Keywords:
Calcifications / Calculi, Radiation safety, Image manipulation / Reconstruction, CT, Radioprotection / Radiation dose, Computer applications, Arteries / Aorta
Authors:
R. W. van Hamersvelt1, A. M. den Harder1, M. J. Willemink1, A. Schilham1, J. W. J. Lammers1, H. Nathoe1, R. P. J. Budde2, T. Leiner1, P. A. de Jong1; 1Utrecht/NL, 2Rotterdam/NL
Methods and Materials
Twenty patients underwent chest CT and 28 patients electrocardiogram-triggered cardiac CT on a 256-slice CT scanner without using contrast.
Each patient was scanned four times (routine dose and approximately 45,
60 and 75% reduced dose),
dose reduction was achieved by reducing mAs.
Images were reconstructed using filtered back projection (FBP),
three hybrid (iDose4) levels and three model-based IR (IMR) levels (Fig. 1).
iDose4 levels 1,
4 and 7 were used for cardiac CT and levels 1,
4 and 6 for chest CT.
IMR levels 1,
2 and 3 were used for both cardiac and chest CT. Each scan was scored by 2 observers on subjective image quality using a 5-point Likert scale (1,
worse; 5,
excellent).
Scores ≤2 were rated non-diagnostic and therefore excluded. In case >20% of the scans at a dose reduction level of a certain reconstruction level were non-diagnostic,
this entire reconstruction level was considered non-diagnostic and therefore excluded from analysis. The mass score of AVC and TAC of diagnostic scans were assessed and compared to the reference scan (FBP; routine dose) using Wilcoxon signed ranks-test.