The invention relates to a subject support device (1) to be used in a projection data acquisition apparatus (2) for acquiring projection data of a subject (3). The subject support device comprises a support component (4) providing a support surface (5) for supporting the subject while acquiring the projection data, a diffraction grating (6) for diffracting x-rays, and a moving unit (7, 8) for moving the support component and the diffraction grating relative to each other. This relative movement can allow for a movement of the support component such that the subject is moved through x-rays (16) for determining projection data of different parts of the subject, while the diffraction grating can still be traversed by the x-rays. These projection data can be used for generating a relatively large phase-contrast and/or dark-field projection image.
