Reproducibility of Novel Soft-Tissue Landmarks on Three-Dimensional Human Facial Scan Images in Caucasian and Asian

Background Three-dimensional surface imaging is established in many disciplines for objective facial acquisition regarding anthropometry. Former studies addressed the validation of landmark-based measurements for single race. In order to distinguish racial difference, the reproducibility of the landmark measurements must first be validated. Objectives Our purpose is to validate the reproducibility of 46 facial soft-tissue landmarks on x, y, z axes to prove their reliability as 3D reference points. Methods The study included 80 European Caucasian and 80 Chinese volunteers. Standardized 3D surface imaging was performed using Vectra 3D system. Two raters identified and defined 46 landmarks (138 coordinates), then repeatedly 3D-imaged volunteers' facial region in separate sessions. Coordinates' reproducibility of landmarks is divided into three categories (< 0.5 mm, < 1 mm, and >1 mm) for intra- and inter-rater reproducibility assessments. Results Coordinates' reproducibility of 160 samples was distributed as follows: Intra-rater: < 0.5 mm (45%), < 1 mm (42%), >1 mm (13%); inter-rater: < 0.5 mm (31.2%), < 1 mm (42%), > 1 mm (26.8%). The reproducibility of landmarks in nasal tip region differs slightly between Caucasians and Asians. Compared to females, males typically have higher landmark reproducibility in lip and chin region. However, there were no differences in the reproducibility ranking of landmarks by gender. Conclusion The majority of the 46 landmarks in the 3D plane are reproducible to 1 mm, which is clinically acceptable. All selected landmarks showed strong consistency across race and gender, suggesting their potential use as reference points in prospective clinical practice.