TRANSURETHRAL PROSTATE ABLATION WITH SALINE ELECTRODE ALLOWS CONTROLLED PRODUCTION OF LARGER LESIONS THAN CONVENTIONAL METHODS

A novel technique for prostate ablation using radiofrequency (RF) ener gy coupled to tissue with interstitial perfusion of saline solutions f rom a screw-tip catheter has been developed, The electrolyte spreads t he current density away from the metal electrode and increases the eff ective electrode surface area, allowing more RF power input. This prev ents tissue desiccation and impedance rise, resulting in controlled pr oduction of large lesions, In this study, we attempted to produce simi lar results using a straight needle and the saline electrode with a tr ansurethral approach and compared the results with those of the same t echnique without electrolyte perfusion (conventional RF method), For t his study, we designed an insulated 22-gauge needle with thermocouples embedded along its length and a 1-cm exposed tip with a retractable i ntraluminal thermocouple, This needle was inserted into the urethra of 10 dogs through a Small perineal incision, Under transrectal ultrasou nd guidance, the exposed tip of the needle was placed in the center of each lobe, The intraluminal thermocouple was moved from the exposed t ip up to the prostate capsule to monitor temperature, The highest powe r that could be applied in conventional RF methods without immediate d esiccation was determined from prelimary experiments as 10 W, Subseque ntly, 10 W of RF power (475 kHz) was delivered in one lobe until eithe r the capsule temperature reached 48 degrees C or high impedance (>400 Omega) occurred, In the other lobe, 50 W of RF energy (475 kHz) and e lectrolyte perfusion (14.6% NaCl, 1 ml/min) were delivered until the c apsule temperature reached 48 degrees C or high impedance occurred. Pr ostate lobe sizes ranged from 3.93 cm(3) to 44.47 cm(3) (mean 15.07 cm (3)), At 10 W without saline perfusion, high impedance from tissue des iccation occurred at 45 +/- 27 seconds, with lesions ranging from 0.06 cm(3) to 0.93 cm(3) (mean 0.34 cm(3)), At 50 W with saline perfusion, there was no tissue desiccation or impedance rise, The RF application time averaged 181 +/- 115 seconds until the capsule reached 48 degree s C, resulting in lesions ranging from 2.53 cm(3) to 22.88 cm(3) (mean 8.54 cm(3)), This study demonstrates that transurethral ablation of t he prostate with a saline electrode allows controlled production of la rger lesions than conventional RF methods, This may permit a single RF application in each lobe to produce lesions effective for the treatme nt of benign prostatic hyperplasia even in large glands.