[Detail recognition in the x-ray picture and the limits of possible reduction in radiation dosage].

The minimal size of details detected on the image with pre-set probability is calculated by means of determination of the spatial frequency at which the contrast of the image detail equals the contrast threshold. The calculated results quite agree with experiment and practice. A comparison of the relative contributions of image and visual noise to the contrast threshold makes possible the estimation of minimal doses at which the quantum fluctuations do not cause yet an essential reduction of the image informativity. These doses depend on size and specific radiation contrast of details which must be detected on the image. The sign of optimal alignment of informativity and dose is the balance of all the main components of noise.