Effective Electromagnetic Coupling and Skin Cooling During RF Heating of Pelvic Tumours

Hyperthermia (i.e. heating of tumour tissue to 40-43°C) is used in clinical oncology to enhance the therapeutic effect of chemotherapy and radiotherapy. Pelvic tumours are usually heated by a phased array of antennas positioned around the patient. Water boluses between the antennas and the patient provide effective coupling of the electromagnetic energy, as well as cooling to avoid overheating of the skin. This study applied treatment planning for five clinical patients to evaluate the impact of the water bolus temperature on the quality of tumour heating. The water bolus temperature was varied between 10°C and 35°C with steps of 5°C and phase-amplitude settings of the antennas were optimized to maximize tumour heating, while maintaining all normal tissue temperatures below 45°C. With a bolus at 10°C only slightly higher (0.2-0.3°C) tumour temperatures were predicted compared with a bolus at 35°C. Thus, with adequate phase-amplitude steering therapeutic tumour temperature levels can be achieved, which are not strongly dependent on the water bolus temperature.