[How tolerant are partial dose values? Some additional remarks on the concept of a tolerance dose]

By means of the NSD formula and its modifications (CRE, TDF) evaluated from radiotherapy experience by Ellis, it is possible to estimate the acceptance of applied radiotherapy and fractionation scheme. Because the parameters of the Ellis formula are calculated from patients data, they show a dispersion as usually in biological systems. These dispersions are considered as entrance error. In mathematical transformations errors are multiplied according to the principle of superposition of errors. Especially when judging tolerance values of organs of risk the dispersion is quite important. The problem of dispersion of resulting partial tolerance values is demonstrated by some examples of clinical cases.