Modification of the biologic dose to normal tissue by daily fraction. Model for calculating normal tissue tolerance.

A method to predict normal tissue injury is proposed that includes high daily doses and unusual times successfully by calculating a new value called BIR (Biologic Index of Reaction). BIR and NSD were calculated for various normal tissue reactions. With the aid of statistical correlation techniques it is found that the BIR model is better than the NSD model in predicting radiation myelopathy and vocal edema and as good as NSD in predicting rib fracture. Neither model predicts pericardial effusion. In no case were the results of BIR inferior to those of NSD.