Use of the adaptive classifier for determination of LD50 in the acute radiation disease

In experiments on female Wistar rats a new method for the determination of LD50 is demonstrated and compared with the classical probit method using the same experimental animals. The method is applicable for the computation of LD50 and analogical quantities in man, too. The method is based on the application of an adaptive logical circuit (ADALINE) trained for the dichotomous prognostic classification of irradiated individuals quod vitam according to a set of clinical and laboratory indicators registered on the third day after irradiation. After the training procedure has been finished, the classifier makes possible an individual prognosis of survival or death. The analogue output signal according to which the classification is performed changes continually from negative to positive values and exhibits S-shaped relation to the radiation dose. Its zero value corresponds to the position of LD50 on the abscissa. For the construction of the searched function, i.e. for the optimum approximation of experimentally obtained values of the output signal, the method of the changeable polyhedron was applied belonging to the optimalization numerical methods used in the regulation technics. The computed value of LD50 was 7.80 Gy in rats very closely corresponding with the value 7.61 Gy determined by means of the classical probit method.