Premium
WE‐G‐BRF‐03: A Quasi‐Cine CBCT Reconstruction Technique for Real‐Time On‐ Board Target Tracking of Lung Cancer Treatment
Author(s) -
Zhang Y,
Yin F,
Ren L
Publication year - 2014
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4889496
Subject(s) - imaging phantom , ground truth , cone beam computed tomography , computer science , nuclear medicine , image registration , artificial intelligence , iterative reconstruction , computer vision , medicine , computed tomography , radiology , image (mathematics)
Purpose: To develop a quasi‐cine CBCT reconstruction technique that uses extremely‐small angle (∼3°) projections to generate real‐time high‐quality lung CBCT images. Method: 4D‐CBCT is obtained at the beginning and used as prior images. This study uses extremely‐small angle (∼3°) on‐board projections acquired at a single respiratory phase to reconstruct the CBCT image at this phase. An adaptive constrained free‐form deformation (ACFD) method is developed to deform the prior 4D‐CBCT volume at the same phase to reconstruct the new CBCT. Quasi‐cine CBCT images are obtained by continuously reconstructing CBCT images at subsequent phases every 3° angle (∼0.5s). Note that the prior 4D‐CBCT images are dynamically updated using the latest CBCT images. The 4D digital extended‐cardiac‐torso (XCAT) phantom was used to evaluate the efficacy of ACFD. A lung patient was simulated with a tumor baseline shift of 2mm along superior‐inferior (SI) direction after every respiratory cycle for 5 cycles. Limited‐angle projections were simulated for each cycle. The 4D‐CBCT reconstructed by these projections were compared with the ground‐truth generated in XCAT.Volume‐percentage‐difference (VPD) and center‐of‐mass‐shift (COMS) were calculated between the reconstructed and the ground‐truth tumors to evaluate their geometric differences. The ACFD was also compared to a principal‐component‐analysis based motion‐modeling (MM) method. Results: Using orthogonal‐view 3° projections, the VPD/COMS values for tumor baseline shifts of 2mm, 4mm, 6mm, 8mm, 10mm were 11.0%/0.3mm, 25.3%/2.7mm, 22.4%/2.9mm, 49.5%/5.4mm, 77.2%/8.1mm for the MM method, and 2.9%/0.7mm, 3.9%/0.8mm, 6.2%/1mm, 7.9%/1.2mm, 10.1%/1.1mm for the ACFD method. Using orthogonal‐view 0° projections (1 projection only), the ACFD method yielded VPD/COMS results of 5.0%/0.9mm, 10.5%/1.2mm, 15.1%/1.4mm, 20.9%/1.6mm and 24.8%/1.6mm. Using single‐view instead of orthogonal‐view projections yielded less accurate results for ACFD. Conclusion: The ACFD method accurately reconstructs snapshot CBCT images using orthogonal‐view 3° projections. It has a great potential to provide real‐time quasi‐cine CBCT images for verification in lung radiation therapy. The research is supported by grant from Varian Medical Systems.