The doctoral thesis was devoted to develop new stability assessment method of x-ray beam in digital radiography. Digital X-ray quality is dependent on both the x-ray beam parameters and exposure. The parameters of an x-ray beam were provided by an x-ray tube current and high voltage. X-ray image quality is dependent on the absorbed dose in the detector. Therefore, the dose distribution in the detector plane characterizes a x-ray beam flow homogeneity, but summary signal picked up by the detector is directly proportional to the dose delivered by x-ray beam. As x-ray photons statistical distribution in time follows the Poisson law, the signal distribution in detector’s pixel matrix is characterized by x-ray photons distribution. This hypothesis was tested. The results of an experimental research showed that hypothesis is wright. The statistical data were verificated by the Kolmogorov-Smirnov criterion (the reliability of 95%) and the Fisher criterion. In the result of the work a new stability assessment method of x-ray beam in digital radiography was developed and tested. The measurements associated with the task of the work were performed in 6 medical institutions using 7 different digital x-ray devices. The results of the work are published in 9 scientific publications and 4 abstracts, as well as presented on 13 international scientific conferences. The work has 98 pages. The work includes 53 figures and 12 attachments.