31 March 2016 Dual energy x-ray imaging and scoring of coronary calcium: physics-based digital phantom and clinical studies
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Abstract
Coronary artery calcification (CAC) as assessed with CT calcium score is the best biomarker of coronary artery disease. Dual energy x-ray provides an inexpensive, low radiation-dose alternative. A two shot system (GE Revolution-XRd) is used, raw images are processed with a custom algorithm, and a coronary calcium image (DECCI) is created, similar to the bone image, but optimized for CAC visualization, not lung visualization. In this report, we developed a physicsbased, digital-phantom containing heart, lung, CAC, spine, ribs, pulmonary artery, and adipose elements, examined effects on DECCI, suggested physics-inspired algorithms to improve CAC contrast, and evaluated the correlation between CT calcium scores and a proposed DE calcium score. In simulation experiment, Beam hardening from increasing adipose thickness (2cm to 8cm) reduced Cg by 19% and 27% in 120kVp and 60kVp images, but only reduced Cg by <7% in DECCI. If a pulmonary artery moves or pulsates with blood filling between exposures, it can give rise to a significantly confounding PA signal in DECCI similar in amplitude to CAC. Observations suggest modifications to DECCI processing, which can further improve CAC contrast by a factor of 2 in clinical exams. The DE score had the best correlation with "CT mass score" among three commonly used CT scores. Results suggest that DE x-ray is a promising tool for imaging and scoring CAC, and there still remains opportunity for further DECCI processing improvements.
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Bo Zhou, Di Wen, Katelyn Nye, Robert C. Gilkeson, David L. Wilson, "Dual energy x-ray imaging and scoring of coronary calcium: physics-based digital phantom and clinical studies", Proc. SPIE 9783, Medical Imaging 2016: Physics of Medical Imaging, 978342 (31 March 2016); doi: 10.1117/12.2217023; https://doi.org/10.1117/12.2217023
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