Coronary plaque imaging by coronary computed tomography angiography

Table 1 Respective pros and cons of multi-detector computed tomography and coronary angiogram for analysis of coronary artery disease

	Pros	Cons
MDCT	It can be performed with short examination times, and is generally available and easily performed	Study population was limited to selected patients chosen for good CTA image quality with absence of motion artifacts or severe calcification
	It is a noninvasive character, and contributes important information of plaque morphology and characterization in the arterial wall	Quantitative measurement of plaque morphology is slightly limited
	Calcium score	Radiation exposure, which is currently between 9 and 1 mSv for a retrospectively gated MDCT coronary angiogram
	Serial MDCT plaque imaging	Contrast medium is used
CAG	Excellent image quality can be observed with absence of artifacts	It is an invasive character, and contributes no plaque morphologic information
	Degree of luminal stenosis can be measured by QCA	Substantial interpretation variability of visual estimates and assessment of lesion severity for diffuse atherosclerotic lesions and intermediate-severity lesions
	Gold standard for the diagnosis of coronary narrowing and clinical decision making for coronary interventions	Catheterization costs are expensive. Contrast medium is used

MDCT: Multi-detector computed tomography; CTA: Computed tomography angiography; CAG: Coronary angiogram; QCA: Quantitative coronary angiography.

Table 2 Various studies reporting analysis of coronary plaque by multi-detector computed tomography

Ref.	n	Imaging techniques	Major findings
Leber et al[12]	59	64-detector	The mean plaque areas and the percentage of vessel obstruction measured by IVUS and 64-slice CT were 8.1 mm2vs 7.3 mm2 (P < 0.03, r = 0.73) and 50.4% vs 41.1% (P < 0.001, r = 0.61), respectively
Kashiwagi et al[13]	105	64-detector	Vascular remodeling and low CT attenuation values had the MDCT morphological features of TCFA observed by OCT, and a ring-like enhancement was one important sign of TCFA
Leber et al[14]	46	16-detector	The MDCT-derived density measurements within coronary lesions revealed significantly different values for hypoechoic (49 HU ± 22), hyperechoic (91 HU ± 22), and calcified plaques (391 HU ± 156, P < 0.02)
Sato et al[15]	102	64-detector	Lumen CSA and percent area stenosis of coronary lesions were closely correlated to those obtained by IVUS, however the lumen CSA measured by CTA was systematically overestimated and percent area stenosis was slightly underestimated
Voros et al[17]	60	64-detector	Low-density noncalcified plaques, the presumed lipid-rich plaques on CT, correlated best with the sum of necrotic core plus fibro-fatty tissue by IVUS/virtual histology
Motoyama et al[18]	71	16, 64-detector	Presence of positive remodeling, non-calcified plaque < 30 HU, and spotty calcification showed a high positive predictive value for with ACS
Ozaki et al[19]	66	16, 64-detector	CTA fails to characterize lesions at risk of intact fibrous cap-ACS which are often referred to as plaque erosions
Sato et al[24]	226	64-detector	Number of coronary plaques in non-culprit lesions was more significantly observed in AMI patients than in SAP patients with normal MPI. Non-calcified, mixed, and vulnerable plaques were more significantly observed in AMI patients than in SAP patients
Leber et al[25]			Non-calcified plaques contribute to a higher degree to the total plaque burden in AMI than in SAP
Schroeder et al[41]	15	4-detector	Mean CT density of 14-47 HU was found in lipid-rich plaque
Pohle et al[43]	32	16-detector	The mean CT attenuation within plaque that corresponded to hyper-echogenic appearance in IVUS was 121 ± 34 HU (n = 76). The mean CT attenuation within plaque that corresponded to hypo-echogenic appearance was 58 ± 43 HU (n = 176, P < 0.001)
Pundziute et al[44]	100	64-detector	In multivariate analysis, significant predictors of events were the presence of CAD, obstructive CAD, obstructive CAD in LM/LAD, number of segments with plaques, number of segments with obstructive plaques, and number of segments with mixed plaques
Pundziute et al[45]	50	64-detector	TCFA on virtual histology IVUS were most prevalent in mixed plaques, suggesting a higher degree of vulnerability of these mixed plaques

IVUS: Intravascular ultrasound; CT: Computed tomography; MDCT: Multi-detector computed tomography; OCT: Optical coherence tomography; CTA: Computed tomography angiography; HU: Hounsfield units; CSA: Cross-sectional area; AMI: Acute myocardial infarction; SAP: Stable angina pectoris; MPI: Myocardial perfusion imaging; TCFA: Thin-cap fibroatheromas; CAD: Coronary artery disease; LAD: Left anterior descending artery.

Table 3 Characteristics of various imaging modalities for analysis of coronary vulnerable plaque

Modalities	Characteristics of vulnerable plaque
MDCT	Low-attenuation, positive remodeling, spotty calcification[18]
	Ring-like enhancement[13], napkin-ring sign[28,29]
IVUS	Low echoic, positive remodeling, spotty calcification[30]
	Echo signal attenuation[31]
OCT	Lipid-rich plaque by a signal-poor region with a diffuse border[32]
	TCFA (large lipid core and a thin fibrous cap < 65 μm)[33]
	Macrophages imaging[34]
Angioscopy	Intensive yellow plaque, presence of thrombus[35]

MDCT: Multi-detector computed tomography; IVUS: Intravascular ultrasound; OCT: Optical coherence tomography; TCFA: Thin-cap fibroatheroma.

Table 4 Coronary plaque characteristics on multi-detector computed tomography and slow-flow phenomenon/cardiac troponin T elevation

Ref.	Minimum CT value (HU)	Positive remo-deling index	Calcification	Ring-like appearance
Nakazawa et al[37]	67.0 ± 10.1	N/A	N/A	55.60%
Uetani et al[38]	< 50	1.10 ± 0.21	37.70%	N/A
Watabe et al[39]	43 (26.5-75.7)	1.20 ± 0.18	Spotty (50%)	31.00%
Kodama et al[40]	23.5 (9.5-40)	1.5 (1.3-1.8)	CPC (63%)	10.00%

CT: Computed tomography; HU: Hounsfield units; CPC: Circumferential plaque calcification; N/A: Not available.