The reconstruction of discretized geometric shapes from empirical data, especially from image data, is important for many applications in medicine, biology, materials science, and other fields. During the last years, a number of techniques for performing such geometrical reconstructions and for conducting shape analysis have been developed. An important mathematical concept in this context are shape spaces. These are high-dimensional quotient manifolds with Riemannian structure, whose points represent geometrical shapes. Using suitable metrics and probability density functions on such manifolds, distances between shapes or statistical shape priors (for utilization in reconstruction tasks) can be defined. A frequently encountered situation is that instead of a set of discrete shapes a series of shapes is given, varying with some parameter (e.g. time). The corresponding mathematical object is a trajectory in shape space. For many analysis questions it is helpful to consider the shape trajectories as such (instead of individual shapes) - often together with co-varying parameters. The focus of this project is to develop new mathematical methods for the analysis, processing and reconstruction of empirically defined shape trajectories. By treating the trajectories as curves in shape space, we plan to exploit the rich geometric structure inherent to these spaces. In consequence, we expect the derived schemes to benefit from a compact encoding of constraints and a superior consistency as compared to their Euclidean counterparts.

Publications

2022
A Hierarchical Geodesic Model for Longitudinal Analysis on Manifolds Journal of Mathematical Imaging and Vision, 64(4), pp. 395-407, 2022 (preprint available as ZIB-Report 21-39) Esfandiar Nava-Yazdani, Hans-Christian Hege, Christoph von Tycowicz PDF (ZIB-Report)
BibTeX
DOI
Analysis of Empirical Shape Trajectories
2020
Geodesic Analysis in Kendall's Shape Space with Epidemiological Applications Journal of Mathematical Imaging and Vision, 62(4), pp. 549-559, 2020 Esfandiar Nava-Yazdani, Hans-Christian Hege, T. J. Sullivan, Christoph von Tycowicz BibTeX
DOI
arXiv
Analysis of Empirical Shape Trajectories
Towards Shape-based Knee Osteoarthritis Classification using Graph Convolutional Networks 2020 IEEE 17th International Symposium on Biomedical Imaging (ISBI 2020), 2020 Christoph von Tycowicz BibTeX
arXiv
DOI
Analysis of Empirical Shape Trajectories
2019
A Geodesic Mixed Effects Model in Kendall's Shape Space Proc. 7th MICCAI workshop on Mathematical Foundations of Computational Anatomy (MFCA), pp. 209-218, Vol.11846, Lecture Notes in Computer Science, 2019 (preprint available as ZIB-Report 19-49) Esfandiar Nava-Yazdani, Hans-Christian Hege, Christoph von Tycowicz PDF (ZIB-Report)
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DOI
Analysis of Empirical Shape Trajectories
Statistical Shape Models - Understanding and Mastering Variation in Anatomy Biomedical Visualisation, Paul M. Rea (Ed.), Springer Nature Switzerland AG, 1, pp. 67-84, 2019, ISBN: 978-3-030-19384-3, ISBN: 978-3-030-19385-0 (preprint available as ZIB-Report 19-13) Felix Ambellan, Hans Lamecker, Christoph von Tycowicz, Stefan Zachow PDF (ZIB-Report)
BibTeX
DOI
Analysis of Empirical Shape Trajectories
2018
A Shape Trajectories Approach to Longitudinal Statistical Analysis ZIB-Report 18-42 Esfandiar Nava-Yazdani, Hans-Christian Hege, Christoph von Tycowicz, T. J. Sullivan PDF
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URN
Analysis of Empirical Shape Trajectories
An Efficient Riemannian Statistical Shape Model using Differential Coordinates Medical Image Analysis, 43(1), pp. 1-9, 2018 (preprint available as ZIB-Report 16-69) Christoph von Tycowicz, Felix Ambellan, Anirban Mukhopadhyay, Stefan Zachow PDF (ZIB-Report)
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DOI
Analysis of Empirical Shape Trajectories
2016
Geometric Flows of Curves in Shape Space for Processing Motion of Deformable Objects Computer Graphics Forum, 35(2), 2016 (preprint available as ZIB-Report 16-29) Christopher Brandt, Christoph von Tycowicz, Klaus Hildebrandt PDF (ZIB-Report)
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DOI
Analysis of Empirical Shape Trajectories
2013
De Casteljau's Algotithm on Manifolds Computer Aided Geometric Design, 30(7), pp. 722-732, 2013 Esfandiar Nava-Yazdani, Konrad Polthier PDF
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DOI
URN
Analysis of Empirical Shape Trajectories