title: Accuracy of linear measurement using cone-beam computed tomography at different reconstruction angles.
abstract: OBJECTIVE
  This study was performed to evaluate the effect of changing the orientation of a reconstructed image on the accuracy of linear measurements using cone-beam computed tomography (CBCT).
  
  
  METHODS
  Forty-two titanium pins were inserted in seven dry sheep mandibles. The length of these pins was measured using a digital caliper with readability of 0.01 mm. Mandibles were radiographed using a CBCT device. When the CBCT images were reconstructed, the orientation of slices was adjusted to parallel (i.e., 0°), +10°, +12°, -12°, and -10° with respect to the occlusal plane. The length of the pins was measured by three radiologists, and the accuracy of these measurements was reported using descriptive statistics and one-way analysis of variance (ANOVA); p<0.05 was considered statistically significant.
  
  
  RESULTS
  The differences in radiographic measurements ranged from -0.64 to +0.06 at the orientation of -12°, -0.66 to -0.11 at -10°, -0.51 to +0.19 at 0°, -0.64 to +0.08 at +10°, and -0.64 to +0.1 at +12°. The mean absolute values of the errors were greater at negative orientations than at the parallel position or at positive orientations. The observers underestimated most of the variables by 0.5-0.1 mm (83.6%). In the second set of observations, the reproducibility at all orientations was greater than 0.9.
  
  
  CONCLUSIONS
  Changing the slice orientation in the range of -12° to +12° reduced the accuracy of linear measurements obtained using CBCT. However, the error value was smaller than 0.5 mm and was, therefore, clinically acceptable.
authors.affiliation: Department of Dental and Maxillofacial Radiology, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Sima
authors.initials: S
authors.lastname: Nikneshan
authors.affiliation: Department of Dental and Maxillofacial Radiology, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Shadi Hamidi
authors.initials: SH
authors.lastname: Aval
authors.affiliation: Department of Advanced Periodontology, School of Dentistry, University of Southern California, Los Angeles, USA.
authors.forename: Neema
authors.initials: N
authors.lastname: Bakhshalian
authors.affiliation: Department of Dental and Maxillofacial Radiology, School of Dentistry, Shahed University of Medical Sciences, Tehran, Iran.
authors.forename: Shahriyar
authors.initials: S
authors.lastname: Shahab
authors.affiliation: Department of Dental and Maxillofacial Radiology, School of Dentistry, Qazvin University of Medical Sciences, Qazvin, Iran.
authors.forename: Mahdis
authors.initials: M
authors.lastname: Mohammadpour
authors.affiliation: Department of Dental and Maxillofacial Radiology, School of Dentistry, Golestan University of Medical Sciences, Golestan, Iran.
authors.forename: Soodeh
authors.initials: S
authors.lastname: Sarikhani
keywords: Cone-Beam Computed Tomography; Dental Implants; Dimensional Measurement Accuracy