Quantitative colorimetry of atherosclerotic plaque using the L*a*b* color space during angioscopy for the detection of lipid cores underneath thin fibrous caps
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Yellow plaques seen during angioscopy are thought to represent lipid cores underneath thin fibrous caps (LCTCs) and may be indicative of vulnerable sites. However, plaque color assessment during angioscopy has been criticized because of its qualitative nature. The purpose of the present study was to test the ability of a quantitative colorimetric system to measure yellow color intensity of atherosclerotic plaques during angioscopy and to characterize the color of LCTCs.
Using angioscopy and a quantitative colorimetry system based on the L*a*b* color space [L* describes brightness (−100 to +100), b* describes blue to yellow (−100 to +100)], the optimal conditions for measuring plaque color were determined in three flat standard color samples and five artificial plaque models in cylinder porcine carotid arteries. In 88 human tissue samples, the colorimetric characteristics of LCTCs were then evaluated.
In in-vitro samples and ex-vivo plaque models, brightness L* between 40 and 80 was determined to be optimal for acquiring b* values, and the variables unique to angioscopy in color perception did not impact b* values after adjusting for brightness L* by manipulating light or distance. In ex-vivo human tissue samples, b* value ≥23 (35.91 ± 8.13) with L* between 40 and 80 was associated with LCTCs (fibrous caps <100 μm).
Atherosclerotic plaque color can be consistently measured during angioscopy with quantitative colorimetry. High yellow color intensity, determined by this system, was associated with LCTCs. Quantitative colorimetry during angioscopy may be used for detection of LCTCs, which may be markers of vulnerability.
KeywordsAngioscopy Quantitative colorimetry Atherosclerotic plaque Imaging
Acute coronary syndromes
Analog to digital
International Committee on Illumination
Hue, saturation, intensity
Lipid core underneath thin fibrous cap
National Television System Committee
Point of interest
Red, green, blue
Region of interest
This study was supported in part by Research Grants from Fukuda Kinenn Foundation (to F.I) and for Cardiovascular Disease (15-5) from The Japanese Ministry of Health, Labor and Welfare (to K.M).
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