Mass Spectrometry Imaging
Mass spectrometry imaging (MSI) is an analytical technique that involves virtually dividing a surface into a grid of pixels. Each pixel is then individually analyzed using a focused source. This source ionizes the material constituting the sample surface through a phenomenon called desorption/ionization. The generated ions are accelerated and transmitted to a mass analyzer, enabling the measurement of their mass-to-charge ratio (m/z). This process results a set of mass spectra associated with their X,Y coordinates. By using data processing tools, the m/z of an ion can be selected to reconstruct a density map (see Figure 1).1 The spatial resolution in MSI depends on the diameter of the probe (focused source). The advantage of MSI is its ability to determine the spatial distribution of various analytes without requiring labeling. This technique has numerous applications, such as metabolomics, lipidomics, pharmacokinetics, etc…2–6
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