Raw data files were first converted from the .raw format into mzml format using version 3.0.2 of the command-line utility msConvertGUI, commercially available from the open-source platform ProteoWizard 2 . The mzml file and the associated position file (xml format) were then combined to produce the MSI data in the vendor neutral imzml format (profile mode) using the in-built converter of Lipostar MSI (Molecular Horizon srl, Bettona, Italy) . The resulting imzml file was then loaded into Lipostar MSI for all subsequent data analysis and visualisation.