Hon.-Prof. Hans-Christian Hege

Projects as a project leader

• CH15

  Analysis of Empirical Shape Trajectories

  Hon.-Prof. Hans-Christian Hege / Prof. Tim Sullivan / Dr. Christoph von Tycowicz

  Project heads: Hon.-Prof. Hans-Christian Hege / Prof. Tim Sullivan / Dr. Christoph von Tycowicz
  Project members: Dr. Esfandiar Navayazdani
  Duration: 01.06.2017 - 31.12.2019
  Status: running
  Located at: Freie Universität Berlin
  

  Description

  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. To develop new mathematical methods for the analysis, processing and reconstruction of empirically defined shape trajectories exploiting the rich geometric structure of shape space.
  
  http://www.zib.de/projects/analysis-empirical-shape-trajectories

• CH8

  X-ray based anatomy reconstruction with low radiation exposure

  Hon.-Prof. Hans-Christian Hege / Dr. Martin Weiser / Dr.-Ing. Stefan Zachow

  Project heads: Hon.-Prof. Hans-Christian Hege / Dr. Martin Weiser / Dr.-Ing. Stefan Zachow
  Project members: Dennis Jentsch
  Duration: -
  Status: completed
  Located at: Konrad-Zuse-Zentrum für Informationstechnik Berlin
  

  Description

  Medical imaging is essential in diagnostics and surgery planning. For representation of bony structures different imaging modalities are used; the leading methods are X-ray projection (projectional radiography) and CT. Disadvantage of these imaging techniques is the ionization caused by X-rays, particularly in CT, where the dose is 250-500 times higher than in classic X-ray projection. From the clinical perspective therefore one would like to replace CT acquisitions by a few possible X-ray projections. The project deals with the ill-posed inverse problem of 3D reconstruction of bony structures from 2D radiographs. Virtual radiographs are generated from virtual bone structure models; these are compared with clinical patient images and incrementally changed until a sufficiently accurate bone model is found whose virtual projections fit to the measured data. By using a statistical shape model as prior knowledge it is possible to formulate a well-posed optimization problem in a Bayesian setting. Using gradient methods and multilevel/multiresolution methods for both the reconstruction parameters and image data, good computational performance is achieved. Uncertainty quantification techniques can be applied to describe the spatially varying accuracy of the reconstructed model. Finding best X-ray projections (recording directions) minimizing both uncertainty and radiation exposure leads to a design of experiments problem. Two flavors of this design optimization are considered: An all-at-once approach finding the best image acquisition setup before any X-ray projections are performed, and a sequential approach determining the best next projection direction based on the accumulated knowledge gained from the previously taken images.
  
  http://www.zib.de/projects/x-ray-based-anatomy-reconstruction-low-radiation-exposure

• GV-AP7

  Modeling synaptic connectivity in anatomically realistic neural networks

  Hon.-Prof. Hans-Christian Hege

  Project heads: Hon.-Prof. Hans-Christian Hege
  Project members: -
  Duration: 01.07.2014 - 31.12.2015
  Status: completed
  Located at: Konrad-Zuse-Zentrum für Informationstechnik Berlin
  

  Description

  The goal of the NeuroConnect project is
  

  • to generate anatomically realistic 3D neural network models,
  • to provide tools to analyze such models and
  • to extract information for numerical simulations of neural activity, particularly the synaptic connectivity.

  
  This requires the development of new methods to effectively specify, visualize, and quantify the information of interest in these potentially large (>500k neurons) and complex neural networks, as well as efficient data structures to represent and process this data. Methods to extract the anatomical data underlying the network model and the modeling approach have been developed in the past Cortex In Silico project.
  
  http://www.zib.de/projects/modeling-synaptic-connectivity-anatomically-realistic-neural-networks

• GV-AP8

  In vivo and in silico analyses in humans: Cartilage loading of patients' individual knees - the role of soft tissue structures

  Hon.-Prof. Hans-Christian Hege / Dr. Martin Weiser

  Project heads: Hon.-Prof. Hans-Christian Hege / Dr. Martin Weiser
  Project members: -
  Duration: 01.10.2014 - 31.01.2019
  Status: completed
  Located at: Konrad-Zuse-Zentrum für Informationstechnik Berlin
  

  Description

  While a relationship between knee joint laxity and osteoarthritis is often assumed, the exact mechanism is not yet fully understood. It is not clear how stabilization by either the cross ligaments or muscle forces affect the local cartilage stress and strain. We develop a comprehensive analysis tool for individual patients. On one hand, we couple a dynamic multibody model to a quasistatic contact solver for the cartilage and validate it against in vivo measurement data from patient groups at Charite. On the other hand, we develop visualization and statistical analysis tools that allow to understand the impact of anatomical variation and cross ligament loss on the mechanical loading of cartilage and correlate this to osteoarthritis progression.
  
  http://www.zib.de/projects/vivo-and-silico-analyses-humans-cartilage-loading-patients%E2%80%99-individual-knees-%E2%80%93-role-soft-tissue

• GV-AP14

  Modeling Synaptic Connectivity in Anatomically Realistic Neural Networks

  Hon.-Prof. Hans-Christian Hege

  Project heads: Hon.-Prof. Hans-Christian Hege
  Project members: -
  Duration: 01.01.2016 - 31.12.2017
  Status: completed
  Located at: Konrad-Zuse-Zentrum für Informationstechnik Berlin
  

  Description

  The goal of the NeuroConnect project is

  • to generate anatomically realistic 3D neural network models,
  • to provide tools to analyze such models and
  • to extract information for numerical simulations of neural activity, particularly the synaptic connectivity.

  
  This requires the development of new methods to effectively specify, visualize, and quantify the information of interest in these potentially large (>500k neurons) and complex neural networks, as well as efficient data structures to represent and process this data. Methods to extract the anatomical data underlying the network model and the modeling approach have been developed in the past Cortex In Silico project.
  
  http://www.zib.de/projects/modeling-synaptic-connectivity-anatomically-realistic-neural-networks