenna with a distal end. The secondary antenna is
deployed from the primary antenna central lumen in a lateral
direction relative to the longitudinal axis. The primary antenna
and secondary antennas are each electromagnetically coupled to the
electromagnetic energy source.
[0017] In another embodiment, a method of ablating a selected
tissue mass is provided utilizing a monopolar multiple antenna
device.
[0018] The monopolar multiple antenna device can be an RF antenna,
a microwave antenna, a short wave antenna and the like. At least
two secondary antennas can be included and laterally deployed from
the primary antenna. The secondary antenna is retractable into the
primary antenna, permitting repositioning of the primary antenna.
When the multiple antenna is an RF antenna, it can be operated in
monopolar or bipolar modes, and is capable of switching between the
two.
[0019] One or more sensors may be positioned at an interior or
exterior of the primary or secondary antennas to detect impedance
or temperature. A feedback control system is coupled to each of the
sensors, the electromagnetic energy source and the primary and
secondary antennas.
[0020] An insulation sleeve can be positioned around the primary
and secondary antennas. Another sensor is positioned at the distal
end of the insulation sleeve surrounding the primary antenna.
[0021] The feedback control device can detect impedance or
temperature at a sensor. In some embodiments, the feedback control
system can include a multiplexer. Further, the feedback control
system can provide an ablation energy output for a selected length
of time, adjust ablation energy output and reduce or cut off the
delivery of the ablation energy output to the antennas. The
feedback control system can include a temperature detection circuit
which provides a control signal representative of temperature or
impedance detected at any of the sensors. The feedback control
system can also include a microprocessor connected to the
temperature detection circuit. Initially, temperature, ablation
duration and energy level are selected and manually input into the
feedback control system. As process parameters change, the initial
manually input values are then automatically modified by the
feedback control system to achieve the desired level of ablation
without impeding out, and minimize the ablation of non-targeted
tissue.
[0022] Further, the multiple antenna device can be a multi-modality
apparatus. One or all of the antennas can be hollow to receive an
infusion medium from an infusion source and introduce the infusion
medium into the targeted tissue mass.
BRIEF DESCRIPTION OF THE FIGURES
[0023] FIG. 1 is a perspective view of the multiple antenna
ablation apparatus of the present invention illustrating a primary
antenna and a single laterally deployed secondary antenna.
[0024] FIG. 2 is a perspective view of a conic geometric ablation
achieved with the apparatus of FIG. 1.
[0025] FIG. 3 is a perspective view of the multiple antenna
ablation apparatus of the present invention with two secondary
antennas.
[0026] FIG. 4 is a perspective view illustrating the adjacent
positioning of the multiple antenna ablation apparatus next to a
selected tissue mass.
[0027] FIG. 5 is a perspective view illustrating the positioning of
the multiple antenna ablation apparatus in the center of a selected
tissue mass, and the creation of a cylindrical ablation.
[0028] FIG. 6(a) is a perspective view of the multiple antenna
ablation of the present invention illustrating two secondary
antennas which provide a retaining and gripping function.
[0029] FIG. 6(b) is a perspective view of the multiple antenna
ablation of the present invention illustrating three secondary
antennas which provide a retaining and gripping function.
[0030] FIG. 6(c) is a cross-sectional view of the apparatus of FIG.
6(b) taken along the lines 6(c)-6(c).
[0031] FIG. 7 is a perspective view of the multiple antenna
ablation of the present invention illustrating the deployment of
three secondary antennas from a distal end of the insulation sleeve
surrounding the primary antenna.
[0032] FIG. 8 is a perspective view of the multiple antenna
ablation of the present invention illustrating the deployment of
two secondary antennas from the primary antenna, and the deployment
of three secondary antennas from the distal end of the insulation
sleeve surrounding the primary antenna.
[0033] FIG. 9 is a block diagram illustrating the inclusion of a
controller, energy source and other electronic components of the
present invention.
[0034] FIG. 10 is a block diagram illustrating an analog amplifier,
analog multiplexer and microprocessor used with the present
invention.
DETAILED DESCRIPTION
[0035] The present invention provides an ablation treatment
apparatus which includes an ablation energy source producing an
electromagnetic energy output. A monopolar multiple antenna device
is included and has a primary antenna with a longitudinal axis, a
central lumen and a distal end, and a secondary antenna with a
distal end. The secondary antenna is deployed from the primary
antenna central lumen in a lateral direction relative to the
longitudinal axis. The primary antenna and secondary antennas are
each electromagnetically coupled to the electromagnetic energy
source.
[0036] As shown in FIG. 1, an ablation treatment apparatus 10
includes a monopolar multiple antenna device 12. Monopolar multiple
antenna device 12 includes a primary antenna 14, and one or more
secondary antennas 16, which are typically electrodes. Secondary
antennas 16 are initially positioned in a primary antenna lumen
when primary antenna 14 is advanced through tissue. When primary
antenna 14 reaches a selected tissue ablation site in a selected
tissue mass, including but not limited to a solid lesion, secondary
antennas 16 are laterally deployed from the primary antenna lumen
and into the selected tissue mass. Ablation proceeds from the
interior of the selected tissue mass in a direction towards a
periphery of the selected tissue mass.
[0037] Each primary and secondary antenna 14 and 16 has an exterior
ablation surface which delivers electromagnetic energy to the
selected tissue mass. The length and size of each ablation surface
can be variable. The length of primary antenna ablation surface
relative to secondary antenna ablation surface can be 20% or
greater, 33 and 1/3% or greater, 50% or greater, 75% or greater,
about the same length, or greater than the length of secondary
electrode ablation surface. Lengths of primary and secondary
antennas 14 and 16 can be adjustable. Primary antenna 14 can be
moved up and down, rotated about its longitudinal axis, and moved
back and forth, in order to define, along with sensors, the
periphery or boundary of the selected tissue mass, including but
not limited to a tumor. This provides a variety of different
geometries, not always symmetrical, that can be ablated. The
ablation can be between the ablation surfaces of primary and
secondary antennas 14 and 16 when operated in a mono-polar mode
with a ground pad.
[0038] Primary antenna 14 is constructed so that it can be
introduced percutaneously or laparoscopically through tissue
without an introducer. Primary antenna 14 combines the function of
an introducer and an electrode.
[0039] In one embodiment, primary antenna 14 can have a. sharpened
distal end 14' to assist introduction through tissue. Each
secondary antenna 16 has a distal end 16' that is constructed to be
less structurally rigid than primary antenna 14. Distal end 16' is
that section of secondary antenna 16 that. is advanced from the
lumen antenna 14 and into the selected tissue mass. Distal end is
typically less structurally rigid that primary antenna 14. However,
even though sections of secondary antenna 16 which are not advanced
through the selected tissue mass may be less structurally rigid
than primary antenna 14.
[0040] Structurally rigidity is determined by, (i) choosing
different materials for antenna 14 and distal end 16' or some
greater length of secondary antenna 16, (ii) using the same
material but having less of it for secondary antenna 16 or distal
end 16', e.g., secondary antenna 16 or distal end 16' is not as
thick as primary electrode 14, or (iii) including another material
in one of the antennas 14 or 16 to vary their structural rigidity.
For purposes of this disclosure, structural rigidity is defined as
the amount of deflection that an antenna has relative to its
longitudinal axis. It will be appreciated that a given antenna will
have different levels of rigidity depending on its length.
[0041] Primary and secondary antennas 14 and 16 can be made of a
variety of conductive materials, both metallic and non-metallic.
One suitable material is type 304 stainless steel of hypodermic
quality. In some applications, all or a portion of secondary
electrode 16 can be made of a shaped memory metal, such as NiTi,
commercially available from Raychem Corporation, Menlo Park,
Calif.
[0042] Each of primary or secondary antennas 14 or 16 can have
different lengths. The lengths can be determined by the actual
physical length of an antenna, the amount of an antenna that has an
ablation delivery surface, and the length of an antenna that is not
covered by an insulator. Suitable lengths include but are not
limited to 17.5 cm, 25.0 cm. and 30.0 cm. The actual length of an
antenna depends on the location of the selected tissue mass to be
ablated, its distance from the skin, its accessibility as well as
whether or not the physician chooses a laproscopic, percutaneous or
other procedure. Further, ablation treatment apparatus 10, and more
particularly multiple antenna device 12, can be introduced through
a guide to the desired tissue mass site.
[0043] An insulation sleeve 18 may be positioned around an exterior
of one or both of the primary and secondary antennas 14 and 16
respectively. Preferably, each insulation sleeve 18 is adjustably
positioned so that the length of an antenna ablation surface can be
varied. Each insulation sleeve 18 surrounding a primary antenna 14
can include one or more apertures. This permits the introduction of
a secondary antenna 16 through primary antenna 14 and insulation
sleeve 18.
[0044] In one embodiment, insulation sleeve 18 can comprise a
polyamide material. A sensor 24 may be positioned on top of
polyimide insulation sleeve 18. The polyamide insulation sleeve 18
is semi-rigid. Sensor 24 can lay down substantially along the
entire length of polyamide insulation sleeve 18. Primary antenna 14
is made of a stainless-steel hypodermic tubing with 2 cm of exposed
ablation surface. Secondary antennas 16 have distal ends 16' that
are made of
[0045] NiTi hypodermic tubing. A handle is included with markings
to show the varying distance of secondary antennas 16 from primary
antenna 14. Fluid infusion is delivered through a Luer port at a
side of the handle. Type-T thermocouples are positioned at distal
ends 16'.
[0046] An energy source 20 is connected to multiple antenna device
12 with one or more cables 22. Energy source 20 can be an RF
source, microwave source, short wave source, laser source and the
like. Multiple antenna device 12 can be comprised of primary and
secondary antennas 14 and 16 that are RF electrodes, microwave
antennas, as well as combinations thereof. Energy source 20 may be
a combination RF/microwave box. Further a laser optical fiber,
coupled to a laser source 20 can be introduced through one or both
of primary or secondary antennas 14 and 16. One or more of the
primary or secondary antennas 14 and 16 can be an arm for the
purposes of introducing the optical fiber.
[0047] Antennas 14 and 16 are each electromagnetically coupled to
energy source 20. The coupling can be direct from energy source 20
to each antenna 14 and 16, or indirect by using a collet, sleeve
and the like which couples antennas 14 and 16 to energy source
20.
[0048] One or more sensors 24 may be positioned on at least a
portion of interior or exterior surfaces of primary antenna 14,
secondary antenna 16 or insulation sleeve 18. Preferably sensors 24
are positioned at primary antenna distal end 14', secondary antenna
distal end 16' and insulation sleeve distal end 18'. Sensors 24
permit accurate measurement of temperature at a tissue site in
order to determine, (i) the extent of ablation, (ii) the amount of
ablation, (iii) 25 whether or not further ablation is needed and
(iv) the boundary or periphery of the ablated mass. Further,
sensors 24 prevent non-targeted tissue from being destroyed or
ablated.
[0049] Sensors 24 are of conventional design, including but not
limited to thermistors, thermocouples, resistive wires, and the
like. Suitable thermal sensors 24 include a T type thermocouple
with copper constantene, J type, E type, K type, fiber optics,
resistive wires, thermocouple IR detectors, and the like. It will
be appreciated that sensors 24 need not be thermal sensors.
[0050] Sensors 24 measure temperature and/or impedance to permit
monitoring and a desired level of ablation to be achieved without
destroying too much tissue. This reduces damage to tissue
surrounding the targeted mass to be ablated. By monitoring the
temperature at various points within the interior of the selected
tissue mass, a determination of the selected tissue mass periphery
can be made, as well as a determination of when ablation is
complete. If at any time sensor 24 determines that a desired
ablation temperature is exceeded, then an appropriate feedback
signal is received at energy source 20 which then regulates the
amount of energy delivered to primary and/or secondary antennas 14
and 16.
[0051] Thus the geometry of the ablated mass is selectable and
controllable. Any number of different ablation geometries can be
achieved. This is a result of having variable lengths for primary
antenna 14 and secondary antenna 16 ablation surfaces as well as
the inclusion of sensors. 24.
[0052] Preferably, distal end 16' is laterally deployed relative to
a longitudinal axis of primary antenna 14 out of an aperture 26
formed in primary antenna 14. Aperture 26 is at distal end 14' or
formed in a side of an exterior of antenna 14.
[0053] In one embodiment, a method for creating an ablation volume
in a selected tissue mass includes; providing a monopolar ablation
device with a primary antenna, a secondary antenna with a distal
end, and an energy source electromagnetically coupled to both
antennas. A ground pad electrode is also included. The primary
antenna is inserted into the selected tissue mass with the
secondary antenna distal end positioned in the primary antenna
lumen. The secondary antenna distal end is advanced out of the
primary antenna lumen into the selected tissue mass in a lateral
direction relative to a longitudinal axis of the primary antenna.
Electromagnetic energy is delivered from one of a primary antenna
ablation surface, a secondary antenna ablation surface or both to
the selected tissue mass. This creates an ablation volume in the
selected tissue mass.
[0054] There is wide variation in the amount of deflection of
secondary antenna 16. For example, secondary antenna 16 can be
deflected a few degrees from the longitudinal axis of primary
antenna 14, or secondary antenna can be deflected in any number of
geometric configurations, including but not limited to a "J" hook.
Further, secondary antenna 16 is capable of being introduced from
primary antenna 14 a few millimeters from primary antenna, or a
much larger distance. Ablation by secondary antenna 16 can begin a
few millimeters away from primary antenna 14, or secondary
electrode 16 can be advanced a greater distance from primary
antenna 14 and at that point the initial ablation by secondary
antenna 16 begins.
[0055] A number of parameters permit ablation of selected tissue
masses, including but not limited to tumors, of different size and
shapes including, a series of ablations having primary and
secondary antennas 14 and 16 with variable length ablation
surfaces, the use of sensors 24 and the use of the feedback control
system.
[0056] As illustrated in FIG. 2, primary antenna 14 has been
introduced into a selected tissue mass 28. One or more secondary
antennas are positioned within a primary antenna lumen as primary
antenna 14 is introduced into and through the selected tissue mass.
Subsequently, secondary antenna distal end 16' is advanced out of
aperture 26 and into selected tissue mass 28. Insulation sleeves 18
are adjusted for primary and secondary antennas 14 and 16
respectively. RF, microwave, short wave and the like energy is
delivery to antenna 16 in a monopolar mode (RF), or alternatively,
multiple antenna device 12 can be operated in a bipolar mode (RF).
Multi antenna device 12 can be switched between monopolar and
bipolar operation and has multiplexing capability between antennas
14 and 16. Secondary antenna distal end 16' is retracted back into
primary antenna 14, and primary antenna is then rotated. Secondary
antenna distal end 16' is then introduced into selected tissue mass
28. Secondary antenna may be introduced a short distance into
selected tissue mass 28 to ablate a small area. It can then be
advanced further into any number of times to create more ablation
zones. Again, secondary antenna distal end 16' is retracted back
into primary antenna 14, and primary antenna 14 can be, (i) rotated
again, (ii) moved along a longitudinal axis of selected tissue mass
28 to begin another series of ablations with secondary antenna
distal end 16' being introduced and retracted in and out of primary
antenna 14, or (iii) removed from selected tissue mass 28. A number
of parameters permit ablation of selected tissue masses 28 of
different sign and shapes including a series of ablations having
primary and secondary antennas 14 and 16 with variable length
ablation surfaces and the use of sensor 24.
[0057] In FIG. 3, two secondary antennas 16 are each deployed out
of distal end 14' and introduced into selected tissue mass 28.
Secondary antennas 16 form a plane and the area of ablation extends
between the ablation surfaces of primary and secondary antennas 14
and 16. Primary antenna 14 can be introduced in an adjacent
relationship to selected tissue mass 28. This particular deployment
is particularly useful for small selected tissue masses 28, or
where piercing selected tissue mass 28 is not desirable. Primary
antenna 14 can be rotated, with secondary antennas 16 retracted
into a central lumen of primary antenna 14, and another ablation
volume defined between the two secondary antennas 16 is created.
Further, primary electrode 14 can be withdrawn from its initial
position adjacent to selected tissue mass 28, repositioned to
another position adjacent to selected tissue mass 28, and secondary
antennas 16 deployed to begin another ablation cycle. Any variety
of different positionings may be utilized to create a desired
ablation geometry for selected tissue mass of different geometries
and sizes.
[0058] In FIG. 4, three secondary antennas 16 are introduced into
selected tissue mass 28. The effect is the creation of an ablation
volume without leaving non-ablated areas between antenna ablation
surfaces. The ablation is complete.
[0059] Referring now to FIG. 5, a center of selected tissue mass 28
is pierced by primary antenna 14, secondary antennas 16 are
laterally deployed and retracted, primary antenna 14 is rotated,
secondary antennas 16 are deployed and retracted, and so on until a
cylindrical ablation volume is achieved. Multiple antenna device 12
can be operated in the bipolar mode between the two secondary
antennas 16, or between a secondary antenna 16 and primary antenna
14. Alternatively, multiple antenna device 12 can be operated in a
monopolar mode.
[0060] Secondary antennas 16 can serve the additional function of
anchoring multiple antenna device 12 in a selected mass, as
illustrated in FIGS. 6(a) and 6(b). In FIG. 6(a) one or both
secondary antennas 16 are used to anchor and position primary
antenna 14. Further, one or both secondary antennas 16 are also
used to ablate tissue. In FIG. 6(b), three secondary antennas are
deployed and anchor primary antenna 14.
[0061] FIG. 6(c) illustrates the infusion capability of multiple
antenna device 12. Three secondary antennas 16 are positioned in a
central lumen 14" of primary antenna 14. One or more of the
secondary antennas 16 can also include a central lumen coupled to
an infusion source. Central lumen 14" is coupled to an infusion
source and delivers a variety of infusion mediums to selected
places both within and outside of the targeted ablation mass.
Suitable infusion mediums include but are not limited to,
therapeutic agents, conductivity enhancement mediums, contrast
agents or dyes, and the like. An example of a therapeutic agent is
a chemotherapeutic agent.
[0062] As shown in FIG. 7 insulation sleeve 18 can include one or
more lumens for receiving secondary antennas 16 which are deployed
out of an insulation sleeve distal end 18'. FIG. 8 illustrates two
secondary antennas 16
[0063] being introduced out of insulation sleeve distal end 18',
and two secondary antennas 16 introduced through apertures 26
formed in primary antenna 14. As illustrated, the secondary
electrodes introduced through apertures 26 provide an anchoring
function. It will be appreciated that FIG. 8 illustrates how
secondary antennas 16 can have a variety of different geometric
configurations in multiple antenna device 12.
[0064] A feedback control system 29 is connected to energy source
20, sensors 24 and antennas 14 and 16. Feedback control system 29
receives temperature or impedance data from sensors 24 and the
amount of electromagnetic energy received by antennas 14 and 16 is
modified from an initial setting of ablation energy output,
ablation time, temperature, and current density (the "Four
Parameters"). Feedback control system 29 can automatically change
any of the Four Parameters. Feedback control system 29 can detect
impedance or temperature and change any of the Four Parameters.
Feedback control system can include a multiplexer to multiplex
different antennas, a temperature detection circuit that provides a
control signal representative of temperature or impedance detected
at one or more sensors 24. A microprocessor can be connected to the
temperature control circuit.
[0065] The following discussion pertains particularly to the use of
an RF energy source and RF multiple antenna device 12. It will be
appreciated that devices similar to those associated with RF
multiple antenna device 12 can be utilized with laser optical
fibers, microwave devices and the like.
[0066] Referring now to FIG. 9, all or portions of feedback control
system 29 are illustrated. Current delivered through primary and
secondary antennas 14 and 16 is measured by current sensor 30.
Voltage is measured by voltage sensor 32. Impedance and power are
then calculated at power and impedance calculation device 34. These
values can then be displayed at user interface and display 36.
Signals representative of power and impedance values are received
by controller 38. A control signal is generated by controller 38
that is proportional to the difference between an actual measured
value, and a desired value. The control signal is used by power
circuits 40 to adjust the power output in an appropriate amount in
order to maintain the desired power delivered at the respective
primary and/or secondary antennas 14 and 16.
[0067] In a similar manner, temperatures detected at sensors 24
provide feedback for maintaining a selected power. The actual
temperatures are measured at temperature measurement device 42, and
the temperatures are displayed at user interface and display 36. A
control signal is generated by controller 38 that is proportional
to the difference between an actual measured temperature, and a
desired temperature. The control signal is used by power circuits
40 to adjust the power output in an appropriate amount in order to
maintain the desired temperature delivered at the respective sensor
24. A multiplexer can be included to measure current, voltage and
temperature, at the numerous sensors 24, and energy is delivered
between primary antenna 14 and secondary antennas 16.
[0068] Controller 38 can be a digital or analog controller, or a
computer with software. When controller 3 8 is a computer it can
include a CPU coupled through a system bus. On this system can be a
keyboard, a disk drive, or other non-volatile memory systems, a
display, and other peripherals, as are known in the art. Also
coupled to the bus are a program memory and a data memory.
[0069] User interface and display 36 includes operator controls and
a display. Controller 38 can be coupled to imaging systems,
including but not limited to ultrasound, CT scanners, X-ray, MRI,
mammographic X-ray and the like. Further, direct visualization and
tactile imaging can be utilized.
[0070] The output of current sensor 30 and voltage sensor 32 is
used by controller 38 to maintain a selected power level at primary
and secondary antennas 14 and 16. The amount of RF energy delivered
controls the amount of power. A profile of power delivered can be
incorporated in controller 38, and a preset amount of energy to be
delivered can also be profiled.
[0071] Circuitry, software and feedback to controller 38 result in
process control, and the maintenance of the selected power, and are
used to change, (i) the selected power, including RF, microwave,
laser and the like, (ii) the duty cycle (on-off and wattage), (iii)
bipolar or monopolar energy delivery and (iv) infusion medium
delivery, including flow rate and pressure. These process variables
are controlled and varied, while maintaining the desired delivery
of power independent of changes in voltage or current, based on
temperatures monitored at sensors 24.
[0072] Referring now to FIG. 10, current sensor 30 and voltage
sensor 32 are connected to the input of an analog amplifier 44.
Analog amplifier 44 can be a conventional differential amplifier
circuit for use with sensors 24. The output of analog amplifier 44
is sequentially connected by an analog multiplexer 46 to the input
of A/D converter 48. The output of analog amplifier 44 is a voltage
which represents the respective sensed temperatures. Digitized
amplifier output voltages are supplied by A/D converter 48 to a
microprocessor 50. Microprocessor 50 may be Model No. 68HCII
available from Motorola. However, it will be appreciated that any
suitable microprocessor or general purpose digital or analog
computer can be used to calculate impedance or temperature.
[0073] Microprocessor 50 sequentially receives and stores digital
representations of impedance and temperature. Each digital value
received by microprocessor 50 corresponds to different temperatures
and impedances.
[0074] Calculated power and impedance values can be indicated on
user interface and display 36. Alternatively, or in addition to the
numerical indication of power or impedance, calculated impedance
and power values can be compared by microprocessor 50 with power
and impedance limits. When the values exceed predetermined power or
impedance values, a warning can be given on user interface and
display 36, and additionally, the delivery of RF energy can be
reduced, modified or interrupted. A control signal from
microprocessor 50 can modify the power level supplied by energy
source 20.
[0075] The foregoing description of a preferred embodiment of the
invention has been presented for purposes of illustration and
description. It is not intended to be exhaustive or to limit the
invention to the precise forms disclosed. Obviously, many
modifications and variations will be apparent to practitioners
skilled in this art. It is intended that the scope of the invention
be defined by the following claims and their equivalents.
* * * * *