Laser bioimaging technique defines pituitary tumors with extreme precision

A laser bioimaging technique could help surgeons more precisely define the locations of pituitary tumors in near-real time.

Researchers at Brigham and Women’s Hospital (BWH; Boston, MA) used a laser bioimaging technique that could help surgeons more precisely define the locations of pituitary tumors in near-real time.

The work involved a visualization technique called matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) that can analyze specific hormones, including growth hormone and prolactin, in tissue. In a study, the researchers found that it is possible to use MALDI MSI to determine the composition of such hormones in a pituitary sample in less than 30 minutes. This could give surgeons critical information to help distinguish tumor from normal gland.

The vast majority of pituitary tumors are noncancerous, but can cause headaches and profound fatigue, and can also disrupt hormone function. Currently, surgeons rely on radiologic images and magnetic resonance imaging (MRI) to gather information about the size and shape of the tumor, but the resolution of such imaging technologies is limited, and additional surgeries to remove more of the tumor may be needed if a patient’s symptoms persist.

To test the MALDI MSI technique, the research team analyzed hormone levels in 45 pituitary tumors and six normal pituitary gland samples, finding a distinct protein signature unique to the normal or tumor sample.

Mass spectrometry, a technique for measuring chemicals present in a sample, is currently used in the operating room to help inform clinical decisions, but up until now, the focus has been on small molecules (metabolites, fatty acids, and lipids) using a different type of approach. By analyzing proteins, MALDI MSI offers a way to visualize hormone levels.

Current methods used to detect hormone levels take too long to fit the time constraints of surgical intervention. Surgeons must either remove a larger amount of potentially healthy pituitary gland or perform follow up surgery if the tumor has not been fully removed.

“We’re hoping that techniques like this one will help move the field toward more precise surgery: surgery that not only removes all of the tumor, but also preserves the healthy tissue as much as possible,” says corresponding author Nathalie Agar, Ph.D., director of the Surgical Molecular Imaging Laboratory in the Department of Neurosurgery at BWH.

In the next phase of their work, Agar and her colleagues plan to test out the technique in BWH’s Advanced Multimodality Image Guided Operating Suite (AMIGO) and analyze the impact of the technique on clinical decision-making.

Full details of the work appear in the Proceedings of the National Academy of Sciences; for more information, please visit http://dx.doi.org/10.1073/pnas.1423101112.

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