The object of the study was spring wheat grain of the Torca variety infested with granary weevil (Sitophilus granarius L.). Weevil-infested kernels were X-rayed for detection of hidden endosperm damage which is connected with the reproductive cycle of the studied insect pest. Digital analysis of infested grain roentgenograms was used to determine the mass loss in wheat kernels. Infestation rate was tested in five periods: zero (control), 5, 10, 15 and 20 days from the moment of infestation. A parabolic dependence of the mass loss on infestation time was found. To determine the mass losses connected with insect growth, a new algorithm was developed, consisting of two steps. In the first step, the volume of a single loss was calculated using the grey scale. Grey values were taken from a calibration marker which was made of plexiglass. In the second step, the mass loss was obtained from the volume and density of endosperm.