Transurethral ultrasound array for prostate thermal therapy: initial studies

TLDR

The study evaluates a transurethral ultrasound applicator for treating benign prostatic hyperplasia and prostate cancer. The device is a tubular multitransducer applicator with four independently powered piezoceramic tubes housed in a water‑cooled catheter, positioned in the prostatic urethra and sonicated to confine heat to the prostate while sparing surrounding tissues. Computer simulations, acoustic measurements, and in vivo dosimetry demonstrate that the applicator can deliver 1.4–2.0 cm radial therapeutic zones at 50–90 °C, sparing the urethral mucosa, with controllable heating and superior spatial localization compared to current transurethral thermal therapies.

Abstract

This study presents the initial evaluation of an applicator designed for transurethral ultrasound thermotherapy (TUST) of prostate tissue in the treatment of benign prostatic hyperplasia (BPH) and cancer. A tubular multitransducer applicator, consisting of four piezoceramic tubes (2.5 mm diameter, 6 mm long, 6.8 MHz) under separate power control, was designed to fit within a semiflexible water-cooled temperature-regulated delivery catheter to be placed within the prostatic urethra during therapy. Sonication patterns were tailored to produce power depositions which avoid nontargeted tissues, such as the rectum. Computer simulations have demonstrated that 1.4-2.0 cm radial therapeutic zones (temperatures /spl ges/50-55/spl deg/C, thermal doses >300 EM/sub 43/) with concurrent sparing of the urethral mucosa can be produced within prostate tissue having blood perfusion as high as 10 kg m/sup -3/ s/sup -1/ within 15-30 min. Acoustic distributions and power output measurements of a prototype applicator have demonstrated acoustic power levels approaching 10 W per each sectored transducer segment are attainable, with beam profiles collimated within the transducer length and with desired circumferential distributions. In vivo thermal dosimetry characterizations of these transurethral applicators have indicated that therapeutic temperatures between 50 and 90/spl deg/C are attainable, controllable in the longitudinal and circumferential directions, and have effective radial heating. These results clearly indicate that transurethral ultrasound applicators have potential to provide improved spatial localization and control of the heating distribution over existing transurethral thermal therapy techniques for both hyperthermia and thermal coagulative therapy of the prostate.