Impact of iterative reconstruction on CT coronary calcium quantification

We evaluated the influence of sinogram-affirmed iterative reconstruction (SAFIRE) on the coronary artery calcium (CAC) score by computed tomography (CT). Seventy patients underwent CAC imaging by 128-slice dual-source CT. CAC volume, mass and Agatston score were calculated from images reconstructed by filtered back projection (FBP) without and with incremental degrees of the SAFIRE algorithm (10-50 %). We used the repeated measuring test and the Steel-Dwass test for multiple comparisons of values and the difference ratio among different SAFIRE groups using the FBP as reference. The median Agatston score (range) decreased with incremental SAFIRE degrees: 163 (0.1 -aEuro parts per thousand 3,393.3), 158.4 (0.3 -aEuro parts per thousand 3,079.3), 137.7 (0.1 -aEuro parts per thousand 2,978.0), 120.6 (0 -aEuro parts per thousand 2,783.6), 102.6 (0 -aEuro parts per thousand 2,468.4) and 84.1 (0 -aEuro parts per thousand 2,186.9) for 0 % (FBP), 10 %, 20 %, 30 %, 40 % and 50 % SAFIRE, respectively (P < 0.05). In comparison with FBP, CAC volume (from 8.1 % to 47.7 %), CAC mass (from 5.3 % to 44.7 %) and CAC Agatston score (from 7.3 % to 48.4 %) all decreased with increasing SAFIRE from 10 % to 50 %, respectively (P < 0.05). High-grade SAFIRE resulted in the disappearance of detectable calcium in three cases with low calcium burden. SAFIRE noise reduction techniques significantly affected the CAC, which potentially alters perceived cardiovascular risk. aEuro cent Iterative reconstruction reduces the amount of coronary calcium detected. aEuro cent Iterative reconstruction potentially changes the calcium-based cardiovascular risk estimation. aEuro cent Incidentally, calcium is no longer detectable using iterative reconstruction.