RESUMEN
This study investigates the reliability and precision of anthropometric measurements collected from 3D images and acquired under different conditions of head rotation. Various sources of error were examined, and the equivalence between craniofacial data generated from alternative head positions was assessed. 3D captures of a mannequin head were obtained with a stereophotogrammetric system (Face Shape 3D MaxiLine). Image acquisition was performed with no rotations and with various pitch, roll, and yaw angulations. On 3D images, 14 linear distances were measured. Various indices were used to quantify error magnitude, among them the acquisition error, the mean and the maximum intra- and inter-operator measurement error, repeatability and reproducibility error, the standard deviation, and the standard error of errors. Two one-sided tests (TOST) were performed to assess the equivalence between measurements recorded in different head angulations. The maximum intra-operator error was very low (0.336 mm), closely followed by the acquisition error (0.496 mm). The maximum inter-operator error was 0.532 mm, and the highest degree of error was found in reproducibility (0.890 mm). Anthropometric measurements from alternative acquisition conditions resulted in significantly equivalent TOST, with the exception of Zygion (l)-Tragion (l) and Cheek (l)-Tragion (l) distances measured with pitch angulation compared to no rotation position. Face Shape 3D Maxiline has sufficient accuracy for orthodontic and surgical use. Precision was not altered by head orientation, making the acquisition simpler and not constrained to a critical precision as in 2D photographs.
Asunto(s)
Cara , Fotogrametría , Cara/diagnóstico por imagen , Cabeza/diagnóstico por imagen , Imagenología Tridimensional , Reproducibilidad de los ResultadosRESUMEN
PURPOSE: To quantify the surface facial asymmetry in a group of young patients with hemifacial microsomia (HFM) and to investigate differences with a homogeneous sample of healthy subjects, using a novel stereophotogrammetric method. MATERIALS AND METHODS: Twelve patients (mean age 13.1 ± 3.1 years) with different degrees of HFM and 15 healthy controls (mean age 12.2 ± 3.5 years) were imaged with a stereophotogrammetric facial scanner. The root mean square error (RMSE) of the distances between the corresponding points of each original photograph and its mirror copy was calculated for the whole face and for each trigeminal third, as defined by the innervation of trigeminal branches. A statistical analysis was performed to compare the RMSE value of all facial areas within each group and between patients and controls. RESULTS: RMSE values progressively increased from the upper to the lower third of face, both in patients and controls. The level of asymmetry was significantly higher in HFM subjects for middle third (p < 0.01), lower third (p < 0.001) and whole face (p < 0.001); no statistically significant differences were found between the groups for the upper third. CONCLUSIONS: The reported technique provides an accurate topographic analysis of the facial asymmetry, and is recommended for conditions such as HFM affecting only part of the face.