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Fluorescent signature discovery helps identify parathyroid glands during endocrine surgery

April 28, 2017

White agreed and they began working together even though they didn't have any funding to support the project. They recruited Phay, who was an attending endocrine surgeon at the time and had access to animal tissue from other experiments being conducted on campus. They tried several different optical techniques, but none of the methods revealed anything distinctive about parathyroid tissue.

Finally, Mahadevan-Jansen decided to try a technique called Raman spectroscopy that fingerprints different organic molecules by subtle changes in the color of reflected light. The effect is very weak and difficult to measure.

When they put thyroid tissue in the instrument, they got a small signal. When they inserted parathyroid tissue, however, the detector saturated. This was totally unexpected because most biological fluorescence takes place in the ultraviolet and visible ranges. Biological molecules rarely fluoresce in the infrared region of the spectrum.

Possible light leak turned out to be a real effect

"At first, we thought it must be a light leak," Mahadevan-Jansen said. When they kept getting the strong signal with several different samples, however, they realized that the effect was real.

Based on this success, Mahadevan-Jansen brought biomedical engineering graduate students Constantine Paras and Matthew Keller on board.

The expanded research team submitted an experimental protocol to Vanderbilt's Institutional Review Board, which must approve all experiments involving animals or people. When it was approved, they gained access to human thyroid and parathyroid tissue.

"The parathyroid tissue from those first dozen patients kept saturating the Raman spectrometer so we had to keep reducing the laser's intensity," Mahadevan-Jansen recalled. "Finally, I realized that the instrument was saturating because the tissue was fluorescing."

When she confirmed that this was happening, the engineer realized that they didn't need the Raman spectroscope. All they needed was a light source in the near infrared and the right kind of near infrared detectors.

Cause of fluorescence remains a mystery

"We still haven't figured out the source of the fluorescence, but that doesn't stand in the way of using this effect to improve the effectiveness of parathyroid surgeries and reduce the damage done to the parathyroid in other endocrine surgeries," Mahadevan-Jansen said.

Meanwhile, White is finishing up her final year as a resident in general surgery. She intends to make endocrine surgery a major part of her practice, so she could be one of the first surgeons whose patients will benefit from the discovery that resulted from her curiosity and initiative as a first-year intern.

Source: Vanderbilt University