Korean J Radiol.  2020 Feb;21(2):210-217. 10.3348/kjr.2019.0557.

In Vivo Detection of Lipid-Core Plaques by Coronary CT Angiography: A Head-to-Head Comparison with Histologic Findings

• Yin WH
• Zhang Y
• Li XN
• Wang HY
• An YQ
• Sun Y
• Hou ZH
• Gao Y
• Lu B
• Zheng Z

• KMID: 2471638
• DOI: http://doi.org/10.3348/kjr.2019.0557

Abstract

OBJECTIVE
We sought to distinguish lipid plaques using a CT quantitative pixel density histogram, based on the pathological diagnosis of lipid cores as the gold standard.
MATERIALS AND METHODS
Eight patients awaiting heart transplantation due to end-stage coronary heart disease underwent coronary CT angiography (CCTA) spectroscopy prior to heart transplantation; coronary artery pathological analysis was performed for all patients. Lipid-core plaques were defined pathologically as manifesting a lipid core diameter > 200 µm, a circumference > 60 degrees, and a cap thickness < 450 µm. The percentage distributions of CT pixel attenuation ≤ 20, 30, 40, and 50 HU were calculated using quantitative histogram analysis.
RESULTS
A total of 271 transverse sections were co-registered between CCTA and pathological analysis. Overall, 26 lipid cores and 16 fibrous plaques were identified by pathological analysis. There was no significant difference in median CT attenuation between the lipid and fibrous plaques (51 HU [interquartile range, 46-63] vs. 57 HU [interquartile range, 50-64], p = 0.659). The median percentage of CT pixel attenuation ≤ 30 HU accounted for 11% (5-17) of lipid-core plaques and 0% (0-2) of fibrous plaques (p < 0.001). The sensitivity and specificity of the method for diagnosing lipid plaques by the average CT pixel attenuation ≤ 30 HU were 80.8% and 87.5%, respectively. The area under the receiver operator characteristics curve was 0.898 (95% confidence interval: 0.765-0.970; 3.0% was the best cut-off value). The diagnostic performance was significantly higher than those of the average pixel CT attenuation percentages ≤ 20, 40, and 50 HU and the mean CT attenuation (p < 0.05).
CONCLUSION
In in vivo conditions, with the pathological lipid core as the gold standard, quantification of the percentage of average CT pixel attenuation ≤ 30 HU in the histogram can be useful for accurate identification of lipid plaques.

Keyword

Coronary CT angiography; Lipid plaque; Quantitative histogram analysis

MeSH Terms

Angiography*
Coronary Disease
Coronary Vessels
Diagnosis
Heart Transplantation
Humans
Methods
Sensitivity and Specificity
Spectrum Analysis

Figure

• 

  Fig. 1 Example of CT quantitative pixel density histogram analysis of lipid and fibrous plaques.A, D. Short-axis coronary CT angiography image with manual tracing of noncalcified plaques. B. X-axis of histogram analysis represents scale of CT value. Y-axis represents total number of CT value. There are 4 pixels with CT attenuation ≤ 30 HU, and 4412 is summation of number of pixels within CT low-density plaque. Therefore, percentage of pixels with CT attenuation ≤ 30 HU in histogram analysis is 0.1% (4/4412), which is below threshold of 3.0%. C. Fibrous plaque (arrow) was diagnosed pathologically. E. Percentage of pixel CT attenuation ≤ 30 HU in histogram analysis is 9.8% (175/1785), which is higher than threshold of 3.0%. F. Lipid core (arrow) was diagnosed pathologically.

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  Fig. 2 Scatter plot of mean CT attenuation (A) and percentage of pixels with attenuation ≤30 HU (B) for plaques identified as fibrous and lipid-core on pathological examination.

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  Fig. 3 Excellent inter-observer reproducibility of measurements of mean CT attenuation (A, B) and percentage of pixel CT attenuation (C, D).SD = standard deviation

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  Fig. 4 Comparison of areas under the receiver operating characteristic curve (AUROC) by 5 methods.AUROC by percentage method with percentage of pixels with attenuation ≤ 30 HU (blue line) was 0.898 (95% confidence interval is 0.765–0.970), which was significantly higher compared with other four methods (all p < 0.05).

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