Inject tumor paint into a patient’s vein, and it will actually cross the blood-brain barrier and find its way to a brain tumor. Then, by shining near-infrared light on a tumor coated with tumor paint, you can make that tumor glow, right there in the OR.
“The surgeons right now use their eyes and their fingers and their thumbs to distinguish cancer from normal brain,” says Olson. But poking around in someone’s brain with only those tools, it’s inevitable surgeons will sometimes miss bits of tumor or, just as bad, damage healthy brain cells.
http://www.npr.org/blogs/health/2015/04/08/397364328/doctors-test-tumor-paint-in-people