Physics Evaluation and Quality Control of Hyperthermia Equipment

Abstract

A typical configuration of modern hyperthermia equipment used in clinics for localized cancer treatment is shown in Fig. 3.1. It can be described as a closed loop system in that the energy deposited into tissues is controlled by a feedback mechanism depending on the temperature of one or more reference probes. The applicator in this system is designed to deposit electromagnetic or ultrasonic energy into tissues which, when absorbed, is converted into heat and raises the temperature of the tumor. The overall goal is to elevate the temperature of the entire tumor to above 42°C while maintaining the hot spots in normal tissues at below 46°C for periods of up to 1 h. Two to ten treatment sessions over a period of 6 weeks may be required for complete therapy. Clinical experience to date has shown that even this seemingly modest goal is difficult to achieve in a reliable and reproducible manner. The reasons for this are manifold. First, there is a lack of standard equipment to deposit energy in a controlled manner and generate optimum heating patterns in specific tumor sites.