Radiation dose to various organs or tissues outside the tumor volume for patients undergoing external radiotherapy

Abstract

The levels of radiation doses due to leakage radiation and the internal scattered radiation imparted to the eyes, thyroid, breast, ovaries and testis of patients treated with a 4 MV linear accelerator, where determined using thermoluminescent dosimeter (TLD). The types of treatment chosen for irradiation (1) the nasopharyngeal region, (2) the breast region, (3) the pelvic region and (4) the whole abdomen. A random phantom was used to determine the doses due to leakage radiation. This phantom is the equivalent standard man and the organs, tissues where anatomically represented. The radiation doses measured for each treatment region varies from 10 rads to about 300 rads, mean organ dose. The minimum value is categorized as lowlevel dose but the maximum value is considered the highlevel dose. The leakage radiation measured from the machine varies from 400 to 1000 mrad. These variations were dependent on the field sizes and the distance of the TL dosemeters from the central beam axis. The minimum value is the presently required limit prescribed by the International Commission on Radiological Protection (ICRP)*.

* The leakage radiation should not exceed 0.2% of the maximum dose at central axis, at a distance of 2 m.