Fluid-Thermal properties of electromagnetic heated water boli used in thermal treatment of superficial cancer

Abstract

Hyperthermia treatment (tissue heating up to 42-45 ºC) based on microwave applicators always uses a temperature controlled coupling medium consisting of deionized water. The bolus prevents blisters in the skin and acts as an impedance matching layer for the electromagnetic energy between the antenna and the treatment volume. Little is known whether practically realizable water flow-rates and other design parameters of the bolus are adequate as to obtain required therapeutic performance during treatment. The goal of this project is to obtain an analysis of which parameters are most crucial to the construction of the bolus. The bolus bag is unintentionally heated by the electromagnetic energy applied to generate a therapeutic effect in the tissue. This effect induce spatio-temporal temperature variations within the bolus bag that are critical to the heating performance (power level and field homogeneity). A 3-D numerical model of a realistic design is made analyzed by numerical computations. Pertinent parameters include flow rate, variable load, ambient temperatures variations, loading at the skin-bolus interface, and heat power deposition patterns within the bolus bag. Post processing of generated data is conducted to acquire information on the simulated quantities. The method used for this analysis is the multi-modal simulation software package Comsol Multiphysics to study the fluid-thermal characteristics of the bolus bag and a recommendations for further simulations and improvements is given.