Proceedings Article | 31 March 2016
KEYWORDS: Calcium, Arteries, Dual energy imaging, X-rays, Algorithm development, X-ray imaging, Image processing, Visualization, Lung, Bone, Heart, Optical simulations
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.
