RELEVANCE OF A NEW IMPEDANCE MATCHING, OR SUBTRAP, METHOD FOR THE REDUCTION OF PAIN DURING HYPERTHERMIA

Capacitive heating is widely used in hyperthermic treatment of human m alignancies. However, the pain on the body surface or thermoesthesia i n the subcutaneous fatty layer may prevent an elevation of temperature in the tumors. Impedance matching is improved by a subtrap method ent ailing the application of two copper plates (10 x 850 x 0.06 mm) as a subtrap circuit to each of two capacitive electrodes. In a clinical tr ial the Tmax, Tave, Tmin for the subtrap method were all higher in com parison with those for the conventional technique (42.5 +/- 0.7 degree s C, 41.9 +/- 1.0 degrees C, 41.3 +/- 1.1 degrees C vs. 41.1 +/- 1.5 d egrees C, 40.6 +/- 1.3 degrees C, 40.0 +/- 1.3 degrees C). Although th e maximal radiofrequency (RF) power applied to patients was higher wit h the subtrap method (875 +/- 189 W vs. 763 +/- 200 W), the incidence of surface pain was reduced dramatically. It is concluded that the sub trap method substantially improves the RF capacitive heating of deep-s eated tumors.