Researchers from the Keck School of Medicine of USC have designed a study, to be conducted on board the upcoming Polaris Dawn mission, that tests a new way to collect X-rays in outer space.

By Zara Abrams

(Photo: iStock)

Today’s spaceflights typically last a few days to a few months, so onboard medical treatment is mostly limited to first aid. But researchers are increasingly exploring new terrain—known as in-flight space medicine—that will be critical for maintaining astronauts’ health during longer missions, such as the 21-month roundtrip to Mars.

Polaris Dawn, the first of three missions in the Polaris Program, is pursuing an array of new frontiers in space. Estimated to launch no earlier March 1, 2023, its crew will aim to achieve the highest-ever orbit of Earth and attempt the first-ever commercial spacewalk. They will also spend up to five days conducting more than 38 studies of human health in space, including a Keck School of Medicine of USC-led effort to study a new approach to X-ray imaging onboard.

“Modern X-ray equipment isn’t practical to send into space because of its significant mass and electricity requirements,” said John Choi, MD, PhD, a resident physician in interventional radiology at the Keck School of Medicine of USC and the leader of the project. “But in order to do true clinical medicine in space during a mission—in-flight space medicine—we’re going to need radiology.”

John Choi, MD, PhD, resident physician in interventional radiology at the Keck School of Medicine of USC (Photo Alissa Diaz)

Ultrasound is the primary diagnostic imaging method currently used in space because ultrasound equipment is relatively portable and does not require much power. But it cannot identify certain life-threatening medical issues, such as a blood clot in a major artery of the heart, lungs or brain.

For that reason, Choi and his colleagues believe that X-ray imaging and radiology—in addition to other medical capabilities and specialties such as surgery, anesthesia and emergency medicine—are crucial for effectively responding to medical emergencies in space. They are now exploring an innovative method that could allow clinicians to use the ambient radiation in space (natural radiation that is always present) to collect X-ray images with minimal equipment.

“In space, we know there’s more ionizing radiation than on Earth,” Choi said. “Can we take advantage of that radiation as a source that allows us to capture an image?”

Harnessing radiation in space

To answer that question, Choi and his team are leveraging technology from a simpler form of X-ray equipment than modern-day digital detectors: film. Because of its lower mass and power requirements, using this simpler equipment to absorb radiation for image generation could eliminate the practical problems with sending equipment into space.

In analog X-ray film imaging, a special “intensifying screen” converts radiation into visible light, which can then be developed on film. The researchers are sending a piece of this intensifying screen into space to test whether there is enough ambient radiation to cause the screen to glow.

Choi and his team are assembling the materials needed to conduct the experiment and the researchers are writing instructions for the Polaris Dawn crew to use when conducting the experiment onboard.

Enhancing health on Earth

The experiment, known as a “proof of principle,” is just the first step to establish whether ambient radiation in space is sufficient to generate X-ray images. If successful, researchers will then need to prove that they can conduct clinically meaningful X-ray exams using the new method.

A technological breakthrough could also offer helpful insights for X-rays on Earth, such as a way to collect images with less radiation. In addition to its goal of advancing human health in space, the Polaris Dawn mission seeks to gain scientific knowledge that could improve medical care closer to home.

“The mission profile of Polaris Dawn affords us some great opportunities to expand our collective knowledge about the human body in space and associated applicability here on Earth,” said Jared Isaacman, mission commander of Polaris Dawn. “Our science and research agenda will enhance the body of knowledge for future long-duration spaceflight which will take us back to the Moon and on to Mars; as well as progress our knowledge and understanding for humankind here on Earth.”

About this research

Choi’s co-investigators are Robert Ryu, professor and chair of the Department of Radiology, Keck School of Medicine of USC; Scott E. Fraser, provost professor of biological sciences and biomedical engineering, stem cell biology and regenerative medicine, Keck School of Medicine of USC and director of science initiatives for USC; and Amran Asadi, a medical engineer at SpaceX.

Funding for this research was provided by the University of Southern California, and the Department of Radiology of the Keck School of Medicine of USC.