title: Accuracy of 3D cephalometric measurements based on an automatic knowledge-based landmark detection algorithm.
abstract: OBJECTIVE
  To evaluate the accuracy of three-dimensional cephalometric measurements obtained through an automatic landmark detection algorithm compared to those obtained through manual identification.
  
  
  METHODS
  The study demonstrates a comparison of 51 cephalometric measurements (28 linear, 16 angles and 7 ratios) on 30 CBCT (cone beam computed tomography) images. The analysis was performed to compare measurements based on 21 cephalometric landmarks detected automatically and those identified manually by three observers.
  
  
  RESULTS
  Inter-observer ICC for each landmark was found to be excellent ([Formula: see text]) among three observers. The unpaired t-test revealed that there was no statistically significant difference in the measurements based on automatically detected and manually identified landmarks. The difference between the manual and automatic observation for each measurement was reported as an error. The highest mean error in the linear and angular measurements was found to be 2.63 mm ([Formula: see text] distance) and [Formula: see text] ([Formula: see text]-Me angle), respectively. The highest mean error in the group of distance ratios was 0.03 (for N-Me/N-ANS and [Formula: see text]).
  
  
  CONCLUSIONS
  Cephalometric measurements computed from automatic detection of landmarks on 3D CBCT image were as accurate as those computed from manual identification.
authors.affiliation: Academy of Scientific & Innovative Research (AcSIR), New Delhi, India.|CSIR-Central Scientific Instruments Organisation, Chandigarh, 160030, India.
authors.forename: Abhishek
authors.initials: A
authors.lastname: Gupta
authors.affiliation: Centre for Dental Education and Research, All India Institute of Medical Sciences, New Delhi, 110029, India.
authors.forename: Om Prakash
authors.initials: OP
authors.lastname: Kharbanda
authors.affiliation: CSIR-Central Scientific Instruments Organisation, Chandigarh, 160030, India.
authors.forename: Viren
authors.initials: V
authors.lastname: Sardana
authors.affiliation: Centre for Dental Education and Research, All India Institute of Medical Sciences, New Delhi, 110029, India.
authors.forename: Rajiv
authors.initials: R
authors.lastname: Balachandran
authors.affiliation: Academy of Scientific & Innovative Research (AcSIR), New Delhi, India. hk_sardana@csio.res.in.|CSIR-Central Scientific Instruments Organisation, Chandigarh, 160030, India. hk_sardana@csio.res.in.
authors.forename: Harish Kumar
authors.initials: HK
authors.lastname: Sardana
mesh_terms: D000465:Algorithms; D059925:Anatomic Landmarks / Q000000981:diagnostic imaging*; D002508:Cephalometry / Q000379:methods; D054893:Cone-Beam Computed Tomography / Q000379:methods; D006257:Head / Q000000981:diagnostic imaging*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D051188:Knowledge Bases; D015588:Observer Variation; D015203:Reproducibility of Results
keywords: 3D cephalometry; Automatic landmarking; CBCT; Cephalometric analysis; Knowledge-based detection