title: Automated analysis of craniofacial morphology using magnetic resonance images.
abstract: Quantitative analysis of craniofacial morphology is of interest to scholars working in a wide variety of disciplines, such as anthropology, developmental biology, and medicine. T1-weighted (anatomical) magnetic resonance images (MRI) provide excellent contrast between soft tissues. Given its three-dimensional nature, MRI represents an ideal imaging modality for the analysis of craniofacial structure in living individuals. Here we describe how T1-weighted MR images, acquired to examine brain anatomy, can also be used to analyze facial features. Using a sample of typically developing adolescents from the Saguenay Youth Study (N = 597; 292 male, 305 female, ages: 12 to 18 years), we quantified inter-individual variations in craniofacial structure in two ways. First, we adapted existing nonlinear registration-based morphological techniques to generate iteratively a group-wise population average of craniofacial features. The nonlinear transformations were used to map the craniofacial structure of each individual to the population average. Using voxel-wise measures of expansion and contraction, we then examined the effects of sex and age on inter-individual variations in facial features. Second, we employed a landmark-based approach to quantify variations in face surfaces. This approach involves: (a) placing 56 landmarks (forehead, nose, lips, jaw-line, cheekbones, and eyes) on a surface representation of the MRI-based group average; (b) warping the landmarks to the individual faces using the inverse nonlinear transformation estimated for each person; and (3) using a principal components analysis (PCA) of the warped landmarks to identify facial features (i.e. clusters of landmarks) that vary in our sample in a correlated fashion. As with the voxel-wise analysis of the deformation fields, we examined the effects of sex and age on the PCA-derived spatial relationships between facial features. Both methods demonstrated significant sexual dimorphism in craniofacial structure in areas such as the chin, mandible, lips, and nose.
authors.affiliation: Rotman Research Institute, Baycrest, Toronto, Ontario, Canada. mchakravarty@rotman-baycrest.on.ca
authors.forename: M Mallar
authors.initials: MM
authors.lastname: Chakravarty
authors.forename: Rosanne
authors.initials: R
authors.lastname: Aleong
authors.forename: Gabriel
authors.initials: G
authors.lastname: Leonard
authors.forename: Michel
authors.initials: M
authors.lastname: Perron
authors.forename: G Bruce
authors.initials: GB
authors.lastname: Pike
authors.forename: Louis
authors.initials: L
authors.lastname: Richer
authors.forename: Suzanne
authors.initials: S
authors.lastname: Veillette
authors.forename: Zdenka
authors.initials: Z
authors.lastname: Pausova
authors.forename: Tomáš
authors.initials: T
authors.lastname: Paus
mesh_terms: D000293:Adolescent; D002648:Child; D005145:Face / Q000033:anatomy & histology*; D005260:Female; D006257:Head / Q000033:anatomy & histology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D025341:Principal Component Analysis; D011795:Surveys and Questionnaires