Abstract: An X-ray image-processing apparatus includes a subtraction circuit for performing subtraction between a mask image and a contrast image, and a grayscale-transforming circuit for transforming the grayscales of the mask image, based upon the grayscales of the contrast image, so as to reduce the difference in the grayscales between these images. This grayscale transformation is performed before the subtraction processing.

Abstract: An X-ray imaging system has an X-ray source, an X-ray image detection section, an X-ray mask member, a drive unit, a memory, a calculating section, and an image output unit. An X-ray image is detected by the X-ray image detection section. The X-ray mask member has X-ray shielding regions, distributed in a predetermined pattern, which locally shield the X-ray. The mask member is driven by the drive unit so that it is inserted in or removed from an X-ray radiation field between the X-ray image detection section and the X-ray source, and is sequentially displaced to predetermined positions in the radiation field. The calculating section calculates scattered X-ray intensity distribution data based on a plurality of transmission X-ray data obtained by irradiating an object with X-rays with the mask member located at different positions in the radiation field, and transmission X-ray data obtained by irradiating the object with X-rays with the mask member located outside this field.