Quantification of coronary arterial calcium by dual energy digital subtraction fluoroscopy

Clinical studies of the heart with fluoroscopy have shown that fluoroscopic visualization of calcium in the coronary arteries is strongly associated with coronary artery disease. However, fluoroscopic detection is limited by its low sensitivity, which is partly due to the interfering background tissue structures and image quantum noise. Moreover, quantification of the absolute amount of calcium in an arterial segment has not been possible. A real-time dual-energy subtraction technique has been investigated as a possible solution to the above problem. In this energy subtraction technique, the kVp and filtration are switched at 30 Hz. In order to assess the potential utility of this videodensitometric technique to quantitate coronary artery calcium, arterial phantoms and excised segments of diseased human arteries were imaged. The low- and high-energy images were corrected for scatter and veiling glare before subtraction. Calcium measurements were made using the tissue-suppressed energy-subtracted images. The estimated calcium phosphate and ashed weights of the calcified arterial segments (N = 20) were highly correlated (slope = 1.04, Intercept = -0.33 mg, r = 0.92).