Segmentation maps of the MALDI-imaging dataset. Optical image (A) and segmentation maps (B-F) of the dataset from Figure 2 but with 80 μm spatial resolution. B. Straightforward k-means clustering of spectra. C. Hierarchical clustering (Euclidean distance, complete linkage) after PCA-reduction of spectra to 70% explained variance. D. Clustering after edge-preserving image denoising; moderate denoising, reprinted from  with permission from American Chemical Society. E-F. Efficient spatially-aware clustering, moderate size of data-adaptive neighborhood (E) and large size of non-adaptive neighborhood (F), reprinted from  with permission from Elsevier.
Alexandrov BMC Bioinformatics 2012 13(Suppl 16):S11 doi:10.1186/1471-2105-13-S16-S11