Accuracy and reliability of 3D stereophotogrammetry: A comparison to direct anthropometry and 2D photogrammetry

Abstract

Objective: To evaluate the accuracy of three-dimensional (3D) stereophotogrammetry by comparing it with the direct anthropometry and digital photogrammetry methods. The reliability of 3D stereophotogrammetry was also examined. Materials and Methods: Six profile and four frontal parameters were directly measured on the faces of 80 participants. The same measurements were repeated using two-dimensional (2D) photogrammetry and 3D stereophotogrammetry (3dMDflex System, 3dMD, Atlanta, Ga) to obtain images of the subjects. Another observer made the same measurements for images obtained with 3D stereophotogrammetry, and interobserver reproducibility was evaluated for 3D images. Both observers remeasured the 3D images 1 month later, and intraobserver reproducibility was evaluated. Statistical analysis was conducted using the paired samples t-test, intraclass correlation coefficient, and Bland-Altman limits of agreement. Results: The highest mean difference was 0.30 mm between direct measurement and photogrammetry, 0.21 mm between direct measurement and 3D stereophotogrammetry, and 0.5 mm between photogrammetry and 3D stereophotogrammetry. The lowest agreement value was 0.965 in the Sn-Prn parameter between the photogrammetry and 3D stereophotogrammetry methods. Agreement between the two observers varied from 0.90 (Ch-Ch) to 0.99 (Sn-Me) in linear measurements. For intraobserver agreement, the highest difference between means was 0.33 for observer 1 and 1.42 mm for observer 2. Conclusions: Measurements obtained using 3D stereophotogrammetry indicate that it may be an accurate and reliable imaging method for use in orthodontics. (Angle Orthod. 2016;86:487-494.)

Three-dimensional evaluation of social smile symmetry

“…Furthermore, the measurements on 3D stereophotogrammetric images have been observed to be accurate and reliable compared to direct anthropometry and 2D photogrammetry. 19 The surface-based alignment algorithm (Iterative Closest Point Algorithm) or the best-fit alignment method used for aligning 3D images is considered a reliable method and is reported 9 to have an alignment error varying from 0.39 to 0.52 mm. The forehead, which is not expected to change, appears to be the region most commonly preferred for alignment in the studies on facial 3D images.…”

A study to evaluate the reliability of using two-dimensional photographs, three-dimensional images, and stereoscopic projected three-dimensional images for patient assessment

“…In addition, the majority felt that projected 3D was better than 3D viewing. This is not surprising as the human face is three-dimensional and therefore information should be displayed in 3D [17][18][19] . The fact that projected 3D was thought to be superior to perspective 3D viewing and increased the contribution of maxillary contribution to the class III deformity highlights the effect that the viewing medium may have on the diagnosis and clinical outcome.…”

Influence of involuntary facial expressions on reproducibility of 3D stereophotogrammetry in children with and without complete unilateral cleft lip and palate from 3 to 18 months of age

“…To estimate the clinical significance of error due to changing facial expressions, it is relevant to compare this error with the system error and with normative data of craniofacial growth. The accuracy of the 3dMD system compared to direct facial anthropometry for linear measurements reportedly ranges from 0.21 to 0.94 mm [9,10,18,19], and for landmark identification it ranges from 0.49 to 0.83 mm [11,20,21]. The mean r value representing the correlation between linear measurements derived from the 3dMD and direct anthropometry was reportedly 0.88 in one study, indicating a very high correlation [22].…”

“…The technique is fast and safe and facilitates data storage for longitudinal analysis [5,6]. Furthermore, its accuracy and reproducibility have been demonstrated in several studies [7][8][9][10].…”