This study evaluated optimal Hounsfield Unit (HU) thresholds for assessing aortic calcification on contrast-enhanced CT and identifying how closely these measurements correspond to conventional non-contrast Agatston scoring.
A total of 1,125 patients undergoing triphasic thoracoabdominal CT angiography were retrospectively analyzed. Fixed HU thresholds ranging from 100 to 900 HU, as well as dynamic patient-specific thresholds, were tested in both arterial and venous phases and compared with non-contrast Agatston scores. The strongest correlations were achieved using a fixed threshold of 300 HU in the venous phase, both for thoracic (ρ = 0.93) and abdominal (ρ = 0.92) aortic calcification. Dynamic thresholding showed lower predictive performance, while substantially higher thresholds (800–900 HU) were required in the arterial phase to achieve optimal agreement.
Although agreement decreased in patients with a high calcium burden, the results suggest that a fixed 300 HU threshold on venous-phase contrast-enhanced CT may serve as a practical surrogate for estimating aortic calcification when dedicated non-contrast imaging is unavailable. The authors highlight the potential value of this approach for opportunistic cardiovascular risk assessment and for extracting additional clinically relevant information from routine CT examinations.