Accuracy and repeatability of cone-beam computed tomography (CBCT) measurements used in the determination of facial indices in the laboratory setup

Summary Aim To assess the three dimensional (3D) surface accuracy of a phantom's face acquired from a cone-beam computed tomography (CBCT) scan and to determine the reliability of selected cephalometric measurements performed with Maxilim® software (Medicim N.V., Mechelen, Belgium). Material and methods A mannequin head was imaged with a CBCT (I-CAT™, Imaging Sciences International, Inc., Hatfield, USA). The data were used to produce 3D surface meshes (Maxilim® and Mimics® , Materialise N.V., Leuven, Belgium) which were compared with an optical surface scan of the head using Focus Inspection® software (Metris N.V., Leuven, Belgium). The intra- and inter-observer reliability for the measurement of distances between facial landmarks with Maxilim® 3D cephalometry were determined by calculating Pearson correlation coefficients and intraclass correlation (ICC). The Dahlberg formula was used to assess the method error (ME). Results (1) The maximal range of the 3D mesh deviations was 1.9 mm for Maxilim® , and 1.8 mm for Mimics® segmentation. (2) Test–retest and inter-observer reliability were high; Pearson's correlation coefficient was 1.000 and the ICC was 0.9998. The ME of the vertical measurements was a little larger than that calculated for the width measurements. Maximum ME was 1.33 mm. Conclusions The 3D surface accuracy of CBCT scans segmented with Maxilim® and Mimics® software is high. Maxilim® also shows satisfactory intra- and inter-assessor reliability for measurement of distances on a rigid facial surface.