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Identifying Coronary Artery Calcification on Non-gated Computed Tomography Scans
Published on: August 28, 2018
Impact of Hybrid Iterative Reconstruction on Agatston Coronary Artery Calcium Scores in Comparison to Filtered Back
V C Obmann1, T Klink2, J T Heverhagen1
1University Institute for Diagnostic, Interventional and Pediatric Radiology, Inselspital - University Hospital Bern, Switzerland.
Insights
Hybrid iterative reconstruction (HIR) closely correlates with filtered back projection (FBP) for coronary artery calcium (CAC) scoring. Identical cardiovascular risk group assignments were observed for HIR levels 1-3, indicating no disadvantages for routine use.
Area of Science:
- Radiology
- Medical Imaging
- Cardiovascular Disease
Background:
- Coronary artery calcium (CAC) scoring is crucial for cardiovascular risk stratification.
- Filtered back projection (FBP) is a traditional image reconstruction method.
- Hybrid iterative reconstruction (HIR) offers potential for improved image quality and reduced radiation dose.
Purpose of the Study:
- To evaluate the impact of HIR on Agatston scores for CAC measurements.
- To determine if HIR alters patient assignment to cardiovascular risk groups compared to FBP.
Main Methods:
- 68 patients underwent cardiac 256-MSCT for CAC scoring.
- Images were reconstructed using both FBP and HIR (levels L1-L7).
- Agatston scores were measured, and cardiovascular risk groups were assigned by two independent readers.
Main Results:
- HIR Agatston scores showed excellent correlation with FBP scores (R > 0.986 for L1-L7).
- HIR resulted in reduced Agatston scores compared to FBP (12.6-3% reduction).
- Identical cardiovascular risk group assignments were achieved with HIR levels 1-3 for all patients.
Conclusions:
- HIR demonstrates excellent correlation with FBP for CAC scoring.
- HIR (levels 1-3) does not change cardiovascular risk group assignment.
- HIR appears safe for routine CAC scoring, warranting further investigation for dose reduction.
Purpose:
To investigate whether the effects of hybrid iterative reconstruction (HIR) on coronary artery calcium (CAC) measurements using the Agatston score lead to changes in assignment of patients to cardiovascular risk groups compared to filtered back projection (FBP).
Materials And Methods:
68 patients (mean age 61.5 years; 48 male; 20 female) underwent prospectively ECG-gated, non-enhanced, cardiac 256-MSCT for coronary calcium scoring. Scanning parameters were as follows: Tube voltage, 120 kV; Mean tube current time-product 63.67 mAs (50 - 150 mAs); collimation, 2 × 128 × 0.625 mm. Images were reconstructed with FBP and with HIR at all levels (L1 to L7). Two independent readers measured Agatston scores of all reconstructions and assigned patients to cardiovascular risk groups. Scores of HIR and FBP reconstructions were correlated (Spearman). Interobserver agreement and variability was assessed with ĸ-statistics and Bland-Altmann-Plots.
Results:
Agatston scores of HIR reconstructions were closely correlated with FBP reconstructions (L1, R = 0.9996; L2, R = 0.9995; L3, R = 0.9991; L4, R = 0.986; L5, R = 0.9986; L6, R = 0.9987; and L7, R = 0.9986). In comparison to FBP, HIR led to reduced Agatston scores between 97 % (L1) and 87.4 % (L7) of the FBP values. Using HIR iterations L1 - L3, all patients were assigned to identical risk groups as after FPB reconstruction. In 5.4 % of patients the risk group after HIR with the maximum iteration level was different from the group after FBP reconstruction.
Conclusion:
There was an excellent correlation of Agatston scores after HIR and FBP with identical risk group assignment at levels 1 - 3 for all patients. Hence it appears that the application of HIR in routine calcium scoring does not entail any disadvantages. Thus, future studies are needed to demonstrate whether HIR is a reliable method for reducing radiation dose in coronary calcium scoring.
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