CORRELATION BETWEEN THERMOSENSOR TEMPERATURE AND TRANSRECTAL ULTRASONOGRAPHY DURING PROSTATE CRYOABLATION

Objective: To determine if the adequacy of freezing in the neurovascul ar bundle region of the prostate during prostate cryotherapy can be mo nitored by transrectal ultrasonography (TRUS). Patients and methods: T he study group consisted of 11 patients undergoing TRUS-guided prostat e cryotherapy. The actual temperature in the gland was monitored with thermosensors placed in each prostatic neurovascular bundle. The 2 cry o-operators, working together and blinded to the actual temperature, u sed sonographic observations to estimate the temperature at the neurov ascular bundles every 2 minutes until they believed that the gland was adequately frozen. The congruity between the estimated and measured t emperatures was analyzed to determine if the operators could accuratel y monitor the progress of cryoablation by ultrasonography. Results: Th ere were a total of 85 data points for which the operators thought tum oricidal cryo-injury had been achieved at the neurovascular bundles (t emperature -20 degrees C or below). For these paints the measured temp erature was on average 6.0 degrees C warmer than the estimated tempera ture (standard deviation, 22). For operator estimates of -20 degrees C or below, the measured temperature was -20 degrees C or below for 37 (44%) data points, between -19 degrees C and 0 degrees C for 32 (38%) and greater than 0 degrees C for 16 (19%). Conclusions: The operators were not able to accurately predict subzero temperatures at the neurov ascular bundle region by TRUS evaluation. Moreover, the bias and magni tude of the error were significant and might lead to inadequate freezi ng of the prostate during attempted cryoablation.