THE HEAT IS ON - BUT HOW - A COMPARISON OF TUMT DEVICES

Objective To compare the heat characteristics of the microwave antenna e. the absorbed energy in the target volume and the cooling capacity o f the catheters of three common devices for transurethral microwave th ermotherapy (TUMT). i.e. the Prostcare, Prostatron and ProstaLund. Mat erials and methods The microwave emission from the respective catheter s or antennae was measured in a tissue-equivalent 'phantom' prostate. From these measurements the distribution of absorbed energy from the r espective catheters and antennae was calculated from the characteristi cs of the phantom, the absorbed energy and the temperature difference before and after heating. The cooling capacity of the different cathet ers were measured by submerging each catheter in a thermally isolated water bath at a known temperature and determining the cooling of the w ater bath caused by the catheter. Results The design of the microwave antenna influenced the heating profile significantly. The energy absor bed by the prostate model varied among the devices. but was between 13 and 21% of the stated applied energy. The cooling capacity also varie d, being least in the Prostcare and greatest in the ProstaLund cathete rs. Conclusions Users of TUMT should be aware of possible back-heating along the catheter, as this limits the microwave power that can be us ed safely. Furthermore, the 'treatment energy', which is commonly used as an indicator to describe the intensity of TUMT treatments, is ambi guous and not stringent, in that the microwave energy absorbed in the prostate is only a small fraction of this value.