No abstract

Microwave thermotherapy is currently used in clinical routines for benign prostatic hyperplasia treatments. The temperature increase is obtained using an endocavitary microwave applicator placed in the prostatic urethra. This urethral applicator after a technical modification can be placed inside the bladder in order to potentiate the effects of the treatment by chemotherapy of vesical carcinoma. This paper deals with electromagnetic studies of this new endocavitary applicator. First of all, the experimental determination of the dielectric permittivities for the propagation domain characterization is achieved in order to be used in the electromagnetic model. Compared to experimental results, these simulations obtained by the finite-difference time-domain formalism allow us to determine the electromagnetic performance of this applicator. Finally, the in vivo study realized on anesthetized dogs to determine the therapeutic protocol associating chemotherapy and thermotherapy in the treatment of the bladder cancer is presented.

Microwave thermotherapy systems used for benign prostatic hyperplasia treatment generally operate with urethral or rectal applicator to deliver the microwave energy in the prostate. This technique does not allow an efficient heating of all the gland particularly in the case of large adenoma or when the treatment is limited to only one heating session. A solution to this problem is given by using simultaneously the rectal and urethral applicators [l]. A complete 915-MHz microwave thermotherapy system is presented with two applicators which can operate independently or simultaneously to deliver the microwave energy in the prostate. Electromagnetic and thermal modeling have been developed for the applicator antenna optimization, to calculate the specific absorption rate (SAR) and the thermal pattern in the prostate for each applicator alone and when they operate together in phase. Different canine experiments have been performed to prove the interest of using the two applicators simultaneously as compared when they operate alone. Hystological examination cuts of the prostate gland after heating have been carried out. I. INTRODUCTJONHE efficiency of microwave thermotherapy to treat benign prostatic hyperplasia has been demonstrated: many medical teams use this technique in clinical routine [2]- [5].Nevertheless urologists still do not agree about the type of applicators. In order to increase the heating volume and above all to homogenize the temperature within the prostate (in the case of prostatic tumors) it is necessary to combine urethral and rectal heating.The aim of this work is to make a thermoregulated focusing rectal applicator to be used simultaneously with an omnidirectional urethral applicator.Radiation diagrams of urethral and rectal applicators are computed out by the finite-difference time-domain (FDTD) method, and determined by experimental measurements. The

A new complete microwave interstitial hyperthermia system monitored automatically by microwave radiometry and working at 434 MHz is described in this paper. This system, which includes a new radiometer with two internal temperature references, is detailed. All its characteristics for microwave heating and radiometry are presented. The new possibilities are shown through numerous experiments on acrylamide phantom and excised tissues, which have been carried out for different antennae implantation corresponding to the clinical situation. The clinic protocol, associate to the brachytherapy, imposes the use of semi-loop catheters. Coaxial antennae, inserted in these catheters, are not, therefore, positioned in a rectilinear manner but undergo a curve. So, models based on the FDTD formalism are developed to determine the theoretical power deposition. Owing to these models, the effects of this physical motive on radiation diagrams can be taken into account. The results of the power deposition are presented for two antennae. Thermal patterns can then be determined by the solution of the bioheat-transfer equation in the steady state. Also, the comparison of the results given by the new interstitial hyperthermia system with those obtained with the previous 915 MHz one shows an improvement of the thermal performances.