Blood perfusion measurements in the canine prostate during transurethral hyperthermia

Using a thermal pulse decay technique, blood perfusion rates were measured within different regions in the canine prostate under normal and hyperthermic conditions induced either by the microwave or the radio frequency heating. Results indicate that, under the normal condition, the periurethral region is most highly perfused with an average rate of 0.60 +/- 0.25 ml/min/gm (n = 4) while the perfusion rate is 0.34 +/- 0.22 ml/min/gm (n = 10) in parenchyma. An approximately 3.5 fold increase in perfusion from the respective baselines was observed in both regions when the local tissue temperature was raised to 41.5 degrees C by the microwave heating. Another 0.5 fold increase was found in parenchyma after the tissue was further heated to 43.1 degrees C at which oscillatory behaviors in tissue temperature have been observed. To further study the cause of these oscillatory behaviors, the instantaneous blood perfusion response to changes in local tissue temperature was investigated using the radio frequency heating. It has been revealed that blood flow acts as a feedback of local tissue temperature in a closed control system. The thermally stimulated blood perfusion increase appeared to be a function of tissue temperature and its temporal gradient. Results from this study have shown experimental evidences of local thermoregulation in the prostate during hyperthermia.