| Title |
Measurements of the Lag Correction Factors based on the Power Spectral Density Under Nonuniform Temporal Gains |
| Authors |
이은애(Eunae Lee) ; 김동식(Dong Sik Kim) |
| DOI |
https://doi.org/10.5573/ieie.2022.59.7.60 |
| Keywords |
Dynamic detector; Fixed pattern noise (FPN); Lag correction factor (LCF); Nonuniform temporal gain (NTG); Power spectral density (PSD) |
| Abstract |
We can acquire x-ray image sequences using a flat-panel dynamic detector. Because of the amorphous structure of the photodiodes, lag signals are produced from the previously exposed images in the current image frame and cause various lag artifacts. Hence, it is required to reduce the lag signal and develop detectors have low lag signals. In order to accurately evaluate the lag signal, the lag correction factor (LCF) is measured by estimating the power spectral density and can correct the measured noise power spectrum that is inflated due to the lag signal. However, the nonuniform temporal gain (NTG), which is from inconsistent x-ray sources and detector readout circuits, can distort the LCF measurements. In this paper, we observe influences of NTG on the PSD-based LCF measurement method, which is employed in IEC62220-1-3, both in theoretical and experimental manners for practically acquired images. Because the spectrum of NTG at low frequencies is relatively high, measurements of LCF can be erroneous and should be corrected. We also compare the performance with a correlation-based LCF measurement method. |