An Experimental Study on the Effect of Combined X-ray and Microwave Hyperthermia on the Rectum and Urinary Bladder of Rats

Lee, Kyung Ja; Rhee, Chung Sik

Abstract

Hyperthermia can enhance the radiation effect as a synergistic reaction in combined X-ray irradiation and hyperthermia; hyperthermia sensitize radilresistant S-phase cells and inhibit cellular recovery from sublethal damage. We fabricated 100 watts, 2450MHz microwave applicator for hyperthermia and planned the method and condition of heating and measured the temperature by usting Agar phantom as a preliminary test. For biological examination, 102 rats were divided into 4 groups as hyperthermia, X-ray irradiation(6Gy-15Gy), combined X-ray and hyperthermia, and normal control groups. Microscopic examination of the rectum and bladder was done and the results were as followings: 1. The microwave generator with 100 watts, 2450MHz magnetron could be heating up to 40degree-50degree C for one hour in living tissue. 2. The thermal distribution in tissue equivalent phantom with microwave can be maintained at 40degree-44degree C in area of 3cm in depth and 2-10cm in diameter. 3. In Hyperthermia alone group, there was submucosal edema of the rectum but no histologic change in the urinary bladder was seen. 4. The minimal necrosis of the mucosa was appeared in the rectum and bladder after 15days of 6Gy and 8Gy irradiation respectively. The minimal necrosis of the muscle layer of rectum and bladder was appeared after 15days of 8Gy and 60days of 10Gy irradiation respectively. 5. In combined group of radiation and hyperthermia, thermal enhancement ratio (calculated at mecrosis of mucosa and muscle layer) of rectum and bladder was 1.0, and it suggest that there is no change of tolerance dose of normal rectum and bladder.