Spring Seminar Series  May 24, 2007
University of Minnesota
School of Statistics
College of Liberal Arts


Structural Adaptive Smoothing in Imaging Problems

Joerg Polzehl
Weierstrass Institut for Applied Analysis and Stochastics

Thursday, May 24, 2007
3:30 PM, 20 Vincent Hall


Minneapolis, East Bank Campus
Social at 3:00 PM, 300 Ford Hall


Abstract

The talk presents a class of structural adaptive smoothing methods developed at WIAS.  The main focus will be on the 
Propagation-Separation (PS) approach proposed in Polzehl and Spokoiny (2006). The method allows to simultaneously
identify regions of homogeneity with respect to a prescribed model (structural assumption) and to use this information
to improve local estimates. This is achieved by an iterative procedure. The name Propagation-Separation is a synonym
for the two main properties of the algorithms. In case of homogeneity, that is if the prescribed model holds with the
same parameters within a large region, the algorithm essentially delivers a series of nonadaptive estimates with
decreasing variance and propagates to the best estimate from this series. Separation means that, as soon as in two
design points i and j significant differences are detected between estimates, observations in j will not be used to
estimate the parameter in j. We establish some theoretical {nonasymptotic} results on properties of the new algorithm.
The power of the approach will be demonstrated for several imaging problems. This includes denoising of greyvalue and
color images, demosaicing and adaptation to anisotropic structures in images. I'll also present how these methods can
be applied in the analysis of functional Magnetic Resonance Imaging experiments and Diffusion Tensor Imaging data.