On the influence of class information in the two-stage clustering of a human brain tumour dataset

Abstract

This paper analyzes, through clustering and visualization, Magnetic Resonance Spectra corresponding to a complex human brain tumour dataset. Clustering is performed as a two-stage process, in which the first stage model is Generative Topographic Mapping (GTM). In semi-supervised settings, class information can be added to refine the clustering process. A class information-enriched variant of GTM, classGTM, is used here for a first cluster description of the data. The number of clusters used by GTM is usually large for visualization purposes and does not necessarily correspond to the overall class structure. Consequently, in a second stage, clusters are agglomerated using the K-means algorithm with different initialization strategies, some of them defined ad hoc for the GTM models. We aim to evaluate how and under what circumstances the use of class information influences tumour cluster-wise class separability in the final result of the two-stage clustering process. © Springer-Verlag Berlin Heidelberg 2007.