Linear Lag Models and Measurements of the Lag Correction Factors

Abstract

For fluoroscopic imaging, flat-panel dynamic detectors can acquire X-ray image sequences with frame rates higher than 300 frames per second. However, the sequentially acquired images have artifacts due to the lag signals, which are caused from trapping charges in the amorphous structure and incomplete reads. Furthermore, the lag signal lowers the noise power spectrum (NPS) of the detector; hence, the detector performance can be inflated. Conventional approaches for correcting the measured NPS are based on the lag correction factor (LCF). Various LCF measurement methods have been developed based on moving average and auto-regressive models. Current methods require high computational complexities with many images. In this paper, we first review the current methods and next propose three LCF measurement methods in simplified forms under an autoregressive model of order 1 based on the temporal periodogram mean and line means. Here, we suggest schemes that deal with several disturbances, such as nonuniform temporal gains and exposure leaks, to accurately measure LCF. A comparative review of the LCF measurement methods can establish a taxonomy of measurements. Through extensive experiments using X-ray images acquired from dynamic detectors, it is shown that the proposed methods yield comparable performances with lower computational complexities compared to the existing methods.