Radiation imaging system and offset correction method thereof

A radiation imaging system comprising:

• a grating composed of two or more grating modules arranged along at least a part of a virtual cylindrical surface having a virtual line as a center axis, the virtual line passing through a focal point of a radiation source, a grating line of the grating being in the same direction as the virtual line;
• a radiation image detector having a detection surface divided into two or more segments, the segments corresponding to the respective grating modules, the detection surface having a charge collection electrode per pixel, the charge collection electrode collecting charge converted by a radiation conversion layer, the charge collection electrode being composed of two or more linear electrode groups arranged to have mutually different phases in a direction orthogonal to the virtual line,
• a phase differential image generator for calculating a phase shift value of an intensity modulated signal to produce a phase differential image based on the phase shift value, the intensity modulated signal representing changes in pixel data obtained by each of the linear electrode groups;
• an offset value storage for storing an offset value of the phase shift value, the offset value corresponding to an inclination angle of the grating module relative to the direction orthogonal to the virtual line, the offset value storage storing the offset values corresponding to the respective segments;
• and
• a correcting section for correcting the phase differential image on a segment-by-segment basis based on the offset value.

An offset correction method for a radiation imaging system comprising the steps of:

• moving one of a first grating and a second grating relative to the other in a direction orthogonal to a virtual line, the first grating being composed of two or more first grating modules arranged along at least a part of a virtual first cylindrical surface having the virtual line as a center axis, the virtual line passing through a focal point of a radiation source, a grating line of the first grating being in the same direction as the virtual line, the second grating being composed of two or more second grating modules arranged along at least a part of a virtual second cylindrical surface, the second cylindrical surface being coaxial with the first cylindrical surface and having a larger radius than the first cylindrical surface, a grating line of the second grating being in the same direction as the virtual line;
• detecting radiation passed through the first grating and the second grating by a detection surface of a radiation image detector to obtain pixel data while one of the first grating and the second grating is moved relative to the other, the detection surface being divided into two or more segments, the segments corresponding to the respective second grating modules;
• calculating a phase shift value of an intensity modulated signal to produce a differential image based on the phase shift value, the intensity modulated signal representing a relation between the pixel data and a relative position between the first grating and the second grating;
• and
• correcting the phase differential image on a segment-by-segment basis based on an offset value of the phase shift value, the offset value corresponding to an inclination angle of the second grating module relative to the direction orthogonal to the virtual line, the offset values being stored corresponding to the respective segments.