Background and Purpose: The effectiveness of any thermotherapy device is determined by the temperatures created and how long they are applied. Understanding the heating characteristics of a thermotherapy device is vital to its correct implementation. Interstitial temperature mapping was used to determine the heat field created within the prostate by the TherMatrx TMx-2000 transurethral microwave thermotherapy (TUMT) device. Gadolinium-enhanced MRI was used to determine the extent, type, and pattern of coagulation necrosis caused by TUMT. Patients and Methods: Interstitial temperature mapping was performed during treatment in five patients with benign prostatic hyperplasia using 24 temperature sensors inserted through the perineum and arrayed throughout the prostate under ultrasound and X-ray guidance. Gadolinium-enhanced MRI scans were performed on all patients 1 week after treatment. Results: Interstitial temperature mapping found the heat field created to peak at the urethral surface near the central part of the catheter antenna. Temperatures decreased at consistent rates of 1 to 1.4°C/mm radially and 0.1 to 0.5°C/mm longitudinally from the peak area. Gadolinium-enhanced MRI showed minimal dispersed necrosis and only in the periurethral area. Conclusions: The TMx-2000 can create temperatures >45°C in areas 3 to 4 mm from the antenna. How ever, the heat pattern and protocol of the TMx-2000 produce necrosis-generating conditions only within a few millimeters of the urethra.
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