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Session: Imaging: CBCT Artifacts [Return to Session]

Scatter Correlation and Correction for Cone-Beam CT Using Dual-Layer Flat Panel Detector

S Gu*, B Qi, H Gao, Tsinghua University, Beijing, CN


WE-IePD-TRACK 1-2 (Wednesday, 7/28/2021) 3:00 PM - 3:30 PM [Eastern Time (GMT-4)]

Purpose: Scatter remains a big challenge and dominating factor of affecting dual-energy CT performance. The goal of this work is to study the correlation and correction of the x rays scattering between the layers for Cone-Beam CT using a prototype dual-layer flat-panel detector.

Methods: A physical model about the relationship of the scatter distribution between layers is proposed, it may be described by a function related to the average scatter energy. Since the average scatter energy and the projection value are both related to the size of the phantom, we approximately assume the correlation is a function of the low and high projections. The dual layer detector consists of a top and bottom CsI scintillator with the same thickness of 550 μm, no extra filter in-between the two layers, the active area of 43.2*43.2 cm2, and the pixel size of 150 µm. Experiments were performed using 120 kV X-ray voltage, 2*2 detector binning mode, and a multi-energy CT phantom (Gammex, Model 1472). The projections of the phantom in short, long axis, and the separate head part were acquired using cone beam and fan beam respectively. The difference between cone beam and fan beam transmission images is considered to be the contribution from scatter.

Results: Three groups of the experiments show that scatter distribution from top (Is1) and bottom (Is2) layers satisfy the relation Is2 = αIs1, where α follows our physics model. The correlation coefficients of the bottom distribution and the normalized top distribution are 99.3%, 99.7%, 93.4%, respectively.

Conclusion: A scatter correlation model is proposed to describe the relationship of the scatter between two layers. The preliminary experimental results are basically consistent with the expectation, further validation of the scatter correlation model and scatter correction are underway with MC simulations and real experiments.

Funding Support, Disclosures, and Conflict of Interest: This project was supported in part by grants from the National Natural Science Foundation of China (No. U20A20169 and No. 12075130).



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