Optimization of hybrid iterative reconstruction level and evaluation of image quality and radiation dose for pediatric cardiac computed tomography angiography

Abstract

Background

Hybrid iterative reconstruction can reduce image noise and produce better image quality compared with filtered back-projection (FBP), but few reports describe optimization of the iteration level.

Objective

We optimized the iteration level of iDose⁴ and evaluated image quality for pediatric cardiac CT angiography.

Materials and methods

Children (n = 160) with congenital heart disease were enrolled and divided into full-dose (n = 84) and half-dose (n = 76) groups. Four series were reconstructed using FBP, and iDose⁴ levels 2, 4 and 6; we evaluated subjective quality of the series using a 5-grade scale and compared the series using a Kruskal-Wallis H test. For FBP and iDose⁴-optimal images, we compared contrast-to-noise ratios (CNR) and size-specific dose estimates (SSDE) using a Student's t-test. We also compared diagnostic-accuracy of each group using a Kruskal-Wallis H test.

Results

Mean scores for iDose⁴ level 4 were the best in both dose groups (all P < 0.05). CNR was improved in both groups with iDose⁴ level 4 as compared with FBP. Mean decrease in SSDE was 53% in the half-dose group. Diagnostic accuracy for the four datasets were in the range 92.6–96.2% (no statistical difference).

Conclusion

iDose⁴ level 4 was optimal for both the full- and half-dose groups. Protocols with iDose⁴ level 4 allowed 53% reduction in SSDE without significantly affecting image quality and diagnostic accuracy.

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