title: It is unclear if adjusting cortical thickness for changes in gray/white matter intensity ratio improves discrimination between normal aging, MCI, and AD.
abstract: The contrast between gray and white matter in MRI is critical for accurately measuring cortical thickness. The gray/white matter intensity ratio (GWIR) has been proposed to be an important adjustment factor for cortical thickness measures in Alzheimer's disease (AD) and mild cognitive impairment (MCI). This study examined the GWIR and its influence on cortical thickness in normal aging, mild cognitive impairment (MCI), and AD. The ability for GWIR to discriminate between these groups was assessed on its own and as an adjustment factor for cortical thickness. Minimal age- and AD-related changes in GWIR were observed. GWIR was not able to differentiate between normal aging, MCI, and AD. However, adjusting cortical thickness for GWIR slightly improved the ability to discriminate between groups and the effect size of cortical thickness increased after adjusting for GWIR. This work demonstrates the ambiguity in adjusting cortical thickness measures for GWIR, particularly when attempting to discriminate between normal aging, MCI, and AD groups.
authors.affiliation: Department of Anatomy and Neurobiology, Boston University School of Medicine, 700 Albany St W701, Boston, MA, 02118, USA, corinna_bauer@meei.harvard.edu.
authors.forename: Corinna M
authors.initials: CM
authors.lastname: Bauer
authors.forename: Howard J
authors.initials: HJ
authors.lastname: Cabral
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Killiany
mesh_terms: D000368:Aged; D000375:Aging / Q000473:pathology*; D000544:Alzheimer Disease / Q000175:diagnosis* / Q000473:pathology*; D002540:Cerebral Cortex / Q000473:pathology*; D060825:Cognitive Dysfunction / Q000175:diagnosis* / Q000473:pathology*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging; D008297:Male; D036421:Nerve Fibers, Unmyelinated / Q000473:pathology; D009483:Neuropsychological Tests; D009929:Organ Size; D012372:ROC Curve; D012680:Sensitivity and Specificity