| Popis: |
A comparison was carried out of different procedures of evaluation of the role of dosage in contact radiation effect. The assets and liabilities of the available methods of evaluation were studied with respect to the Ellis--time-dose-fractionation and linear-quadratic concepts. It was demonstrated that the sublethal damage repair model evolved by H.D.Thames and R.G. Dale (11, 16) in the framework of linear-quadratic approach to protracted irradiation can be used to compute iso-effective dosage when high or low loses are employed for fractionated intracavitary irradiation. A correction for dosage is a function of time of dose application and should be made for each fractionation regiment, i.e. number of fractions per week, dose per fraction, specifically in each case. The Thames-Dake model provides a means for establishing critical dosage for a modality of fractionated contact irradiation which is clinically significant, i.e. it differs from the set value by more than 5%. This, in turn, means that the absorbed dose should exceed the previously set one by at least 5%. |
