Facial three-dimensional surface imaging: reliability and validity of handheld structured light scanners and a static stereophotogrammetry system

Introduction Several new systems of three-dimensional (3D) surface imaging of the face have become available to assess changes following orthognathic or facial surgery. Before they can be implemented into practice their reliability and validity must be established. Our aim was therefore to study 3dMD (stereophotogrammetry), Artec Eva and Artec Space Spider (both structured light scanners) regarding intra- and inter-system reliability and validity. Material and Methods Intra- and inter-system reliability expressed in root mean square (RMS) distance was determined by scanning multiple times a mannequin’s head and faces of healthy volunteers. Validity was determined by comparing linear measurements of scans with known distances of a 3D printed model. Post-processing errors were calculated. Results Intra-system reliability of mannequin’s head was best for the Artec Space Spider (0.04 mm Spider; 0.07 mm 3dMD; 0.08 mm Eva;). Inter-system reliability of the mannequin’s head showed least differences between Artec Space Spider and Artec Eva. Intra-system reliability of human subjects was best for the Artec Space Spider (0.15 mm Spider; 0.20 mm Eva; 0.23 mm 3dMD). Inter-system reliability of human subjects showed least differences between Artec Eva and Artec Space Spider. Validity of linear measurements was most accurate in the Artec Space Spider. Post-processing error was 0.01mm for all systems. Conclusion The Artec Space Spider was the most reliable and valid scanning system.