Reducing cone beam CT scan height as a method of radiation reduction for photorealistic three-dimensional orthognathic planning.

OBJECTIVES: To determine the superimposition accuracy of full-face stereophotographic images with 22 cm and 13 cm cone beam computed tomography (CBCT) scans. MATERIAL AND METHODS: 22 cm CBCT scans and corresponding stereophotographic images (3 dMD) for 30 subjects requiring orthognathic surgery were randomly selected. A 13 cm CBCT scan was generated from the 22 cm scan for each subject. All scans and images were converted into STL format. For each subject, the 22 cm and 13 cm CBCT scans were imported into CAD/CAM software and each superimposed with the corresponding 3 dMD image. A one-sample t-test was used to test the null hypothesis that the difference in the 90th percentile of the mean absolute distance between the two 3dMD images when aligned on the 22 cm and the 13 cm CBCT scans was not clinically significant (<0.5 mm). RESULTS: The 90th percentile of the mean absolute distance between the two 3 dMD surfaces using the 22 cm and 13 cm CBCT scans was significantly less than 0.5 mm (p < 0.001; 0.2 +/- 0.2 mm; 95% CI, 0.16-0.30 mm). CONCLUSIONS: There is no difference in the accuracy of superimposition of a stereophotogrammetry image with a 22 cm CBCT scan or a 13 cm CBCT scan. It should now be possible to use a 13 cm CBCT scan and a full-face stereophotogrammetry image during 3D orthognathic planning to reduce radiation exposure.