Label-Free Delineation of Brain Tumors by Coherent Anti-Stokes Raman Scattering Microscopy in an Orthotopic Mouse Model and Human Glioblastoma

Abstract

BackgroundCoherent anti-Stokes Raman scattering (CARS) microscopy provides fine resolution imaging and displays morphochemical properties of unstained tissue. Here, we evaluated this technique to delineate and identify brain tumors.MethodsDifferent human tumors (glioblastoma, brain metastases of melanoma and breast cancer) were induced in an orthotopic mouse model. Cryosections were investigated by CARS imaging tuned to probe C-H molecular vibrations, thereby addressing the lipid content of the sample. Raman microspectroscopy was used as reference. Histopathology provided information about the tumor's localization, cell proliferation and vascularization.ResultsThe morphochemical contrast of CARS images enabled identifying brain tumors irrespective of the tumor type and properties: All tumors were characterized by a lower CARS signal intensity than the normal parenchyma. On this basis, tumor borders and infiltrations could be identified with cellular resolution. Quantitative analysis revealed that the tumor-related reduction of CARS signal intensity was more pronounced in glioblastoma than in metastases. Raman spectroscopy enabled relating the CARS intensity variation to the decline of total lipid content in the tumors. The analysis of the immunohistochemical stainings revealed no correlation between tumor-induced cytological changes and the extent of CARS signal intensity reductions. The results were confirmed on samples of human glioblastoma.ConclusionsCARS imaging enables label-free, rapid and objective identification of primary and secondary brain tumors. Therefore, it is a potential tool for diagnostic neuropathology as well as for intraoperative tumor delineation.

Raman spectroscopy as a promising noninvasive tool in brain cancer detection

“…Advancements over RS, including stimulated RS and Coherent Anti-Stokes Raman Scattering have shown encouraging outcomes in brain cancer diagnosis. [45][46][47][48][49][50][51] Further, market-assessment and safety studies, followed by clinical trials are needed to advance the technology as an intraoperative guidance tool. In conclusion, RS, as shown by several recent reports, is a promising tool which can aid in improving the accuracy of brain tumor diagnosis and surgical procedures.…”

Detection of human brain tumor infiltration with quantitative stimulated Raman scattering microscopy

“…Prior to the demonstration of SRS in 2008 (16), coherent anti-Stokes Raman scattering (CARS) microscopy was proposed for brain tumor imaging (37) because of its ability to detect tumor infiltration based on alterations in the CH range of the Raman spectrum and tissue architecture in glioma models (38). SRS was later shown to have superior nuclear contrast in comparison to CARS (19).…”

Rapid, label‐free identification of cerebellar structures using multiphoton microscopy

“…Spectral confocal reflectance microscopy and near-infrared reflectance microscopy have detected myelinated axons in health and disease on fluorescent transgenic mice [16,17]. Coherent antistokes Raman scattering microscopy and stimulated Raman microscopy have identified brain tumor with high chemical selectivity [18,19]. Compared with these methods, although the imaging depth of MPM is limited to resolve deeper structures, MPM has ability to not only reveal axons but also visualize cell morphology and the extracellular matrix of tissue by unfixed, unstained, and non-fluorescent specimen at subcellular resolution.…”