Correlation between thermosensor temperature and transrectal ultrasonography during prostate cryoablation.
OBJECTIVE
To determine if the adequacy of freezing in the neurovascular bundle region of the prostate during prostate cryotherapy can be monitored by transrectal ultrasonography (TRUS).


METHODS
The study group consisted of 11 patients undergoing TRUS-guided prostate cryotherapy. The actual temperature in the gland was monitored with thermosensors placed in each prostatic neurovascular bundle. The 2 cryo-operators, working together and blinded to the actual temperature, used sonographic observations to estimate the temperature at the neurovascular bundles every 2 minutes until they believed that the gland was adequately frozen. The congruity between the estimated and measured temperatures was analyzed to determine if the operators could accurately monitor the progress of cryoablation by ultrasonography.


RESULTS
There were a total of 85 data points for which the operators thought tumoricidal cryo-injury had been achieved at the neurovascular bundles (temperature -20 degrees C or below). For these points the measured temperature was on average 6.0 degrees C warmer than the estimated temperature (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 degree C for 32 (38%) and greater than 0 degree C for 16 (19%).


CONCLUSIONS
The operators were not able to accurately predict subzero temperatures at the neurovascular bundle region by TRUS evaluation. Moreover, the bias and magnitude of the error were significant and might lead to inadequate freezing of the prostate during attempted cryoablation.
Steed
J
J
Department of Diagnostic Imaging, Foothills Hospital, Calgary, Alta.
Saliken
J C
JC
Donnelly
B J
BJ
Ali-Ridha
N H
NH
D001831:Body Temperature; D003452:Cryosurgery; D005544:Forecasting; D005615:Freezing; D006801:Humans; D008297:Male; D016343:Monitoring, Intraoperative; D015588:Observer Variation; D011446:Prospective Studies; D011467:Prostate / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000294:innervation / Q000503:physiopathology; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000601:surgery*; D012007:Rectum; D016037:Single-Blind Method; D013821:Thermometers; D018084:Ultrasonography, Interventional