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Improvement of Digitally Reconstructed Radiograph Quality of Thoracic 4D Cone Beam Computed Tomography

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M Wang

M Wang1,2*, G Sharp2, S Rit3, V Delmon3, G Wang1, (1) Tsinghua University, Beijing, China, (2) Massachusetts General Hospital, Boston, MA, (3)University of Lyon, Villeurbanne, France

MO-F-WAB-9 Monday 4:30PM - 6:00PM Room: Wabash Ballroom

Purpose: 4D cone beam computed tomography (4DCBCT) suffers from poor image quality, which limits its use as a reference image for image-guided procedures that use radiography and fluoroscopy. This abstract demonstrates improved image quality in Digitally Reconstructed Radiographs (DRR) derived from thoracic 4DCBCT.

Methods: In our method, projection images are used to create both a phase-rebinned 4D volume and streak-free 3D volume. These volumes are combined into a new 4DCBCT that includes stationary voxels from 3D volume and moving voxels from 4D volume. Stationary voxels include the chest wall, which has only small motion during breathing, and moving voxels include the soft tissues inside chest wall, such as lung, heart, and abdomen. The chest wall was segmented from 3D volume, and the segmented result was used to replace corresponding voxels in 4D volume. To generate the DRR, only high intensity voxels, including chest wall, heart, abdomen, main vessels and bronchi, and tumor, were used. This method reduced streak artifacts of 4DCBCT volume, but preserved the motion information present within the lungs and diaphragm.

Results: DRR images computed from 4DCBCT are visually poor because of the streak artifacts, while DRR images computed from 3DCBCT suffer from motion blur. The DRR computed from the combined 3D and 4D volumes are visually more similar to the original projection images at corresponding projection angles.

Conclusion: DRR image quality declined because of the streak artifacts in 4DCBCT. By combining 4D volume and streak-free 3D volume and extracting the high intensity voxels to generate DRR, the streak artifacts can be effectively reduced, which results in improvement of the DRR image quality.

Funding Support, Disclosures, and Conflict of Interest: This work was supported by the National Basic Research Program of China (973) under Grant 2011CB707701 and research foundation of Tsinghua University. None of the authors has a conflict of interest.

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