Elsevier

Academic Radiology

Volume 19, Issue 11, November 2012, Pages 1324-1331
Academic Radiology

Original investigation
Coronary Artery Stent Evaluation by Combining Iterative Reconstruction and High-resolution Kernel at Coronary CT Angiography

https://doi.org/10.1016/j.acra.2012.06.013Get rights and content

Purpose

To evaluate stent lumen visualization by combining high-resolution cardiac kernel and the iterative reconstruction (iDose) on an anthropomorphic moving heart phantom and in patients at coronary computed tomography (CT) angiography.

Materials and Methods

We used the moving heart phantom and a 64 detector-row CT, retrospectively gated helical scanning, and image reconstruction. The heart rate was set at nonpulsating condition of 0 beats/min, 50 beats/min, and 80 beats/min. The 120-kV images were reconstructed in synchronization with electrocardiogram data using filtered back projection (FBP) or iDose algorithm and standard kernel/filter (CB) or high-resolution kernel/filter (CD). We measured image noise, the kurtosis, and stent lumen diameter in the phantom study. We also assessed the visual inspections by two radiologists.

Results

With cardiac motion at 50 and 80 beats/min, the difference of kurtosis improved with CD relative to CB (P < .05). iDose algorithm with level 7 provided lowest noise, with no statistically significance in difference of the kurtosis relative to level 4 (P > .05). Without cardiac motion at 0 beats/min, the stent lumen diameter measurements with CD kernel were better relative to CB kernel (P < .05). In addition, no significant difference was found in stent lumen diameter between iDose level 4 and level 7 (P > .05).

Conclusion

The use of iDose and a sharp kernel allowed improved stent visualization at a lower radiation dose.

Section snippets

Materials and methods

This study was approved by our institutional review board; informed patient consent for retrospective analyses was waived.

Results

As shown in Figure 4, image noise on phantom images without cardiac motion (0 beats/min) obtained at 900 and 450 effective mAs with FBP and the CB kernel was 12.7 HU and 19.3 HU, respectively; it was 32.9 HU and 61.5 HU with the CD kernel. This shows that image noise increased as the effective current-time product decreased. With iDose level 4, the image noise on images obtained at 450 effective mAs was 14.3 HU and 34.6 HU with the CB and the CD kernel, respectively; these values were 9.2 HU

Discussion

CTCA is the most promising combination of temporal and spatial resolution. Use of the iDose algorithm with the high-resolution kernel at CTCA facilitates the reduction in image noise and improves visualization of the stent lumen because of a reduction in blooming artifacts. We compared images acquired with the FBP algorithm with CB and CD kernels and images obtained with the iDose algorithm with CB and CD kernels with respect to image noise, kurtosis, and the diameter of the stent lumen.

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