title: Evaluation of tuned-aperture computed tomography depth discrimination for image series acquired variously with linear horizontal, linear vertical, and conical beam projection arrays.
abstract: OBJECTIVE
  To compare depth discrimination by using tuned-aperture computed tomography (TACT) variously with linear horizontal, linear vertical, combined linear horizontal and linear vertical, and conical beam projection arrays.
  
  
  METHODS
  The first test object was a metallic mesh angled at 30 degrees to the surface of a computed dental radiography size No. 1 x-ray sensor. The second test object was a dry human mandible. The sensor was mounted on an optical bench constructed to permit free and precise geometrical settings for the horizontal and vertical angulations of the x-ray beam. The extent of blurring of horizontal and vertical wires in each TACT reconstructed image slice was observed for each of the tested beam projection arrays.
  
  
  RESULTS
  With a linear horizontal beam projection array, it was not possible to determine the depth of structures parallel to the horizontal dimension, such as the mandibular canal. With a linear vertical beam projection, it was not possible to determine the depth of structures parallel to the vertical dimension. A conical array of beam projections was best suited to the task of depth discrimination of objects in all planes. The best second alternative was a combination of linear vertical and linear horizontal projections.
  
  
  CONCLUSIONS
  Beam projection geometry is important for the accurate depth discrimination of TACT reconstructed images. A conical beam projection array is ideal.
authors.affiliation: Department of Oral and Maxillofacial Radiology, Tokyo Dental College, Chiba, Japan. kazyama@tdc.ac.jp
authors.forename: K
authors.initials: K
authors.lastname: Yamamoto
authors.forename: K
authors.initials: K
authors.lastname: Nishikawa
authors.forename: N
authors.initials: N
authors.lastname: Kobayashi
authors.forename: K
authors.initials: K
authors.lastname: Kuroyanagi
authors.forename: A G
authors.initials: AG
authors.lastname: Farman
mesh_terms: D003722:Dental Alloys; D005069:Evaluation Studies as Topic; D006801:Humans; D066298:In Vitro Techniques; D008334:Mandible / Q000000981:diagnostic imaging; D009532:Nickel; D019047:Phantoms, Imaging; D014025:Titanium; D014057:Tomography, X-Ray Computed / Q000295:instrumentation* / Q000379:methods
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium