Impact of Iterative Reconstruction on CT Coronary Calcium Quantification

OBJECTIVES: We evaluated the influence of sinogram-affirmed iterative reconstruction (SAFIRE) on the coronary artery calcium (CAC) score by computed tomography (CT).

METHODS: 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.

RESULTS: The median Agatston score (range) decreased with incremental SAFIRE degrees: 163 (0.1 - 3,393.3), 158.4 (0.3 - 3,079.3), 137.7 (0.1 - 2,978.0), 120.6 (0 - 2,783.6), 102.6 (0 - 2,468.4) and 84.1 (0 - 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.

CONCLUSIONS: SAFIRE noise reduction techniques significantly affected the CAC, which potentially alters perceived cardiovascular risk.

PMID: 24057202

Posted in Computed Tomography and tagged , , , .

One Comment

  1. Main findings as listed by the authors:

    – IR by SAFIRE reduces the amount of detected coronary calcification.
    – CAC parameters decreased similarly in proportion to the SAFIRE algorithm.
    – High-grade SAFIRE can incorrectly result in a negative CAC score.
    – In a proportion of patients low grade SAFIRE increases the CAC score.

    The authors also mention: “Wether a reduction of calcium mass is the result of decreased attenuation or reduced image noise at the borders remains unclear”.

    I found this paper to be very interesting as it brings new questions to the table. Should we change our CAC detection thresholds when using IR?

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