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Initial results of multilevel principal components analysis of facial shape

Farnell, Damian ORCID:, Galloway, Jennifer ORCID:, Zhurov, Alexei ORCID:, Richmond, Stephen ORCID:, Katic, Visnja and Pirttiniemi, Pertti 2017. Initial results of multilevel principal components analysis of facial shape. Presented at: MIUA 2017: Annual Conference on Medical Image Understanding and Analysis, Edinburgh, UK, 11-13 July 2017. Published in: Valdes Hernandez, Maria and Gonzalez Castro, Victor eds. Medical Image Understanding and Analysis. Communications in Computer and Information Science , vol.723 Cham: Springer, pp. 674-685. 10.1007/978-3-319-60964-5_59

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Traditionally, active shape models (ASMs) do not make a distinction between groups in the subject population and they rely on methods such as (single-level) principal components analysis (PCA). Multilevel principal components analysis (PCA) allows one to model between-group effects and within-group effects explicitly. Three dimensional (3D) laser scans were taken from 240 subjects (38 Croatian female, 35 Croatian male, 40 English female, 40 English male, 23 Welsh female, 27 Welsh male, 23 Finnish female, and 24 Finnish male) and 21 landmark points were created subsequently for each scan. After Procrustes transformation, eigenvalues from mPCA and from single-level PCA based on these points were examined. mPCA indicated that the first two eigenvalues of largest magnitude related to within-groups components, but that the next largest eigenvalue related to between-groups components. Eigenvalues from single-level PCA always had a larger magnitude than either within-group or between-group eigenvectors at equivalent eigenvalue number. An examination of the first mode of variation indicated possible mixing of between-group and within-group effects in single-level PCA. Component scores for mPCA indicated clustering with country and gender for the between-groups components (as ex-pected), but not for the within-group terms (also as expected). Clustering of component scores for single-level PCA was harder to resolve. In conclusion, mPCA is viable method of forming shape models that offers distinct advantages over single-level PCA when groups occur naturally in the subject population.

Item Type: Conference or Workshop Item (Paper)
Date Type: Publication
Status: Published
Schools: Dentistry
Subjects: R Medicine > RK Dentistry
Uncontrolled Keywords: multilevel principal components analysis; active shape models; facial shape
Publisher: Springer
ISBN: 978-3-319-60964-5
ISSN: 1865-0937
Last Modified: 02 Feb 2023 02:08

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