Rapid Mass Spectrometry Technique Identifies Brain Tumors in Situ

A new diagnostic tool could provide near-real time intraoperative molecular diagnosis and margin assessment of brain tumors, according to a new study.

Researchers at Purdue University (Purdue, West Lafayette, IN, USA) and Brigham and Women's Hospital (Boston, MA, USA) developed the new tool, which sprays a microscopic stream of charged solvent onto tissue surfaces to gather information on molecular makeup, producing a color-coded image that reveals the nature and concentration of tumor cells. The tool relies on an ambient mass spectrometry analysis technique called desorption electrospray ionization (DESI), which evaluates the distribution and amounts of lipids within the brain tissue.

While conventional mass spectrometry requires chemical separations, manipulations of samples, and containment in a vacuum chamber for ionization and analysis, the DESI technique eliminates these requirements by performing the ionization step directly on surfaces outside of the mass spectrometers. Lipid patterns that correspond to the different types and grades of cancer and concentrations of tumor cells can then be identified using a software program that characterizes the brain tumors, detect boundaries between healthy and cancerous tissue, and displays the results in a color-coded map. The study was published on January 29, 2013, in the Proceedings of the National Academy of Sciences of the United States of America (PNAS).

“We hope to eventually be able to perform this analysis during surgery to help guide brain surgeons so that the borders of tumors can be identified and the cancer status of a site can be established before any tissue is removed,” said lead author Professor of Chemistry R. Graham Cooks, PhD, of Purdue. “We aren't there yet, but this was a critical step in the process. It shows we've found easily identifiable molecular patterns that can be used to diagnose the type and concentration of cancer cells.”

“The new tool is able - in a matter of seconds - to identify and classify glioma and meningioma tumors and recognize the tumor grade,” said study coauthor Sandro Santagata, MD, a pathologist at Brigham and Women's Hospital. “It is able to establish the same type of assessment the pathology offers, but at a pace that is compatible with surgery.”
Pathological examination of specimens taken from the brain during surgery provides the most specific information about the tissue and diagnosis of the cancer. However, this examination of frozen sections takes about half an hour, which is too long for it to be useful in examining multiple samples and guiding surgery.

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