Microwave applicator for transurethral hyperthermia of benign prostatic hyperplasia.

An applicator for heating the prostate gland using a transurethral approach is described. This technique uses three microwave antennas and a thermometry sensor attached to the outer surface of a balloon (Foley) type urological catheter. Each microwave antenna also includes a built-in thermistor to control temperature and balance power. The balloon catheter assures rapid and reproducible localization of the antennas in the prostatic urethra. The two-dimensional SAR and steady-state temperature distributions surrounding the applicator in tissue equivalent phantom are reported. Longitudinal temperature distributions measured in situ at the applicator-urethral interface and the longitudinal and radial temperature distributions measured in normal canine prostate are presented and discussed. The technique appears to be capable of elevating temperature to greater than 42 degrees C in a cylindrically symmetrical volume up to 5 cm length and 0.5 cm radial penetration surrounding the applicator.