Formalin Fixation as Tissue Preprocessing for Multimodal Optical Spectroscopy Using the Example of Human Brain Tumour Cross Sections

Figure 2

UV mean spectra and corresponding PCA models: UV absorption mean spectra of nonfixed (a, c) and formalin-fixed (b, d) brain tumour tissue cross sections in the range from 230 nm to 380 nm. The spectra are vertically displaced, and SNV transformed. (e) and (g) 3D scores plot with PC1 versus PC2 versus PC3 to differentiate between nonfixed tissue samples. (f) and (h) 3D scores plot with PC1 versus PC2 versus PC3 to differentiate between formalin-fixed tissue samples. The representative tumour entities for the tissue samples A to D with different malignancies are fibrous meningioma (sample (A)), oligodendroglioma (sample (B)), anaplastic ependymoma (sample (C)), and glioblastoma (sample (D)). The representative tumour entities for the tissue samples E to H with different malignancies are plexus papilloma (sample (E)), oligodendroglioma (sample (F)), anaplastic oligodendroglioma (sample (G)), and glioblastoma (sample (H)). Corresponding loadings plots of PC1 (black), PC2 (red), and PC3 (blue) for nonfixed (i, k) and formalin-fixed (j, l) cross sections.