Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Thermal applicators
Reexamination Certificate
2000-01-03
2002-07-23
Bockelman, Mark (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Thermal applicators
C607S102000, C607S113000, C607S156000
Reexamination Certificate
active
06424869
ABSTRACT:
BACKGROUND OF THE INVENTION
This application relates to transurethral hypothermia apparatus. It relates more particularly to a dual mode (i.e heating and sensing) transurethral microwave warming apparatus.
It is well known that heat can be used to reduce an enlarged prostate. Benign prostatic hyperplasia (BPH) is a common disease among aging men that may lead to several complications such as urinary tract infection, acute urinary retention or uremia. In the U.S. alone, there are approximately 400,000 transurethral resection procedures performed each year involving general anesthesia and hospitalization to treat the above problem. Many patients are poor surgical risks due to age and possible co-existing health problems.
Microwave hyperthermia appears to be a practical alternative to transurethral resection for the prostate, the usual surgical procedure. Microwave transurethral hyperthermia involves insertion of a small catheter, including a microwave antenna, into the bladder via the urethra. This procedure can be performed in an outpatient basis without the need for general anesthesia.
It is also well known that hyperthermia can be used as an adjunct to ionizing radiation as a treatment for a malignant disease. According to the American Cancer Society, cancer of the prostate is currently the second most lethal cancer in American men. Numerous studies have demonstrated that microwave hyperthermia can be a valuable adjunct to radiation therapy in the treatment of prostrate cancer. The combination of microwave heating and ionizing radiation is far more effective than either of the treatments alone, thereby significantly reducing the level of ionizing radiation required. However, the success of hypothermia rests on the ability to effectively heat the tumor volume to therapeutic temperatures without causing damage to the adjacent normal tissue.
Conventional transurethral catheters used in prostrate applications have multiple lumens with at least one lumen dedicated to the microwave antenna or applicator. The catheter also has other working lumens used for coolant, drainage, temperature probes and inflation fluid, e.g. air, for inflating a balloon at the tip of the catheter for positioning the catheter after insertion.
FIG. 5
of the drawings shows a conventional transurethral catheter used in prostate applications. It includes an elongated probe or body
10
having a plurality of length-wise lumens. There is a central lumen
12
with a counterbore
12
a
for accommodating a coaxial cable
14
. The cable's center conductor extends to the distal end of lumen
12
and constitutes an antenna
16
. Probe
10
also has a second, generally U-shaped lumen
18
whose legs
18
a
are located radially outboard lumen
12
and which provides a path for the circulation of a coolant fluid through the probe to cool the external surfaces of the probe. As noted previously, catheters of this type usually include a balloon
22
adjacent to the distal end of probe
10
. Therefore, an additional lumen
24
extends along probe
10
to carry the inflation fluid to the balloon. Various other working lumens may extend along probe
10
. For example, there may be a lumen
25
which runs the length of the probe and is used for the drainage of body fluids after the catheter is inserted in a patient. There may also be a lumen indicated at
26
for accommodating one or more heat sensors
30
such as a thermocouple, thermister or fiberoptic device. All of the working lumens extend to the proximal end of the probe
10
where they connect to tubes which lead to various units supporting the above-described functions of the lumens. The
FIG. 5
catheter is fully described in U.S. Pat. No. 5,234,004.
As seen from the above patent, with the balloon
22
in its deflated condition shown in solid lines in
FIG. 5
, the distal end
10
a
of the probe
10
may be inserted into the urethra up to the level of the tissue to be treated by the thermal affect at which level the balloon
22
reaches the patient's bladder. Thus, after inflating the balloon by flowing an inflation fluid such as air through lumen
24
so that the balloon expands as shown in phantom in
FIG. 5
, the catheter is locked in the bladder neck thereby achieving a precise positioning of antenna
16
relative to the patient's prostate which surrounds the urethra, that position being maintained during the entire treatment.
After probe
10
has been positioned thusly, microwave power may be delivered via cable
14
to antenna
16
which produces a radiation pattern that heats the tissue near the probe. Preferably, a coolant is circulated through lumen
18
in order to lower the surface temperature of probe
10
to prevent overheating the tissue right next to the probe. As described in the above patent, a heat sensor
30
may be present in lumen
26
for sensing the temperature on or inside probe
10
. The output from the sensor can then be used to control the power delivered to antenna
16
so that the tissue to be subjected to the thermal effect is heated to within a selected temperature range.
Transurethral catheters of the above type are disadvantaged in that the fluid-carrying lumens
18
,
24
and
25
are located between antenna
16
and the tissue surrounding probe
10
. Resultantly, the various fluids flowing through those lumens perturb the antenna pattern and absorb microwave energy. The same is true with the temperature sensor(s)
30
in lumen
26
. The result is that the catheter may heat the adjacent tissue unevenly so that some tissue is heated excessively while other tissue is not heated enough to achieve the desired thermal effect. This problem is exacerbated by the fact that the temperature sensor(s)
30
measure the temperature on or in probe
10
, not the actual temperature of the tissue surrounding the probe. The upshot is that prior catheters of this type do not achieve the desired degree of temperature control of the tissue being heated.
The conventional catheters suffer also because of the presence of temperature sensing devices in the catheters. More particularly, thermisters and thermocouples require connecting wires which are prone to failure. They also reduce the catheter's flexibility making it more difficult to thread the catheter through the urethra. On the other hand, fiberoptic sensors are fragile and quite expensive thereby increasing the overall cost of the apparatus.
Accordingly, it is an object of the present invention to provide improved transurethral microwave warming apparatus particularly adapted to treat benign prosthetic hyperplasia.
Another object of the invention is to provide such apparatus which includes a catheter able to heat the tissue to be treated relatively uniformly.
Another object of the invention is to provide apparatus of this type which can precisely monitor the actual temperature of the tissue being treated.
A further object of the invention is to provide transurethral microwave warming apparatus which accurately monitors tissue temperature without the need for thermocouples, fiberoptic circuitry or other temperature sensing hardware in the apparatus' catheter or probe.
Yet another object of the invention is to provide a transurethral microwave catheter which is quite flexible to facilitate passage through the urethra.
A further object of the invention is to provide such a catheter which is relatively inexpensive to manufacture in quantity.
Other objects will, in part, be obvious and will, in part, appear hereinafter.
The invention accordingly comprises the features of construction, combination of elements and arrangement of parts which will be exemplified in the following detailed description, and the scope of the invention will be indicated in the claims.
SUMMARY OF THE INVENTION
Our dual mode transurethral warming apparatus includes a urethral catheter dimensioned for insertia through the urethra. The catheter includes an elongated flexible tube having a plurality of longitudinal lumens extending between the ends of the tube. A coaxial cable extends along one of the lumens to
Carr Kenneth L.
Regan James F.
Bockelman Mark
Cesari and McKenna LLP
Meridian Medical Systems, LLC
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