Supplementary Materials Probabilistic segmentation of mass spectrometry images helps select important ions and characterize confidence in the resulting segments July 20, 2015 Kyle D. Bemis 1 , April Harry 1 , Livia S. Eberlin 2 , Christina R. Ferreira 2 , Stephanie M. van de Ven 3 , Parag Mallick 3 , Mark Stolowitz 3 , Olga Vitek 4,5 1 Department of Statistics, Purdue University, West Lafayette, IN USA 47907 2 Department of Chemistry, Purdue University, West Lafayette, IN USA 47907 3 Canary Center at Stanford for Cancer Early Detection, Stanford University School of Medicine, Palo Alto, CA USA 94304 4 College of Science, Northeastern University, Boston, MA USA 02115 5 College of Computer and Information Science, Northeastern University, Boston, MA USA 02115 1