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In this article, we report data on vessel wall thickness parameters derived from different arterial segments of the circle of Willis and its primary branches in patients with and without cerebrovascular disease. Also data on inter-rater reliability and agreement of the derived vessel wall parameters are reported. For further interpretation and discussion please refer to the research article “ex vivo vessel wall thickness measurements of the human circle of Willis using 7T MRI” (Harteveld et al., in press) [1].

Background and aims: MRI can detect intracranial vessel wall thickening before any luminal stenosis is present. Apart from representing a vessel wall lesion, wall thickening could also reflect normal (age-related) variations in vessel wall thickness present throughout the intracranial arterial vasculature. The aim of this study was to perform vessel wall thickness measurements of the major intracranial arteries in ex vivo circle of Willis (CoW) specimens using 7T MRI, to obtain more detailed information about wall thickness variations of the intracranial arteries. Methods: Fifteen human CoW specimens were scanned at 7T MRI with an ultrahigh-resolution T1-weighted sequence. Five specimens were used for validation of MRI measurements with histology and evaluation of inter-rater reliability and agreement. The other 10 specimens from patients with (n = 5) and without (n = 5) cerebrovascular disease were used for vessel wall thickness measurements over the entire length of the major arterial segments of the CoW using MRI only. Results: MRI measurements showed excellent agreement with histology. Mean wall thickness varied from 0.45 to 0.66 mm, minimum wall thickness from 0.31 to 0.42 mm, maximum wall thickness from 0.52 to 0.86 mm, and normalized wall index from 0.64 to 0.75. On average, vessel walls were thicker for symptomatic patients compared to asymptomatic patients. Conclusions: High-resolution MRI enables accurate measurement of vessel wall thickness in ex vivo CoW specimens. Vessel wall thickness measurements over the entire length of segments showed considerable variation both within and between arterial segments of patients.

Background and aimsIntracranial atherosclerosis is one of the main causes of ischemic stroke. However, the characteristics of intracranial arteries and atherosclerosis have rarely been studied. Therefore, we systematically investigated atherosclerotic changes in all arteries of the Circle of Willis (CoW).MethodsSixty-seven CoWs obtained at autopsy from randomly chosen hospital patients (mean age, 67.3 ± 12.5 years), of which a total of 1220 segments were collected from 22 sites. Atherosclerotic plaques were classified according to the revised American Heart Association classification and were related to local vessel characteristics, such as the presence of an external and internal elastic lamina and the elastic fibre density of the media.Results181 out of the 1220 segments had advanced plaques (15%), which were mainly observed in large arteries such as the internal carotid, middle cerebral, basilar and vertebral artery. Only 11 out of 1220 segments (1%) showed complicated plaques (p

Intracranial atherosclerosis, one of the leading causes of ischemic stroke, is associated with an increased risk for recurrent stroke and dementia.1,2 Individuals of Asian, Hispanic, and African American ancestry are especially affected. Recent European studies revealed a much higher prevalence of intracranial lesions than commonly presumed, suggesting that intracranial atherosclerotic disease is potentially the most common cause of ischemic stroke worldwide.1,3 Ischemic strokes are clinically categorized into 5 subtypes based on their underlying cause: large-artery atherosclerotic stenosis, small-artery disease (lacunes), cryptogenic, major-risk-source cardiogenic embolism, and unusual (eg, dissections, arteritis). Most nonlacunar ischemic strokes are thought to be thromboembolic, which presumably also accounts for most cryptogenic strokes. Embolic sources include minor-risk or covert cardiac sources, veins via paradoxical embolism, and nonocclusive atherosclerotic plaques in the aortic arch or cervical or cerebral arteries.4 Besides embolic strokes, 2 other mechanisms have been associated with intracranial atherosclerosis-related strokes, namely hypoperfusion through a stenotic artery causing watershed or border-zone stroke and plaque overgrowth of perforator artery ostia, which is associated with penetrating artery disease and lacunar infarcts and has been related to cryptogenic strokes.5–7 Even mild stenosis of intracranial atherosclerotic arteries (

BACKGROUND AND PURPOSE: In recent years, several high-resolution vessel wall MR imaging techniques have emerged for the characterization of intracranial atherosclerotic vessel wall lesions in vivo. However, a thorough validation of MR imaging results of intracranial plaques with histopathology is still lacking. The aim of this study was to characterize atherosclerotic plaque components in a quantitative manner by obtaining the MR signal characteristics (T1, T2, T2*, and proton density) at 7T in ex vivo circle of Willis specimens and using histopathology for validation. MATERIALS AND METHODS: A multiparametric ultra-high-resolution quantitative MR imaging protocol was performed at 7T to identify the MR signal characteristics of different intracranial atherosclerotic plaque components, and using histopathology for validation. In total, 38 advanced plaques were matched between MR imaging and histology, and ROI analysis was performed on the identified tissue components. RESULTS: Mean T1, T2, and T2* relaxation times and proton density values were significantly different between different tissue components. The quantitative T1 map showed the most differences among individual tissue components of intracranial plaques with significant differences in T1 values between lipid accumulation (T1 = 838 ± 167 ms), fibrous tissue (T1 = 583 ± 161 ms), fibrous cap (T1 = 481 ± 98 ms), calcifications (T1 = 314 ± 39 ms), and the intracranial arterial vessel wall (T1 = 436 ± 122 ms). CONCLUSIONS: Different tissue components of advanced intracranial plaques have distinguishable imaging characteristics with ultra-high-resolution quantitative MR imaging at 7T. Based on this study, the most promising method for distinguishing intracranial plaque components is T1-weighted imaging.