[Factors influencing the response of normal tissue to radiation]

The dose modifying effects of the age, anatomic location of the normal tissue, positioning of animal during irradiation, preliminary treatment, number of fractions and time interval between doses on response of the normal tissues to radiation were studied, using various kinds of response of mouse hind legs such as early skin reaction, epilation, skin contraction, ulcer formation, leg contraction and growth retardation of femur. The dose modifying factors varied with the kinds and the levels of injuries, meaning that it is very important to define what the critical normal tissue is and its end point first of all, when we discuss the dose modifying factors with respect to the therapeutic gain factors.