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Streaking artifacts reduction in four‐dimensional cone‐beam computed tomography
Author(s) -
Leng Shuai,
Zambelli Joseph,
Tolakanahalli Ranjini,
Nett Brian,
Munro Peter,
StarLack Joshua,
Paliwal Bhudatt,
Chen GuangHong
Publication year - 2008
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 - 10.1118/1.2977736
Subject(s) - streaking , image guided radiation therapy , computer vision , artificial intelligence , cone beam computed tomography , undersampling , computer science , streak , imaging phantom , iterative reconstruction , reduction (mathematics) , medical imaging , optics , physics , mathematics , computed tomography , medicine , radiology , geometry
Cone‐beam computed tomography (CBCT) using an “on‐board” x‐ray imaging device integrated into a radiation therapy system has recently been made available for patient positioning, target localization, and adaptive treatment planning. One of the challenges for gantry mounted image‐guided radiation therapy (IGRT) systems is the slow acquisition of projections for cone‐beam CT (CBCT), which makes them sensitive to any patient motion during the scans. Aiming at motion artifact reduction, four‐dimensional CBCT (4D CBCT) techniques have been introduced, where a surrogate for the target's motion profile is utilized to sort the cone‐beam data by respiratory phase. However, due to the limited gantry rotation speed and limited readout speed of the on‐board imager, fewer than 100 projections are available for the image reconstruction at each respiratory phase. Thus, severe undersampling streaking artifacts plague 4D CBCT images. In this paper, the authors propose a simple scheme to significantly reduce the streaking artifacts. In this method, a prior image is first reconstructed using all available projections without gating, in which static structures are well reconstructed while moving objects are blurred. The undersampling streaking artifacts from static structures are estimated from this prior image volume and then can be removed from the phase images using gated reconstruction. The proposed method was validated using numerical simulations, experimental phantom data, and patient data. The fidelity of stationary and moving objects is maintained, while large gains in streak artifact reduction are observed. Using this technique one can reconstruct 4D CBCT datasets using no more projections than are acquired in a 60 s scan. At the same time, a temporal gating window as narrow as 100 ms was utilized. Compared to the conventional 4D CBCT reconstruction, streaking artifacts were reduced by 60% to 70%.

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