[Physical principles of optimization of roentgenologic studies]

According to the recommendations issued by the International Commission for Radiation Protection a solution to the problem of the appropriateness of measures aimed at reducing irradiation doses, depends upon the consideration of all the pros and cons. Approaches to a quantitative evaluation of the benefit and damage of x-ray examination are considered. Damage is regarded as a risk of developing unfavorable complications of irradiation by a patient. Proceeding from the threshold-free linear concept, an effective equivalent dose is taken for a measure of damage, the quality of x-ray image for a measure of benefit. The contrast of visualized x-ray image is used for its approximate evaluation. Effectiveness function which is equal to the ratio of the quantitative benefit-damage measures, was drawn. A mathematical model of optimization with account of the heterogeneity of the studied object and the energy spectrum of x-ray radiation was developed on the basis of the above criterion. With the help of this model optimum regimens were obtained for radiography of the stomach on the RUM-20 apparatus with ZnSl.Cds-Ag screen.