Figure 3

Quantitative assessment of concordance between polarimetric and DESI-MS signals. (A) Grayscale polarimetric heterogeneity image of the analyzed slice with the six small targeted ROIs highlighted. This image is the same polarimetric image shown in Fig. 2, reproduced here for better presentation of the assignment of ROIs 1–6 used in this quantitative assessment. (B) Average relative ion intensity of markers corresponding to necrotic (red, m/z 572.48) and viable (green, m/z 391.25) cancer tissue. ROIs are grouped based on the depolarization of the tissue analyzed. The viable cancers ROIs with lower depolarization values contain a greater abundance of viable cancer marker ion, and the opposite is true for necrotic centers (revealed by elevated depolarization) where the relative abundance of necrotic cancer marker ion is largest. Border regions show equal representation of both populations (C) Histograms of the pixel-wise distribution of relative ion intensity of each marker with inset histograms of the distribution of depolarization. The histogram distributions match that of average values shown in (B) both in MS and polarimetry, with correspondence between two techniques. (D) DESI-MS molecular images of m/z 391.25 (marker for viable cancer sites, in green) and m/z 572.48 (marker for necrosis cancer sites, in red) for ROIs selected in (A) overlaid on same polarimetric heterogeneity image in grayscale. MS images of each ROI overlaying the necrotic and viable markers. In areas with high depolarization the necrotic marker is significantly more intense while in regions with low depolarization the viable marker is more intense. In border regions, the intensities are roughly equivalent.