title: Automated 3D closed surface segmentation: application to vertebral body segmentation in CT images.
abstract: OBJECTIVE
  A fully automated segmentation algorithm, progressive surface resolution (PSR), is presented in this paper to determine the closed surface of approximately convex blob-like structures that are common in biomedical imaging. The PSR algorithm was applied to the cortical surface segmentation of 460 vertebral bodies on 46 low-dose chest CT images, which can be potentially used for automated bone mineral density measurement and compression fracture detection.
  
  
  METHODS
  The target surface is realized by a closed triangular mesh, which thereby guarantees the enclosure. The surface vertices of the triangular mesh representation are constrained along radial trajectories that are uniformly distributed in 3D angle space. The segmentation is accomplished by determining for each radial trajectory the location of its intersection with the target surface. The surface is first initialized based on an input high confidence boundary image and then resolved progressively based on a dynamic attraction map in an order of decreasing degree of evidence regarding the target surface location.
  
  
  RESULTS
  For the visual evaluation, the algorithm achieved acceptable segmentation for 99.35 % vertebral bodies. Quantitative evaluation was performed on 46 vertebral bodies and achieved overall mean Dice coefficient of 0.939 (with max [Formula: see text] 0.957, min [Formula: see text] 0.906 and standard deviation [Formula: see text] 0.011) using manual annotations as the ground truth.
  
  
  CONCLUSIONS
  Both visual and quantitative evaluations demonstrate encouraging performance of the PSR algorithm. This novel surface resolution strategy provides uniform angular resolution for the segmented surface with computation complexity and runtime that are linearly constrained by the total number of vertices of the triangular mesh representation.
authors.affiliation: School of Electrical and Computer Engineering, Cornell University, Ithaca, NY, USA. sl2543@cornell.edu.
authors.forename: Shuang
authors.initials: S
authors.lastname: Liu
authors.affiliation: School of Electrical and Computer Engineering, Cornell University, Ithaca, NY, USA.
authors.forename: Yiting
authors.initials: Y
authors.lastname: Xie
authors.affiliation: School of Electrical and Computer Engineering, Cornell University, Ithaca, NY, USA.
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Reeves
mesh_terms: D000465:Algorithms; D015519:Bone Density; D050815:Fractures, Compression / Q000000981:diagnostic imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D015203:Reproducibility of Results; D016103:Spinal Fractures / Q000000981:diagnostic imaging; D013131:Spine / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods
keywords: Closed surface segmentation; Cortical surface; Low-dose CT; Vertebral body segmentation