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Low Dose CBCT Reconstruction Via Prior Contour Based Total Variation Regularization (PCTV)

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Y Chen

Y Chen1*, F Yin2 , Y Zhang3 , L Ren4 , (1) Duke University, Durham, NC, (2) Duke University Medical Center, Durham, NC, (3) Duke University Medical Center, Durham, NC, (4) Duke University Medical Center, Durham, NC


MO-AB-FS4-6 (Monday, July 31, 2017) 7:30 AM - 9:30 AM Room: Four Seasons 4

Purpose: Compressed sensing reconstruction using total-variation (TV) tends to over-smooth the edge information by uniformly penalizing the image gradient. The goal of this study is to develop a novel prior contour based TV (PCTV) method to enhance the edge information in compressed sensing reconstruction for CBCT.

Methods: The edge information is extracted from prior planning-CT images via edge detection. Planning-CT is registered with on-board CBCT reconstructed with TV method through rigid or deformable registration. The CT edge contour is then mapped to CBCT based on the registration, and is then used as the weighting map for TV regularization to enhance edge information in CBCT reconstruction. The PCTV method was evaluated using both extended-cardiac-torso (XCAT) phantom and brain patient data. In XCAT study, breathing amplitude change was simulated from CT to CBCT volume, and deformable registration was performed for edge mapping from CT to CBCT. Noise was simulated to evaluate the robustness of the method. In brain patient study, rigid registration was performed for edge mapping. 45 hall-fan projections over 360˚ and 50 full-fan projections over 200˚ scan angle were used in the XCAT and patient studies, respectively. Results were compared with both TV and edge preserving TV (EPTV) methods.

Results: Compared to TV and EPTV, PCTV enhanced the edge information of bone, lung vessels and tumor in XCAT reconstruction and complex bony structures in head CBCT. In XCAT study, compared with ground truth, relative error were 1.54%, 0.73% and 0.24% and edge cross correlation were 0.63, 0.70 and 0.79 for TV, EPTV and PCTV, respectively. Edge enhancement by PCTV was reduced slightly with noise but was still superior to other methods.

Conclusion: PCTV can preserve edge information as well as reduce streak artifacts and noise in limited-projection CBCT reconstruction. PCTV is superior to TV and EPTV methods in edge enhancement.

Funding Support, Disclosures, and Conflict of Interest: This work was supported by NIH grant R01 CA-184173.

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