Radiation penetration system and calibration of the same

Abstract

Position errors of the flat-panel detector in the axes system of the radiation penetration system relative to a necessitated position which remain, for example, after a coarse setup of the radiation penetration system are balanced and thus the accuracy of the radiation penetration system is brought almost randomly close to the accuracy which would have resulted if the flat-panel detector had been exactly adjusted mechanically subsequently by executing a geometrical correction of the radiation penetration raw image, so that a change of a projection of the penetrated object in the radiation penetration raw image due to the position error is reduced or corrected.

1 . A method for calibrating a radiation penetration system comprising a radiation source, a flat-panel detector for generating radiation penetration raw images of an object, a manipulator which is implemented to change a relative position between the radiation source, the object and the flat-panel detector, wherein the axes system is defined by at least one movement axis of the manipulator and one beam axis between the radiation source and the flat-panel detector, and a preprocessor for applying correction data to the radiation penetration raw images of the object to acquire radiation penetration images of the object, comprising
 generating radiation penetration raw images of a calibration object in different relative positions changed with respect to each other by the manipulator between the radiation source, the calibration object and the flat-panel detector on the basis of radiation which penetrates the calibration object between the radiation source and the flat-panel detector, by the flat-panel detector; and   readjusting the correction data depending on the radiation penetration raw images of the calibration object so that the application of the readjusted correction data leads to a geometrical correction of the radiation penetration raw images, so that a change of a projection of the object in the radiation penetration raw image due to a position error of the flat-panel detector in the axes system relative to a necessitated position is reduced, wherein the position error of the flat-panel detector is defined as
 a tilting of a column or line direction of the flat-panel detector relative to a rotation or translation positioning axis of the manipulator, or 
 a tilting of the column or line direction of the flat-panel detector relative to a trajectory along which the flat-panel detector moves relative to the object between the plurality of radiation penetration raw images. 
   
     
     
         2 . The method according to  claim 1 , wherein the flat-panel detector comprises an irregularity in the distribution of pixel positions in an image plane of the flat-panel detector and the method further comprises providing the flat-panel detector in a pre-calibrated state, wherein the correction data is preset such that the same correct the irregularity of distribution of the pixel positions in the image plane, so that the application of the thus preset correction data leads to a regular pixel grid, wherein the generation is executed in the pre-calibrated state and the readjustment uses the radiation penetration raw images of the calibration object in a version wherein the preset correction data are applied to the same. 
     
     
         3 . The method according to  claim 1 , wherein the radiation penetration system further comprises a reconstructor which is implemented to reconstruct the object from a plurality of radiation penetration images which were acquired by the processor from radiation penetration raw images which were generated by the flat-panel detector by changing the relative position between the radiation source, the object and the flat-panel detector between the radiation penetration raw images, wherein the reconstructor is implemented to assume a position correctness of the flat-panel detector in the axes system in the reconstruction. 
     
     
         4 . The method according to  claim 3 , wherein the preprocessor and the reconstructor are implemented such that the resolution of the radiation penetration images of the object is adjustable by adjusting a binning extent from the resolution in which the geometrical correction is executed to the resolution of the radiation penetration images of the object. 
     
     
         5 . A device for calibrating a radiation penetration system comprising a radiation source, a flat-panel detector for generating radiation penetration raw images of an object, a manipulator which is implemented to change a relative position between the radiation source, the object and the flat-panel detector, wherein the axes system is defined by at least one movement axis of the manipulator and a beam axis between the radiation source and the flat-panel detector, and a preprocessor for applying correction data to the radiation penetration raw images of the object to acquire radiation penetration images of the object, comprising
 a generator for generating radiation penetration raw images of a calibration object in different relative positions changed with respect to each other by the manipulator between the radiation source, the calibration object and the flat-panel detector on the basis of radiation which penetrates the calibration object between the radiation source and the flat-panel detector, by the flat-panel detector; and   a readjuster for readjusting the correction data depending on the radiation penetration raw images of the calibration object so that the application of the readjusted correction data leads to a geometrical correction of the radiation penetration raw images, so that a change of a projection of the object in the radiation penetration raw image due to a position error of the flat-panel detector in the axes system relative to a necessitated position is reduced, wherein the position error of the flat-panel detector is defined as
 a tilting of a column or line direction of the flat-panel detector relative to a rotation or translation positioning axis of the manipulator, or 
 a tilting of the column or line direction of the flat-panel detector relative to a trajectory along which the flat-panel detector moves relative to the object between the plurality of radiation penetration raw images. 
   
     
     
         6 . A radiation penetration system comprising a device for calibrating the radiation penetration system according to  claim 5 . 
     
     
         7 . The radiation penetration system according to  claim 6 , wherein the flat-panel detector comprises an irregularity in the distribution of pixel positions in an image plane of the flat-panel detector and wherein the flat-panel detector is in a pre-calibrated state, wherein the correction data is preset such that the same correct the irregularity of distribution of the pixel positions in the image plane, so that the application of the thus preset correction data leads to a regular pixel grid, the generator for generating executes the generation in the pre-calibrated state and the readjuster for readjusting uses the radiation penetration raw images of the calibration object in the readjustment in a version wherein the preset correction data are applied to the same. 
     
     
         8 . The radiation penetration system according to  claim 6 , wherein the radiation penetration system further comprises a reconstructor which is implemented to reconstruct the object from a plurality of radiation penetration images which were acquired by the processor from radiation penetration raw images which were generated by the flat-panel detector by changing the relative position between the radiation source, the object and the flat-panel detector between the radiation penetration raw images, wherein the reconstructor is implemented to assume a position correctness of the flat-panel detector in the axes system in the reconstruction. 
     
     
         9 . The radiation penetration system according to  claim 8 , wherein the preprocessor and the reconstructor are implemented such that the resolution of the radiation penetration images of the object is adjustable by adjusting a binning extent from the resolution in which the geometrical correction is executed to the resolution of the radiation penetration images of the object. 
     
     
         10 . The radiation penetration system according to  claim 6 , wherein the readjuster for readjusting the correction data is implemented such that the position error of the flat-panel detector additionally comprises tilting of an image plane of the flat-panel detector from a perpendicular alignment with respect to a beam axis between the radiation source and the flat-panel detector. 
     
     
         11 . A non-transitory computer readable medium having stored thereon a computer program comprising a program code for executing the method according to  claim 1  when the program is executed on a computer.