title: Improved reliability of hippocampal atrophy rate measurement in mild cognitive impairment using fluid registration.
abstract: MRI-derived rates of hippocampal atrophy may serve as surrogate markers of disease progression in mild cognitive impairment (MCI). Manual delineation is the gold standard in hippocampal volumetry; however, this technique is time-consuming and subject to errors. We aimed to compare regional non-linear (fluid) registration measurement of hippocampal atrophy rates against manual delineation in MCI. Hippocampi of 18 subjects were manually outlined twice on MRI scan-pairs (interval+/-SD: 2.01+/-0.11 years), and volumes were subtracted to calculate change over time. Following global affine and local rigid registration, regional fluid registration was performed from which atrophy rates were derived from the Jacobian determinants over the hippocampal region. Atrophy rates as derived by fluid registration were computed using both forward (repeat onto baseline) and backward (baseline onto repeat) registration. Reliability for both methods and agreement between methods was assessed. Mean+/-SD hippocampal atrophy rates (%/year) derived by manual delineation were: left: 2.13+/-1.62; right: 2.36+/-1.78 and for regional fluid registration: forward: left: 2.39+/-1.68; right: 2.49+/-1.52 and backward: left: 2.21+/-1.51; right: 2.42+/-1.49. Mean hippocampal atrophy rates did not differ between both methods. Reliability for manual hippocampal volume measurements (cross-sectional) was high (intraclass correlation coefficient (ICC): baseline and follow-up, left and right, >0.99). However, the resulting ICC for manual measurements of hippocampal volume change (longitudinal) was considerably lower (left: 0.798; right: 0.850) compared with regional fluid registration (forward: left: 0.985; right: 0.988 and backward: left: 0.975; right: 0.989). We conclude that regional fluid registration is more reliable than manual delineation in assessing hippocampal atrophy rates, without sacrificing sensitivity to change. This method may be useful to quantify hippocampal volume change, given the reduction in operator time and improved precision.
authors.affiliation: Department of Neurology, Alzheimer Centre, VU Medical Centre, PO Box 7057, 1007 MB Amsterdam, The Netherlands. L.vandepol@vumc.nl
authors.forename: L A
authors.initials: LA
authors.lastname: van de Pol
authors.forename: J
authors.initials: J
authors.lastname: Barnes
authors.forename: R I
authors.initials: RI
authors.lastname: Scahill
authors.forename: C
authors.initials: C
authors.lastname: Frost
authors.forename: E B
authors.initials: EB
authors.lastname: Lewis
authors.forename: R G
authors.initials: RG
authors.lastname: Boyes
authors.forename: R A
authors.initials: RA
authors.lastname: van Schijndel
authors.forename: P
authors.initials: P
authors.lastname: Scheltens
authors.forename: N C
authors.initials: NC
authors.lastname: Fox
authors.forename: F
authors.initials: F
authors.lastname: Barkhof
mesh_terms: D000368:Aged; D000465:Algorithms; D001185:Artificial Intelligence; D001284:Atrophy / Q000473:pathology; D003072:Cognition Disorders / Q000473:pathology*; D004311:Double-Blind Method; D005260:Female; D006624:Hippocampus / Q000473:pathology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010363:Pattern Recognition, Automated / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique