Accuracy evaluation of tridimensional images performed by portable stereophotogrammetric system / Avaliação da acurácia de imagens tridimensionais realizadas em sistema de estereofotogrametria portátil

Abstract Introduction Human facial characteristics vary according to individual dental occlusion, facial harmony, orofacial musculature and the format and configuration of craniofacial structures. Traditionally, anthropometric measurements have been acquired through direct evaluation of subjects in a clinical environment using calipers and metric tapes to measure distances between arches and landmarks. Scientific breakthroughs have enabled the digitization of data and introduced the possibility of quick, precise, radiation-free acquisitions; details can be archived for future analysis and easily shared with patients and colleagues. Among new facial analysis methods, the stereophotogrammetry technique has emerged, which uses a group of cameras to take many photographs of a subject in rapid succession from multiple angles. Nowadays, portable stereophotogrammetric systems are being proposed, as they are more practical and easier to use. Objective The aim of this work was to analyze the accuracy and reproducibility of a portable 3D stereophotogrammetric system (Vectra H1, Canfield, Fairfield, NJ, USA) in measuring soft facial tissues of 30 participants, defining measures of a cube and comparing these measurements with those obtained by a set 3D stereophotogrammetric system (Vectra M3, Canfield, Fairfield, NJ, USA) with previously validated accuracy and reproducibility through quantitative analysis of possible errors. Material and method Thirty temporary landmarks were used to measure (in mm) 34 distances in 30 participants (n = 30). Regarding the cube, 12 angles and 9 linear distances were evaluated. Result The results obtained by the established methodology indicated that the Vectra H1 portable system has shown accuracy and reproducibility equal to that of the Vectra M3 set system. Conclusion Data analysis and correlation to literature findings show Vectra H1's capability to reliably capture tridimensional images, which makes it practical for use in diverse clinical applications.

Resumo Introdução A configuração e o formato das estruturas craniofaciais, a oclusão dentária, a musculatura orofacial bem como a harmonia facial são determinantes para as características próprias da face humana. Instrumentos manuais como paquímetro e fitas métricas têm sido tradicionalmente utilizados para realizar as medidas antropométricas, diretamente de um sujeito em ambiente clínico. O avanço tecnológico possibilitou transformar a aquisição destas medidas analógicas em medições digitais, tornando possível aquisições rápidas, precisas e sem radiação. Tais informações podem, ainda, ser arquivadas para futuras análises e compartilhamento de informações com colegas e pacientes. A estereofotogrametria tem se destacado dentre as novas técnicas de captação de imagens tridimensionais, onde um grupo de câmeras de rápida captura fotografam a imagem do indivíduo a partir de variadas angulações. Atualmente, sistemas portáteis de estereofotogrametria vêm sendo propostos no mercado por apresentarem maior praticidade e simplicidade no manuseio. Objetivo A proposta do presente estudo foi avaliar a precisão e a reprodutibilidade de um sistema de estereofotogrametria 3D portátil (Vectra H1, Canfield Scientific, Fairfield, NJ, EUA) em medições dos tecidos moles faciais de 30 participantes e de um cubo de medidas definidas, comparando tais medidas com as obtidas por um sistema de estereofotogrametria 3D fixo (Vectra M3, Canfield Scientific, Fairfield, NJ, EUA), de precisão e reprodutibilidade estabelecidas e validadas, através de análise quantitativa dos possíveis erros. Material e método Foram realizadas marcações craniométricas transitórias em tecido mole da face nos 30 participantes do estudo (n=30), sendo estes submetidos à aquisição de imagens pela técnica da estereofotogrametria, tanto pelo sistema fixo Vectra M3, quanto pelo sistema portátil Vectra H1. Trinta pontos de referência (landmarks) foram utilizados para realizar as medidas (em mm) de 34 distâncias. Quanto ao cubo, foram avaliados, no total, 20 ângulos, 20 áreas e 9 distâncias lineares. Resultado Os resultados obtidos pela metodologia estabelecida mostraram que o sistema portátil Vectra H1 apresentou precisão e repetibilidade comparáveis com o sistema fixo Vectra M3. Conclusão A análise dos dados, juntamente com a correlação aos achados da literatura, evidenciam a capacidade do Vectra H1 de capturar imagens tridimensionais de modo eficaz, o que torna viável seu uso nas mais diversas aplicações clínicas.

Repeatability Study of Angular and Linear Measurements on Facial Morphology Analysis by Means of Stereophotogrammetry.

The aim of this study was to analyze the repeatability in a stereophotogrammetry digital system used for the evaluation of facial morphology. Thirty healthy Brazilian, 18 to 45 years old (26.71 ±â€Š6.53), had 11 reference landmarks marked on their faces by the same examiner and were photographed with an interval of 1 week by the VECTRA M3. Nine angular measurements (nasolabial, mentolabial, nasofrontal, maxillofacial, nasal, maxillary, mandibular, facial convexity, full facial convexity) and 2 linear measurements (middle facial height and lower facial height) were taken. Repeatability was analyzed by the mean absolute differences, relative error of magnitude, technical error of measurement, intraclass correlation coefficient, and Bland-Altman analysis. Paired t test sought any systematic errors between the acquisitions. Associations among body mass index, age, and the error in the measurements were made using the Pearson correlation coefficient. For the technical error of measurement, the nasolabial and mentolabial angles showed values >2° (clinical limit set for this study). For the relative error of measurement, most of the measures were rated between good and excellent. The maxillofacial angle was only moderate. There was a systematic error for middle facial height. The nasolabial, mentolabial, facial convexity, full facial convexity, maxillofacial, and nasofrontal angles presented intraclass correlation coefficient values rated as excellent. The relationship between age/body mass index and the error found between measurements was not confirmed. The nasolabial and mentolabial angles should be interpreted with caution due to the variability showed. The results found stereophotogrammetry to be repeatable, giving accurate measures within the references established for this study.