title: A two-stage rule-constrained seedless region growing approach for mandibular body segmentation in MRI.
abstract: OBJECTIVE
  Extraction of the mandible from 3D volumetric images is frequently required for surgical planning and evaluation. Image segmentation from MRI is more complex than CT due to lower bony signal-to-noise. An automated method to extract the human mandible body shape from magnetic resonance (MR) images of the head was developed and tested.
  
  
  METHODS
  Anonymous MR images data sets of the head from 12 subjects were subjected to a two-stage rule-constrained region growing approach to derive the shape of the body of the human mandible. An initial thresholding technique was applied followed by a 3D seedless region growing algorithm to detect a large portion of the trabecular bone (TB) regions of the mandible. This stage is followed with a rule-constrained 2D segmentation of each MR axial slice to merge the remaining portions of the TB regions with lower intensity levels. The two-stage approach was replicated to detect the cortical bone (CB) regions of the mandibular body. The TB and CB regions detected from the preceding steps were merged and subjected to a series of morphological processes for completion of the mandibular body region definition. Comparisons of the accuracy of segmentation between the two-stage approach, conventional region growing method, 3D level set method, and manual segmentation were made with Jaccard index, Dice index, and mean surface distance (MSD).
  
  
  RESULTS
  The mean accuracy of the proposed method is [Formula: see text] for Jaccard index, [Formula: see text] for Dice index, and [Formula: see text] mm for MSD. The mean accuracy of CRG is [Formula: see text] for Jaccard index, [Formula: see text] for Dice index, and [Formula: see text] mm for MSD. The mean accuracy of the 3D level set method is [Formula: see text] for Jaccard index, [Formula: see text] for Dice index, and [Formula: see text] mm for MSD. The proposed method shows improvement in accuracy over CRG and 3D level set.
  
  
  CONCLUSIONS
  Accurate segmentation of the body of the human mandible from MR images is achieved with the proposed two-stage rule-constrained seedless region growing approach. The accuracy achieved with the two-stage approach is higher than CRG and 3D level set.
authors: NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore, Singapore, jidongxu@nus.edu.sg.
authors: Dong Xu
authors: DX
authors: Ji
authors: Kelvin Weng Chiong
authors: KW
authors: Foong
authors: Sim Heng
authors: SH
authors: Ong
mesh_terms: D000465:Algorithms; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008334:Mandible / Q000033:anatomy & histology*; D015203:Reproducibility of Results
references: Neuroimage. 2010 Jan 1;49(1):225-39
references: 19732839
references: Comput Med Imaging Graph. 2001 Nov-Dec;25(6):511-21
references: 11679214
references: Comput Med Imaging Graph. 2004 Jul;28(5):267-78
references: 15249072
references: Comput Med Imaging Graph. 2009 Oct;33(7):537-46
references: 19473814
references: Hum Brain Mapp. 2002 Nov;17(3):143-55
references: 12391568
references: Med Eng Phys. 2006 May;28(4):339-47
references: 16112889
references: Med Image Anal. 2000 Sep;4(3):219-33
references: 11145310
references: Med Image Anal. 2011 Feb;15(1):155-68
references: 20951075
references: IEEE Trans Med Imaging. 1996;15(3):314-26
references: 18215912
references: Neuroimage. 2002 Nov;17(3):1587-98
references: 12414297
references: Neuroimage. 2006 Jul 1;31(3):1116-28
references: 16545965
references: Med Image Anal. 2007 Aug;11(4):325-35
references: 17482502
references: Neuroimage. 2009 Oct 1;47(4):1394-407
references: 19389477
references: IEEE Trans Med Imaging. 2001 Jan;20(1):45-57
references: 11293691
references: Hum Brain Mapp. 2005 Dec;26(4):273-85
references: 15966000