title: Accuracy assessment of the axial images obtained from cone beam computed tomography.
abstract: OBJECTIVE
  The aim of this study was to evaluate accuracy of linear measurements assessed from axial tomograms and the influence of the use of different protocols in two cone beam CT (CBCT) units.
  
  
  METHODS
  A cylinder object consisting of Nylon® (Day Brazil, Sao Paulo, Brazil) with radiopaque markers was radiographically examined applying different protocols from NewTom 3G(TM) (Quantitative Radiology s.r.l, Verona, Veneto, Italy) and i-CAT(TM) (Imaging Sciences International, Hatfield, PA) units. Horizontal (A-B) and vertical (C-D) distances were assessed from axial tomograms and measured using a digital calliper that provided the gold standard for actual values.
  
  
  RESULTS
  There were differences when considering acquisition protocols to each CBCT unit. Concerning all analysed protocols from i-CAT(TM) and Newtom 3G(TM), both A-B and C-D distances presented underestimated values. Measurements of the axial images obtained from NewTom 3G(TM) (6 inch 0.16 mm and 9 inch 0.25 mm) were similar to the ones obtained from i-CAT(TM) (13 cm 20 s 0.3 mm, 13 cm 20 s 0.4 mm and 13 cm 40 s 0.25 mm).
  
  
  CONCLUSIONS
  The use of different protocols from CBCT machines influences linear measurements assessed from axial images. Linear distances were underestimated in both equipments. Our findings suggest that the best protocol for the i-CAT(TM) is 13 cm 20 s 0.3 mm and for the NewTom 3G(TM), the use of 6 inch or 9 inch is recommended.
authors.affiliation: Faculdade São Leopoldo Mandic, School of Dentistry, Campinas, Brazil. prof.francine@slmandic.edu.br
authors.forename: Francine Kühl
authors.initials: FK
authors.lastname: Panzarella
authors.forename: J L C
authors.initials: JL
authors.lastname: Junqueira
authors.forename: L B
authors.initials: LB
authors.lastname: Oliveira
authors.forename: N S
authors.initials: NS
authors.lastname: de Araújo
authors.forename: C
authors.initials: C
authors.lastname: Costa
mesh_terms: D000704:Analysis of Variance; D002138:Calibration; D054893:Cone-Beam Computed Tomography / Q000295:instrumentation / Q000379:methods; D057918:Fiducial Markers; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D018709:Statistics, Nonparametric; D015898:Tomography Scanners, X-Ray Computed; D014963:X-Ray Intensifying Screens