Quantification of carotid plaque lipid content with magnetic resonance T2 mapping in patients undergoing carotid endarterectomy

Abstract

Background and purposeTechniques to stratify subgroups of patients with asymptomatic carotid artery disease are urgently needed to guide decisions on optimal treatment. Reliance on estimates of % luminal stenosis has not been effective, perhaps because that approach entirely disregards potentially important information on the pathological process in the wall of the artery.MethodsSince plaque lipid is a key determinant of plaque behaviour we used a newly validated, high-sensitivity T2-mapping MR technique for a systematic survey of the quantity and distribution of plaque lipid in patients undergoing endarterectomy. Lipid percentage was quantified in 50 carotid endarterectomy patients. Lipid distribution was tested, using two imaging indices (contribution of the largest lipid deposit towards total lipid (LLD %) and a newly-developed LAI ‘lipid aggregation index’).ResultsThe bifurcation contained maximal lipid volume. Lipid percentage was higher in symptomatic vs. asymptomatic patients with degree of stenosis (DS ≥ 50%) and in the total cohort (P = 0.013 and P = 0.005, respectively). Both LLD % and LAI was higher in symptomatic patients (P = 0.028 and P = 0.018, respectively), suggesting that for a given plaque lipid volume, coalesced deposits were more likely to be associated with symptomatic events. There was no correlation between plaque volume or lipid content and degree of luminal stenosis measured on ultrasound duplex (r = -0.09, P = 0.53 and r = -0.05, P = 0.75), respectively. However, there was a strong correlation in lipid between left and right carotid arteries (r = 0.5, P <0.0001, respectively).ConclusionsPlaque lipid content and distribution is associated with symptomatic status of the carotid plaque. Importantly, plaque lipid content was not related to the degree of luminal stenosis assessed by ultrasound. Determination of plaque lipid content may prove useful for stratification of asymptomatic patients, including selection of optimal invasive treatments.

Construction of dual nanomedicines for the imaging and alleviation of atherosclerosis

“…However, after the administration of CD-MNPs, no changes in signal intensity were observed in the carotid artery wall in T2WI. Since quantitative T2 mapping can provide absolute physical measurements of plaque components [39,40], it characterizes the atherosclerotic plaque precisely and provides in vivo T2 values of plaque components. The Fe 3 O 4 NPs deposit on the plaque area and shorten the T2 relaxation time.…”

T2 mapping MRI technique quantifies carotid plaque lipid, and its depletion after statin initiation, following acute myocardial infarction

“…Bright-blood, time-of-flight (TOF) angiography of the carotid arteries was acquired to localize carotid bifurcation and atherosclerotic plaque. Multi-slice carotid T2 maps were generated from 14 images with echo times TE = 9-127 ms and repetition time TR = 2 s as previously described [18,19]. Ten slices of 2 mm thickness each, covering 2 cm of both carotid arteries were acquired.…”

“…T2 mapping is a newly-validated MRI technique that accurately identifies plaque lipid, at a voxel by voxel level based on its physical properties [4,12,18,19]. This technique has also enabled investigation of the relationship between lipid distribution and the symptomatic status in the carotid arteries, beyond the volumetric quantification of vessel lipid content [18].…”

Current concepts in atherosclerosis

“…Beyond the category of the atherosclerotic patients, i.e. presenting with stroke or myocardial infarction, it is now increasingly recognised that certain individuals have susceptibility to calcific disease, inflammation, risk of thrombosis or tendency for lipid accumulation [3,22]. While a certain drug may be effective in tackling a specific disease substrate, the overall outcome may become 'diluted' and undermine the efficacy of the drug.…”