Figure 3. Spatial maps of principal component (PC) 1 score at three unique regions within a single tumour irradiated to 15 Gy.

The spatial variation of PC1 scores demonstrates tissue heterogeneity within an individual tumour. Map areas are 120 μm² for (a) and (b), 210 μm² for (c) and images are formed with 15 μm² pixels which correspond with the x and y step sizes during Raman map acquisition. Pixels with slashes indicate pixels for which no PC score information is available because the spectrum at that pixel was excluded from PCA (for reasons discussed in methods section).