A ‘‘Fresnel-transducer’’ for prostate hyperthermia treatment

Abstract

Simulations and construction methods will be described for a novel ‘‘Fresnel-transducer.’’ The transducer is designed for transrectal hyperthermia treatment of prostate cancer as an adjuvant to radiotherapy or chemotherapy. Forty nine 6.3 mm diameter 1.5 MHz PZT elements are arranged in a 3 by 7 cm honeycomb-like pattern. They are individually aimed so that their beams partially converge behind the prostate. The increased beam density away from the transducer compensates for the loss of acoustic intensity due to attenuation. The aiming of the beams is additionally biased toward the periphery of the heated region to compensate for cooling from lateral heat conduction. The elements are divided into three interspersed sets, each driven at a slightly different frequency, to minimize stationary Moire interference bands between the beams. The combined effect is to uniformly raise the prostate temperature to 43<th>°C without overheating the rectal wall. [Research supported by the Department of Defense Congressionally Directed Medical Prostate Cancer Research Program.]