Department of Energy Lab Produces World’s First-of-a-Kind Lung Phantom

Phantoms are replicas of human organs that interact with x-rays and gamma rays the same way real organs do in people.

They’re made by pouring a mixture of polyurethane and calcium carbonate into silicone rubber molds, which are based on plaster casts of a cadaver’s organs.

Lawrence Livermore National Laboratory previously had the only Thorium-232 lung phantom in the world prior to RESL, however it was not in equilibrium.

It takes around 50 years for Thorium-232 to break down or decay into a series of other elements before it can reach equilibrium—or when the radioactivity of all these elements remains constant.

Having the decay series in equilibrium allows researchers to know exactly how much Thorium-232 is in the body or lungs without measuring for it directly.

Thorium-232 emits alpha radiation that isn’t easily detectible because it is absorbed by body tissue. The other elements in the decay series emit gamma radiation, which can be detected and used to inform calculations of the amount of Thorium-232 in the body.

RESL incorporated the entire Thorium-232 decay series into its lung phantom by using 60-year-old thorium oxide material stored at Idaho National Laboratory before verifying the results.

The whole process took less than a year and is currently the only one of its kind in the world to reach equilibrium.

"Thorium is three times more abundant than uranium in the Earth’s crust and can also be used as nuclear fuel,” said Guy Backstrom, the director of RESL. “As the clean energy revolution takes place across America, the responsible development of all energy resources will help ensure our continued leadership in clean energy. RESL’s world-class scientists make sure that the measurements made to monitor the workers that are developing these energy systems remain safe.”