Recording and Transferring Head Positions to the Virtual Head Using a Multicamera System and Laser Level. KY Tian, ZL Xue, XJ Liu, X Wang, Z Li.

Date: June 2015.
Source: Journal of Oral & Maxillofacial Surgery.
Purpose: To fulfill the requirements of computer-aided orthognathic surgery, we developed a method of recording head positions in pitch and roll, and tested its accuracy and reliability.
Materials and Methods: A laser level was used to project a horizontal laser line onto a volunteer’s face. The three-dimensional (3D) photo of the volunteer was then taken to capture the laser line using the 3dMDface System, so the head positions could be recorded. To test the accuracy and reliability of our method, thirty-five head positions were recorded and compared with the positions recorded by the gyroscope method (Pn for pitch and Rn for roll). A cone beam computed tomography (CBCT) scan was also taken, during which head position was recorded by the gyroscope (P0 and R0). CBCT data was imported into the ProPlan CMF 1.3 software and a virtual head was created. To reproduce each recorded head position, each 3D photo was superimposed onto the virtual head through surface registration, and the virtual head was rotated to make the laser line parallel to the coordinate axes in both the lateral and frontal views; the rotation angles were recorded, respectively, as Pn’ and Rn’. Under ideal conditions, Pn’ should equal Pn-P0, and Rn’ should equal Rn-R0. The accuracy was evaluated using the Bland-Altman method. Reliability was tested by intraclass correlation coefficient (ICC) analysis.
Results: The 95% limits of agreement between the rotation angles recorded by our method (Pn’, Rn’) and the gyroscope method (Pn-P0, Rn-R0) were (-0.598°, 1.589°) and (-1.156°, 1.674°) for pitch and roll, respectively: such a difference was generally accepted as being accurate. The ICCs were 0.996 (0.992, 0.998) for pitch and 0.998 (0.997, 0.999) for roll.
Conclusion: The 3dMDface System and laser level method of recording head positions was accurate and reliable.
Article: Recording and Transferring Head Positions to the Virtual Head Using a Multicamera System and Laser Level.
Authors: Kaiyue Tian, MD (Resident), Zhulin Xue, MD (Resident), Xiaojing Liu, MD (Associate chief physician), Xing Wang, DDS, MD. PhD (Professor), Zili Li, MD (Associate professor) at The Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, Beijing, China.