U.S. patent application number 09/113683 was filed with the patent office on 2001-06-14 for balloon catheter for intra-urethral radio-frequency urethral enlargement.
This patent application is currently assigned to Phyllis K. Kristal. Invention is credited to COSMAN, ERIC R., GOLDBERG, S. NAHUM, MCGOVERN, FRANCIS J., RITTMAN, WILLIAM J. III.
Application Number | 20010003798 09/113683 |
Document ID | / |
Family ID | 26695113 |
Filed Date | 2001-06-14 |
United States Patent
Application |
20010003798 |
Kind Code |
A1 |
MCGOVERN, FRANCIS J. ; et
al. |
June 14, 2001 |
BALLOON CATHETER FOR INTRA-URETHRAL RADIO-FREQUENCY URETHRAL
ENLARGEMENT
Abstract
Relief of urethral obstruction is achieved by heat ablation of
prostatic tissue by an ablation instrument passed within the
urethra to a position in the prostate near the point of urethral
obstruction. An electrode is coupled to a high-frequency power
supply to ablatively heat the urethra and the prostatic tissue near
the urethra. Guidance of the electrode placement may be monitored
by an imaging device. The instrument may consist of a catheter with
an inflatable balloon structure for positioning the instrument. The
temperature of the tissue may be sensed at the electrode to control
the high-frequency heating energy and ablation process.
Inventors: |
MCGOVERN, FRANCIS J.;
(LEXINGTON, MA) ; GOLDBERG, S. NAHUM; (BROOKLINE,
MA) ; COSMAN, ERIC R.; (BELMONT, MA) ;
RITTMAN, WILLIAM J. III; (LYNNFIELD, MA) |
Correspondence
Address: |
PETER J. DEVLIN
FISH & RICHARDSON P.C.
225 FRANKLIN STREET
BOSTON
MA
02110-2804
US
|
Assignee: |
Phyllis K. Kristal
|
Family ID: |
26695113 |
Appl. No.: |
09/113683 |
Filed: |
July 10, 1998 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09113683 |
Jul 10, 1998 |
|
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09021802 |
Feb 11, 1998 |
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Current U.S.
Class: |
606/41 ; 607/105;
607/113; 607/99 |
Current CPC
Class: |
A61B 2018/00678
20130101; A61B 2018/00797 20130101; A61B 2018/00547 20130101; A61B
2218/002 20130101; A61B 2018/00577 20130101; A61B 2018/00875
20130101; A61B 2018/0022 20130101; A61B 2018/1253 20130101; A61B
2018/00702 20130101; A61B 2018/00815 20130101; A61B 2018/00755
20130101; A61B 2090/3782 20160201; A61B 2018/00791 20130101; A61B
2018/00505 20130101; A61B 2018/1467 20130101; A61B 2218/007
20130101; A61B 18/1485 20130101; A61B 2018/00821 20130101; A61B
18/1815 20130101; A61B 2018/00083 20130101 |
Class at
Publication: |
606/41 ; 607/99;
607/105; 607/113 |
International
Class: |
A61B 018/14 |
Claims
What is claimed is:
1. A system for intra-urethral high-frequency heating of an
operative field that includes at least a portion of a prostate of a
patient, whereby the system enlarges at least a portion of a
urethra of a patient, the system comprising: a generator of a
high-frequency electrical signal; a catheter, adapted to be
inserted into the urethra through a penis of the patient, the
catheter comprising: a proximal end, a distal end, an outer
surface, a portion of the outer surface comprising an electrically
conductive electrode, whereby the catheter may be positioned within
the urethra proximate to the prostate to make electrical contact
with the urethra, an inflatable balloon near the distal end of the
catheter wherein the inflatable balloon is adapted to be inflated
within a bladder of the patient to stably position the electrically
conductive electrode within the urethra and proximate to the
prostate; an electrical connection between the electrically
conductive electrode and the generator, allowing the high-frequency
signal from the generator to induce ablative heating of a portion
of the urethra and a portion of prostate tissue near the urethra,
thereby causing urethral enlargement.
2. The system of claim 1, wherein the catheter further comprises an
inflation channel that connects the inflatable balloon to an
inflation port at the proximal end of the catheter, whereby the
balloon may be inflated or deflated by passage of fluid through the
inflation port.
3. The system of claim 1 wherein the catheter further comprises a
drainage channel which connects a distal opening at the distal end
of the catheter with a proximal port at the proximal end of the
catheter, wherein urine may be drained from the bladder by flowing
into the distal opening, through the drainage channel, and out of
the proximal port when the catheter is positioned within the
urethra and the balloon is inflated within the patient's
bladder.
4. The system of claim 1 wherein the electrically conductive
electrode comprises a metal ring.
5. The system of claim 1 wherein the electrically conductive
electrode has a predetermined size and a predetermined position in
relation to the balloon so that the electrically conductive
electrode will be positioned in a desired position within the
urethra to achieve a desired location of ablative heating.
6. The system of claim 1 wherein the electrically conductive
electrode comprises a metal ring of predetermined length affixed
around the catheter and is spaced apart from the balloon by a
predetermined distance.
7. The system of claim 1 wherein the catheter further comprises a
temperature sensor located near the electrically conductive
electrode, the temperature sensor being adapted to be connected to
a temperature monitor external to the patient's body so that the
temperature of the urethra near the electrically conductive
electrode can be monitored during the ablative heating.
8. The system of claim 1 wherein the electrically conductive
electrode is electrically exposed over only a portion of the area
around the circumference of the catheter so that the heat ablation
will occur in a selected direction relative to the circumference of
the catheter.
9. The system of claim 1 wherein the electrically conductive
electrode comprises more than one electrically exposed area of the
catheter.
10. The system of claim 1 wherein the catheter further comprises
two internal channels which are not connected together, a first one
of the internal channels adapted to enable inflation of the
balloon, and a second one of the internal channels adapted to
enable drainage of urine from a bladder of the patient.
11. The system of claim 10 wherein the catheter further comprises
an internal cooling channel which extends from the proximal end of
the catheter to a location proximate the electrically conductive
electrode, the cooling channel being located within the catheter to
enable circulation of cooling fluid injected into an end of the
cooling channel at the proximal end of the catheter whereby to cool
the electrically conductive electrode.
12. The system of claim 1 wherein the catheter includes only two
internal channels that are adapted to carry fluid, a first one of
the two internal channels having a port at the proximal end of the
catheter to allow inflow of fluid to inflate the balloon, and a
second one of the two internal channels having a distal opening at
the distal end of the catheter and a proximal opening at the
proximal end of the catheter to allow drainage of urine from the
bladder of the patient when the catheter is inserted into the
urethra and the balloon is inflated in the bladder.
13. The system of claim 1 wherein the catheter includes only one
mono-directional fluid channel, wherein the fluid channel connects
a distal opening at the distal end of the catheter to a proximal
opening at the proximal end of the catheter whereby, when the
catheter is inserted into the urethra and the balloon is inflated
within the bladder of the patient, the fluid channel provides a
fluid path for draining urine from the bladder via the distal
opening to the proximal opening.
14. The system of claim 1 wherein the catheter further comprises a
plurality of channels and all of the channels have only one channel
end that opens at the proximal end of the catheter to prevent
circulation within the catheter of a fluid injected into the
proximal end, whereby the catheter is adapted to prevent cooling of
the electrically conductive electrode by a cooling fluid.
15. The system of claim 1 wherein the catheter includes a plurality
of fluid carrying channels and all of of the fluid carrying
channels connect to at most one fluid carrying port at the proximal
end of the catheter.
16. The system of claim 1 wherein the catheter further comprises
internal channels which are only of a fluid non-circulating
configuration, whereby fluid injected into a channel from the
proximal end of the catheter has no recirculation pathway for the
fluid to exit from the channel at the proximal end of the
catheter.
17. The system of claim 1 wherein the catheter further comprises:
at least one channel with an inflation port at the proximal end of
the catheter for inflation of the balloon by a fluid; at least one
channel to drain urine from the bladder of the patient; and at
least one channel to enable circulation of coolant fluid within the
catheter to cool the electrically conductive electrode.
18. A method of relieving urethral obstruction in a patient having
a urethra, a prostate and a bladder, the method comprising the
steps of: providing a catheter that comprises: an electrically
conductive electrode which comprises a portion of an external
surface of the catheter, and an inflatable balloon proximate to a
distal end of the catheter wherein the inflatable balloon may be
inflated by injection of fluid through a port in the catheter;
inserting the catheter into the urethra of the patient a distance
sufficient to provide contact between the electrode and at least a
portion of the urethra and to insert the balloon into the bladder
of the patient; inflating the balloon; positioning the electrode
within the urethra of the patient at a location in the prostate
where urethral enlargement is desired; applying a high-frequency
signal to the electrode to induce heat ablation of at least a
portion of the urethra and at least a portion of periurethral
tissue in the patient, thereby inducing ablative reduction of
tissue mass of the urethra and nearby tissue to reduce the urethral
obstruction.
19. The method of claim 18 wherein the catheter further comprises a
channel for circulating cooling fluid from a coolant supply
external to the body of the patient, the method further comprising
the step of concurrently applying the high-frequency signal to the
electrode and circulating cooling fluid within the channel, thereby
to enlarge the region of ablation within the prostate.
20. The method of claim 18 wherein the positioning step further
comprises the step viewing an operative field within the patient to
position the electrode relative to the obstruction.
21. The method of claim 18 further comprising the step of measuring
a temperature of tissue proximate the electrode.
22. The method of claim 18 further comprising the step of measuring
an impedance of tissue proximate the electrode.
23. The method of claim 18 wherein the electrode comprises a
plurality of electrically conductive areas separated by at least
one electrical insulator.
24. The method of claim 18 wherein the catheter includes only two
internal channels that are adapted to carry fluid, a first one of
the two internal channels having a port at a proximal end of the
catheter to allow inflow of fluid to inflate the balloon, and a
second one of the two internal channels having a distal opening at
a distal end of the catheter and a proximal opening at a proximal
end of the catheter to allow drainage of urine from the bladder of
the patient when the catheter is inserted into the urethra and the
balloon is inflated in the bladder.
25. A catheter for intra-urethral high-frequency heating of an
operative field that includes at least a portion of a prostate of a
patient, whereby the catheter may be used to enlarge at least a
portion of a urethra of a patient, the catheter comprising: a
proximal end, a distal end, an outer surface, a portion of the
outer surface comprising an electrically conductive electrode,
whereby the catheter may be positioned within the urethra proximate
to the prostate to make electrical contact with the urethra; and an
inflatable balloon near the distal end of the catheter wherein the
inflatable balloon is adapted to be inflated within a bladder of
the patient to stably position the electrically conductive
electrode within the urethra and proximate to the prostate.
26. The catheter of claim 25 wherein the electrically conductive
electrode comprises a metal ring.
27. The catheter of claim 25 wherein the electrically conductive
electrode has a predetermined size and a predetermined position in
relation to the balloon so that the electrically conductive
electrode will be positioned in a desired position within the
urethra to achieve a desired location of ablative heating.
28. The catheter of claim 25 further comprising a temperature
sensor located near the electrically conductive electrode, the
temperature sensor being adapted to be connected to a temperature
monitor external to the patient's body so that the temperature of
the urethra near the electrically conductive electrode can be
monitored during the ablative heating.
29. The catheter of claim 25 wherein the catheter includes only two
internal channels that are adapted to carry fluid, a first one of
the two internal channels having a port at a proximal end of the
catheter to allow inflow of fluid to inflate the balloon, and a
second one of the two internal channels having a distal opening at
a distal end of the catheter and a proximal opening at a proximal
end of the catheter to allow drainage of urine from the bladder of
the patient when the catheter is inserted into the urethra and the
balloon is inflated in the bladder.
30. The catheter of claim 25 further including at least one
electric insulator affixed over at least a portion of the
electrode.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of application
Ser. No. 09/021,802, filed on Feb. 11, 1998, entitled "METHOD AND
SYSTEM FOR PERFORMING INTRA-URETHRAL RADIO-FREQUENCY URETHRAL
ENLARGEMENT."
FIELD OF THE INVENTION
[0002] This invention relates generally to advances in medical
systems and procedures for prolonging or improving human life. More
particularly, this invention relates to an improved method and
system for alleviating urinary obstruction caused by enlargement of
the prostate by performing intra-urethral radio-frequency ablation
for urethral enlargement.
BACKGROUND OF THE INVENTION
[0003] A majority of all males over 60 years old experience partial
or complete urinary obstruction because of enlargement of the
prostate. This condition usually originates from benign prostatic
hyperplasia (BPH), which is an increase in cell mass near the
urethra, or less likely, from prostate cancer. Both these
conditions involve an increase in prostatic tissue mass, which in
its increased state encroaches on the urethra and obstructs the
urinary pathway.
[0004] In the case where urinary obstruction is caused by BPH, a
common treatment involves a medical procedure using a medical
side-cutting instrument and/or endoscope to surgically enlarge a
passageway for urine flow through the prostate. The side-cutting
instrument or an endoscope is passed through the penis into the
urethra and is surgically used to remove prostate tissue and part
of the urethra at the point of obstruction. This procedure is
referred to as "Trans-urethral Resection of the Prostate" (or
"TURP").
[0005] This procedure, although effective, is invasive and
complicated. For example, it requires the use of anesthesia and
substantial hospital care. It also has the risk of causing
bleeding. Moreover, it is expensive and causes great discomfort and
trauma to the patient. For example, chapter 18, entitled
"Complications of Transurethral Resection of the Prostate," by R.
Sunshine and M. Droller, of a book entitled Urologic Complications,
Medical and Surgical, Adult and Pediatric, edited by Fray S.
Marshall (Yearbook Medical Publishers, 1986), elaborates on the
various complications of the TURP procedure.
[0006] In the case where urinary obstruction results from prostatic
cancer, surgical prostatectomies are commonly used to eliminate the
obstruction. However, surgical prostatectomies have serious side
effects and risks, including impotence and urinary
incontinence.
[0007] In recent years, less invasive systems and procedures that
inflict less trauma on patients have been attempted. One such
procedure, called "Trans-urethral Needle Ablation" (or "TUNA"),
involves passing a radio-frequency (RF) instrument such as a
catheter, cannula, sheath, or scope into the urethra. The RF
instrument houses special RF electrode tips that emerge from the
side of the instrument. The tips are pushed out of the instrument
along off-axis paths to pierce the urethral wall and pass into the
prostatic tissue outside of the urethra. As a result of the various
electrodes emerging from the side of the instrument, such
radio-frequency instruments are frequently complex and
expensive.
[0008] By heating the prostate with RF power applied through the
electrode tips emerging from the side of the radio-frequency (RF)
instrument, the prostate tissue surrounding the urethra is ablated.
Specifically, heat ablation is performed at multiple locations
outside the urethra to provide a series of ablations, thereby
causing the prostate tissue outside the urethra to die and necrose.
Subsequent to heating, the necrotic tissue is absorbed by the body
or excreted, thereby reducing the tissue mass outside the urethra,
which consequently reduces the urethral obstruction.
[0009] For further explanation of this system and procedure, one
can consult a research paper published by Goldwasser et al.,
entitled "Transurethral needle ablation (TUNA) of the prostate
using low-level radio-frequency energy: an animal experimental
study;" Eur. Urol., vol. 24, pp. 400-405 (1993); and a research
paper published by Schulman, et al., entitled "Transurethral needle
ablation (TUNA); safety, feasibility, and tolerance of a new office
procedure for treatment of benign prostate hyperplasma;" Eur.
Urol., vol. 24, pp. 415-423 (1993). Also, product literature on the
TUNA system available from a company named Vitamed, Inc., of Menlo
Park, California, carries some description of the procedure.
[0010] The TUNA system and procedure is generally used to relieve
urethral obstruction caused by BPH. It favors a transurethral
approach because the target tissue to be ablated is generally near
to it. However, again, although the TUNA system and procedure is
effective, it requires epidural or general anesthetic, and
generally causes the patient great discomfort and pain. Moreover,
the TUNA procedure is medically and technically very complex for
surgeons to perform, requiring a complicated and expensive catheter
or sheath or RF electrode system to perform it. Also, it is a
relatively blind procedure in the sense that the ends of the RF
electrodes emerging at the side of the radio-frequency electrode
system, once they penetrate the target tissue, cannot be seen. Nor
is there any technique for providing a visual representation of
them. Furthermore, the TUNA system and procedure attempts to leave
the urethra intact and uninjured by the application of RF heating,
which is difficult to achieve, making its outcome uncertain. The
TUNA system and procedure causes scratching of the urethra,
bleeding or irritation from a cystoscope, cannula, catheter, or
tissue-piercing electrode tips passed into the urethra.
Furthermore, the TUNA procedure produces trapped coagulated and
necrotic tissue or fluid in the interstitial region of the prostate
outside the urethra. This can result in swelling and increased
pressure of tissue outside the prostate as the necrotic tissue is
absorbed by the body. Such pressure can compress the urethra to
further enhance its obstruction.
[0011] It is observed that such techniques have not been directed
at creating ablation of urethra or the periurethral region (the
region surrounding the urethra or the critical prostate region) for
the reasons discussed above. Accordingly, it would be desirable to
have an effective technique to perform intra-urethral RF electrode
ablation of the urethra and periurethral tissue for the purposes of
alleviating urinary obstruction caused by enlargement of the
prostate and that avoids the limitations of the art.
[0012] Another system and procedure contemplated by Onik et al. is
described in their research paper entitled "Transrectal
ultrasound-guided percutaneous radical cryosurgical ablation of the
prostate;" Cancer, vol. 72, pp. 1291-1299 (1993). This technique is
utilized for the treatment of prostate cancer and involves
disposing cryogenic (freezing) probes in the prostate for ablating
the cancer cells. Onik et al. propose passing a cryogenic probe
transperineally (through the perineum) into the prostate. At the
same time, an imaging ultrasonic probe is passed through the rectum
and is used to visualize the position of the cryogenic probe and
the volume of cryogenic ablation in the prostate. This technique
requires use of cryogenic probes (also referred to as cryo-probes)
having relatively large diameters. The cryo-probes are complex in
construction and operation and require elaborate cooling and
thawing cycles, making the procedure typically quite complicated
and expensive. It is technically challenging and critical to
maintain precise temperatures at the target tissue area to prevent
hemorrhaging when removing the probe and also to prevent freezing
sensitive rectal mucosa tissue.
[0013] One more recent procedure contemplated and reported by
McGahan, et al., in their research paper entitled "Percutaneous
Ultrasound-Guided Radio-frequency Electrocautery Ablation of
Prostate Tissue in Dogs," Acad. Radiol., pp. 61-64 (1994), involves
placing an RF electrode transrectally into the prostate of a dog
under rectal ultrasound guidance. Their intent was solely to
explore the feasibility of ablating cancerous tumors within the
peripheral region of the prostate. Their research treated only
normal animals and no ablation of cancer tissue was actually
performed. McGahan et al. hoped to prevent RF heat ablation of the
urethra (which is located centrally in the prostate). To achieve
their objective, they suggested that the urethra should be
irrigated with saline solution, using a catheter, to prevent RF
heat damage to the urethra and periurethral tissue. They concluded
that their system and procedure was impractical for ablating
prostate cancer cells, because the RF lesions were limited to 1 to
1.5 cm in diameter, which they felt would be too small to
adequately treat malignant cancer cells.
[0014] Generally, prostate cancer primarily occurs in the
peripheral (non-central) zone of the prostate. It is often
multi-focal, near the rectal wall, and near nerves controlling
potency. Recognizing the restraints and delicate circumstances,
McGahan et al., were discouraged by the results of their research.
They concluded that their technique may be applicable to only a
small percentage of prostate carcinomas, specifically those that
are small and can be imaged by ultrasound. In their paper, they
emphasized their concern for preventing RF heat damage to the
rectal mucosa tissue. Thus, as a result of their efforts to treat
prostate cancer, which is predominantly located in the peripheral
non-central part of the prostate, they focused their research
efforts on the peripheral, peri-rectal regions of the prostate.
Their research did not contemplate RF ablation in the central
periurethral region to produce an ablation cavity near the urethra
or to ablate the urethra itself. In fact, they explicitly sought to
avoid injury of the urethra by avoiding treatment of periurethral
tissues. Their method and objectives were directed to cancer and
were found to be disadvantageous for treatment of BPH or for
treating urethral or periurethral tissues by radio-frequency (RF)
ablation to relieve urinary obstruction.
[0015] It should be recognized that the theory behind and practice
of RF heat lesion has been known for decades, and a wide range of
RF generators and electrodes for accomplishing such practice exist.
For example, equipment for performing heat lesions is available
from Radionics, Inc., located in Burlington, Mass. Radio-frequency
(RF) ablation is well known and described in medical and clinical
literature. To that end, a research paper by E. R. Cosman, et al.,
entitled "Theoretical Aspects of Radio-frequency Lesions in the
Dorsal Root Entry Zone;" Neurosurgery, vol. 15; no. 6, pp. 945-950
(1984), describing various techniques associated with
radio-frequency lesions, is incorporated herein by reference. Also,
a research paper by S. N. Goldberg, et al., entitled "Tissue
Ablation with Radio-frequency: Effect of Probe Size, Gauge,
Duration, and Temperature on Lesion Volume;" Acad. Radiol., vol. 2;
pp. 399-404 (1995), describes techniques and considerations
relating to tissue ablation with radio-frequency energy.
[0016] In addition, a paper by S. N. Goldberg, et al., entitled
"Hepatic Metastases: Percutaneous Radio-Frequency Ablation with
Cooled-Tip Electrodes," Radiology, vol. 205, no. 2, pp. 367-373
(1997), describes various techniques and considerations relating to
tissue ablation with radio-frequency electrodes having cooled
electrode tips. Cooled ablation electrodes will maintain tissue
near the electrode at lowered temperatures which are below ablation
temperatures. Cooling of the urethra by a catheter is suggested by
McGahan et al., cited above, to prevent RF heat damage to the
urethra and periurethral tissue.
[0017] Generally, cooled radio-frequency electrodes having an
elongated shaft or catheter structure have cooling channels within
the electrode structure. These cooling channels, for example, may
comprise a first channel to carry cooled fluid from an external
source, which is connected to the electrode at its proximal end.
The coolant fluid is carried through the first channel to provide
cooling to the electrode end, which is typically near the distal
end of the electrode structure. The electrode structure typically
also comprises a second channel within the electrode structure that
is connected near the distal end to the first channel and which is
adapted to bring the cooling fluid from the distal electrode region
back to the source. Such recirculating channels for cooling fluid
move the cooled fluid in one direction from the fluid source to the
electrode and then back to the source. For a self-contained,
internally cooled, electrode structure, the cooling channels would
be inside the structure and sealed from other channels that may
exist within the catheter such as for urinary drainage or for
inflation of a balloon tip. Thus cooled electrode structures add a
complexity of structure compared to non-cooled electrode
structures.
[0018] Use of cooled ablation devices placed inside the urethra
would have the objective of sparing the urethra from heat damage
during the time when heating of prostatic tissue is occurring at a
distance from the urethra.
[0019] Transurethral microwave thermotherapy (or "TUMT") has been
used to treat BPH and illustrates the use of a cooled catheter
which also delivers heat energy to the prostate. A catheter which
has a microwave probe inside it is inserted into the urethra to the
point of the prostate. The microwave probe is typically a microwave
antenna which is located inside the catheter near its distal end
and is connected to an external generator of microwave power
output. In this way the prostate is heated by radiative
electromagnetic heating. At the same time the catheter is cooled by
circulation of a coolant fluid within the catheter. The objective
is, as stated above, to cool the urethra and thereby prevent damage
to it by the heating process which is occurring in prostatic tissue
that is outside of and at a distance from the urethra. Thus, the
TUMT procedure seeks to preserve the urethra and the prostate
tissue immediately outside the urethra by cooling the catheter with
fluid coolant that is circulated within the catheter. In TUMT, the
microwave antenna is located inside the catheter and not in
conductive electrical contact with the urethra. The microwave
heating in the TUMT procedure occurs in the prostatic tissue
located at a distance away from the urethra as a result of the
simultaneous cooling action of the channels within the catheter and
the deposition of microwave power into the prostate tissue from the
radiated energy from the antenna. Thus the prostatic tissue
immediately around the urethra and the urethra itself are
deliberately spared from receiving an ablative level of heating in
the TUMT procedure. Further explanation of the TUMT system and
procedure can be found in the paper by Blute, et al., entitled
"Transurethral microwave thermal therapy for the management of
benign prostatic hyperplasia: results of the United States
prostration cooperative study." J. Urol., vol. 150, pp. 1591-1596
(1993).
[0020] However, for reasons described above, such techniques have
never been performed to ablate the periurethral region and the
urethra itself using an intra-urethral RF electrode that does not
pierce the urethra. Accordingly, an effective technique for
performing intra-urethral RF electrode ablation to achieve urethral
enlargement is desirable for purposes of alleviating urinary
obstruction caused by enlargement of the prostate.
SUMMARY OF THE INVENTION
[0021] The present invention is directed to a system and procedure
for radio-frequency (RF) heat ablation of prostatic tissue through
the use of an RF electrode, which is advanced into the urethra
through the penis and positioned intra-urethrally (within the
urethra). The ablation is performed for the treatment of benign
prostatic hyperplasia (BPH) and the associated alleviation of
urethral obstruction. It would also be used for other diseases such
as prostate cancer to relieve urethral obstruction. The system and
procedure of the present invention are different from any of the
systems and procedures discussed in the background section. The
advantages of the present system and method reside in their
combined simplicity, economy, control, consistency, enablement of
good ablation position and shape, and clinical effectiveness.
[0022] As one example, urinary bladder outlet obstruction can be
effectively treated using the present system and technique, which
is minimally invasive. The technique of the present invention
involves inserting an RF electrode into the urethra to the region
of urethral obstruction in the prostate. The conductive portion of
the RF electrode remains within the urethra. This avoids the more
difficult and uncomfortable transurethral approach of the TUNA
system procedure discussed above, and may be done without need for
passing one or more side-outlet RF electrodes through the urethral
wall (via a transurethral approach) into the prostatic tissue
surrounding the urethra. In various embodiments, the present system
and procedure may include image guidance, which may be performed in
a variety of ways including ultrasound, CT, MRI, fluoroscopy,
X-rays, or other well known imaging techniques.
[0023] In accordance with one embodiment of the invention, an RF
electrode may comprise a flexible rubber urethral catheter having
an inflatable balloon tip and urinary drainage channel. An
electrically conductive RF surface-mounted electrode is attached to
the catheter proximal to the balloon portion. This RF electrode can
contact electrically the urethral tissue when the catheter is
inserted through the penis into the urethra. The balloon may be
inflated when the distal portion of the catheter is within the
patient's bladder thereby enabling the catheter and the electrode
portion to be fixed in a desired position relative to the prostate
and urethra. The RF electrode may be determined to be at a desired
position in the prostate by a simple traction of the balloon on the
bladder. This also ensures against migration or change of position
of the electrode from its proper position relative to the prostate
and critical structures. X-ray, fluoroscopic, ultrasound, CT, or
MRI imaging information can be made of the position of the
electrode within the prostate and urethra.
[0024] An electrical connection is made from the RF electrode to an
RF power generator external to the patient's body. The output from
the generator is used to heat and thus ablate the urethral tissue
and surrounding prostatic tissue near the RF electrode location.
This creates a cavity and expanded opening of the urethra to
relieve the urinary obstruction caused by BPH or other prostatic
disease.
[0025] In contrast to the TUNA technique, the RF electrode of the
present invention can be used without piercing the urethra. It
enables patients who cannot tolerate the TUNA system and procedure
to receive RF ablation treatment. For example, such patients could
be those requiring anticoagulation medication for cardiac or
neurological problems who should not risk bleeding from a punctured
urethra.
[0026] In a technique performed according to the present invention,
an RF heat lesion is made to ablate the urethra and the
periurethral region (i.e., tissue near or on the urethral tube) to
induce necrosis of the prostate tissue near the urethra and of the
urethra itself. This induces a symmetric cavity to be formed via
obliteration of the urethra and the central region of the prostate
in the patient's body a few days after the procedure is performed.
The cavity provides direct communication to and widening of the
urethral channel. In accordance with one embodiment of the
invention, lesion sizes of 1 to 2 cm diameter can be made, which
thereafter induce similar sized cavities to be formed, thereby
enlarging the urethral passage. These exemplary lesion sizes,
similar to those made by the TURP procedure, have proven to be
adequate to provide relief from BPH.
[0027] It should be noted that in contrast to McGahan et al.'s
conclusion that such lesion sizes are inadequate for the ablation
of prostate carcinomas, the lesion sizes are adequate in treating
BPH.
[0028] Also, the present technique avoids the need to observe
McGahan et al.'s admonition to avoid heat injury of the urethra,
and corresponding necessity for the irrigation and cooling of the
urethra as suggested by the article by McGahan et al. By ablating
the urethra itself, the present technique has the added advantage
of avoiding the possibility of necrotic tissue and liquid becoming
entrapped outside the urethra if the urethra is left intact, as in
the case of the TUNA and McGahan et al. procedures.
[0029] The system and procedure of the present invention differs
from TUMT techniques which seek to preserve the urethra by fluid
cooling within the electrode catheter. The present technique seeks
to ablate a portion of the urethra and periurethral tissue and so
directly widen the urethral channel. The present technique has the
advantage over the TUMT technique of not requiring added
coolant-carrying channels within the catheter which increase
complexity and cost of the TUMT electrode systems. The electrodes
of the present invention are also simpler than the TUMT devices.
The present invention involves a simply constructed RF electrode
that makes direct electrical contact with the urethra as compared
to an internally located and complex microwave antenna structure in
the case of the TUMT device.
[0030] The system and method of the present invention has the
further advantage of increased simplicity, safety, and economy. The
electrode structure is of a simple construction and geometry in one
form not requiring coolant channels (although other versions can be
made with cooling channels). This has the advantage that the
catheter and electrode are easy to construct and therefore
economical. It can be inserted easily by any urologist or clinical
assistant. Also, it is well tolerated by patients, even those who
are in frail health. It is safe, because the simple use of the
inflatable balloon within the urethra combined with catheter
traction and X-ray imaging with contrast injection assures the
correct positioning of the conductive RF electrode within the
urethra and prostate.
[0031] These features and advantages as well as others of the
present method and system will become apparent in the detailed
description that follows.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] In the drawings, which constitute a part of the
specification, embodiments exhibiting various forms and features
hereof are set forth, specifically:
[0033] FIG. 1 shows an embodiment of a prostate ablation electrode
integrated with a balloon tip catheter with an externally
positioned RF electrode and added elements for expanded lesions or
temperature sensing in accordance with the present invention.
[0034] FIG. 2 shows a schematic diagram in partial sectional view
of a balloon catheter of FIG. 1 with RF electrode portion, RF
connections, and temperature sensors in accordance with the present
invention.
[0035] FIG. 3 shows a cross-sectional view of the RF balloon
catheter of FIGS. 1 and 2 in accordance with the present
invention.
[0036] FIG. 4 shows another cross-sectional view of the RF balloon
catheter of FIGS. 1 and 2 in accordance with the present
invention.
[0037] FIG. 5 shows another cross-sectional view of the RF balloon
catheter of FIGS. 1 and 2 in accordance with the present
invention.
[0038] FIG. 6 shows another cross-sectioned view of an RF balloon
catheter with a multi-sector electrode in accordance with the
present invention.
[0039] FIG. 7 shows another cross-sectioned view of an RF balloon
catheter with an asymmetrical electrode in accordance with the
present invention.
[0040] FIG. 8 shows another embodiment of the present invention
having a catheter with internal cooling channels and segmented RF
electrodes.
[0041] FIG. 9 shows a flow chart of a process employed in operating
a system in accordance with the present invention; and
[0042] FIG. 10 illustrates a cavity in the prostate contiguous with
the urethra induced by a system and method according to the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0043] FIG. 1 shows one embodiment of a system and procedure
according to the present invention involving a catheter structure
201, which is passed into the urethra U through the penis PN. The
catheter 201 has an RF electrode ring structure 202, which is
positioned in prostate P according to clinical needs to alleviate
urethral obstruction. At the distal end of the catheter, there is
an inflatable balloon structure 210 shown in an inflated state.
There is further a distal tip 214 which defines an opening (i.e.,
port) 217. Urine within bladder B can flow according to an arrow F1
into the opening 217 and out a proximal end of the catheter, as
illustrated by an arrow F2.
[0044] Rubber catheters with balloon ends are used commonly by
urologists. Examples of such catheters are SILASTIC.RTM. Foley
catheters distributed by the Bard Urological Division of Covington,
Ga.
[0045] FIG. 1 shows an embodiment of the present invention in which
such a catheter is augmented by the RF ring structure 202 and other
components. In the disclosed embodiment, the ring structure 202 is
connected internally through the catheter 201 to an RF hub portion
220, a connection cable 224, and a high frequency generator 227.
The generator 227 supplies a high frequency electrical signal
(e.g., a radio-frequency "RF" signal) to the RF electrode ring
structure 202. The resulting heating of the tissue near the
electrode caused by high frequency current dissipating power into
the tissue can give rise to an ablation isotherm surface 230 (the
dashed line).
[0046] Temperature sensors may be located at multiple points along
the catheter 201 within the prostate. The temperature sensor may be
built inside the catheter or on its surface. The sensor may be a
thermistor, thermocouple, or other type of temperature sensor.
Temperature signals may be carried by connection wires (e.g.,
connection 234) extending inside the catheter to an external tissue
temperature monitor (represented by tissue monitor 237) to enable
thermal monitoring of the ablation process by the clinician as
described previously. Specifically, the measured temperature at the
sensor is representative of the temperature of the urethra and the
nearby prostate tissue.
[0047] Alternatively, the tissue monitor 237 could monitor the
impedance of the tissue at the ring structures 202 or 300. This can
give an indication of location in the prostate or the nature of the
RF ablative heating process.
[0048] Monitoring of high frequency output parameters from the
generator 227 may be accomplished by monitor 240. The monitor 240
may have lesion parameter readouts such as a digital meter reading
for display of power, current, voltage, impedance, or other
parameters associated with the RF lesion process.
[0049] The system in accordance with the present invention, shown
in FIG. 1, may be used according to the following illustrated
example. The catheter 201 is sterile and disposable. It includes an
RF ring structure 202 with hub or connection structures 220, as
described above. The catheter 201 is inserted into the penis PN
according to common practice until the balloon structure 210 is
within the bladder B. The balloon is then inflated by a syringe 260
attached to an inflation hub 264, which is standard on Foley
balloon catheters. Inflation by the syringe plunger 270 injects
fluid (gas or liquid) into the balloon 210, thereby inflating the
balloon and enabling it to be retained within the bladder B.
Contrast fluid that is visible on X-ray or fluoroscopic images of
the patient's body can be used to inflate the balloon and thus
confirm the balloon's position. An internal channel within the
catheter 201 communicates the gas or liquid inflation from source
260 to the balloon 210.
[0050] Once the catheter is so entrapped within the bladder B by
the inflation of the balloon 210, urine within the bladder B can
flow according to the arrow F1 through the distal tip opening 217.
It can drain through an internal channel and out of the catheter by
a catheter hub (i.e., a drain port) 280, as illustrated by the
arrow F2. The internal channel within catheter 201 connects the
hole 217 at the tip to the drain port 280. With the balloon
inflated inside the bladder, X-ray contrast medium may be injected
through the hub 280 into the bladder B. An imaging system 285 such
as a fluoroscope or X-ray machine can then be used to image the
catheter tip 214, the balloon 210, the bladder B, and the RF
electrode ring structure 202 together. A separate display device
290 maybe used for providing the image. For example, an X-ray
imaging detector may collect X-ray images from X-rays emitted from
an X-ray imaging system 285. The detector 290 is within the field
of imaging illustrated by the dashed lines 293 and 294. Such X-ray
images may be used to verify that the RF electrode 202 is properly
placed with respect to the bladder and the prostate P. Imaging
machine 285 could alternatively represent a CT, MRI, ultrasound, or
other type of imaging device. Safety is increased by imaging
confirmation that the RF ring structure 202 is within the prostate
at a desired point, typically at the point of urethral obstruction.
For example, it may be desired to position the RF electrode 202
sufficiently away from the sphincter SP, which is a critical
structure that if ablated could cause incontinence. The imaging
step plus the balloon immobilization can help to assure this.
[0051] Another step to help secure the catheter and RF electrode in
place, and to confirm that placement, is to pull gently (apply
traction) on the catheter by the hub 280. This will draw balloon
210 snugly against the bladder neck region AP. It will in turn
securely position the RF electrode 202 at its desired position in
the prostate P. This is a significant advantage of the present
invention because it ensures in a simple way to confirm that the
positioning of the catheter is correct and that the catheter will
not move. Repeated X-ray contrast injection and imaging is easily
done to double check the proper positioning at any time.
[0052] Connection of the RF electrode 202 to the high frequency
generator 227 can then proceed by the connection 224. The
connection 224 runs inside catheter 201 to the electrode element
202 and/or 300. Controls 228 control the power level of the RF
output from generator 227 to provide the heat ablation around the
RF electrode 202 at the desired levels. Such controls may be manual
knobs, automatic processes, computer controls, etc.
[0053] The radio-frequency generator 227 may be an electrical unit
with, for example, a radio-frequency, microwave, or other high
frequency power supply that can deliver a high-frequency electrical
signal to the electrode 202. In accordance with known technology
for generating radio-frequency (RF) lesions, as described in the
Cosman and Goldberg articles described above, a high-frequency
signal applied to the exposed electrode 202 generates a heated
region around it, which in turn produces a heat lesion or ablation
zone 230 around the exposed electrode 202. The size of the ablation
zone or heat lesion 230 may be increased by increasing the power
that is applied to the tissue from the energy source 227. Thus, the
size or volume of the ablation zone 230 can be graded and
controlled around the urethral channel.
[0054] Also shown is a reference surface electrode 203 which is
connected to generator 227 by cable 231 and contacts the patient's
body PB (e.g., the patient's skin or other part of the body). (To
reduce the complexity of FIG. 1, only a portion of the patient's
body PB is shown.) The electrode 203 serves, as is common practice,
as a reference or return electrode for the RF current emitted from
the RF electrode 202. This is a standard electrical arrangement for
so-called monopolar RF ablating (described in the paper by E. R.
Cosman cited in the Background section above). Examples of RF
lesion generators and RF electrodes using this configuration can be
found in the product literature of Radionics, Inc., Burlington,
Mass.
[0055] A specific illustration of how urinary blockage is reduced
in accordance with the system of FIG. I follows. By carefully
placing the RF electrode within the catheter and positioning the
exposed conductive electrode 202 in an appropriate portion of the
urethra U where there is a urinary obstruction, an effective
ablation of the prostate can be accomplished. By supplying an RF
output from the energy source 227 to the electrode 202, heating of
the urethra adjacent to the electrode 202 and the surrounding
periurethral tissue in the vicinity of the electrode will
occur.
[0056] When RF energy is delivered from the energy source 227, as
in FIG. 1, dissipation of the energy around the RF electrode 202
causes a heating zone to occur around the electrode. This will
cause a zone of heat ablation 230, which engulfs the urethra U and
the periurethral tissue within the dashed line volume. The zone 230
indicated by the dashed line would, for example, illustrate a
typical isotherm surface area or area of constant temperature
within which all tissue is raised to a lethal or ablation
temperature. An example of a desired temperature for ablation to
kill prostate tissue is approximately 50.degree. C. maintained for
six minutes. It should be recognized that variations, depending on
the desired outcome, are possible.
[0057] An ablation isotherm surface, therefore, is an indication of
the region in which the cells are dead. At 50.degree. C. or higher
temperatures, tissue necrosis is induced in the isotherms within
the volume encompassed by the isotherm surface area. Liquefaction
of the necrotic tissue occurs within days from the day of
treatment. If such an ablation isotherm area (corresponding to
ablation or necrosis), as illustrated by the dashed line 230,
engulfs the urethra in the region where there is a urethral
restriction, then in a matter of days after treatment, the entire
periurethral zone, including the urethra within the isotherm
surface area, is obliterated and liquefied. The flow of urine from
the bladder through the urethra will then carry away the
liquefaction and debris from the necrotic tissue away and out of
the body through the urethra.
[0058] FIG. 10 illustrates the effects induced by the system and
method for RF urethral enlargement by thermal ablation according to
the present invention. The inventive system and procedure
obliterates the urethra and region within the ablation isotherm
surface boundary to induce a cavity 800. The urethra and prostatic
tissue that previously was within this cavity volume has been
necrosed and liquefied and passed out through the urethra U by the
flow of urine, indicated by the arrows F, from the bladder B out
through the penis PN (FIG. 1). The urethral wall has been
obliterated to open the channel in communication with the remaining
segments of the urethra. The cavity 800 is generally symmetric
about the urethra to open a lumenal volume, thereby reducing the
restriction of flow that previously existed with the urethral
obstruction. Because the cavity 800 is located around the urethra,
it is typically axially central to the prostatic gland. There is
the advantage that the cavity has a smooth, contiguous continuity
with the urethral structures connected to it, increasing the
likelihood of laminar fluid flow after the cavity 800 has been
formed. Since the cavity is in the periurethral region, the
inventive technique also has the advantage that it is remote from
various critical structures such as nerves in the outer prostate
and the rectal wall.
[0059] By way of further explanation, the urethral wall and the
periurethral tissue that is in the area of the zone of necrosis is
liquefied and carried away by urine flow F. As the urethral
cross-sectional area is increased, the impedance to flow of the
urine is substantially reduced and the flow vector F is increased
in magnitude, restoring normal voiding function or improving
voiding rate. The body reacts to this procedure by creating a new
epithelial layer of cells, within a matter of a few weeks, to cover
the interior surface of the cavity 800.
[0060] Because a typical isotherm surface area (in ablation zone
230, FIG. 1) is created in a generally central area of the prostate
due to the intra-urethral location of the RF electrode, the
peripheral annulus of the prostate acts as a natural margin of
safety or thermal buffer zone for the critical organs, which
typically lie outside the peripheral region or just outside the
prostate. These would include critical nervous structures and the
rectum wall and mucosa.
[0061] In accordance with one embodiment, a heat lesion of desired
size is formed by controlling the temperature of the heated urethra
and prostate tissue immediately surrounding the RF electrode 202 to
approximately 90.degree. C. At this temperature using, for example,
a catheter with a diameter of approximately 2 mm, an ablation
volume may be formed having a diameter of approximately 1 to 1.5
cm. This ablation volume will engulf the urethra and the
periurethral tissue and be entirely contiguous with the remaining
urethra connected to it. The size of the heat lesion is
visualizable on CT or MRI image scanning at the same time or after
the lesion is made.
[0062] In accordance with other embodiments, depending on the
lesion sizes desired, other electrode temperatures or prostate
tissue temperatures ranging, for example, between 50 and
100.degree. C. are used. The desired lesion sizes are determined
(for example 0.3 to 5.0 cm) depending on the size and geometry of
the patient's prostate or urethral obstruction or other clinical
considerations.
[0063] Typically, the energy source 227 has a power range from 0 to
approximately 50 watts, although 20 watts or less is generally
adequate to achieve the temperatures cited above.
[0064] In various embodiments, a typical catheter 201 may have a
diameter in the range of 1 to 10 mm to produce lesions of a few
centimeters. The width of the electrode may be, for example,
between 5 to 60 mm, depending on the application. It should be
recognized that varying sizes, geometries, electrode
configurations, diameters and lengths, etc. may be used for the RF
electrode 202 to produce RF heat lesions.
[0065] The catheter 201 may have properties to optimize
visualization. For example, a roughened surface on components of
the catheter 201 may make it more exogenic and visible in
ultrasonic imaging. Furthermore, a metal electrode may be visible
in an X-ray image to locate the position of the electrode in the
prostate during the procedure. Alternatively, the catheter may
include MRI or CT compatible material so that it is visible in MRI
or CT imaging without substantial artifacts. These imaging
techniques may be used prior, during, or after the procedure to
monitor the placement of the catheter and the progress of the
necrotic periurethral cavity after ablation.
[0066] The embodiment of FIG. 1 shows the RF electrode ring
structure 202 in an intra-urethral position. As discussed above,
the heat generated in the tissue near the ring structure 202
produced by connection of the electrode 202 to the generator 227
will ablate and necrose the urethra and periurethral prostatic
tissue near the RF electrode ring 202. Also shown on the catheter
201 is a second element 300 which in various embodiments can be a
second RF electrode or a temperature sensor. For example, if the
region of ablation 230 (the dashed line) needs to be extended to
include a region around the electrode 300, then the output from the
generator 227 could be applied to the electrode 300. This could be
accomplished by a switching system in control unit 228 and
appropriate cable connections within connector 224 and 220. This
illustrates that multiple RF electrodes can be placed on the same
catheter structure 201 to grade the size of the ablation according
to clinical needs.
[0067] Alternatively, if the structure 300 contains temperature
sensors, then the tissue monitor 237 can read out tissue
temperature near the structure 300 as an indication of ablation
size. For example, if the temperature sensor in 300 reads less than
50.degree. C., then this would indicate that the ablation zone 230
has not reached into the region near the structure 300.
[0068] In another example, the impedance of the tissue near
elements 202 or 300, or between these elements, could be measured
and monitored by the tissue monitor 237. The tissue monitor 237 can
be used to determine if the catheter and electrodes are properly
placed in the prostate tissue or to determine if the ablation
process is complete. Impedance values and changes may indicate the
kind of tissue near the electrodes and may indicate if heat
ablation has occurred.
[0069] In accordance with another embodiment of the present
invention, the catheter may not include the temperature sensor. The
correlation of an ablation size desired to a certain electrode
geometry may be determined by considering RF generator parameters
such as power output, voltage, and current. Generally, it can be
determined that ablation temperatures of greater than 50.degree. C.
in the prostate tissue can be induced, for example, by way of RF
power or current levels greater than known amounts. This
information can be used by clinicians to induce sufficient ablation
sizes to alleviate urinary obstructions by the intra-urethral
method, depending on clinical circumstances.
[0070] Readout of RF output parameters from the generator 227 can
be accomplished by a monitor and display system in the monitor 240
or the generator 227 itself. In various embodiments, this system
may involve computers, controls, feedback systems, electronics, and
even computer graphic displays to illustrate the parameters by a
computer graphic workstation during the progress of the
ablation.
[0071] In the exemplary embodiment of FIG. 1, the catheter 201 can
be made from SILASTIC.RTM. rubber, as manufactured by Dow Corning,
of Minneapolis, Minn. Its diameter is approximately 2 to 8 mm, and
its length is in the range of 30 to 40 cm. However, other smaller
or larger dimensions may suit varying clinical needs. The electrode
structures 202 and 300 can be made from stainless steel rings and
bonded to the SILASTIC substrate of the catheter 201. Other
materials or plated structures may also be used, including but not
limited to Inconel, titanium, or copper plated with gold, or other
materials, structures, or metals to suit various clinical needs.
The balloon structure and body of the catheter could be similar to
the Foley catheter mentioned above with inflatable balloon 210,
distal tip 214, port 217, an injection port 264, and the main
urinary drainage hub 280. In addition, the hub or other connection
220 for the high frequency and thermal monitoring cabling can be
adapted to connect the RF electrode 202 or element 300 to the
external devices 227, 228, 237, or 240. Internal connection wires
within the SILASTIC rubber body of the catheter 201 connect to the
RF electrodes 202 and 300, as well as to temperature sensors within
the catheter at various points.
[0072] A urological RF catheter, as in FIG. 1, is easily inserted
into the urethra and can remain in place within the patient for
several days. Diagnostic X-ray images can be taken with an X-ray
imaging machine, as illustrated by the X-ray system 285 and the
imaging detector 290. This confirms the position of the RF
electrode ring 202 in the prostate. Intra-urethral RF ablation is
performed when the positioning of the catheter is appropriate, and
can be repeated and enlarged as necessary according to the
description above. As stated above, the catheter can be left in
place in the patient with the balloon inflated for several days
after ablation until the ablated zone has fully liquefied. The
catheter balloon can then be deflated, and the catheter removed
from the urethra, whereupon the necrotic fluid from the ablation
zone and the obliterated portion of urethral tissue will be washed
away by the urine flow from the bladder B out the urethra.
[0073] One advantage of using a catheter-type RF electrode such as
the embodiment shown in FIG. I is that minimal anesthesia is
necessary in inserting the electrode into the urethra. Such
catheter structures are familiar to urologists and can be inserted
into the patient in the supine position with ease and comfort. A
further advantage is that no endoscope is needed to insert it into
the urethra or to visualize its position in the prostate. It can be
used in an office setting, and not necessarily in a sterile
operating room environment, thereby making the procedure more
widely available to patients and reducing hospital expenses. It is
also relatively economical because it has low construction
complexity and can thus be used disposably from a factory-packaged
sterile pouch. This is of increasing importance in an increasingly
cost conscious medical environment.
[0074] Also shown in FIG. 1, as an augmentation of the system, is
an external coolant supply 273 with cooling connection(s) 271. This
may supply cooled fluid such as saline to flow within a
recirculating channel in catheter 201 to cool the electrode 202.
Such cooling capability may or may not be included in the balloon
catheter depending on clinical needs.
[0075] Referring now to FIG. 2, a cross-sectional diagram
illustrates various aspects of the distal end of a balloon
radio-frequency urethral catheter in accordance with the present
invention. This sectional view, which shows only the distal section
of a catheter embodiment of the present invention, may correspond,
for example, to a catheter similar to that in FIG. 1 described
above. The catheter body 501 may be made of a rubber material such
as silicone. It may be soft and flexible to accommodate the
delicate urethral environment. At the distal end is the inflated
balloon 507, which also is made of a thin elastic rubber such as
silicone. The balloon 507 may be secured in a sealed fashion by
joints such as 511 to the catheter material 501. A channel 514
inside the catheter structure 501 allows an inflating fluid such as
air or saline to fill the interior of the balloon 507. Injection of
the fluid is indicated by the arrow 517, which may correspond to
the influx of air as produced by the plunger system 260 in FIG. 1.
The channel 514 may connect to the interior of the coupling hose
267 that attaches further to the inflating system 260 in FIG. 1. A
side window 520 (i.e., port) in the wall of the catheter, but
inside the balloon region, allows the in-flowing air to inflate the
balloon, as indicated by the arrow 522.
[0076] At the distal tip 530 there is a hole in the body of the tip
534, which may correspond to the hole 217 in FIG. 1. When the
catheter is inserted into the urethra and the balloon is secured
within the bladder, as shown in FIG. 1, then urine can flow into
the hole, as indicated by the arrow 537. An internal channel 540 is
constructed within the body 501 of the catheter to allow the flow
of the urine backwards towards the hub end of the catheter
structure. For example, referring to FIG. 1, the channel 540 may be
connected to the proximal hub 280 to allow the outflow of urine, as
indicated by arrow F2.
[0077] An RF conductive electrode 550 is shown in a location
proximal to the balloon 507. It may be, for example, a metal
conductive ring which is bonded to the catheter rubber structure
501 with appropriate silicone cement. The length of the ring is
indicated by L in FIG. 2. It is spaced by a distance D from the
proximal portion of the balloon 507. The parameters L and D may be
specified according to clinical needs and the particular anatomy of
the patient being treated. For example, if it is known that a
larger lesion is to be made because of a longer portion of urethral
obstruction, then the length L could be made longer. The length of
the RF electrode may range from one to several millimeters, and
even as much as a centimeter, or two, or more. The distance D may
also be gauged depending on how far back from the neck of the
prostate the heat ablation is desired to be located. D may also be
a parameter which is specified according to clinical needs. For
example, balloon catheters may come in various model numbers with
specification of L and D and the diameter of the catheter body
itself according to clinical criteria
[0078] Also shown in FIG. 2 are wire electrical connections 544 and
547. These connect to or are near to the RF electrode 550. For
example, wires 544 may be welded or bonded at point 551 to the RF
electrode 550. The wires 544 may provide the connection to the high
frequency generator 227 in FIG. 1 (i.e., they are electrically
connected to the cable 224). Also, electrical connection wire(s)
547 may be a thermal-sensing or impedance-sensing connection to a
point 557 near or on the surface of electrode 550. For example,
element 557 may be a thermistor or thermocouple junction, and the
connection cables 547 may be electrical connections to a thermal
sensor (e.g., tissue monitor 237, FIG. 1) that enables readout of
the temperature of prostatic tissue near the RF electrode 550
during the heating process. The electrical connectors 544 and 547,
for example, may be directed within the channel 540 and branched
through the rubber wall of the catheter at its proximal end to the
connection 220, as shown in FIG. 1. Connectors 544 may connect to
cables 224, and connections 547 may connect to cables 234 and/or
224. It should be understood that the electrode 550 may consist of
several segments as discussed herein. In this case, several
connectors (544/547) may be used to connect to each segment of the
electrode 550.
[0079] FIG. 3 illustrates a cross-sectional view of the catheter
embodiment shown in FIGS. 1 and 2 and through the section plane A
indicated in FIG. 2. The catheter in this example is generally of a
rounded form comprising the body material 560. The inflation
channel within that body is illustrated by 564 and corresponds to
the channel 514 in FIG. 2. The draining channel for urine discharge
from the bladder is illustrated by 567 and corresponds to the
channel 540 in FIG. 2. These channels could be molded within the
catheter body 501 of FIG. 2 by extrusion or casting. The two
channels 567 and 564 are sufficient to provide urine drainage from
the bladder and air inflation of the balloon, respectively.
Uni-directional flow (channel 567) of the urine from the distal to
proximal end and a unidirectional flow (channels 564) of the air
from the proximal to distal end would implement the drainage and
inflation functions. Alternatively, injection of contrast medium
into the balloon in the bladder in channel 564 would involve flow
from the proximal to distal end of the catheter.
[0080] Referring to FIG. 4, a sectional view of the catheter
structure of FIG. 1 and FIG. 2 is shown through the sectional plane
B of FIG. 2. The silicone rubber body 570 of the catheter is
surrounded in this example by the metal ring 571 (which may
correspond to electrode 550, FIG. 2). This ring may be a thin
stainless steel ring which is bonded by silicone cement to the
silicone catheter base 570. It may be made of other materials which
suit the clinical need. For example, if the structure is desired to
be MRI compatible, the ring could be made of titanium, copper, gold
plated copper, or Inconel, depending on the design criteria. Again,
the channels 564 and 567 are shown. The RF electrode conductor
element 571 (550, FIG. 2) is positioned on the external surface of
the catheter structure. Thereby, when inserted into the urethra,
the RF electrode 550 will be in direct electrical contact with the
urethral tissue immediately adjacent to it (see electrode 202 in
FIG. 1). Thus, current from the high frequency generator 227 in
FIG. 1, when connected to the catheter, will emanate directly into
the adjacent urethral tissue from the RF electrode 550. This will
cause radio-frequency or high frequency heating of the urethra and
immediately adjacent (peri-urethral) tissue in accordance with the
present invention.
[0081] Referring to FIG. 5, a sectional view of the catheter shown
in FIG. 2 is illustrated through the plane C of FIG. 2. The rubber
flexible body 580 is shown with channel 564 and 567, as described
above. The electrical connections 544 and 547, as shown in FIG. 2,
are illustrated here in sectional view by the elements 584 and 587,
respectively. These electrical connections could be made of a
variety of metals and could have multiple electrical strands within
them, each insulated one from the other. The connections may
contain copper, stainless steel, braided metal, thermocouple
junction wires, or other electrical materials with appropriate
insulation to suit the construction and clinical needs. For
example, if flexibility and strength are needed to produce the
electrical connection to the RF electrode 550 in FIG. 2, then
structure 584 may be a stainless steel braided wire together with a
copper electrical conductor to produce low impedance and
structurally sound connection. Element 587 may provide connections
to a temperature sensor, in which case a bi-metal pair of
thermocouple wires may be used, each separated one from the
other.
[0082] It is noted that various types and configurations of RF
electrode structures are possible. For example, instead of a solid
metal ring, element 550 in FIG. 2 could be a spiral wound or
braided electrical wire structure and fixed onto the external
surface of the catheter or built into the underlying substrate of
rubber body 501. The catheter may have embedded in it wires within
the rubber portion 501 to form a mesh or braid of exposed
electrical elements to produce a similar RF conductive electrode
surface.
[0083] FIG. 6 shows another embodiment of the invention wherein
rather than a continuous circular, cylindrical ring, such as
illustrated in FIG. 2 and FIG. 4, the RF element could be sectors
601 and 602 of a ring bonded onto the surface of the body 570 in
FIG. 4. These annular sectors, therefore, could give directional
selectivity to the heating of the urethra and surrounding prostate.
For example, a left semi-circle 601 and right semi-circle 602 could
be present instead of the continuous circular ring in FIG. 4. If
each semi-ring is connected to the opposite poles of the output of
generator 227 in FIG. 1, then there would be a bipolar electrical
configuration. Accompanying independent electrical connection wires
606 and 608, analogous to wire 547 in FIG. 2, within the body 501
of the catheter could make connection from the generator 227 to the
independent bipolar electrode surfaces of 601 and 602, as just
described.
[0084] FIG. 7 shows another variant on the construction of the
example shown in FIG. 2 and FIG. 4 in which the cylindrical ring
571 is insulated on a portion of its area by the insulation layer
630. When connected to the RF generator, this would project the
radio-frequency current into the surrounding tissue through the
exposed portion of ring 571 to one particular azimuthal angle (the
left side of the catheter as viewed in FIG. 7) relative to the
catheter body 570. Thus selective heating in the particular
direction may be implemented. The insulation layer 630 may be
constructed of, for example, plastic, Teflon, polyurethane,
polyethylene or some other type of insulating coating or sheet.
[0085] As another embodiment of the invention, multiple
radio-frequency electrode conductive sectors such as 550 in FIG. 2
may be placed along the elongated length of the catheter 501. For
example, several rings (or portions of rings) such as ring 202 or
300 in FIG. 1 may be present that are spaced apart in the
longitudinal direction of the catheter. They may have independent
electrical connections analogous to the connection 544 (and/or 547)
to ring 550 in FIG. 2. The clinician may then have the option of
connecting one or more or a variety of patterns of the electrical
rings to produce smaller or larger or more selective heat ablations
of the urethra and the prostate surrounding it. The application of
output from the generator 227 to a multiplicity of such rings
spaced in known positions along the catheter may be controlled by
the controller 228 in FIG. 1. Thus the size, length, and depth of
the heat ablation within the urethra and the periurethral tissue
may be graded and changed according to clinical needs.
[0086] Again, as shown in FIG. 1, other electrical rings such as
300 could be present on the catheter. This would also require
electrical connections, which could be run along the elongated
length of the catheter from the distal electrodes, to the proximal
hub, and out to external apparatus. Such connections might comprise
additional radio-frequency connectors to the generator, impedance
monitoring connections to an impedance monitor, or thermo-sensing
connections to thermal sensors in the catheter. Such electrical
connections could also be drawn through the channel 540 of FIG. 2.
Alternatively, all of the electrical connections as shown in FIG. 2
could be embedded within the walls of the rubber catheter structure
itself, and become an integral part of the cross-sectional
structure rather than being passed through fluid (liquid or air)
channels within the structure. In a further alternative embodiment,
a separate channel could be placed within the catheter to house
only the electrical connections. A variety of geometric and
configurational variations are possible to construct catheters in
accordance with the present invention by those skilled in the art
of making such implant catheters.
[0087] Referring to FIG. 8, an alternative embodiment of the
present invention is shown as illustrated by a cross-sectional view
through a catheter such as in FIG. 1 in which cooling channels are
introduced into the catheter structure to enable cooling of the RF
electrode portions. For example, in the catheter as shown in FIGS.
1 and 2, it may be desired in certain situations to enlarge a
lesion size within the prostate and therefore to have the option of
cooling the RF electrode ring 571 or not cooling the RF electrode
ring 571. In this way, for example, a urethral and periurethral
lesion can be made by not cooling the ring 571, and previously or
subsequently an enlarged lesion may be made to engulf more of the
prostate by cooling the exposed portions of the RF electrode ring
571 during the application of RF power to the prostate.
Construction of cooled RF electrodes has been described by Goldberg
et al. and referred to in the Background section above. The
catheter in FIG. 1 may have added ports at or near the hub end 280
to accommodate circulation of coolant fluid into the catheter from
an external coolant supply 273 and through internal cooling
channels, as shown in FIGS. 1 and 8.
[0088] As illustrated in FIG. 8, the catheter body is illustrated
as for example through section B in FIG. 2. The catheter body 560
again is made of a flexible rubber. The balloon inflation channel
564 and urine drainage channel 567 are present, as above. A
conductive, surface mounted RF electrode ring 571 is cemented to
the body 560, as in the previous examples. In addition in this
embodiment, added channels 640 and 641 are shown in cross-sectional
view. Channel 640 may carry cooling fluid from the proximal hub to
the region of the distal RF electrode, and channel 641 may carry
the coolant fluid back from the RF electrode to the proximal hub.
Illustration of coolant connection 271 and coolant supply 273 are
shown in FIG. 1. The two channels may be connected within the
catheter near the catheter's distal end to enable the fluid
recirculation. This circulation process thereby would cool the
exposed RF electrode surfaces that are in contact with the urethral
tissue. For example, in the embodiment of FIG. 8, there are
insulated portions 633 and 637 which cover a portion of the
electrode ring 571. The exposed electrical surfaces 644 and 647 are
then sectors along the ring. The proximity of the cooling channels
640 and 641 will cool the exposed surfaces 644 and 647,
respectively. Thus, if an enlarged lesion is desired within the
prostatic tissue, the RF power can be applied as in the examples
above, thereby heating the tissue in proximity and at a distance
from surfaces 644 and 647. The degree of power can be increased and
the degree of urethral ablation enlarged by use of the cooling
channels 460 and 461. By reference, the use of cooled RF electrodes
is described in the papers of Goldberg, as cited above.
[0089] In a situation where only a urethral and near urethral
tissue ablation is desired, cooling channels such as those shown in
FIG. 8 are not necessary or may not be used to circulate coolant.
As for example in the examples of FIGS. 2, 3, 4, 5, 6, and 7, a
more simplified internal channel structure with only balloon
inflation and urinary drainage channels are shown, which will
reduce the complexity and the cost of such a balloon type RF
ablation urethral electrode.
[0090] It is further noted that if a balloon type distal end for
the catheter electrode is not present, as described in several
embodiments of the parent application, then the catheter
cross-sectional structures become even simpler. If there are no
inflation or drainage channels within the catheter and no cooling
channels within the catheter, then there can be no need for any
such channels at all. The electrical connections, as shown in the
above figures for the radio-frequency connection, temperature
connection, impedance monitoring, etc., may be either embedded
directly in the flexible rubber of the catheter or they may be
passed through an internal channel whose function is to allow such
electrical connections to be assembled within the catheter in the
manufacturing process.
[0091] Referring now to FIG. 9, a flow chart is shown to illustrate
the process of intra-urethral RF ablation using a balloon catheter
for relief of urinary obstruction. The procedure starts by
selecting the appropriate RF balloon catheter (step 700). This may
involve selecting the diameter, length, balloon size, ring
dimensions and positions, use of multi-ring balloon catheter, use
of catheters with temperature sensing, impedance monitoring rings,
multiple temperature sensors along its longitudinal length, and
other specifications of the balloon catheter, some of which have
been described above in connection with FIGS. 1 through 8. For
example, by knowledge from diagnostic imaging of the size of the
patient's prostate and the position of the obstruction, the
appropriate length of RF electrode segment L, as shown in FIG. 2,
as well as its separation D from the balloon, as shown in FIG. 2,
may be selected. For this purpose, the catheters may come packaged
with particular dimensions of L, D, catheter diameter, catheter
length, etc. to suit specific clinical needs.
[0092] The next step may be insertion of the catheter into the
urethra (step 704). Insertion of catheters is a common technique
and can involve use of Foley-type catheters for urine drainage.
During this step, diagnostic imaging such as ultrasound, CT, MRI,
or X-rays may be used to monitor the position and depth of the
catheter. For this purpose, the catheters as shown in FIGS. 1
through 8 above may be in part radiopaque or have radiopaque
markings on them so that their tip position and electrode position
can be visualizable in X-ray, CT, MR, or other types of
imaging.
[0093] Referring further to FIG. 9, once it is determined that the
tip end of the catheter is properly within the patient's bladder,
the balloon tip may be inflated within the patient's bladder (step
708 in FIG. 9). This step may be followed by further imaging (e.g.,
ultrasound, CT, MR, fluro, or X-ray diagnostic imaging) to confirm
that the balloon is properly placed. For example, in step 711 of
FIG. 9, a radiopaque contrast medium (contrast agent) is injected
into the bladder through, for example, the hub 280 in FIG. 1 so
that it emanates from the port opening 217 in FIG. 1 to produce a
radiopaque contrast of the bladder (step 711). In this way, the
position of the balloon within the bladder and against the neck AP
in FIG. 1 can be confirmed. Alternatively, step 708 may involve
inflating the balloon with radiopaque contrast fluid for X-ray
confirmation.
[0094] The balloon may be secured in its position by applying
traction or gentle pulling (step 714 in FIG. 9) so that the balloon
fits snugly against the neck of the prostate and bladder junction.
At this point, the RF electrode ring 202 is at a known position
relative to the neck of the bladder. That position may be
pre-selected by the dimension D, as shown in FIG. 2. This is a
simply implemented but important safety step to assure the proper
location of the RF electrode with respect to the prostate prior to
making a heat ablation.
[0095] At this point, further X-ray, fluoroscopic, ultrasound, or
other imaging confirmation may be used to verify that the RF
electrode and the balloon are in the proper place (step 716). When
this confirmation is made, the connections to the external RF
generator may be made as shown in FIG. 1, and the output from the
generator 227 of FIG. 1 may then be delivered through the catheter
connections to the RF electrode 202 in FIG. 1 (step 721).
[0096] As the heat ablation process begins, the ablative
destruction of the urethra and periurethral tissue will begin and
increase near the position of the RF electrode. This process can be
monitored by observing the high frequency generator parameters on
monitoring device 240 in FIG. 1 (step 724 of FIG. 9). Various other
tissue monitoring such as temperature sensing and impedance
monitoring at the RF electrode or ancillary rings such as 300 in
FIG. 1 may be carried out in this step 724. The control of the RF
generator may be done manually, automatically, or by computer, as
in the control unit 228 of FIG. 1.
[0097] In step 727 of FIG. 9, the clinician determines the
sufficiency of the heat ablation to produce the desired clinical
effect of reducing urinary obstruction. This will be based on his
experience, the visualization of the ablation parameters, and the
particular clinical situation.
[0098] To elaborate further on the steps of making the heat
ablation, the step 721 of FIG. 9 can involve elevating the voltage,
current, or power applied by the high frequency generator. The
generator may have manual controls such as knobs or other elements
to control its output levels that can be actuated at this point.
Alternatively, the process may be automated with a set power or
temperature level predetermined on the generator control system and
an automatic or semi-automatic achievement of that high frequency
control parameter reached by an appropriate feedback and control
system within the generator. These elements can all be built into
the energy source 227, for example, illustrated in FIG. 1.
[0099] The actual parameters of the RF power delivered to the RF
electrode within the urethra may be recorded and monitored (step
724). Parameters of interest can include the temperature recorded
at the RF electrode, the temperatures recorded at satellite
electrodes, for example which can be placed in the prostate,
rectum, or other neighboring bodily locations within the operative
field. Other recorded parameters can be the RF power, current,
voltage, impedance, and so on. The time of RF power application may
also be monitored in step 724. A predetermined set time of exposure
of the RF power to the electrode may be desirable, depending on
clinical needs. The duration of heating may depend on the reading
of temperature sensors in the prostate or the RF electrode at
various positions. Knowledge of these RF parameters and the
geometry and size of the RF electrode can assist in guiding the
surgeon as to the size of the lesion and resultant
urethral/prostatic cavity that will be produced. For example, it
may be known from clinical experience that certain size ablations
can be induced for certain electrode geometry types with a known
value of RF power, current or voltage. Alternatively, a known
ablation temperature as recorded in one or more of the temperature
monitors, sustained for a desired time, may be the criterion for
ending the ablation process. As represented in FIG. 9, these
parameters may be monitored during the ablation process and
influence the decision of the clinician to terminate or continue
the process according to experience and parameter values. By
reference, the measurement of parameters is illustrated by use of
lesion generator systems of Radionics (Burlington, Mass.). For
example, the model RFG3C lesion generator sold by Radionics, Inc.
provides impedance monitoring similar to that discussed above. It
should be appreciated that other forms of tissue monitoring may be
used. For example, oxygen levels or ionic concentration as are
known in the art may be measured.
[0100] The decision on the adequacy of the duration and parameter
settings to achieve the correct RF heat ablation effect on the
prostate that is sufficient to reduce urinary obstruction is
determined at step 727 of FIG. 9. The decision to stop the
procedure when it is believed that the cavity is adequate may also
be made at this step.
[0101] In accordance with one embodiment of the present invention,
the clinician may choose an RF electrode geometry of a certain
size, diameter, and length. The clinician may know from experience
that insertion of such catheter-electrode intra-urethrally, the
electrode having a built-in temperature sensor, and delivering RF
power to raise the measured temperature at the electrode to a
certain temperature value will produce a known and generally
adequate ablation cavity to alleviate urinary obstruction.
[0102] In accordance with another embodiment of the present
invention, the RF electrode may not include a temperature sensor.
The correlation of ablation size desired for a given electrode
geometry may be determined by considering RF parameters such as
power, output, voltage, and current. Generally, it can be
determined that ablation temperatures of greater than 50.degree. C.
in the prostate tissue can be induced, for example, by RF power or
RF current levels greater than known amounts. In that embodiment,
desired levels for these RF power and current parameters may be
achieved by the clinician for a desired duration of RF power
application to alleviate the urinary obstruction by creating a
sufficient intra-urethral cavity. It is understood that there may
be a variable range of these parameters, time durations, and
electrode geometries according to the experience acquired by
clinicians to achieve adequate ablation cavities.
[0103] In accordance with one embodiment of the present invention,
if CT, MR, or other imaging techniques are used during ablation,
then they may be used to monitor or to decide on adequate ablation
size. This is included as an alternative or added monitoring step
in block 724. For example, certain MR images can be used to
visualize the thermal distribution around the electrode, and thus
to indicate the desired end-point for a prostate ablation.
[0104] An added or alternative process in accordance with the
present invention is to perform an RF heat ablation together with
cooling the electrode by circulation of coolant inside the balloon
catheter. This is indicated as an added or alternative step as part
of step block 721 in FIG. 9.
[0105] The use of intra-urethral RF electrodes herein has the
advantages of simplicity, economy, control, consistency,
reproducibility, and patient tolerance compared to other techniques
such as TURP, TUNA, and TUMT aimed at treating BPH or prostate
cancer. The present system and method maintains the RF electrode
within the urethra, and does not pierce the urethral wall. As
described, the heat ablation process using an intra-urethral
electrode according to the invention has the effect in one of the
embodiments of ablating the urethral wall and periurethral tissue
to open the channel and to destroy the urethra near the electrode.
This has advantages over other methods and apparatus which seek to
leave the urethra intact or unablated, such as TUNA, McGahan et
al.'s procedure, and TUMT cited above. In the present invention,
because the electrode does not pierce the urethra, the risk of
hemorrhage is reduced. Furthermore, with the RF electrode within
the urethra, and with use of imaging control as described above,
there is a more exact knowledge of the ablation zone in the central
prostate region to reduce the chance of damaging sensitive
structures. Thus, with patients in whom bleeding is a problem, such
as those in frail health on anti-coagulation medication for cardiac
or neurological disorders, the present intra-urethral approach has
an advantage over approaches such as TURP and TUNA where deliberate
scraping, cutting, or piercing of the urethra will cause irritation
and bleeding.
[0106] A further advantage of the present invention is that there
is more precise control of the placement of the electrode (e.g.,
202) in the prostate and increased safety against heat ablation of
the wrong tissue region. In the various embodiments, the position
of the electrode may be determined by placement of the balloon tip
in the bladder. This, in turn, may ensure that the electrode is
correctly positioned in relation to the prostate, bladder neck, and
sphincter. This is measurable by the catheter parameters selected
as described above and visualizable with ultrasound, X-ray, CT, or
MRI. Therefore, the positioning and extent of the ablation zone is
better controlled with the present invention than with other
systems and methods. Furthermore, because the system and method of
the present invention locates the ablative cavity in the central
periurethral region of the prostate, the risk of damage to critical
structures such as the rectal mucosa, the rectal wall, neural
structures, or seminal channels is reduced.
[0107] A further advantage of the present system and method is that
it enables direct widening of the urethral channel without
preserving the urethra itself. This is in contrast to the TUNA
procedure, the technique of McGahan, and the TUMT procedure in
which preservation of the urethra itself is a primary objective. In
one embodiment of the present invention, an objective is
destruction of the urethra near the site of the RF electrode. This
has the advantage that the region of necrosis, including the
urethra and surrounding prostatic tissue, will be liquefied and
swept away by the urine passing through the urethra without the
possibility of entrapment of coagulated tissue or necrotic material
outside of the urethra. Such entrapment is possible in the
technique of TUNA, McGahan, or TUMP, where regions of ablation and
necrosis are outside the intact urethra. This can cause swelling of
the tissue around the urethra as absorption of necrotic tissue
proceeds, resulting in continued pressure to the urethra and
further closing down of the urethral channel. These other
techniques have the further disadvantage that an increase in
osmotic particles within the interstitial prostatic medium can take
days or weeks to absorb, resulting in extended irritation,
swelling, urinary obstruction, and risk. By contrast, in the
present invention, this post-ablation debris is naturally swept
away in the urethral cavity and contiguous urethral stream, thus
avoiding the above-mentioned disadvantages of other techniques.
[0108] Because it is better tolerated and of less risk and expense
than TURP, TUNA, TUMT, and non-central radio-frequency lesion
making (viz. McGahan, et al.), the present invention is indicated
for a wider population of patients, and potentially will achieve
more effective clinical results. Also, the present system and
method widens the urethral channel, as does, for example, TURP, but
does so without the side effects of bleeding. Also, the present
invention has the advantage over the TURP or TUNA techniques in
that it requires only minimal anesthetic and no hospitalization.
Therefore, the present invention will be far better tolerated by
patients, especially those who are in frail health and for whom a
TURP procedure may be too risky to endure.
[0109] The present system and method of intra-urethral ablation has
the further advantage of safety compared to TURP, TUNA, TUMT, or
non-central lesion approaches (such as McGahan, et al.). Urologists
are trained to do catheter placements in the urethra, so that the
catheter and electrode placement of the present system and method
is natural and safe for them to perform. The electrode placement
being visualizable and mechanically determinable in the present
invention has the advantage of simple and certain control compared
to TURP, TUNA, TUMT, or non-central RF lesion techniques for which
the electrode position or location of ablation is less definite in
some cases. Minimal anesthetic is required for the present
invention, which is not the case for TURP, where bleeding and
discomfort is significant. Minimizing anesthetic is important since
its administration and consequences are not risk free, especially
for patients in fragile health. The use of a flexible catheter is
easily tolerated by the patient and enables an exact positioning of
the RF electrode within the prostatic body, yielding safer
knowledge of the ablative cavity position.
[0110] Yet another advantage of the present invention is that the
ablation cavity is made contiguous to and central to (in the case
of a symmetric electrode) the stream of the urethral passage. Thus,
the urethral enlargement is a smooth, symmetrically placed cavity.
This will produce a more laminar flow of the urine from the bladder
through the urethra, which in turn will reduce the turbulence and
possibility of pockets of stagnation of fluid in the widened region
of the prostatic passage.
[0111] Yet a further advantage of the present system and method is
that the electrode system and process of use is simple and more
economical than for the TURP, TUNA, and TUMT techniques. This will
lead to a less expensive procedure than TURP, TUNA, or TUMT
procedures, making it amenable to and more cost effective for a
wider patient population. The use of a flexible balloon RF
catheter, as one embodiment cited above, has the advantage of
economy and simplicity of structure. It can be provided as a
disposable device that ensures sterility and cleanliness for each
application.
[0112] Yet a further advantage of the present invention is that the
electrode construction and geometry is simpler and less expensive
than the electrode structure for a cooled microwave catheter, as
used in TUMT. For example, in the exemplary embodiments of FIGS. 1
through 7, only two channels are required. One channel is for
inflation of the balloon. The other channel is for drainage of
urine from the bladder or alternatively injection of contrast media
into the bladder. In the case of TUMT, where cooling of the
catheter and electrode is an objective, further channels within the
catheter must be present to enable circulation of coolant fluid.
For example, a channel which carries the fluid from the proximal
end of the catheter to the distal tip would be needed and another
channel which carries the recirculated fluid from the distal tip to
the proximal end must be built into the TUMT catheter structure.
Such extra circulation channels for cooling fluid can be built into
the present invention structure as illustrated above, but it is not
a requirement in the situation where cooling of the electrode is
not desired. When cooling of the balloon electrode is required,
added channels (as illustrated in FIG. 8 above) can be introduced
to recirculate coolant near the surface mounted RF electrode
portion. The present invention has the further advantage that heat
ablation of the urethra and the prostate can be done to widen the
urethral channel and also another ablation step can be made with
circulating coolant of the electrode and nearby tissue to enlarge
the region of heat ablation or to augment the ablation zone in
desired directions.
[0113] Forms and embodiments of the intra-urethral radio-frequency
urethral ablation system and method are provided involving various
electrode designs with and without temperature monitoring, and in
various electrode geometries. However, it should be recognized that
other obvious forms may be used. For example, various materials,
configurations, and control and display systems can be employed in
a system or method for performing intra-urethral prostate ablation,
with or without the capability of cooling the electrode, without
departing from the scope of the invention.
[0114] In view of these considerations, as would be apparent by
persons skilled in the art, implementations and system should be
considered broadly and with reference to the claims set forth
below:
* * * * *