title: Robustness of automated hippocampal volumetry across magnetic resonance field strengths and repeat images.
abstract: BACKGROUND
  Low HCV has recently been qualified by the European Medicines Agency as a biomarker for enrichment of clinical trials in predementia stages of Alzheimer's disease. For automated methods to meet the necessary regulatory requirements, it is essential they be standardized and their performance be well characterized.
  
  
  METHODS
  The within-image and between-field strength reproducibility of automated hippocampal volumetry using the Learning Embeddings for Atlas Propagation (or LEAP) algorithm was assessed on 153 Alzheimer's Disease Neuroimaging Initiative subjects.
  
  
  RESULTS
  Tests/retests at 1.5 T and 3 T, and a comparison between 1.5 T and 3 T, yielded average unsigned variabilities in HCVs of 1.51%, 1.52%, and 2.68%. A small bias between field strengths (mean signed difference, 1.17%; standard deviation, 3.07%) was observed.
  
  
  CONCLUSIONS
  The measured reproducibility characteristics confirm the suitability of using automated magnetic resonance imaging analyses to assess HCVs quantitatively and to represent a fundamental characterization that is critical to meet the regulatory requirements for using hippocampal volumetry in clinical trials and health care.
authors.affiliation: IXICO Plc, London, UK; Department of Computing, Imperial College London, London, UK.
authors.forename: Robin
authors.initials: R
authors.lastname: Wolz
authors.affiliation: Eli Lilly and Company, Indianapolis, IN, USA.
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Schwarz
authors.affiliation: Eli Lilly and Company, Indianapolis, IN, USA.
authors.forename: Peng
authors.initials: P
authors.lastname: Yu
authors.affiliation: Eli Lilly and Company, Indianapolis, IN, USA.
authors.forename: Patricia E
authors.initials: PE
authors.lastname: Cole
authors.affiliation: Department of Computing, Imperial College London, London, UK.
authors.forename: Daniel
authors.initials: D
authors.lastname: Rueckert
authors.affiliation: Department of Radiology, Mayo Clinic and Foundation, Rochester, MN, USA.
authors.forename: Clifford R
authors.initials: CR
authors.lastname: Jack
authors.affiliation: Icon Medical Imaging, Warrington, PA, USA.
authors.forename: David
authors.initials: D
authors.lastname: Raunig
authors.affiliation: IXICO Plc, London, UK. Electronic address: derek.hill@ixico.com.
authors.forename: Derek
authors.initials: D
authors.lastname: Hill
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D000544:Alzheimer Disease / Q000175:diagnosis*; D060825:Cognitive Dysfunction / Q000175:diagnosis; D003937:Diagnosis, Differential; D005260:Female; D006624:Hippocampus / Q000473:pathology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008609:Mental Status Schedule; D015203:Reproducibility of Results
keywords: Alzheimer's disease; Clinical trials; Hippocampus; Reproducibility; Segmentation; Test/retest