Validation and reproducibility of a high-resolution three-dimensional facial imaging system

Abstract 

Objective

To assess the accuracy and reproducibility of a high-resolution three-dimensional imaging system (Di3D).

Design

The three-dimensional imaging system was validated in vitro using 12 adult facial plaster casts, which had landmarks marked, and the positions of the landmarks on the three-dimensional images captured by Di3D were compared with those obtained by a coordinate measuring machine (CMM).

Methods

Operator error was measured by repeatedly locating landmarks on the three-dimensional image. Reproducibility error of the images was calculated by capturing three-dimensional images of the facial casts on two separate occasions; the Euclidean distance between the two matched sets of coordinates was then calculated. The Di3D system error was assessed by calculating the three-dimensional global positions of landmarks on the three-dimensional images and comparing them with those obtained by CMM (gold standard).

Results

The operator error in placement of landmarks on the three-dimensional model was 0.07mm, range 0.02–0.11mm. The reproducibility of the Di3D capture was 0.13mm, range 0.11–0.14mm. The mean distance between the CMM and Di3D landmarks, which constitutes the Di3D system error, was an average of 0.21mm, range 0.14–0.32mm.

Conclusions

The Di3D system error was within 0.2mm, which is clinically acceptable, and offers considerable improvement in stereophotogrammetry for facial capture and analysis.

Keywords: Imaging, Stereophotogrammetry, Validation, Reproducibility