Assessment of coronary artery calcium using dual-energy subtraction digital radiography

Abstract

Cardiovascular disease is the leading cause of global mortality, yet its early detection remains a vexing problem of modern medicine. Although the computed tomography (CT) calcium score predicts cardiovascular risk, relatively high cost ($250-400) and radiation dose (1-3 mSv) limit its universal utility as a screening tool. Dual-energy digital subtraction radiography (DE; <$60, 0.07 mSv) enables detection of calcified structures with high sensitivity. In this pilot study, we examined DE radiography's ability to quantify coronary artery calcification (CAC). We identified 25 patients who underwent non-contrast CT and DE chest imaging performed within 12 months using documented CAC as the major inclusion criteria. A DE calcium score was developed based on pixel intensity multiplied by the area of the calcified plaque. DE scores were plotted against CT scores. Subsequently, a validation cohort of 14 additional patients was independently evaluated to confirm the accuracy and precision of CAC quantification, yielding a total of 39 subjects. Among all subjects (n = 39), the DE score demonstrated a correlation coefficient of 0.87 (p < 0.0001) when compared with the CT score. For the 13 patients with CT scores of <400, the correlation coefficient was -0.26. For the 26 patients with CT scores of ≥400, the correlation coefficient yielded 0.86. This pilot study demonstrates the feasibility of DE radiography to identify patients at the highest cardiovascular risk. DE radiography's accuracy at lower scores remains unclear. Further evaluation of DE radiography as an inexpensive and low-radiation imaging tool to diagnose cardiovascular disease appears warranted.

Fig. 1

Detection of CAC by CT and DE: a CT coronal reconstruction of CAC in the proximal LAD (white arrow). b Corresponding standard PA radiograph suspicious for CAC (white arrow). c Corresponding DE image demonstrating calcification in the region of the LAD (black arrow)

Fig. 2

Detection of CAC by CT and DE: a CT coronal reconstruction demonstrating calcium in the LAD, which is marked by the white arrow. The white arrowhead points to a pacer wire. b Corresponding standard PA radiograph without CAC. The white arrowhead points to a pacer wire. c Corresponding DE image demonstrating calcification in the region of the LAD

Fig. 3

Correlation of DE and CT scores: a. Test cohort DE score versus CT score. The DE scores of the test cohort (n = 25) are plotted against their respective CT scores. b. Validation cohort DE score versus CT score. The DE scores of the validation cohort (n = 14) are plotted against their respective CT scores