title: Influence of the number of basis images and projection array on caries detection using tuned aperture computed tomography (TACT).
abstract: OBJECTIVE
  to determine if the number of basis images and spatial distribution of the projection array used for TACT slice generation influence observer performance in caries detection.
  
  
  METHODS
  In the first experiment, 2, 4, 8 and 12 basis projections of each of 40 teeth were acquired using a CMOS digital radiography sensor. Projections were distributed radially in space using a 20 degree angular disparity. TACT slices were generated from the four subgroups of images, presented to eight observers, and viewed on a high-resolution monitor. Observers scored the presence/absence of caries using a 5-point confidence scale. Gold standard was histological examination of tooth sections. ROC curves measured observer diagnostic performance. ANOVA tested for significant differences between observers and experimental conditions. In the second experiment, the number of basis projections judged to be satisfactory for TACT slice generation was used. Horizontal and vertical linear arrays of projections were compared to the circular projection array.
  
  
  RESULTS
  There was a statistically significant difference between the numbers of basis projections in the detection of both occlusal (P=0.006) and proximal caries (P=0.005). No significant difference was found between projection arrays in the detection of either occlusal (P=0.065) or proximal (P=0.515) caries.
  
  
  CONCLUSIONS
  The number of TACT basis projections significantly influences caries detection. Eight or more images should be used. Either linear-vertical, linear-horizontal or circular arrays of basis projections may be used for TACT slice generation in caries detection tasks.
authors.affiliation: Department of Stomatology, Federal University of Santa Catarina School of Dentistry, Rod. Admar Gonzaga, 841/427 Itacorubi, Florianopolis, SC-Brazil 88034-000. murillo@ccs.ifsc.br
authors.forename: M
authors.initials: M
authors.lastname: Abreu
authors.forename: D A
authors.initials: DA
authors.lastname: Tyndall
authors.forename: J B
authors.initials: JB
authors.lastname: Ludlow
authors.forename: C J
authors.initials: CJ
authors.lastname: Nortjé
mesh_terms: D000704:Analysis of Variance; D019540:Area Under Curve; D001641:Bicuspid / Q000000981:diagnostic imaging; D016001:Confidence Intervals; D003731:Dental Caries / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D016013:Likelihood Functions; D008963:Molar / Q000000981:diagnostic imaging; D015588:Observer Variation; D012372:ROC Curve; D011856:Radiographic Image Enhancement / Q000295:instrumentation; D019252:Radiography, Dental, Digital / Q000295:instrumentation; D015203:Reproducibility of Results; D013223:Statistics as Topic; D014057:Tomography, X-Ray Computed / Q000379:methods*