Enhancement of soft-tissue contrast in cone-beam CT using an anti-scatter grid with a sparse sampling approach. (February 2020)

• Record Type: Journal Article
• Authors: Cho, Sanghoon; Lim, Sunho; Kim, Changhwan; Wi, Sunhee; Kwon, Taejin; Youn, Won Sik; Lee, Sang Hyun; Kang, Bo Sun; Cho, Seungryong
• Is Part Of: Physica medica. Volume 70(2020)
• Page Start: 1
• Page End: 9
• Publication Date: 2020-02
• Subjects: Cone-beam CT (CBCT) -- Anti-scatter grid -- Scatter correction; Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2020.01.004
• Languages: English
• ISSNs: 1120-1797

Abstract

Highlights: Use of anti-scatter grids with high grid-ratio in CBCT is justified. Sparse-view CBCT scanning is desirable when using such grids. Exposure per view needs to be increased to balance the noise. The proposed method increases low-contrast visibility in CBCT. Abstract: Purpose: Anti-scatter grids suppress the scatter substantially thus improving image contrast in radiography. However, its active use in cone-beam CT for the purpose of improving contrast-to-noise ratio (CNR) has not been successful mainly due to the increased noise related to Poisson statistics of photons. This paper proposes a sparse-view scanning approach to address the above issue. Method: Compared to the conventional cone-beam CT imaging framework, the proposed method reduces the number of projections and increases exposure in each projection to enhance image quality without an additional cost of radiation dose to patients. For image reconstruction from sparse-view data, an adaptive-steepest-descent projection-onto-convex-sets (ASD POCS) algorithm regularized by total-variation (TV) minimization was adopted. Contrast and CNR with various scattering conditions were evaluated in projection domain by a simulation study using GATE. Then we evaluated contrast, resolution, and image uniformity in CT image domain with Catphan phantom. A head phantom with soft-tissue structures was also employed for demonstrating a realistic application. A virtual grid-based estimation and reduction of scatter has also been implemented for comparison with the real anti-scatter grid. Results: In the projection domain evaluation, contrast and CNR enhancement was observed when using an anti-scatter grid compared to the virtual grid. In the CT image domain, the proposed method produced substantially higher contrast and CNR of the low-contrast structures with much improved image uniformity. Conclusion: We have shown that the proposed method can provide high-quality CBCT images particularly with an increased contrast of soft-tissue at a neutral dose for image-guidance.