Medical-imaging techniques could aid waste clean-up

Doctors typically use SPECT scans to take 3-D images of internal organs, but Clemson University researchers are re-purposing the technology in a project that could help clean up waste left from nuclear-weapons production.

Brian Powell and his team are pioneering the use of SPECT scans to examine how water and radionuclides move through soil packed into columns that are a little larger than the tube at the center of a paper towel roll.

The columns allow researchers to study how buried waste could react with soil and groundwater and what might happen if waste were to leak into the environment.

The U.S. Department of Energy spends $6 billion each year on cleaning up waste generated during nuclear-weapons production, and the Clemson research could help enhance safety and make the work more cost-effective, Powell said.

Researchers across the country are beginning to take note of the team’s use of SPECT scans.

Four Clemson researchers and three collaborators from The Netherlands co-authored a paper on the technique, and it was published in the journal Environmental Science & Technology.

The Energy Department’s Office of Science published a summary of the paper on its website, helping spread the word to other researchers who might want to use the same technique. New collaborations with national labs are also expected to help take what has been a South Carolina project to the rest of the country.

“Being able to monitor the inside of a column during the experiment is really transformative,” said Powell, the Fjeld Professor in Nuclear Environmental Engineering and Science.

SPECT stands for single-photon emission computerized tomography. When used in a hospital, the technique allows doctors to take 3-D pictures of internal organs and see how they work.

The Clemson team uses SPECT and another medical technology, x-ray computed tomography (CT) scans, to see what is happening inside soil-packed columns without breaking them open, which destroys them.

While other researchers have used CT scans, the Clemson team is among the first to employ SPECT scans to examine processes in soil, said Stephen Moysey, a co-author on the paper and associate professor of environmental engineering and earth sciences at Clemson.

“In the past when you did all these experiments, all you could really measure was what’s coming out of the samples,” he said. “You don’t know what’s happening inside the sample very well. With these imaging technologies, it’s giving us a whole new insight into what is actually going on.”

Researchers fill the columns with soil and pump in clean water to simulate groundwater. Then researchers switch to a solution with a radioisotope tracer, Powell said.

“As soon as that goes in, then we really start monitoring the column,” he said.

The monitoring includes SPECT and CT scans for three-dimensional images. Later, researchers switch to a different fluid that pushes out the radioisotopes and allows the team to monitor chemical reactions.

For other experiments, researchers use larger columns. They access them by passing through a locked gate and walking up a set of metal steps to the top of an outdoor testbed with two rows of 20 columns, each 28 inches long and weighing about 60 pounds.

Due to the larger size, the columns are analyzed using a unique one-dimensional measurement system built by Toshiba Professor of Nuclear Engineering Tim DeVol’s research group.

Rain falls on the soil samples, and microbes are allowed to build up.

“We’re trying to be more representative of what would happen in nature,” Moysey said. “The samples can be imaged, not exactly in the same way as CT or SPECT, but we’re still using non-

invasive imaging and detection tools to understand what’s happening inside that sample without having to open it up.”

The experiments are part of a $5.25-million study that is funded by the Department of Energy’s Experimental Program to Stimulate Competitive Research. Researchers are early into the fourth year of a five-year grant.

The project includes collaborators from South Carolina State University and the University of South Carolina. It has involved 49 students, 24 faculty members and nine postdoctoral researchers and has resulted in three Ph.D. dissertations, 12 master’s theses and 26 academic papers, Powell said.

David Freedman, chair of the Department of Environmental Engineering and Earth Sciences, said the summary on the Department of Energy website shows there is high interest in the research.

“The work that Dr. Powell and his team are doing has been very good for the state and is now spreading to the rest of the nation,” he said. “We are well positioned for maximum impact.”

Anand Gramopadhye, dean of the College of Engineering, Computing and Applied Sciences, congratulated the team.

“The Department of Energy article is a testament to the high-value scholarship that Dr. Powell brings to the college,” Gramopadhye said. “His team is making strides in research aimed at enhancing the disposal of nuclear-weapons production waste, which is crucial to national security.”

The title of the paper is “High-Resolution 4D Preclinical Single-Photon Emission Computed Tomography/X-ray Computed Tomography Imaging of Technetium Transport within a Heterogeneous Porous Media.” Authors are Mine Dogan, Moysey, Ruud M. Ramakers, DeVol, Frederik J. Beekman, Harald C. Groen and Powell.

You can find the Department of Energy summary here: https://science.energy.gov/bes/highlights/2017/bes-2017-11-d/