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Validation and reproducibility of a high-resolution three-dimensional facial imaging system
1Glasgow Dental Hospital & School, 378 Sauchiehall Street, Glasgow, G2 3JZ, UK.
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.
