title: The effect of morphometric atlas selection on multi-atlas-based automatic brachial plexus segmentation.
abstract: OBJECTIVE
  The present study aimed to measure the effect of a morphometric atlas selection strategy on the accuracy of multi-atlas-based BP autosegmentation using the commercially available software package ADMIRE® and to determine the optimal number of selected atlases to use. Autosegmentation accuracy was measured by comparing all generated automatic BP segmentations with anatomically validated gold standard segmentations that were developed using cadavers.
  
  
  METHODS
  Twelve cadaver computed tomography (CT) atlases were included in the study. One atlas was selected as a patient in ADMIRE®, and multi-atlas-based BP autosegmentation was first performed with a group of morphometrically preselected atlases. In this group, the atlases were selected on the basis of similarity in the shoulder protraction position with the patient. The number of selected atlases used started at two and increased up to eight. Subsequently, a group of randomly chosen, non-selected atlases were taken. In this second group, every possible combination of 2 to 8 random atlases was used for multi-atlas-based BP autosegmentation. For both groups, the average Dice similarity coefficient (DSC), Jaccard index (JI) and Inclusion index (INI) were calculated, measuring the similarity of the generated automatic BP segmentations and the gold standard segmentation. Similarity indices of both groups were compared using an independent sample t-test, and the optimal number of selected atlases was investigated using an equivalence trial.
  
  
  RESULTS
  For each number of atlases, average similarity indices of the morphometrically selected atlas group were significantly higher than the random group (p < 0,05). In this study, the highest similarity indices were achieved using multi-atlas autosegmentation with 6 selected atlases (average DSC = 0,598; average JI = 0,434; average INI = 0,733).
  
  
  CONCLUSIONS
  Morphometric atlas selection on the basis of the protraction position of the patient significantly improves multi-atlas-based BP autosegmentation accuracy. In this study, the optimal number of selected atlases used was six, but for definitive conclusions about the optimal number of atlases and to improve the autosegmentation accuracy for clinical use, more atlases need to be included.
authors.affiliation: Department of Anatomy, Ghent University, De Pintelaan 185, 9000, Ghent, Belgium. Joris.vandevelde@ugent.be.|Department of Radiotherapy, Ghent University, De Pintelaan 185, 9000, Ghent, Belgium. Joris.vandevelde@ugent.be.
authors.forename: Joris
authors.initials: J
authors.lastname: Van de Velde
authors.affiliation: Department of Anatomy, Ghent University, De Pintelaan 185, 9000, Ghent, Belgium. Johan.Wouters@ugent.be.
authors.forename: Johan
authors.initials: J
authors.lastname: Wouters
authors.affiliation: Department of Radiotherapy, Ghent University, De Pintelaan 185, 9000, Ghent, Belgium. Tom.Vercauteren@uzgent.be.
authors.forename: Tom
authors.initials: T
authors.lastname: Vercauteren
authors.affiliation: Department of Radiotherapy, Ghent University, De Pintelaan 185, 9000, Ghent, Belgium. Werner.Degersem@uzgent.be.
authors.forename: Werner
authors.initials: W
authors.lastname: De Gersem
authors.affiliation: Department of Radiology, Ghent University, De Pintelaan 185, 9000, Ghent, Belgium. Eric.achten@ugent.be.
authors.forename: Eric
authors.initials: E
authors.lastname: Achten
authors.affiliation: Department of Radiotherapy, Ghent University, De Pintelaan 185, 9000, Ghent, Belgium. Wilfried.Deneve@uzgent.be.
authors.forename: Wilfried
authors.initials: W
authors.lastname: De Neve
authors.affiliation: Department of Anatomy, Ghent University, De Pintelaan 185, 9000, Ghent, Belgium. Tom.Vanhoof@ugent.be.
authors.forename: Tom
authors.initials: T
authors.lastname: Van Hoof
mesh_terms: D001271:Atlases as Topic; D001917:Brachial Plexus / Q000033:anatomy & histology*; D002102:Cadaver; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012984:Software