title: Anatomical Study and Locating Nasolacrimal Duct on Computed Topographic Image.
abstract: OBJECTIVE
  We performed a novel anatomical and radiological investigation to understand the structure of nasolacrimal duct (NLD) and to provide data to help surgeons locate the openings of NLD efficiently based on landmarks.
  
  
  METHODS
  We examined the NLD region using computed tomography images of 133 individuals and 6 dry skull specimens. Multiplanar reconstruction of the computed tomography images was performed, and the anatomical features of the NLD were studied in the coronal, sagittal, and axial planes. The long and short diameters of NLD were measured along its cross-section. The position of NLD was localized using the nostril, concha nasalis media, and medial orbital corner as landmarks. The free and open source software, 3D Slicer, was used for the segmentation of the NLD and 3D visualization of the superior and inferior openings of the NLD.
  
  
  RESULTS
  The length, angle, and diameter of NLD were significantly influenced by the age in females compared to those in males. The inferior opening of the NLD could be located efficiently using the nostril and the midsagittal line while the superior opening of NLD could be located using the medial orbital corner. Third, 3D Slicer enabled us to measure the distance between the skin and the bony structure in the image.
  
  
  CONCLUSIONS
  Our study indicates that the sex and age of the patient should be considered while selecting the optimal NLD stent for a patient, and that the precise location of NLD in reference to landmarks can simplify the surgical difficulties and reduce the risk of injury during the transnasal operation.
authors.affiliation: *Department of Endocrine †Department of Neurosurgery, First Hospital of Jilin University, Changchun, China ‡Surgical Planning Lab, Brigham and Woman Hospital, Harvard Medical School, Boston, MA §Department of Ophthalmology, Second Hospital of Jilin University ||Department of Thyroid Surgery ¶Department of Radiology, First Hospital of Jilin University, Changchun, China.
authors.forename: Siwen
authors.initials: S
authors.lastname: Zhang
authors.forename: Ye
authors.initials: Y
authors.lastname: Cheng
authors.forename: Jianan
authors.initials: J
authors.lastname: Xie
authors.forename: Zhengmin
authors.initials: Z
authors.lastname: Wang
authors.forename: Fan
authors.initials: F
authors.lastname: Zhang
authors.forename: Longquan
authors.initials: L
authors.lastname: Chen
authors.forename: Yan
authors.initials: Y
authors.lastname: Feng
authors.forename: Guixia
authors.initials: G
authors.lastname: Wang
mesh_terms: D000328:Adult; D059925:Anatomic Landmarks / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography / Q000379:methods*; D009296:Nasal Cavity / Q000000981:diagnostic imaging; D009301:Nasolacrimal Duct / Q000000981:diagnostic imaging*; D055815:Young Adult