[The influence of motion artifacts conditioned by reconstruction, on the coronary calcium score in multislice spiral CT]

Evaluation of reconstruction windows for multislice computed tomography in quantification of coronary calcium

RATIONALE AND OBJECTIVES

To search for an optimum reconstruction window in retrospectively gated multislice computed tomography (MSCT) for quantification of coronary calcium.

MATERIALS AND METHODS

Coronary calcium quantified was examined as Agatston and volume scores by two experienced observers at 10 time points across the R-R interval of the electrocardiogram in 42 patients. A combination of statistical approaches was used to evaluate the distributions of minimum and maximum scores and of interobserver variability for both scoring methods across the cardiac cycle.

RESULTS

Based on the combination of evaluation approaches, 60% to 70% of the R-R interval appeared to be the optimum time point for obtaining maximum calcium scores with minimum interobserver variability. The optimum time point was more clearly defined for the Agatston score than for the volume score.

CONCLUSION

A reconstruction window beginning at 60% to 70% of the R-R interval seems to be most advantageous for retrospective gating of MSCT studies performed to quantify coronary calcium.

Variation of the coronary calcium score depending on image reconstruction interval and scoring algorithm

RATIONALE AND OBJECTIVES

To evaluate the reconstruction interval dependent bandwidth of the coronary calcium score, considering different methods of image reconstruction and quantification of coronary calcifications.

MATERIALS AND METHODS

Seventy-five patients underwent coronary calcium scoring by use of retrospectively ECG-gated multislice spiral CT. In all patients overlapping and nonoverlapping image reconstruction was performed every 10% of the RR-interval. Coronary calcium score was calculated for every reconstructed image series using the Agatston score and a volumetric scoring method. In 25 patients the analysis was performed twice to determine the reconstruction interval dependent intraobserver variability.

RESULTS

For nonoverlapping image reconstruction the median of the calcium score determined by the Agatston method ranged from 125.8 to 216.2 and from 166.9 to 211.7 for the volumetric scoring method. For overlapping image reconstruction the corresponding values ranged from 91.6 to 160.5 for the Agatston score and 128.3 to 175.3 for the volumetric calcium score. Reconstruction interval dependent median (mean) variation of the coronary calcium score ranged from 24.1 (45.5)% for nonoverlapping image reconstruction using the Agatston score to 17.5 (25.2)% utilizing a volumetric calcium score with overlapping image reconstruction. There was no statistical significant (P< 0.05) difference between the different methods. Intraobserver variability for the different image reconstruction intervals ranged from 0.78% to 21.51%. The least intraobserver variability was found for overlapping image reconstruction during the diastole using the volumetric scoring method.

CONCLUSIONS

Diastolic image reconstruction at 50% or 60% of the RR-interval is recommendable for retrospectively ECG-gated multislice spiral CT. Volumetric calcium scoring and overlapping image reconstruction are beneficial to reduce the variation of the coronary calcium score.