Prostatic and Periprostatic Interstitial Temperature Measurements in Patients Treated with Transrectal Thermal Therapy (Local Intracavitary Microwave Hyperthermia)

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Abstract
One of the questions raised regarding the use of transrectal thermal therapy in the treatment of benign prostatic hyperplasia (BPH) is whether there is a uniform and safe temperature distribution within the prostate. Our study represents the first attempt in humans to map the interstitial thermal distribution in the prostate during transrectal thermal therapy. With the patient under local anesthesia and under ultrasound guidance, a transperineal 3-point thermocouple was placed into various areas of the prostate in 15 patients. Prostatic-urethral thermocouple distance ranged from 1 to 3 cm. A urethral catheter containing a 5-point linear array thermocouple was placed and the balloon was inflated so that the proximal point was at the bladder neck and the remaining points were at 1 cm. intervals along the prostatic urethra. Power (25 watts) was delivered via the Primus (Technomatix) transrectal microwave applicator with simultaneous cooling of the rectal mucosa (between 12 and 14C). Treatment was delivered for 60 minutes and temperatures were recorded. In the prostatic substance a maximal temperature of 45C was observed during the heat-up phase and this decreased as the vasoactive response occurred. Temperature along the prostatic urethra varied between 40 and 43C and never exceeded 44C. A similar distribution of temperature was registered in the thermocouple points in the prostatic substance. The anticipated thermal dose of 41.5 +/- 1C for 60 minutes was achieved in the prostatic substance as measured by the sensors in the prostatic urethra and interstitial sensors. The results suggest that transrectal thermal therapy delivers a uniform and safe distribution of heat in the prostatic substance and urethra. Clinical trials are currently underway to ascertain the efficacy of transrectal thermal therapy in the management of BPH.