Physical aspects of clinical implementation of Clini-therm's 915 MHZ contact applicators

The capability of 915 MHz contact applicators to impart uniform heating, irrespective of physiologic variables as vascularity, in clinically encountered configurations was investigated in a static, sectioned phantom (Guy muscle). Liquid crystal sheets enabled rapid visualization of transverse and longitudinal thermal distributions, indicating regions of nonuniform heating. Fiber optic probes (GaAs) could then be positioned for quantitative assessment of the SARs. Surface irregularities requiring oblique incidence or distilled water baggies can result in significant shifts in the SAR uniformity, i.e., hot or cold spots. Also, the introduction of saline and/or mesh shields can cause irregular heating patterns if improperly used. The methods used and the magnitude of these irregular thermal distributions are discussed