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Anthropometric Precision and Accuracy of Digital Three-Dimensional Photogrammetry: Comparing the Genex and 3dMD Imaging Systems with One Another and with Direct Anthropometry

Weinberg, Seth M. MA*†; Naidoo, Sybill RN, MSN, CPNP; Govier, Daniel P.§; Martin, Rick A. MD∥; Kane, Alex A. MD§; Marazita, Mary L. PhD*¶**††

Journal of Craniofacial Surgery: May 2006 - Volume 17 - Issue 3 - pp 477-483
Anatomic Studies

A variety of commercially available three-dimensional (3D) surface imaging systems are currently in use by craniofacial specialists. Little is known, however, about how measurement data generated from alternative 3D systems compare, specifically in terms of accuracy and precision. The purpose of this study was to compare anthropometric measurements obtained by way of two different digital 3D photogrammetry systems (Genex and 3dMD) as well as direct anthropometry and to evaluate intraobserver precision across these three methods. On a sample of 18 mannequin heads, 12 linear distances were measured twice by each method. A two-factor repeated measures analysis of variance was used to test simultaneously for mean differences in precision across methods. Additional descriptive statistics (e.g., technical error of measurement [TEM]) were used to quantify measurement error magnitude. Statistically significant (P < 0.05) mean differences were observed across methods for nine anthropometric variables; however, the magnitude of these differences was consistently at the submillimeter level. No significant differences were noted for precision. Moreover, the magnitude of imprecision was determined to be very small, with TEM scores well under 1 mm, and intraclass correlation coefficients ranging from 0.98 to 1. Results indicate that overall mean differences across these three methods were small enough to be of little practical importance. In terms of intraobserver precision, all methods fared equally well. This study is the first attempt to simultaneously compare 3D surface imaging systems directly with one another and with traditional anthropometry. Results suggest that craniofacial surface data obtained by way of alternative 3D photogrammetric systems can be combined or compared statistically.

From the *Center for Craniofacial and Dental Genetics, Department of Oral Medicine and Biology, School of Dental Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA; Department of Anthropology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA; Department of Plastic and Reconstructive Surgery, Washington University School of Medicine, St. Louis, Missouri, USA; §Cleft Palate and Craniofacial Deformities Institute, St. Louis Children's Hospital, Section of Pediatric Plastic Surgery, Washington University School of Medicine, St. Louis, Missouri, USA; Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri, USA; Department of Oral and Maxillofacial Surgery, School of Dental Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA; **Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania, USA; ††Department of Psychiatry, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.

Pittsburgh, Pennsylvania, USA

Address correspondence and reprint request to Seth M. Weinberg, Center for Craniofacial and Dental Genetics, 100 Technology Drive, Suite 500, Pittsburgh, PA 15219; E-mail: smwst46@sdmgenetics.pitt.edu

Sources of support: NIH/NIDCR grants P60-DE13076, P50-DE016215, and R01-DE016148.

© 2006 Mutaz B. Habal, MD