Advances in MRI for the evaluation of carotid atherosclerosis

Abstract

Carotid artery atherosclerosis is an important source of mortality and morbidity in the Western world with significant socioeconomic implications. The quest for the early identification of the vulnerable carotid plaque is already in its third decade and traditional measures, such as the sonographic degree of stenosis, are not selective enough to distinguish those who would really benefit from a carotid endarterectomy. MRI of the carotid plaque enables the visualization of plaque composition and specific plaque components that have been linked to a higher risk of subsequent embolic events. Blood suppressed T 1 and T 2 weighted and proton density-weighted fast spin echo, gradient echo and time-of-flight sequences are typically used to quantify plaque components such as lipid-rich necrotic core, intraplaque haemorrhage, calcification and surface defects including erosion, disruption and ulceration. The purpose of this article is to review the most important recent advances in MRI technology to enable better diagnostic carotid imaging.Internal carotid artery atherosclerosis is a significant source of mortality and morbidity in the Western world.1,2 MRI enables the visualization of plaque composition, and specific plaque constituents have been linked to a higher risk of subsequent embolic events. Currently, either the sonographic or angiographic degree of carotid stenosis is used as a marker of severity for assessing carotid disease and risk of stroke. 3,4 However, there is mounting evidence that suggests that the degree of stenosis is not enough to accurately characterize carotid plaque burden and vulnerability.High-resolution, multicontrast carotid MRI protocols have been used to depict atherosclerotic components within carotid plaques, the validity of these protocols have been evaluated using histopathology, and the protocols have been applied in multicentre trials.5-7 Blood suppressed T 1 and T 2 weighted and proton density (PD)-weighted fast spin echo (FSE) and gradient echo time-of-flight sequences are typically used 8 to quantify plaque components such as lipidrich necrotic core (LRNC), 5,9-11 intraplaque haemorrhage (IPH), 5,12-15 calcification 5,9 and surface defects including erosions, disruption and ulceration. 11,[16][17][18] In addition, the intrareader, interreader 14,[19][20][21] and the interscan reproducibility 20,22,23 of quantitative measures associated with both morphology and composition have been reported. Novel MR-defined plaque features of vulnerability are emerging and appear promising for the identification of the vulnerable plaque. A recent systematic review of 9 studies with 779 subjects demonstrated that the presence of IPH, LRNC and thinning/rupture of the fibrous cap (FC) is linked to an increased risk of future stroke or transient ischaemic attack (TIA). 24 The hazard ratios for each of them as predictors of subsequent ischaemic events were 4.59 [95% confidence interval (CI), 2.91-7.24], 3.00 (95% CI, 1.51-5.95) and 5.93 (95% CI, 2.65-13.20), respectively. In a separate meta-a...

Modifiable Factors Leading to Increased Length of Stay after Carotid Endarterectomy

“…[17-19] In this study we found pre-operative cerebral arteriogram as the only imaging modality correlating with LOS. Yet, only 5% of patients underwent arteriogram and on review of the cases they were patients referred from neurology with complex intracranial and extracranial cerebrovascular disease.…”

Immunohistochemical Analysis of Cerebral Thrombi Retrieved by Mechanical Thrombectomy from Patients with Acute Ischemic Stroke

“…Nevertheless, also in the pathogenesis of peripheral ( i.e. , outside the central nervous system) macroangiopathic atherosclerosis, various immune cells are involved [ 41 , 42 , 43 ] and there is ongoing effort for in vivo visualization of atherosclerotic plaque composition [ 44 , 45 ]. Importantly, and in contrast to Niesten and co-workers [ 12 ] who reported AIS subtype-specific differences regarding the percentage of RBC infiltration, we found no differences in immune cell infiltration within the clots when having a detailed look at AIS subtypes according to TOAST criteria.…”

Nonstenotic carotid plaque on CT angiography in patients with cryptogenic stroke

“…17 High-resolution carotid plaque MRI 18,19 is a technique that enables more detailed characterization of plaque composition than CTA, with identification of vulnerable plaque features such as intraplaque hemorrhage, lipid-rich necrotic core, and thinned or disrupted fibrous cap. [20][21][22] A study 23 using high-resolution MRI to examine nonstenotic carotid plaque in a smaller series of patients with cryptogenic stroke found high-risk imaging features indicative of type VI plaque (American Heart Association 24 ) in 38% (12/32) of carotid arteries ipsilateral to ischemic stroke, and no type VI plaque on the contralateral side. The absence of high-risk plaque on the contralateral side differs from our study, which found bilateral plaque $3 mm in 15% of patients with ESUS, and bilateral plaque $4 mm in 5% of patients.…”