X-ray CT system to generate tomographic phase contrast or dark field exposures

An x-ray CT system comprising:

• a source/detector system that generates tomographical phase contrast or dark field exposures, said source/detector system being mounted on a gantry rotatable around a system axis,
• said source/detector system comprising an x-ray source having a grating structure that emits bands of emission maxima and emission minima of a generated x-ray radiation arranged like a grating, with a grating period (p0), that emits a beam fan of x-rays widening in two places with a max fan angle (2xφmax) in the rotation plane of the gantry and a Z-angle (2xξmax) perpendicular to the rotation plane of the gantry;
• said source/detector system comprising a detector arrangement with a plurality of grating/detector modules arranged in parallel, each module comprising, one after another in the beam direction, at least one phase grating (G1i) that generates an interference pattern, an analysis grating (G2i) with a directly connected detector with a plurality of detector elements to determine phase (x0), average radiation intensity (Imed) and amplitude (Iamp) of the average intensity of the radiation per detector element given relative displacement of one of the upstream grating structures, the grating lines of all grating structures (G0, G1i, G2i) being aligned parallel to one another and parallel to the system axis;
• and
• a distance (I) between the grating structure (G0) of the x-ray source and the phase grating (G1,i) of the respective grating/detector modules being adapted depending on the fan angle corresponding to a period (p0i') of the grating structure (G0) of the x-ray source that is projected onto the grating/detector module at the respective fan angle (φi).