Abstract
OBJECTIVE: Raman spectroscopy (RS)reveals the molecular composition of tissues and proved to be suitable for intraoperative in situ diagnosis of glioma, including IDH1 genotype. We aimed to investigate fresh tissue biopsies to approximate the the potential and limitations of intraoperative Raman spectroscopy. METHODS: 208 biopsies were obtained during brain tumor surgery and without any further processing analyzed by RS. Samples from epilepsy surgery served as nontumor control tissues. Spectra were obtained with a RamanRxn1T (Kaiser Optical Systems Inc) coupled to a microscope at five positions of each sample. Data analysis was performed using MATLAB and statistical analysis using Fisher’s coefficient. RESULTS: RS of 51 meningioma, 53 primary GBM, 19 recurrent GBM, 11 astrocytoma, 8 oligodendroglioma, 6 oligoastrocytoma, 8 neurinoma, 24 metastases, and 16 other tumors were acquired. Furthermore, three samples of necrotic tissue and nine nontumor human brain tissue were analyzed. Raman bands related to hemoglobin (754 cm-1 and 1540-1570 cm-1) reliably detected contamination with blood. Moreover, an band at 959 cm-1 indicated PO4-groups of calcium hydroxyapatite. All tumor types showed a significant reduction in the spectral range 1050-1150 cm-1 compared to non-tumor brain tissue according to the Fisher’s coefficient. In GBM, bands related to lipids (1297, 2850, 3011 cm-1) were strongly reduced, teh protein band at 1660 cm-1 was increased. Neurinoma exhibited additional peaks at 1158 and 1521 cm-1 which are assigned to carotinoids. Cholesterol at 700 cm-1 was largely missing in brain metastases, whereas collagen related signals were increased. Raman spectra of meningioma were characterized by higher intensities of bands assigned to (phospho)lipids and DNA compared to dura. CONCLUSION: The RS of fresh biopsies measured wthin the OR were in accordance to previous data from tissue sections. Perspectively, this provides a concept for in situ tissue classification to assist neuropathologists and neurosurgeons for intraoperative - integrated diagnosis.