For every 100,000 people in the United States (US), approximately 221 have been diagnosed with brain tumors, 138,054 with a malignant tumor and more than 550,042 with a non-malignant tumor. Metastatic brain tumors are the most common. Surgery is an essential component in the treatment of these brain tumors. However surgeons face challenges when removing brain tumors. They need to remove all the tumor without leaving behind any cells that could start a new tumor. They also need to be extremely careful not to damage any healthy tissue to minimize any risk to the patient.

According to Dr. Orringer, co-lead author of a recent study of a new laser microscope, and lecturer at the University of Michigan (UM) Medical School Department of Neurosurgery, survival for many patients is still poor despite recent advances in brain tumor surgery.

However, a new laser-based technology may make brain tumor surgery more accurate for surgeons, enabling them to tell cancer tissue from normal brain tissue at the microscopic level while they are operating.thereby avoiding leaving any cells behind that could cause a new tumor. In essence, the surgeons can see the tiniest areas of tumor cells in brain tissue.

In this study, Orringer and his colleagues describe the use of stimulated Raman scattering (SRS) microscopy for differentiating healthy human and mouse brain tissue from tumor-infiltrated brain based on histoarchitectural and biochemical differences. Unlike traditional histopathology, SRS is a label-free technique that can rapidly performed in situ. SRS microscopy was able to differentiate tumor from nonepoplastic tissue in an infiltrative human glioblastoma zenograph mouse model based on their different Raman spectra. This is the first time SRS microscopy has been used in a living organism to see the “margin” of the tumor, the boundary area where tumor cells infiltrate among normal cells, which is the most difficult area for the surgeon to operate, especially when a tumor has invaded a region with an important function. By providing rapid intraoperative assessment of brain tissue, SRS microscopy may ultimately improve the safety and accuracy of surgeries where boundaries are visually indistinct.

The SRS microscope distinguished between dense brain tumor tissue and the normal healthy grey and white matter of the brain may be as accurate as hematoxylin and eosin (H&E) staining, the current method for diagnosing brain tumors. The advantage of SRS microscopy over H&E staining is that it can be done in real time, during the brain operation, without having to remove and processing the tissue. In their paper, they recount how they tested the two methods against each other to arrive at this conclusion. The treatment is not yet available for use in patients. The team now wants to make the technology smaller and more stable so it can be used in an operating room. They are planning to start a validation study next year, using brain tissue from volunteer patients.