Low- vs. standard-dose coronary artery calcium scanning

This study was designed to assess the accuracy of coronary artery calcium scans (CACS) acquired at radiation doses below mammography and low-dose lung scanning, compared with standard-dose CACS.

CACS was performed in 102 consecutive patients at 120 kVp; all were imaged at standard-dose mAs levels ranging from 30 to 80 mAs determined by their weight, with iterative reconstruction (IR) level 3, and at 50% of the standard-dose mAs with IR level 7 to compensate for the expected increased noise with lower mAs. The low- vs. standard-dose mAs was 24.5 ± 8.8 vs. 48.5 ± 17.8 mAs (P < 0.0001), and the radiation exposure was 0.37 ± 0.16 vs. 0.76 + 0.34 mSv (P < 0.0001). The Agatston score correlation between the low and high dose was excellent (r = 0.998, P < 0.0001) over a range of scores from 0 to 2512. The weighted kappa for agreement of standard CAC risk categories was 0.95 (95% CI 0.83-0.97). The mean of the differences between individual low- and standard-dose Agatston scores was 17.4 ± 25.8, lower than the reported variability of two scans performed with the same mAs.

There was excellent agreement of CACS-based risk classification at low and standard doses, with lower interscan variability than with reported identical doses. The low-dose CACS radiation exposure was less than the approved screening tools of mammography and low-dose lung scanning.