Abstract 205: Longitudinal Study of Intracranial Atherosclerosis Using 3D High Resolution MRI Imaging

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Hypothesis: The progression of asymptomatic intracranial atherosclerotic disease (ICAD) remains relatively unknown. We sought to determine whether the progression of ICAD over 24 months can be quantitatively detected using 3D high-resolution vessel wall MRI.

Methods: 28 participants with identified ICAD (14 male; mean age, 80.1±4.94 years, ranges, 71 to 89) were enrolled from Atherosclerosis Risk in Communities Study. The baseline MRI exams were performed on a 3T Siemens scanner that included 3D time-of-flight MRA and 3D black blood MRI (BBMRI) (e.g., acquired resolution: TOF, 0.55 x 0.5 x 0.5 mm3; BBMRI, 0.5 mm3) for identifying atherosclerosis in major intracranial arteries. The follow-up MRI exams were repeated to determine the progression of ICAD. The mean time interval between two scans was 2.65±1.48 years. Three trained readers independently measured the degree of stenosis, plaque thickness, and normalized wall index for both normal wall and identified plaques in both visits. Plaque progression was defined by plaque showing > 2 measurement error of increase in plaque thickness. Reliability was assessed by intraclass correlations (ICC).

Results: Inter- and intra-reader reliability for MRI measurements ranged from fair to excellent (ICC, 0.58-0.82). The mean coefficient of variation was 10% for mean wall thickness, 13% for maximum wall thickness and 12% for normalized wall index. Of the 28 participants with ICAD identified at baseline, 18 of 28 participants (64%) had either new plaques or evidence of plaque progression. A total of 152 and 163 plaques were identified at baseline and follow-up, respectively. Among 152 plaques, 45 (30%) progressed, and mean, maximum wall thickness, stenosis and normalized wall index increased 36%, 28%, 27% and 14%, respectively (Table 1).

Conclusion: 3D High-resolution vessel wall MRI is reliable tool for measuring changes in ICAD plaque and provides insight into the natural history of ICAD progression in general population.

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