title: Atlas-based analysis of cardiac shape and function: correction of regional shape bias due to imaging protocol for population studies.
abstract: BACKGROUND
  Cardiovascular imaging studies generate a wealth of data which is typically used only for individual study endpoints. By pooling data from multiple sources, quantitative comparisons can be made of regional wall motion abnormalities between different cohorts, enabling reuse of valuable data. Atlas-based analysis provides precise quantification of shape and motion differences between disease groups and normal subjects. However, subtle shape differences may arise due to differences in imaging protocol between studies.
  
  
  METHODS
  A mathematical model describing regional wall motion and shape was used to establish a coordinate system registered to the cardiac anatomy. The atlas was applied to data contributed to the Cardiac Atlas Project from two independent studies which used different imaging protocols: steady state free precession (SSFP) and gradient recalled echo (GRE) cardiovascular magnetic resonance (CMR). Shape bias due to imaging protocol was corrected using an atlas-based transformation which was generated from a set of 46 volunteers who were imaged with both protocols.
  
  
  RESULTS
  Shape bias between GRE and SSFP was regionally variable, and was effectively removed using the atlas-based transformation. Global mass and volume bias was also corrected by this method. Regional shape differences between cohorts were more statistically significant after removing regional artifacts due to imaging protocol bias.
  
  
  CONCLUSIONS
  Bias arising from imaging protocol can be both global and regional in nature, and is effectively corrected using an atlas-based transformation, enabling direct comparison of regional wall motion abnormalities between cohorts acquired in separate studies.
authors.affiliation: Department of Anatomy with Radiology, Faculty of Medical and Health Sciences, University of Auckland, 85 Park Road, Auckland 1142, New Zealand. a.young@auckland.ac.nz.
authors.forename: Pau
authors.initials: P
authors.lastname: Medrano-Gracia
authors.forename: Brett R
authors.initials: BR
authors.lastname: Cowan
authors.forename: David A
authors.initials: DA
authors.lastname: Bluemke
authors.forename: J Paul
authors.initials: JP
authors.lastname: Finn
authors.forename: Alan H
authors.initials: AH
authors.lastname: Kadish
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Lee
authors.forename: Joao A C
authors.initials: JA
authors.lastname: Lima
authors.forename: Avan
authors.initials: A
authors.lastname: Suinesiaputra
authors.forename: Alistair A
authors.initials: AA
authors.lastname: Young
mesh_terms: D000328:Adult; D000465:Algorithms; D001271:Atlases as Topic; D015982:Bias; D016208:Databases, Factual; D005260:Female; D064368:Healthy Volunteers; D006352:Heart Ventricles / Q000033:anatomy & histology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D015233:Models, Statistical; D015588:Observer Variation; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D016276:Ventricular Function; D055815:Young Adult
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