Tissue Heating: Applicator Types and Analysis by Phantom Models

Abstract

Electromagnetic radiofrequency (RF) heating of tissues for therapeutic application may be accomplished by a number of methods. Four major methods have been used for localized heating of various parts of the body. These include the use of invasive or direct contact electrodes or probes placed in the tissue area to be heated, 2) noncontacting capacitor type electrodes placed adjacent to the tissue areas to be heated, 3) inductive heating by magnetic field coils placed near or against the tissue to be heated, and 4) radiation field at very high to microwave frequncies. A fifth method useful for heating small biological bodies such as laboratory animals for biological effects research, frozen organs for transplant, or refrigerated blood products prior to transfusion, involves exposure in waveguides or resonant cavities. Radiation fields may be produced by radiators placed close to, but not in contact with, the tissues or by specially designed direct contact applicators that provide efficient coupling between the source and the tissue. Better localization of heating in deep tissues may be obtained by the use of multiple applicators or phased arrays of any of the first four of the above applicators.