Author: Emi Ai Eastman, Chao Guo, Christina Lee, Xinhua Li, Alexander W. Scott, Yifang (Jimmy) Zhou 👨🔬
Affiliation: Cedars-Sinai Medical Center 🌍
Purpose:
Smoking is one of the risk factors for coronary artery disease. It is desirable to estimate the coronary artery calcification (CAC), a key biomarker for atherosclerosis and cardiovascular events, during lung cancer screening (LCS) CT scans (standard protocol, non-gated). While the Agatston score is the gold standard for CAC quantification, it requires dedicated ECG-gated CT scans. This study investigates the feasibility of assessing CAC using low-dose LCS CT scans and evaluates the impact of cardiac phase on scoring consistency.
Methods:
A CIRS Dynamic Cardiac Phantom with nine calcification inserts (diameter: 1.2–5 mm; density: 100–400 mg/cc) was scanned using a Siemens Force scanner. Two protocols were used: ECG-gated CAC scoring (CTDIvol = 1.74 mGy) and non-gated LCS (CTDIvol = 2 mGy), simulating heart rates of 50–100 BPM. Calcium scores were calculated using clinical software, with non-gated LCS scores compared to gold standard ECG-gated scores.
Results:
ECG-gated scans showed consistency in Agatston scores across five runs at 50 BPM (55.5, 58.6, 59.8, 57.7, 59.1; coefficient of variation < 0.1). Non-gated LCS scans at 50 BPM, however, exhibited significant variability, with one run showing score up to 50% lower than that of another run (26.9, 27.5, 33.7, 43.5, 27.5; coefficient of variation ≈ 0.2). This variability was most pronounced at cardiac phases near 50–55% of R-R interval and was reproducible across heart rates (50–100 BPM) and calcification inserts (diameter ≥ 3 mm; density ≥ 100 mg/cc).
Conclusion:
Cardiac phase significantly impacts CAC quantification in non-gated LCS scans, especially at 50–55% R-R interval. Challenges arise with calcifications <3 mm or densities <250 mg/cc, which may not be reliably detected. While non-gated LCS shows potential for cardiovascular risk evaluation, its consistency remains limited compared to ECG-gated scans, offering a complementary but less reliable approach.