TEMPERATURE-MEASUREMENTS AND HISTOLOGY OF THE CANINE PROSTATE DURING TRANSURETHRAL HYPERTHERMIA

Intraprostatic temperature measurements during transurethral hyperther mia at 44.5C were obtained in 5 dogs. Temperatures were also recorded in the bladder neck wall and the rectal wall. After completion of the temperature measurements, hyperthermia was continued for 3 hours. The prostates were then removed and taken for histologic examination immed iately after hyperthermia and 1 week and 1 month later. The mean tempe ratures obtained in the 5 canine prostates were 44.5 +/- 0.4C at the h eating electrode; 43.8 +/- 0.4C at a distance of 3 mm. from the electr ode; 42.6 +/- 0.5C, 40.8 +/- 0.4C and 39.4 +/- 0.5C, 6, 9 and 12 mm. f rom the heating electrode, respectively, in the right, prostatic lobe. Similar temperatures were measured in the left lobe. The thermal grad ient in the prostatic tissue was therefore about 4C per 1 cm. On histo logy, hemorrhagic necrosis of the prostatic tissue adjacent to the ure thra was found. These histologic changes were found as much as 5 mm. f rom the heating antenna (where the temperatures measured were above 43 C). The findings of our study may have major clinical importance. We f ound that thermal energy above 43C provides enough penetration to caus e tissue damage and be clinically effective in most patients, while th e thermal gradient around the heating electrode of 4C per 1 cm. is ste ep enough to confine histologic damage within the prostate.