FDID Analysis of SAR Distribution Produced by Interstitial Hyperthermic Applicators

In this paper; the Specific Absorption Rate (SAR) distributions of interstitial microwave radiating applicators operating in a layered tissue at 915 and 432 MHz were numerically determined by using the Finite-Difference Time-Domain (FDTD) method. The analysis is performed by computing a 2D map of the SAR deposition along the entire applicator comprising the insertion point of the catheter; where hot spots may be generated due to the skin/fat/muscle interfaces. The numerical scheme is based on the Finite-Difference approximations of Maxwell’s equations in a cylindrical coordinate system which takes advantage of the intrinsic rotational symmetry of the analysis domain to reduce the 3D problem to an exact 2D one The proposed method is applied to the electromagnetic (EM) analysis of single or multiple sectioned radiating structures operating in a realistic clinical condition. Results are shown which indicate the presence of a significant rise of SAR at the skin/fat/muscle interfaces when the applicator operates at the lower frequency.