title: Precision assessment of stereo-photogrammetrically derived facial landmarks in infants.
abstract: BACKGROUND
  In order to examine the suitability of an anthropometric imaging device for a particular study population, it is necessary to assess measurement error on members of the population.
  
  
  OBJECTIVE
  We provide an analysis of the precision of a stereo-photogrammetric tool in locating 3D landmark coordinates on images of infants and present the results in a way that facilitates direct comparison with some of the precision results found in the literature.
  
  
  METHODS
  Intra- and inter-observer precision are examined for 26 landmarks on 21 infants. Mean absolute differences for landmark coordinates and linear distances, mean landmark coordinate errors, and relative errors of magnitude are calculated.
  
  
  RESULTS
  Relative error of magnitude is less than 4% for the majority of intra- and inter-observer inter-landmark distance comparisons. Landmarks lying on the midline of the face and on smooth regions with gentle curvature, in particular the sellion, glabella and nasion, have relatively low precision.
  
  
  CONCLUSIONS
  Our precision values compare well with those reported in published studies on landmark location in 3D surface images.
authors.affiliation: MRC/UCT Medical Imaging Research Unit, Department of Human Biology, University of Cape Town, Observatory 7925, Cape Town, South Africa.
authors.forename: Tinashe E M
authors.initials: TE
authors.lastname: Mutsvangwa
authors.forename: Mahalingam
authors.initials: M
authors.lastname: Veeraragoo
authors.forename: Tania S
authors.initials: TS
authors.lastname: Douglas
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D005145:Face / Q000033:anatomy & histology*; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation* / Q000379:methods*; D007223:Infant; D019047:Phantoms, Imaging; D010780:Photogrammetry / Q000295:instrumentation* / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity