Theoretical Temperature Distributions Produced by an Annular Phased Array-Type System in CT-Based Patient Models

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Abstract
Theoretical calculations for the specific absorption rate (SAR) and the resulting temperature distributions [for cancer hyperthermia] produced by an annular phase array (APA)-type system are made. The finite element numerical method is used in the formulation of both the electromagnetic (EM) and thermal boundary value problems. A number of detailed 2-dimensional patient models based on CT [computed tomography]-scan data from the pelvic, visceral, and thoracic regions are generated to simulate a variety of tumor locations and surrounding normal tisues. The SAR values from the EM solution are put into the bioheat transfer equation, and steady-state temperature distributions are calculated for a wide range of blood flow rates. Based on the theoretical modeling, the APA shows no preferential heating of superficial over deep-seated tumors. However, in most cases for all 3 regions of the human trunk only fair thermal profiles (therapeutic area near 60%) are obtained in tumors with little or no blood flow and poor temperature patterns (therapeutic area < 50%) are found in tumors with moderate to high perfusion rates. These theoretical calculations should aid the clinician in the evaluation of the effectiveness of APA-type devices in heating tumors located in the trunk region.