Validity of the 3D VECTRA photogrammetric surface imaging system for cranio-maxillofacial anthropometric measurements

The use of three-dimensional (3D) photography for anthropometric measurements is of increasing interest, especially in the cranio-maxillofacial field. Before standard implementation, accurate determination of the precision and accuracy of each system is mandatory.

A mannequin head was labelled with 52 landmarks, and 28 three-dimensional images were taken using a commercially available five-pod 3D photosystem (3D VECTRA; Canfield, Fairfield, NJ) in different head positions. Distances between the landmarks were measured manually using a conventional calliper and compared with the digitally calculated distances acquired from labelling by two independent observers. The experimental set-up accounted for clinical circumstances by varying the positioning (vertical, horizontal, sagittal) of the phantom.

In the entire calliper measurement data set (n = 410), a significant difference (p = 0.02) between the directly measured and corresponding virtually calculated distances was found. The mean aberration between both modalities covering all data was 7.96 mm. No differences (p = 0.94) between the two groups were found using a cut-off of 10 % (leaving n = 369 distances) due to considerable errors in direct measurements and the necessary manual data translation. The mean diversity of both measurement modalities after cut-off was 1.33 mm (maximum, 6.70 mm). Inter-observer analysis of all 1,326 distances showed no difference (p = 0.99; maximal difference, 0.58 mm) in the digital measurements.

The precision and accuracy of this five-pod 3D photosystem suggests its suitability for clinical applications, particularly anthropometric studies. Three-hundred-and-sixty degree surface-contour mapping of the craniofacial region within milliseconds is particularly useful in paediatric patients. Proper patient positioning is essential for high-quality imaging.