Abstract
Scatter contamination is one of the main sources of decreasing the image quality in cone-beam computed tomography (CBCT). The moving blocker method is economic and effective for scatter correction (SC), which can simultaneously estimate scatter and reconstruct the complete volume within the field of view (FOV) from a single CBCT scan. However, at the regions with large intensity transition in the projection images along the axial blocker moving direction, the estimation of scatter signal from blocked regions in a single projection view can produce large error and cause significant artifacts in reconstructed images and null the usability of these regions. Furthermore, blocker edge detection error can significantly deteriorate both primary signal and scatter signal estimation and lead to unacceptable reconstruction results. In this study, we propose to use the adjacent multi-view projection images to jointly estimate scatter signal more accurately. In return, the more accurately estimated scatter signal can be utilized to detect blocker edges more accurately for greatly improved robustness of moving-blocker based SC. The experimental results using a Catphan phantom and an anthropomorphic pelvis phantom CBCT data show that the new method can effectively suppress the estimation errors of scatter signal in the fast signal transition regions and is able to correct the blocker detection errors. This development will expand the utility of moving-blocker based SC for the target with sharp intensity changes in the projection images and provide the needed robustness for its clinical translation.
Highlights
Come-beam computed tomography (CBCT) is being widely used as an image guidance tool in radiation therapy nowadays
The multi-view SC (MVSC) method corrected this overestimation by utilizing more sample points from adjacent projection views and led to more gradual scatter transition
The root mean square error (RMSE) values are largely reduced from 379 (WOSC) to 29 (SVSC) and 29 (MVSC) for regions of interest (ROIs)-1, from 304 (WOSC) to 32 (SVSC) and 31 (MVSC) for ROI-2, from 305 (WOSC) to 35 (SVSC) and 34 (MVSC) for ROI-3. These results demonstrate that MVSC eliminates the artifacts caused by the lack of scatter signal samples in the boundary region, and maintains the superior scatter correction performance of the original single-view SC (SVSC) method for the other regions
Summary
Come-beam computed tomography (CBCT) is being widely used as an image guidance tool in radiation therapy nowadays. The quality of CBCT image is important to localize and delineate the tumor and to define relevant volumes when the patient is in the treatment position [1]. Due to the use of the flat panel detector (FPD), the large amount of scatter signal deteriorates the projection images and greatly reduces the quality of CBCT images [2]. The manifest shading artifacts can lead to decreased image contrast and inaccurate CT number, which makes it difficult to contour the target and other volumes and to calculate the correct. The funder had no role in study design, data analysis, decision to publish, or preparation of the manuscript
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