Shape Analysis of the Human Hippocampus Using Spherical Harmonics: An Application to Alzheimer's Disease

Jänicke, Heike
Abstract in English: 
Every year a higher life expectancy is reported for people living in industrial countries. With increasing age, the risk of getting Alzheimer's Disease increases as well. Alzheimer's Disease is a neurodegenerative disease that is characterised by progressive deterioration of brain tissue. One of the first regions in the brain to be affected is the hippocampus. A common method to quantify the deterioration of the hippocampus is to measure its volume. However, decreasing volume is no specific marker of Alzheimer's Disease, but can be caused by other diseases as well. Thus, the deformation has to be observed in more detail, which can be done using shape analysis. A powerful shape analysis technique is the approximation of the surface by means of spherical harmonics. A process chain computing such an approximation is explained in this thesis. Therefore, the data is triangulated, forming a closed manifold. Afterwards, a homogeneous mapping of the surface to the unit sphere is computed in two steps. First an initial spherical parametrisation is computed, which is optimised afterwards to resemble the properties of the initial surface. The optimisation is mandatory, to allow for inter-subject comparability. The optimised parametrisation defines a function on the sphere, that can be approximated by spherical harmonics, a set of basis functions on the unit sphere. This procedure results in a mathematical description of the surface that can be analysed statistically. The method is applied to data of Alzheimer's Disease patients.
Promoter / Gefördert durch: 
Deutscher Akademischer Austauschdienst (DAAD), Max-Planck-Institut für Kognitions und Neurowissenschaften (Leipzig), Karolinska-Institut (Stockholm, Schweden)
Pages / Seitenanzahl: 
2006-13.pdf7.99 MB