Development of Non-Contact Rectangular Resonant Cavity Applicator with 2-D Ultrasound Temperature Measurement System

Summary form only given. We proposed a method of heating deep tumors using a resonant cavity applicator as one method of hyperthermia treatment. The feature of this heating method is that it enables deep heating without contact between a human surface and the applicator [1]. We also proposed a method to measure temperature distributions inside the human body while heating tumors by applying image processing from two ultrasonic images before and after heating [2]. In the present study, a prototype ultrasound imaging system was incorporated in the proposed rectangular resonant cavity applicator system. A rectangular resonant cavity applicator was combined with the system for capturing ultrasound images before and after heating. This imaging system was mainly composed of a control computer, an electric slider and an ultrasound probe. A fixing jig was attached to the tip of the electric slider to fix the ultrasound probe. Heating experiments to check the accuracy of temperature measurements were carried out. In the heating experiments of the agar phantom using this system, first the ultrasound image before heating was taken and then the ultrasound probe was moved to the outside of the resonant cavity. After heating the agar phantom at the power of 50 W for 15 minutes, the ultrasound probe was again moved inside the resonant cavity by the electric slider, an ultrasound image after heating was captured. By applying image processing to these two ultrasound images, 2-D temperature distributions were measured. Also, temperatures inside the agar phantom during the heating experiments were measured using optical fiber thermometers. A comparison between measured temperature profiles by optical fiber thermometers and ultrasound images. It is found that the central area of the agar phantom concentrically heated by using the proposed applicator. The maximum temperature increase (AT°C) in the agar phantom was approximately 6°C. When comparing the measured temperature profiles by optical fiber thermometers and ultrasound images, both resulted in an error of 0.5°C.