Fig. 1

CBCT scanning register with laser scanning. Each CBCT scanning file of different voxel size (.125 mm, .20 mm, .30 mm, .40 mm) and different HU (0, 100, 200, 300, 400) was then individually superimposed on the laser scanning file (labeled as the reference file) by means of an automated best-fit algorithm. A .5-mm threshold parameter was set as the critical value to analyze deviations between the laser scanning file (reference file) and each CBCT scanning file (test file). The darker the color is, the larger the variance is, and the lighter the color is, the smaller the variance is. For the same HU value (column), with the increase of voxel size, the color becomes darker, showing the increase of the variance between the CBCT file and the laser file. For the voxel size (line), each voxel size has an optimal HU value with the lightest color (100 for .125 mm, 200 for .2 mm, 300 for .3 mm, and 400 for .4 mm)