Image quality produced by different cone-beam computed tomography settings

Introduction: The aim of this study was to evaluate image quality at different cone-beam computed tomography settings and 3 fields of view. Methods: A Hitachi CB MercuRay (Hitachi Medical Systems, Tokyo, Japan) was modified to allow different setting combinations. The variables consisted of 4 milliampere settings (2, 5, 10, and 15 mA), 2 kilovolt (peak) settings (100 and 120 kV[p]), presence or absence of a copper filter, and 3 fields of view (6, 9, and 12 in). Thirty-two scans were taken on a cadaver head and 16 scans on a dry skull. The groups were divided by field of view, and the images were ranked by at least 30 judges. Diagnostic quality was addressed in a questionnaire. Descriptive statistics and rankings were calculated with Excel 2003 (Microsoft, Redmond, Wash) and the Friedman and Wilcoxon signed rank tests with SPSS software (version 14.0.1; SPSS, Chicago, Ill). Results: The presence or absence of a filter showed significant differences (P <.006) in 2 pairs of the 9-in field of view. Variation in kilovolt (peak) settings showed significant differences (P <.006) in the 6-in 5-mA images with a filter. Altering the milliampere settings showed significant differences (P <.008) in the 6- and 12-in groups. The 9-in group showed significant differences between 2 mA and 10 and 15 mA. Overall, the 6-, 9-, and 12-in images had diagnostic quality 56%, 99%, and 99% of the time, respectively. Conclusions: Presence or absence of a filter and the kilovolt (peak) setting did not affect overall image quality. Images taken at lower milliampere settings showed good diagnostic quality.