Accuracy of CBCT Measurements of a Human Skull

The purpose of this study is to assess the accuracy and reproducibility of cone-beam computed tomography (CBCT) measurements of a human dry skull by comparing them to direct digital caliper measurements. Heated gutta-percha was used to mark 13 specific distances on a human skull, and the distances were directly measured using a digital caliper and on CBCT images obtained with Iluma (3M Imtec, OK, USA) and 3D Accuitomo 170 (3D Accuitomo; J Morita Mfg. Corp., Kyoto, Japan) CBCT imaging systems. Iluma images were obtained at 120 kVp and 3.8 mA and reconstructed using voxel sizes of 0.2 and 0.3 mm(3). Accuitomo images were obtained at 60 kVp and 2 mA and a voxel size of 0.250 mm(3). In addition, 3-D reconstructions were produced from images obtained from both systems. All measurements were made independently by three trained observers and were repeated after an interval of 1 week. Agreement between observers and image type was assessed by calculating Pearson correlation coefficients, with a level of significance set at p < 0.05. Pearson correlation coefficients between readings ranged from 0.995 to 1 for all image types. Correlations among observers were also very high, ranging from 0.992 to 1 for the first reading and from 0.992 to 1 for the second reading for the different image types. All CBCT image measurements were identical and highly correlated with digital caliper measurements. Accuracy of measurements of various distances on a human skull obtained from different CBCT units and image types is comparable to that of digital caliper measurements.