title: Morphometric Atlas Selection for Automatic Brachial Plexus Segmentation.
abstract: OBJECTIVE
  The purpose of this study was to determine the effects of atlas selection based on different morphometric parameters, on the accuracy of automatic brachial plexus (BP) segmentation for radiation therapy planning. The segmentation accuracy was measured by comparing all of the generated automatic segmentations with anatomically validated gold standard atlases developed using cadavers.
  
  
  METHODS
  Twelve cadaver computed tomography (CT) atlases (3 males, 9 females; mean age: 73 years) were included in the study. One atlas was selected to serve as a patient, and the other 11 atlases were registered separately onto this "patient" using deformable image registration. This procedure was repeated for every atlas as a patient. Next, the Dice and Jaccard similarity indices and inclusion index were calculated for every registered BP with the original gold standard BP. In parallel, differences in several morphometric parameters that may influence the BP segmentation accuracy were measured for the different atlases. Specific brachial plexus-related CT-visible bony points were used to define the morphometric parameters. Subsequently, correlations between the similarity indices and morphometric parameters were calculated.
  
  
  RESULTS
  A clear negative correlation between difference in protraction-retraction distance and the similarity indices was observed (mean Pearson correlation coefficient = -0.546). All of the other investigated Pearson correlation coefficients were weak.
  
  
  CONCLUSIONS
  Differences in the shoulder protraction-retraction position between the atlas and the patient during planning CT influence the BP autosegmentation accuracy. A greater difference in the protraction-retraction distance between the atlas and the patient reduces the accuracy of the BP automatic segmentation result.
authors.affiliation: Department of Anatomy, Ghent University, Ghent, Belgium; Department of Radiotherapy, Ghent University, Ghent, Belgium. Electronic address: joris.vandevelde@ugent.be.
authors.forename: Joris
authors.initials: J
authors.lastname: Van de Velde
authors.affiliation: Department of Anatomy, Ghent University, Ghent, Belgium.
authors.forename: Johan
authors.initials: J
authors.lastname: Wouters
authors.affiliation: Department of Radiotherapy, Ghent University, Ghent, Belgium.
authors.forename: Tom
authors.initials: T
authors.lastname: Vercauteren
authors.affiliation: Department of Radiotherapy, Ghent University, Ghent, Belgium.
authors.forename: Werner
authors.initials: W
authors.lastname: De Gersem
authors.affiliation: Department of Radiotherapy, Ghent University, Ghent, Belgium.
authors.forename: Fréderic
authors.initials: F
authors.lastname: Duprez
authors.affiliation: Department of Radiotherapy, Ghent University, Ghent, Belgium.
authors.forename: Wilfried
authors.initials: W
authors.lastname: De Neve
authors.affiliation: Department of Anatomy, Ghent University, Ghent, Belgium.
authors.forename: Tom
authors.initials: T
authors.lastname: Van Hoof
mesh_terms: D000368:Aged; D059925:Anatomic Landmarks / Q000000981:diagnostic imaging*; D001917:Brachial Plexus / Q000000981:diagnostic imaging*; D002102:Cadaver; D004210:Dissection; D005260:Female; D006801:Humans; D008297:Male; D008488:Medical Illustration; D058958:Organs at Risk / Q000000981:diagnostic imaging*; D056888:Patient Positioning; D012015:Reference Standards; D012782:Shoulder / Q000502:physiology; D014057:Tomography, X-Ray Computed