title: Minimum number of basis projections for caries detection with local CT.
abstract: OBJECTIVE
  To investigate the relationship between the number of basis projections for local computed tomography (CT) and the detection of proximal caries and to find a minimum number of projections needed to maintain diagnostic accuracy.
  
  
  METHODS
  We presented observers (n = 12) with stacks of both axial and vertical CT slices of 23 extracted teeth placed in a dry human mandible. The slices were prepared with 14, 20, 33 and 100 basis projections. The observers scored the proximal surfaces for the presence of caries on a 1-5 confidence scale. The performance of the varying number of projections was compared with conventional digital radiographs.
  
  
  RESULTS
  The performance of all four CT modalities was significantly better than conventional radiographs (P = 0.005 to P = 0.021) and showed a consistent increase with the number of projections. Diagnostic performance depended significantly on lesion depth (P = 0.00), but not on observer.
  
  
  CONCLUSIONS
  We conclude that the number of CT projections used can be reduced at least to 20 with the diagnostic performance still markedly better than that of conventional film, provided that the observer can make use of both axial and vertical stacks of CT slices.
authors.affiliation: Department of Oral Radiology, Academic Center for Dentistry Amsterdam (ACTA), Louwesweg 1, 1066EA Amsterdam, The Netherlands. a.v.daatselaar@acta.nl
authors.forename: A N
authors.initials: AN
authors.lastname: van Daatselaar
authors.forename: D A
authors.initials: DA
authors.lastname: Tyndall
authors.forename: H
authors.initials: H
authors.lastname: Verheij
authors.forename: P F
authors.initials: PF
authors.lastname: van der Stelt
mesh_terms: D003731:Dental Caries / Q000000981:diagnostic imaging*; D006801:Humans; D016014:Linear Models; D015588:Observer Variation; D012372:ROC Curve; D011829:Radiation Dosage; D019252:Radiography, Dental, Digital; D036542:Tomography, Spiral Computed; D014057:Tomography, X-Ray Computed / Q000379:methods*