Reproducibility of Lumen and Vessel Wall Measurements in Carotid Magnetic Resonance Imaging

Atherosclerotic carotid artery disease is estimated to represent the etiology for one quarter of all strokes. Carotid magnetic resonance imaging and magnetic resonance angiography are promising tools in the evaluation of carotid atherosclerotic vascular disease. In this study, we evaluate the reliability of high resolution carotid wall magnetic resonance (MR) imaging by investigating the inter-observer, intra-observer, and inter-scan variability in measurements of carotid vessel total lumen area and mean wall thickness. This HIPAA compliant study received IRB approval and all subjects gave written informed consent. Nineteen subjects were imaged on a 3T MRI scanner with custom-built 4-element receive-only phased-array coils optimized for carotid anatomy. Three observers manually drew regions of interest around the lumen and outer wall for both left and right carotid arteries. Intraclass correlation coefficients (ICC) showed excellent agreement between Observer 1 and the others (>0.92). A two- way analysis of variance (ANOVA) found no significant difference between observers (p>0.05). Intra-observer variability for Observer 1 was measured by coefficient of variation (CV) with 0.03 for total lumen area and 0.03 for mean wall thickness. Similarly, the inter-scan variability of Observer 1 was found by CV to be 0.05±0.02 for total lumen area and 0.04±0.03 for mean wall thickness. Our results demonstrate that the MR measurements of total lumen area and mean wall thickness are highly reproducible and provide a reliable foundation for the evaluation of carotid atherosclerotic vascular disease.