| | The Accuracy of Cephalometric Tracing SuperimpositionPresented in part at the 85th Annual Meeting of the American Association of Oral and Maxillofacial Surgeons, Orlando, Florida, September 10-14, 2003.
PurposeThe purpose of this study was to compare the accuracy of 4 methods for cephalometric tracing superimposition. They are the FH@Porion method, S-N@Sella method, least-squared averaged 5 landmarks (LS-5) method, and manual geometric method. Materials and MethodsEight lateral cephalometric radiographs were used. Cephalometric tracing was performed by 2 examiners. One had extensive experience in landmark digitization while the other had minimal experience. The radiographs were scanned and the reference landmarks ANS, Point A, Point B, and Pogonion were digitized, creating 8 master tracings. Then 6 digital copies of each master tracing were made, 3 for each examiner. Subsequently, the examiners were asked to digitize and trace predetermined cranial base landmarks and structures. Tracings occurred at 1-month intervals. As a result, 3 separate tracings of each set were obtained from each examiner. The tracings of each set were superimposed using 4 different methods in the CASSOS software (SoftEnable Technology Ltd, Hong Kong SAR, China). For each method of superimposition, the coordinates of ANS, Point A, Point B, and Pogonion were recorded. Their means and variances were calculated. The variance represents the variability of the superimposition method. A general linear model for repeated measures was computed to test whether there were statistically significant differences among the 4 superimposition methods, 2 examiners, 4 reference landmarks, and 2 directions. Because the distribution of the variances was skewed, they were transformed to log variances. Finally, the errors of the superimposition in millimeters for each given examiner, superimposition method, reference landmark, and direction (X, Y) were calculated. ResultsThere was a statistically significant difference in measurement variability among the 4 superimposition methods (P < .001). For both examiners, the variability of the different superimposition methods from the highest to the lowest was: Frankfort Plane registered at Porion method, Sella-Nasion registered at Sella method, least-square averaged 5 landmarks method, and the manual geometric method. In addition, there was a statistically significant difference in the magnitude of superimposition errors between the 2 examiners (P < .001). The experienced examiner was consistently more precise than the inexperienced examiner across all methods. Moreover, there was a statistically significant difference among 4 reference landmarks (P < .001). For both examiners, the recorded variability of each given reference landmark from the lowest to the highest was: ANS, Point A, Point B, and Pogonion. Furthermore, the variability differences between horizontal and vertical directions did not reach a conventional level of significance (P = .123). Finally, the recorded errors in millimeters for each superimposition method were summarized. A smaller error in millimeters represented a higher accuracy in superimposition. The error of using manual geometric or LS-5 methods for both examiners was less than 0.50 mm, while the error of using the other 2 methods was up to 0.99 mm for the experienced examiner and 2.88 mm for the inexperienced examiner. ConclusionThe error of both manual and LS-5 methods was within 0.5 mm. The LS-5 method had its advantage because it could be automated by the computer. ⁎ Major, United States Army Dental Corp, and Attending Oral and Maxillofacial Surgeon, Department of Oral and Maxillofacial Surgery, Reynolds Army Community Hospital, Fort Sill, OK; Former Resident, Department of Oral and Maxillofacial Surgery, Dental Branch, The University of Texas Health Science Center, Houston, TX. † Director, Surgical Planning Laboratory, Department of Oral and Maxillofacial Surgery, The Methodist Hospital Research Institute; and Assistant Professor, Division of Pediatric Plastic Surgery, Department of Surgery, Medical School, The University of Texas Health Science Center, Houston, TX. ‡ Chairman, Department of Oral and Maxillofacial Surgery, The Methodist Hospital Research Institute; and Associate Professor, Division of Pediatric Plastic Surgery, Department of Surgery, Medical School, The University of Texas Health Science Center, Houston, TX. § Instructor, Department of Computer Science, City University of Hong Kong, China. ‖ Professor, Departments of Pediatrics and Obstetric and Gynecology; and Director, Design and Analysis Support Services, The University of Texas Health Science Center, Houston, TX. ¶ Professor, Division of Pediatric Plastic Surgery, Department of Surgery, Medical School, The University of Texas Health Science Center, Houston, TX. # Manager of Operational Projects/Plan, Department of Internal Medicine, University of Texas Medical Branch, Galveston, TX. ⁎⁎ Assistant Professor, Department of Bioengineering, Rice University, Houston, TX. †† PhD Student, Department of Bioengineering, Rice University, Houston, TX.  Address correspondence and reprint requests to Dr Xia: 6560 Fannin St, Suite 1228, Houston, TX 77030
PII: S0278-2391(05)01675-7 doi:10.1016/j.joms.2005.10.028 © 2006 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved. | |
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