Facial landmark localization by curvature maps and profile analysis.

Carsten Lippold,Burkhard Drerup,Kristina Schreiber,Kim Wangdo,Tatjana Moiseenko,Gholamreza Danesh,Christian Kirschneck,Xiang Liu

doi:10.1186/1746-160x-10-54

Abstract

IntroductionThree-dimensional landmarks of the face are important for orthodontic examination, harmony assessment and treatment planning. Currently, facial landmarks are often measured by orthodontists via direct observation and manual soft tissue image analysis. This study wants to evaluate and present an objective method for measuring selected facial landmarks based on an analysis of curvature maps and of sagittal profile obtained by a laser-scanning method.MethodsThe faces of 15 people were scanned in 3D by means of the laser scanner FastSCAN™. It allowed the recording of a curvature map of the face in under a minute, which depicted the distribution of Gaussian and mean curvatures. The median-sagittal profile line of the face was localized in this map, and a mathematical analysis comprising its first and second derivatives was performed. Anatomical landmarks were identified and facial measurements performed. To assess validity the obtained data were compared with manual measurements by orthodontists by means of Lin’s concordance correlation CCC coefficient and reliability was determined by consecutive measurements.ResultsFacial landmarks, such as the soft tissue glabella and nasal tip, could be easily and accurately identified and located. Lin’s CCC showed substantial agreement between digital and manual measurements for 4 of the 7 distances evaluated. Larger discrepancies were due to inadequate image quality and scanning errors. Reliability of consecutive measurements by the same operator was excellent.ConclusionsIn our pilot study the three-dimensional laser-scanning method FastSCAN™ allowed a reliable and accurate identification of anatomical landmarks of the face. The obtained distances between certain landmarks, such as the intercanthal distance, were largely consistent with those from manual measurements. Due to its easy and rapid implementation, the method facilitates facial analysis and could be a clinically valid alternative to manual measurements, when remaining problems in scanning accuracy can be resolved.

Highlights

Three-dimensional landmarks of the face are important for orthodontic examination, harmony assessment and treatment planning
Surface scanning and curvature maps Measurements were performed with the FastSCANTM laserscanning system (Polhemus, Colchester, Vermont, USA) [3]
The distances obtained from the curvature maps of the FastSCANTM laser-scanning system are consistent with

Summary

Introduction

Three-dimensional landmarks of the face are important for orthodontic examination, harmony assessment and treatment planning. Anatomical surface landmarks of the face are visually or palpably detectable and can be used as reference points for clinical measurements. This is important for orthodontists and maxillofacial soft tissue profile considerably. This paper proposes and evaluates a new method for localizing important anatomical landmarks of the face and calculating facial parameters and distances required by orthodontists. This method aims to eliminate the subjective errors made by manual measurements and to simplify facial analysis by automatically obtaining landmarks and distances with a high level of accuracy and reproducibility

Methods

Results

Discussion

Conclusion