Effect of hybrid iterative reconstruction technique on quantitative and qualitative image analysis at 256-slice prospective gating cardiac CT.

OBJECTIVES

To evaluate the effect of hybrid iterative reconstruction on qualitative and quantitative parameters at 256-slice cardiac CT.

METHODS

Prospective cardiac CT images from 20 patients were analysed. Paired image sets were created using 3 reconstructions, i.e. filtered back projection (FBP) and moderate- and high-level iterative reconstructions. Quantitative parameters including CT-attenuation, noise, and contrast-to-noise ratio (CNR) were determined in both proximal- and distal coronary segments. Image quality was graded on a 4-point scale.

RESULTS

Coronary CT attenuation values were similar for FBP, moderate- and high-level iterative reconstruction at 293 ± 74-, 290 ± 75-, and 283 ± 78 Hounsfield units (HU), respectively. CNR was significantly higher with moderate- and high-level iterative reconstructions (10.9 ± 3.5 and 18.4 ± 6.2, respectively) than FBP (8.2 ± 2.5) as was the visual grading of proximal vessels. Visualisation of distal vessels was better with high-level iterative reconstruction than FBP. The mean number of assessable segments among 289 segments was 245, 260, and 267 for FBP, moderate- and high-level iterative reconstruction, respectively; the difference between FBP and high-level iterative reconstruction was significant. Interobserver agreement was significantly higher for moderate- and high-level iterative reconstruction than FBP.

CONCLUSIONS

Cardiac CT using hybrid iterative reconstruction yields higher CNR and better image quality than FBP.

KEY POINTS

• Cardiac CT helps clinicians to assess patients with coronary artery disease • Hybrid iterative reconstruction provides improved cardiac CT image quality • Hybrid iterative reconstruction improves the number of assessable coronary segments • Hybrid iterative reconstruction improves interobserver agreement on cardiac CT.