Investigation of the Lag Effect in X-Ray Flat-Panel Detector for Cone-Beam Computed Tomography

The purpose of this work is to investigate the factors determining the magnitude and nature of the lag effect (residual signal) in the Varian PaxScan 4343CB flat-panel detector. Depending on the detector mode, typical value of residual signal is 1-2% after single exposed frame, increasing up to 3% after multiple exposures. The lag effect is the cause of up to 3.6% error of average flat-field signal measurement if used for averaging series of continuously exposed frames, which leads to incorrect assessment of X-ray attenuation coefficients. Spatial dependence of the lag effect is confirmed; the results of correction of projection images using spatially localized impulse response functions are demonstrated.