Ever seen a picture of a nuclear power plant, with the water around reactors glowing an eerie blue? That’s due to something called Cherenkov radiation, a release of energy when charged particles pass through material with such force and speed that it sort of exceeds the speed of light in that material.

Turns out, we humans emit Cherenkov radiation when hit with X-rays during cancer treatment. The energy output is tiny so we’re not exactly Dr. Manhattan, the aquamarine dude from Watchman comics, but there is a glow, and it carries information.

Now some folks at Dartmouth think they can help doctors make use of that information.

Professor Brian Pogue

“There are so many people involved in radiation therapy, and it’s all done with computer simulations. ... The radiation therapist doesn’t have their hands around all that,” said Brian Pogue, who is a professor of engineering, of physics and of surgery (yes, surgery) at Dartmouth and its medical and engineering schools. “This gives them a real, tangible visualization of what is happening.”

X-rays and other charged particles are emitted by a linear accelerators and focused on tumors to kill them. Radiation can damage healthy cells of course, so precise dosage and aim is vital. The idea of the Dartmouth researchers is to use cameras to visualize the faint Cherenkov radiation, improving treatment and reducing side effects such as skin reactions.

Sounds obvious and easy, but not so.

“The problem is that the (Cherenkov radiation) is many orders of magnitude less intense than normal room lighting,” said David Gladstone of Norris Cotton Cancer Center, where he is chief of Clinical Physics. (What a title to put on your business card: There’s way more overlap between medicine and physics than I ever realized.)

Gladstone and his team, including Ph.D. students, took up the problem after Pogue mentioned the idea of allowing therapists to somehow visualize Cherenkov radiation. Eventually they realized that the trick is to take pictures only when the linear accelerator is actually firing, which happens in bursts that are 3 millionths of a second long, occurring every 10 thousands of a second.