Korean J Radiol.  2019 May;20(5):729-738. 10.3348/kjr.2018.0435.

Coronary CT Angiography with Knowledge-Based Iterative Model Reconstruction for Assessing Coronary Arteries and Non-Calcified Predominant Plaques

• Li T
• Tang T
• Yang L
• Zhang X
• Li X
• Luo C

• KMID: 2442707
• DOI: http://doi.org/10.3348/kjr.2018.0435

Abstract

OBJECTIVE
To assess the effects of iterative model reconstruction (IMR) on image quality for demonstrating non-calcific high-risk plaque characteristics of coronary arteries.
MATERIALS AND METHODS
This study included 66 patients (53 men and 13 women; aged 39-76 years; mean age, 55 ± 13 years) having single-vessel disease with predominantly non-calcified plaques evaluated using prospective electrocardiogram-gated 256-slice CT angiography. Paired image sets were created using two types of reconstruction: hybrid iterative reconstruction (HIR) and IMR. Plaque characteristics were compared using the two algorithms. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the images and the CNR between the plaque and adjacent adipose tissue were also compared between the two reformatted methods.
RESULTS
Seventy-seven predominantly non-calcified plaques were detected. Forty plaques showed napkin-ring sign with the IMR reformatted method, while nineteen plaques demonstrated napkin-ring sign with HIR. There was no statistically significant difference in the presentation of positive remodeling, low attenuation plaque, and spotty calcification between the HIR and IMR reconstructed methods (all p > 0.5); however, there was a statistically significant difference in the ability to discern the napkin-ring sign between the two algorithms (χ2 = 12.12, p < 0.001). The image noise of IMR was lower than that of HIR (10 ± 2 HU versus 12 ± 2 HU; p < 0.01), and the SNR and CNR of the images and the CNR between plaques and surrounding adipose tissues on IMR were better than those on HIR (p < 0.01).
CONCLUSION
IMR can significantly improve image quality compared with HIR for the demonstration of coronary artery and atherosclerotic plaques using a 256-slice CT.

Keyword

Coronary artery disease; Atherosclerosis; Image reconstruction; Multidetector computed tomography; Computed tomography angiography

MeSH Terms

Adipose Tissue
Angiography*
Atherosclerosis
Coronary Artery Disease
Coronary Vessels*
Female
Humans
Image Processing, Computer-Assisted
Male
Methods
Multidetector Computed Tomography
Noise
Plaque, Atherosclerotic
Prospective Studies
Signal-To-Noise Ratio

Figure

• 

  Fig. 1 CT value measurement in coronary artery segments (arrows) on IMR images.CT values were measured in lumen of left main trunk, proximal, middle, and distal segments of right coronary artery, LAD artery, and proximal and distal segments of left circumflex artery. IMR = iterative model reconstruction, LAD = left anterior descending

• 

  Fig. 2 CT value measurement in coronary artery segments (arrows) on HIR images in same patient.HIR = hybrid iterative reconstruction

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  Fig. 3 Plaque identification and CT value measurement.A. Non-calcified plaque was detected on proximal segment of LAD on curved reformation. B. CT value of plaque and adjacent perivascular adipose tissue measurement. Ar = area, Av = average, Max = maximum, Min = minimum, SD = standard deviation

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  Fig. 4 Noise measurement.Noise was defined as SD measured in background (air) anterior to patients' chest wall. Area of region of interest for measuring noise was about 50 mm2.

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  Fig. 5 Representative figures of napkin-ring sign in 47-year-old male patient.Top figures show that napkin-ring sign of LAD plaque can be detected using IMR algorithm, but not on HIR image (bottom figures).

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  Fig. 6 Representative figures of napkin-ring sign in 64-year-old female patient.Top figures show that napkin-ring sign of LAD plaque can be detected using IMR algorithm, but not on HIR image (bottom figures).

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