title: Variability of carotid artery measurements on 3-Tesla MRI and its impact on sample size calculation for clinical research.
abstract: Carotid MRI measurements are increasingly being employed in research studies for atherosclerosis imaging. The majority of carotid imaging studies use 1.5 T MRI. Our objective was to investigate intra-observer and inter-observer variability in carotid measurements using high resolution 3 T MRI. We performed 3 T carotid MRI on 10 patients (age 56 +/- 8 years, 7 male) with atherosclerosis risk factors and ultrasound intima-media thickness > or =0.6 mm. A total of 20 transverse images of both right and left carotid arteries were acquired using T2 weighted black-blood sequence. The lumen and outer wall of the common carotid and internal carotid arteries were manually traced; vessel wall area, vessel wall volume, and average wall thickness measurements were then assessed for intra-observer and inter-observer variability. Pearson and intraclass correlations were used in these assessments, along with Bland-Altman plots. For inter-observer variability, Pearson correlations ranged from 0.936 to 0.996 and intraclass correlations from 0.927 to 0.991. For intra-observer variability, Pearson correlations ranged from 0.934 to 0.954 and intraclass correlations from 0.831 to 0.948. Calculations showed that inter-observer variability and other sources of error would inflate sample size requirements for a clinical trial by no more than 7.9%, indicating that 3 T MRI is nearly optimal in this respect. In patients with subclinical atherosclerosis, 3 T carotid MRI measurements are highly reproducible and have important implications for clinical trial design.
authors.affiliation: Gill Heart Institute, University of Kentucky, Lexington, KY 40536, USA. masyed2@uky.edu
authors.forename: Mushabbar A
authors.initials: MA
authors.lastname: Syed
authors.forename: John N
authors.initials: JN
authors.lastname: Oshinski
authors.forename: Charles
authors.initials: C
authors.lastname: Kitchen
authors.forename: Arshad
authors.initials: A
authors.lastname: Ali
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Charnigo
authors.forename: Arshed A
authors.initials: AA
authors.lastname: Quyyumi
mesh_terms: D002339:Carotid Arteries / Q000473:pathology*; D002340:Carotid Artery Diseases / Q000473:pathology*; D002986:Clinical Trials as Topic; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D018401:Sample Size; D012720:Severity of Illness Index; D017539:Tunica Intima / Q000473:pathology; D017540:Tunica Media / Q000473:pathology