The deterministic effect has been mainly discussed for radiation risk in the field of radiotherapy. On the other hand, as the care rate for radiotherapy is increasing the stochastic effect will become more important for radiotherapy patients. Especially, the mean bone marrow dose will be more important for calucuration of population dose. In this paper, tissue or organ dose to estimate the radiation risk for several radiotherapy technique was measured using Rando phantom and TLD tips. The mean bone marrow dose per target absorbed dose of 1000 cGy was calculated. As the results, the mean bone marrow dose include irradiated volume was as follow : right angled two fields irradiation for maxillary sinus; 20.7 cGy, two opposed fields irradiation for larynx; 11.0 cGy, two opposed fields irradiation for mediastinum; 91.0 cGy, rotation irradiation for esophagus; 38.5 cGy, two opposed fields irradiation for whole pelvis; 200.3 cGy, inverted Y opposed two fields irradiation for lower abdomen; 276.2 cGy. In contradistinction, the mean bone marrow dose outside of the irradiated volume was as follow : right angled two fields irradiation for maxillary sinus; 4.8cGy, two opposed fields irradiation for larynx; 2.8 cGy, two opposed fields irradiation for mediastinum; 6.4 cGy, rotation irradiation for esophagus; 18.2 cGy, two opposed fields irradiation for whole pelvis; 19.3 cGy, inverted Y opposed two fields irradiation for lower abdomen; 36.0 cGy.
