For example, bone and lung are two tissue types that have been associated with suboptimal outcomes or local progression with radiofrequency ablation due to high baseline impedance ( 2, 11– 17). Microwaves are capable of propagating through and effectively heating many types of tissue, even those with low electrical conductivity, high impedance, or low thermal conductivity. RF heating requires an electrically conductive path, is limited in areas of low electrical conductivity, and only results in heating of tissues immediately adjacent to the electrode ( 3, 9– 10). This mechanism of heating differs substantially from radiofrequency (RF) ablation, which creates heat via resistive heating when electrical current passes through the ionic tissue medium. Due to the radiating nature of the antenna, direct heating occurs in a volume of tissue around the antenna. Microwave energy radiates into the tissue through an interstitial antenna which functions to couple energy from the generator power source to tissue.

Reprinted from Curr Probl Diagn Radiol, 38(2), Brace C, Microwave Ablation Technology: what every user should know, 61–67, 2009 with permission from Elsevier. Schematic demonstrates how an alternating electromagnetic field causes polar molecules to continuous realign, producing kinetic energy and in turn, heat.

Slot antenna for microwave ablation