Newly developed transurethral radiofrequency thermotherapy device for benign prostatic hyperplasia: a pilot study in canine prostate

Abstract

The safety and efficacy of transurethral microwave thermo-therapy (TUMT) for the treatment of symptomatic benign prostatic hyperplasia (BPH) have been demonstrated in the urological literature. Since a radiofrequency electromagnetic wave has deeper and more even transmission of heat to tissues than a microwave, we have developed a new prototype device for transurethral thermotherapy using a radiofrequency electromagnetic wave. The device consists of a microcomputer-controlled heat generator operating at 8 Mhz, a temperature monitoring system, a urethral cooling system and a urethral applicator and a rectal thermosensor probe. A balloon electrode encased in a specialized Foley catheter is connected parallel to twin plate electrodes on both sides of the pelvic region. An 8-MHz electromagnetic wave is directed to the prostate by means of capacitive coupling. The water coolant continuously perfused through the catheter allows high temperatures within the prostate while preserving the urethral mucosa. Heating experiment using agar phantom showed the hot spots to be distributed at 0·5–3 cm from the catheter surface. Heating experiment using canine prostates demonstrated that an intraprostatic temperature of > 48°C could be achieved while the urethral and rectal temperatures had not exceeded 36 and 40°C respectively. Histological examination immediately after the experiment showed the urethral mucosa to be preserved while coagulation necrosis of the periurethral prostate accompanied with congestion and hemorrhage of small blood vessels were observed at 5–8 mm from the urethra. The bladder and the rectum showed no gross alterations. Histopathological examination 10 days after the experiment revealed the intact urethral mucosa and mild mononuclear infiltration around the destroyed periurethral glands. These studies demonstate the short-term safety and efficacy of transurethral radiofrequency thermotherapy in the canine prostate. Further studies will be necessary to determine the clinical effectiveness with the device in patients with symptomatic BPH.

Key Words:

• Hyperthermia
• transurethral
• radiofrequency waves
• canine prostate
• equipment evaluation