Handling misalignment in differential phase contrast imaging

A method for handling misalignment in an X-ray imaging system for differential phase contrast imaging, comprising the following steps:

• a) providing a differential phase contrast setup with an X-ray source, an X-ray detector, a processing unit, and a grating arrangement comprising a source grating, a phase grating and an analyser grating, wherein the source grating is arranged between the X-ray source and the phase grating, and the analyser grating is arranged between the phase grating and the detector;
• wherein the X-ray source and the source grating are provided as a rigid X-ray source unit;
• and wherein the phase grating, the analyser grating and the detector are provided as a rigid X-ray detection unit;
• b) determining a misalignment of at least one of the gratings with an optical measurement system, wherein the measurement system comprises at least three sensors at different corners of the X-ray detection unit, wherein the at least three sensors are provided as at least three 4-quadrant photodiodes, wherein an optical source device fixedly attached to the X-ray source unit is configured to generate a light beam to each of the 4-quadrant photodiodes, and wherein the 4-quadrant photodiodes measure the movement in the plane of the detector and an angular tilt with respect to the light beam;
• c) computing a correction signal based on the determined misalignment.

A non-transitory computer readable medium having stored thereon a computer program for handling misalignment in an X-ray imaging system for differential phase contrast imaging, said computer program having instructions executable by a processor for performing a plurality of acts, from among said plurality there being the acts of:

• i) for a differential phase contrast setup that includes an X-ray source, an X-ray detector, a processing unit, and a grating arrangement comprising a source grating, a phase grating and an analyzer grating;
• wherein the source grating is arranged between the X-ray source and the phase grating, and the analyzer grating is arranged between the phase grating and the detector;
• wherein the X-ray source and the source grating are provided as a rigid X-ray source unit;
• wherein the phase grating, the analyzer grating and the detector are provided as a rigid X-ray detection unit;
• wherein an optical measurement system for determining a misalignment of at least one of the gratings comprises at least three sensors at different corners of the X-ray detection unit;
• and wherein the at least three sensors are provided as at least three 4-quadrant photodiodes, an optical source device being fixedly attached to the X-ray source unit,
• generating by said optical source device, a light beam to each of the 4-quadrant photodiodes, wherein 4-quadrant photodiodes measure the movement in the plane of the detector and an angular tilt with respect to the light beam,
• determining, from the measurement by the 4-quadrant photodiodes, a misalignment of the differential phase contrast setup between said X-ray source unit and said X-ray detection unit;
• and
• computing a correction signal based on the determined misalignment.

An X-ray imaging system for differential phase contrast imaging, comprising

• a differential phase contrast setup that includes:
• an X-ray source;
• an X-ray detector;
• a grating arrangement comprising a source grating, a phase grating and an analyzer grating, wherein the source grating is arranged between the X-ray source and the phase grating, and the analyzer grating is arranged between the phase grating and the detector;
• wherein the X-ray source and the source grating are provided as a rigid X-ray source unit and wherein the phase grating, the analyzer grating and the detector are provided as a rigid X-ray detection unit a cross-section of which has a periphery, said X-ray detection unit having corners along said periphery;
• an optical measurement system that comprises at least three sensors spaced apart along said periphery, said sensors being at different ones of said corners of the X-ray detection unit, wherein each of the sensors has a surface for receiving light, said surface divided into quadrants for separate light measurements per quadrant, an optical source device fixedly attached to said X-ray source being configured for generating a light beam to the surfaces of each of said at least three sensors, wherein said optical measurement system is configured to determine, from output of said at least three sensors, a misalignment of at least one of the gratings, as to movement in the plane of the detector and as to angular tilt with respect to the X-ray source;
• and
• a processing unit configured to provide a correction signal based on the determined misalignment.