Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Thermal applicators
Reexamination Certificate
1999-10-01
2001-08-07
Gibson, Roy (Department: 3739)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Thermal applicators
C607S102000, C607S096000
Reexamination Certificate
active
06272384
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the field of microwave therapy, and more specifically to the control of microwave power in a microwave therapy apparatus.
BACKGROUND OF THE INVENTION
EP-A-370 890 in the name of Technomed Medical Systems, S.A. (“the '890 Publication”) discloses a microwave therapy probe for treatment of the prostate. The probe includes means for cooling the urethral wall of the prostate during treatment. The probe disclosed in this publication also includes temperature measuring sensors. More specifically, the probe includes a fibre-optic temperature sensor to measure the temperature at the surface of the urethral probe, and an interstitial probe to measure the temperature inside of the prostate. The '890 Publication suggests controlling the power delivered to the probe by a microwave generator according to the temperature measured by the temperature sensors, and according to the temperature of the coolant. No further explanation as to temperature control is given in this publication. There is nothing in this publication suggesting to the person of ordinary skill in the art that the temperature of the coolant could vary.
The transurethral microwave apparatus sold by Technomed Medical Systems under the trademark PROSTATRON uses a rectal probe for monitoring treatment and an urethral probe containing the microwave antenna. Four temperature sensors are present in the apparatus: one sensor is located in the urethral probe and the other three sensors are located on the surface of a specially designed rectal probe, which sensors face the prostate. A description of this probe is given in FR-A-2 660 561.The urethral probe utilizes a coolant to cool the surface of the probe facing the urethral wall. In this apparatus, the microwave power and the temperature of the coolant are computer controlled. The coolant is kept at a constant temperature of about 20° C. Microwave power gradually increases up to about 60 W or 70 W during the first 20 minutes of the treatment. The power is then held constant unless a preset maximum temperature is measured by one of the sensors. In that case, the microwave emission is stopped to permit cooling of the rectum or the urethra and thereby prevent overheating. This technique prevents overheating the rectum wall or burning of the urethra. When the temperatures drop to below a threshold, microwave emission is resumed. This apparatus permits a shorter treatment duration, typically one session of less than one hour, and provides proper and efficient treatment of the patient.
U.S. Pat. No. 5,509,929 assigned to Technomed Medical Systems, S.A. discloses a microwave urethral probe with an inflatable balloon for anchoring the probe in the bladder of a patient. The primary active heating part of the microwave antenna is arranged to direct microwave energy on the prostatic tissues located near the bladder neck when the probe is in an operational position.
U.S. Pat. No. 5,843,144 assigned to Urologix Inc. discloses a method for treating benign prostatic hyperplasia with microwave thermal therapy. The probe described in this patent has a microwave antenna, an inflatable balloon for anchoring the probe in the bladder of the patient, and coolant duct for cooling the urethral wall near the prostate. The main heating part of the antenna is located below the bladder neck, substantially in the center of the prostate. This patent suggests minimizing the number of interruptions of microwave power applied to prostatic tissues. To achieve this result, the patent suggests applying prechilling to the urethral wall before beginning microwave treatment. The coolant is then maintained at a constant temperature during the treatment phase. After the end of the treatment, the coolant is maintained at a low temperature to reduce edema. The total duration of the treatment according to this patent is around 88 minutes, 67 minutes of which correspond to the microwave generating phases, i.e., microwave power ramping up for about 17 minutes and continuous heating of tissues for about 50 minutes. To control microwave power during the continuous heating of tissues, this patent suggests monitoring the rectal temperature and the probe temperature, and increasing or decreasing power to maintain the temperature of the rectum below 42° C. and maintain the probe temperature within 1° C. of 40° C. There is no provision for automatically adjusting the power to meet these temperature targets.
SUMMARY OF THE INVENTION
The present invention is based on the recognition that power interruptions have a negative impact on the intraprostatic temperature, and that a more efficient treatment may be achieved if such interruptions are minimized. The method of the present invention therefore provides a solution for treating tissues with a minimum number of interruptions in the delivery of microwave power. In view of the limited number of temperature measurements, the method of the present invention may easily be carried out.
The present invention also provides a solution to the problem of a shorter treatment duration. The method of the present invention thereby allows for shorter treatment duration, and thus improves patient's comfort during and after treatment.
The present invention thereby provides an apparatus for treating the prostate, having a urethral probe with a microwave antenna and ducts for circulating a coolant, a microwave generator applying microwave energy to the microwave antenna, and coolant circulating system to circulate the coolant and control the temperature of the coolant. The temperature of the coolant is controlled according to the microwave power applied to the antenna.
Preferably, the temperature of the coolant decreases as the microwave power increases. In one embodiment of the present invention, the temperature of the coolant decreases linearly as the microwave power increases. In another embodiment, the temperature of the coolant varies between a maximum value near to the temperature of the body and a minimum value lower than the temperature of the body.
The apparatus preferably includes a rectal temperature sensor. The microwave power applied to the microwave antenna is controlled according to the temperature measured by the sensor. In another embodiment, the apparatus comprises a rectal temperature sensor, and the microwave power applied to the microwave antenna is controlled only according to the temperature measured by the rectal sensor.
The apparatus may also include a feedback control to control the microwave power applied to the antenna. The feedback control may be a proportional integral feedback control. The microwave power applied to the antenna may be controlled according to the following formula:
Power
=
K
·
(
(
T
Set
-
T
Measured
)
+
1
τ
i
∫
(
T
Set
-
T
Measured
)
·
ⅆ
t
)
with Power the power applied, T
measured
the temperature sensed by the sensor and T
set
a target temperature. In this formula, K is preferably between 5 and 20 W/°K and &tgr;
i
is preferably between 15 s and 300 s.
REFERENCES:
patent: 4190053 (1980-02-01), Sterzer
patent: 4375220 (1983-03-01), Matvias
patent: 4601296 (1986-07-01), Yerushalmi
patent: 4662383 (1987-05-01), Sogawa et al.
patent: 4676258 (1987-06-01), Inokuchi et al.
patent: 4813429 (1989-03-01), Eshel et al.
patent: 4967765 (1990-11-01), Turner et al.
patent: 5007437 (1991-04-01), Sterzer
patent: 5234004 (1993-08-01), Hascoet et al.
patent: 5304214 (1994-04-01), DeFord et al.
patent: 5330518 (1994-07-01), Neilson et al.
patent: 5344435 (1994-09-01), Turner et al.
patent: 5391197 (1995-02-01), Burdette et al.
patent: 5404881 (1995-04-01), Cathaud et al.
patent: 5413588 (1995-05-01), Rudie et al.
patent: 5423811 (1995-06-01), Imran et al.
patent: 5433740 (1995-07-01), Yamaguchi
patent: 5464437 (1995-11-01), Reid et al.
patent: 5464445 (1995-11-01), Rudie et al.
patent: 5480417 (1996-01-01), Hascoet et al.
patent: 5496271 (1996-03-01), Burton et al.
patent: 5509929 (1996-04-01), Hascoet et al.
patent: 5520684 (1996-05-01), Imran
Lassal Olivier
Simon Eric
Gibson Roy
Kinney & Lange , P.A.
Urologix Inc.
LandOfFree
Microwave therapy apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Microwave therapy apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Microwave therapy apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2524299