Determination and correction of non-linear detector pixels in X-ray apparatus involves using uniform test image in conjunction with corrective, masking and differencing techniques

摘要

A uniformly-illuminated test image of X-radiation is recorded by the pixelated detector. The test image is corrected for offset and gain. The corrected image is filtered, especially using a median filter. The size of the filter mask is made a function of the quality of gain correction, the noise in the test image and the expected cluster size of non-linear pixels. The difference between the filtered test image and the unfiltered offset and gain corrected test image is formed. All pixels in the difference image, in which the gray value exceeds an upper threshold, or falls below a lower threshold are determined. These are identified as non-linear detector pixels. On recording the next X-ray image, the gray values of the pixels identified are always matched with those of the surrounding pixels.