title: Scan-rescan and intra-observer variability of magnetic resonance imaging of carotid atherosclerosis at 1.5 T and 3.0 T.
abstract: Carotid atherosclerosis measurements for eight subjects at baseline and 14 +/- 2 days later were examined using 1.5 T and 3.0 T magnetic resonance imaging (MRI). A single observer blinded to field strength, subject and timepoint manually segmented carotid artery wall and lumen boundaries in randomized images in five measurement trials. Mean increases in the signal-to-noise ratios (SNR) for T1-weighted images acquired at 3.0 T compared to 1.5 T were 90% (scan) and 80% (rescan). Despite significantly improved SNR and contrast-to-noise ratios (CNR) for images acquired at 3.0 T, vessel wall volume (VWV) intra-observer variability was not significantly different using coefficients of variation (COV), and intraclass correlation coefficients (ICC). VWV interscan variability and consistency at both field strengths were not statistically different (1.5 T/3.0 T COV = 5.7%/7.8%, R(2) = 0.96 for 1.5 T and R(2) = 0.87 for 3.0 T). A two-way analysis of variance showed a VWV dependence on field strength but not scan timepoint. In addition, a paired t-test showed significant differences in VWV measured at 3.0 T as compared to 1.5 T. These results suggest that although images acquired at 1.5 T have lower SNR and CNR VWV, measurement variability was not significantly different from 3.0 T VWV and that VWV is field-strength dependent which may be an important consideration for longitudinal studies.
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, 100 Perth Drive, London, N6A 5K8 Canada. avidal@imaging.robarts.ca
authors.forename: Arvin
authors.initials: A
authors.lastname: Vidal
authors.forename: Yves
authors.initials: Y
authors.lastname: Bureau
authors.forename: Trevor
authors.initials: T
authors.lastname: Wade
authors.forename: J David
authors.initials: JD
authors.lastname: Spence
authors.forename: Brian K
authors.initials: BK
authors.lastname: Rutt
authors.forename: Aaron
authors.initials: A
authors.lastname: Fenster
authors.forename: Grace
authors.initials: G
authors.lastname: Parraga
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D002339:Carotid Arteries / Q000473:pathology*; D002340:Carotid Artery Diseases / Q000473:pathology*; D015350:Contrast Sensitivity; D005260:Female; D006801:Humans; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods; D008297:Male; D008875:Middle Aged; D015588:Observer Variation