Clinical ResearchMultidetector-Row Computed Tomography in Evaluation of Atherosclerotic Carotid Plaques Complicated with Intraplaque Hemorrhage
Introduction
Large randomized controlled trials demonstrated benefit of carotid endarterectomy (CEA) in symptomatic patients with high-degree carotid artery stenosis.1, 2 Asymptomatic patients benefit less from CEA, with absolute risk reduction of only about 1% annually during 5-year follow-up.3, 4 Therefore, a large number of asymptomatic patients must be operated to prevent a small number of neurological events. The total number of operated asymptomatic patients may be lowered if subgroups of asymptomatic patients who benefit most from CEA could be identified. Several studies have shown a higher incidence of neurological incidents in patients with so-called soft plaques (plaques predominantly consisting of lipids, tissue debris, and hemorrhage).5, 6, 7, 8, 9, 10 Ultrasound analysis of carotid plaques demonstrated that hypoechoic plaques represent an independent risk factor for stroke incidence in adults aged 65 years or older.11 Takaya et al.12 followed asymptomatic patients for 38 months and showed that patients with intraplaque hemorrhage on initial magnetic resonance imaging (MRI) had a 5.2 times higher incidence of cerebrovascular events. The American Heart Association (AHA) classification of atherosclerotic plaques defines eight types of plaques, according to histological content (Table I).13, 14 Atherosclerotic carotid plaques complicated with intraplaque hemorrhage (AHA type VIb) are considered unstable and are associated with a higher incidence of cerebrovascular events.12, 15, 16, 17 Computed tomographic (CT) angiography demonstrated high accuracy in diagnosing carotid artery stenosis.18, 19, 20, 21, 22 An additional feature of CT is its ability to measure tissue density (expressed as number of Hounsfield units [HU]). Thus, it can provide some information about the type of analyzed tissue. Atherosclerotic carotid plaques with lower tissue density on multidetector-row CT (MDCT) are associated with a lower incidence of cerebrovascular events.6, 7 While single slice CT showed conflicting results in determining carotid plaque composition, MDCT showed good correlation of findings with histological analysis of coronary plaques.23, 24, 25, 26, 27 Histological analysis of coronary plaques showed that remodeling of atherosclerotic plaque changes its histological content. Therefore, the period between imaging and histological analysis should be as short as possible.28 We compared results of MDCT and histological analysis and calculated sensitivity and specificity of MDCT in detection of AHA type VIb atherosclerotic carotid plaques (plaques complicated with intraplaque hemorrhage, most often containing a mixture of lipids, hemorrhage, and necrotic debris). CEA was performed within 1 week of MDCT.
Section snippets
Materials and Methods
Carotid plaques from 31 consecutive patients operated for carotid artery stenosis were included in this prospective study. There were 21 male and 10 female patients, aged 51-87, median 70, years. There were six symptomatic and 25 asymptomatic patients (Table II). Patients who experienced cerebral insult, transient ischemic attack, or amaurosis fugax on the side of the affected carotid artery within 6 months of MDCT were considered symptomatic.
Indications for CEA were symptomatic patients with
Results
There were 14 (45%) AHA VIb plaques and 17 (55%) plaques of other AHA types (V, VII, and VIII). Median MDCT tissue density of type VIb plaques was 22 HU (range –17 to 31), and median tissue density of noncalcified segments of noncomplicated plaques was 59 HU (range –6 to 150) (p = 0.0062, Mann-Whitney U-test) (Fig. 5). ROC analysis showed 100% sensitivity and 64.7% specificity of MDCT in detecting plaques complicated with intraplaque hemorrhage, with tissue density of 31 HU as a threshold value
Discussion
This study showed that MDCT could detect atherosclerotic carotid plaque complicated with hemorrhage with 100% sensitivity, with tissue density of 31 HU as a threshold value. Previous studies showed inconclusive results regarding the accuracy of single-slice CT in analyzing plaque composition.23, 24 De Weert et al.29 showed good correlation between in vivo MDCT findings and histological findings; however, in their analysis of 15 carotid plaques, the period between MDCT evaluation and
Conclusion
MDCT showed a very high level of sensitivity and a moderate level of specificity in detecting hemorrhage within atherosclerotic carotid plaque. Plaques with tissue density over 31 HU on MDCT were not complicated with intraplaque hemorrhage. Technical advancements of CT equipment may probably increase the specificity of the method.
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Cited by (37)
Pearls and Pitfalls of Carotid Artery Imaging: Ultrasound, Computed Tomography Angiography, and MR Imaging
2023, Radiologic Clinics of North AmericaExtracranial Vascular Disease: Carotid Stenosis and Plaque Imaging
2021, Neuroimaging Clinics of North AmericaCitation Excerpt :Recognizing IPH on CT and US can be more difficult. There is evidence that so-called soft plaque seen on CTA, and echolucent plaque seen on US, likely has some component of IPH, because both of these plaque features confer increased risk.30,31,38–40 Lipid-rich necrotic core (LRNC) is another high-risk plaque feature than can be appreciated on imaging.
Carotid artery imaging: The study of intra-plaque vascularization and hemorrhage in the era of the “vulnerable” plaque
2020, Journal of NeuroradiologyCitation Excerpt :Some CT characteristics of AP like Hounsfield Unit (HU) attenuation and the presence of neovascularization, are associate with increased risk of ischaemic cerebrovascular events [48], even if identification of IPH in CTA is still debated [50]. Two different researches by Ajduk et al. [49,50] showed that IPH shows low HU values, between -17 and +31, whereas a study by Wintermark et al. [51] underlined that the densities of IPH and connective tissues are really similar. U-King-Im et al. [52] studied features of IPH in a comparative study between CT and MRI, and they found that the presence of plaque ulceration was a more reliable tool to predict the presence of IPH on MR in comparison with the mean plaque density on CTA, with high sensitivity, specificity and negative predictive value.
Recommendations for the Assessment of Carotid Arterial Plaque by Ultrasound for the Characterization of Atherosclerosis and Evaluation of Cardiovascular Risk: From the American Society of Echocardiography
2020, Journal of the American Society of EchocardiographyCitation Excerpt :Compared to surgical specimens, multidetector computed tomography (CT) has shown a 94% sensitivity and 99% specificity for the detection of ulcerated plaques.77 When compared to histology, a 100% sensitivity and 64% specificity for the detection of intraplaque hemorrhage has been reported78 Carotid plaque characteristics assessed by CT have been correlated to acute stroke events.79,80 The major disadvantages of CT for plaque assessment are the radiation exposure and need for iodinated contrast.
Non-invasive carotid artery imaging to identify the vulnerable plaque: Current status and future goals
2015, European Journal of Vascular and Endovascular SurgeryCitation Excerpt :IPH is associated with very low HU values (−17 HU to 31 HU).32,33 MDCTA was able to detect plaques complicated with haemorrhage with good sensitivity (100%) and moderate to good specificity (64% and 70%).34,35 A further study showed good correlation of CTA with histology for large haemorrhages.36
Plaque hemorrhage in carotid artery disease: Pathogenesis, clinical and biomechanical considerations
2014, Journal of BiomechanicsCitation Excerpt :DECT has been reported to improve the ex vivo differentiation between soft tissues (Zachrisson et al., 2010). Results from 31 patients indicated that multidetector CT showed a high level of sensitivity and a moderate level of specificity in detecting atherosclerotic carotid plaques complicated with hemorrhage (Ajduk et al., 2009). It was found that the density difference (∆HU) between early and delayed phases was associated with tissue type in carotid plaques.