Signal Lag Measurements Based on Temporal Correlations

In fluoroscopic imaging, we can acquire x-ray image sequences using a flat-panel dynamic radiography detector. Because of the charge trapping at photodiodes, lag signals occur at the sequentially acquired images and produce lag artifacts. To design low-lag detectors, accurately measuring an amount of the lag signal is important. In the standard of IEC62220-1-3, a lag correction factor (LCF) is measured to obtain a true noise power spectrum, in which a temporal power spectral density (PSD) is employed using steady-state images. However, various noise signals can easily distort the PSD curve and cause erroneous measurements of LCF. In this letter, we propose a measurement algorithm for LCF using the correlation coefficients from steady-state images based on a linear lag model. This method can be a generalized version of a method that is based on the first-order regression model and has a characteristic that is resistant to various noises. Hence, for the standard, the proposed algorithm can be an alternative approach to the PSD method.