Based on the test object and the given data from the detectors, a set of formulas connecting the characteristics of digital radiography (DR) systems with the parameters of the X-ray radiation source is checked. The obtained formulas can give a rational choice of the source and the X-ray detector for a nondestructive test. A series of calculations for the DR characteristics of systems based on the CdWO ₄ panel detectors with the 0.3-mm thickness for medium and high X-ray energies was carried out. A series of experiments was carried out to determine the X-ray attenuation rate with the maximum energies of 4.5 and 9 MeV for steel plates with a mass thickness from 20 to 80 g/cm ² . A comparison of the experimental and calculated data on the attenuation rate showed a good convergence for the range of mass thicknesses of the test object fragments. The calculation results and the results of experimental studies prove the correctness of the proposed method for calculating and evaluating the basic parameters of DR systems under the condition of rigid slit collimation of X-ray radiation for inspection of large objects from highly scattering materials.