A Study on Energetic Efficiency of Coil Antennas Used for RF Diathermy

Plane-geometry single- and multileaf coil antennas fed by radio-frequency (RF) generators are frequently used to produce electric currents and therapeutic ohmic heating in sub- cutaneous fat and muscle tissues by electromagnetic induction. In particular, the butterfly (two-leaf) configuration has been regarded as a high-efficiency geometry for diathermy purposes. The aim of this letter is to prove by numerical simulation that any multileaf coil is significantly less efficient than the round one and that, in general, efficiency worsens with increasing the number of leaves. Simulation results show that for a given power density to be deposited in the tissue, replacing a single leaf with a multileaf structure causes an increase of energy consumption by at least 20%.