Soft Tissue Comparisons between 2D Cephalograms and 3D Images

OBJECTIVE: The aim of this study was to assess the feasibility of superimposition techniques when combining 3D surface imaging with 2D lateral cephalometric radiographs.

METHODS: The study was a prospective evaluation of superimposition techniques obtained from a cohort of 40 patients who underwent orthognathic surgery in a private practice environment. Surgical records were obtained from Lateral Cephalometric radiographs taken using a Kodak 9000 machine and the 3D images were obtained from the 3dMD stereo photogrammetric camera capture system. Pre and Post Lateral Cephalomteric records (Pre-C and Post-C) were superimposed on the cranial base on the S-N line whilst Pre and Post 3D surgical records (Pre-3D and Post 3D) were superimposed on the regional best fit method. This method comprised a pre-determined sub routine of selecting the broadest surface areas of the foreheads and upper portions of the nose. Once this was achieved, a complex mathematical algorithm or “best fit” calculation was carried out on the selected surfaces. Each set of superimposed records were analysed and 5 soft tissue landmarks were plotted (Nasion, tip of nose, upper lip, lower lip and chin point). The differences between the 5 surface points were analysed for each set of records.

RESULTS: The final sample consisted of 34 subjects with full records. A total of 680 surface landmarks were plotted and analysed. The mean differences of the soft tissue landmarks were analysed for each pair of data sets and were found to range between 1.06 – 8.07mm and 1.26 – 7.34mm for Lateral Cephalometric and 3D readings respectively. Paired t-tests were carried out using the SPSS 15.0 software and showed that the results were not statistically significant between the superimposition techniques on the image capture systems (P>0.5).

CONCLUSIONS: This study demonstrated that the types of superimposition techniques used in the imaging modalities were comparable with one another. Furthermore, recommendations could be made for future mid treatment soft tissue evaluations to be carried out using a non-invasive imaging device (3dMD Capture system).