For more than 65 years, humans have been soaring through space.
Since the first spaceflight by cosmonaut Yuri Gagarin in April 1961, the human presence in space has become a constant, with a revolving team of international spacefarers residing aboard the International Space Station.
In the coming decades, our presence in space is likely to expand – and with it, the need for vital medical tools to keep our cosmic explorers healthy.
Now, for the first time, astronauts in orbit have taken diagnostic-quality X-rays of their own bodies – the culmination of years of work. The results are now published in the journal Radiology.
For more than four decades, ultrasound has been the only practical medical imaging technology available to astronauts in orbit.
This technology works by propagating high-frequency sound waves into the human body and observing how they bounce back from the tissues therein. Obtaining and interpreting ultrasound images requires considerable training, but the technology is very versatile.
By contrast, X-ray imaging requires an X-ray source, a detector on the opposite side of the body, and a human patient perfectly positioned between them. You also need everything to stay still long enough for the imaging to succeed.
Ultrasound became the standard imaging tool for space because it is portable and safe, and its transducer can be pressed directly against the body, making it much easier to use in a microgravity environment where everything tends to float away.
In recent years, X-ray imaging technology has been shrinking, and with the emergence of small, portable, battery-operated devices, scientists started to believe that in-orbit X-ray imaging might be possible.
A major breakthrough took place in 2022, when scientists managed to take X-ray images aboard a parabolic flight that briefly simulates orbital microgravity.
But, having shown that the technique can work for seconds at a time, the next hurdle was seeing if it could work in an orbital context.
The setting was SpaceX's Fram2, an all-civilian spaceflight mission on a 3.5-day polar orbital flight aboard the spacecraft Resilience. (Fram2 was named after the ship that carried renowned polar explorers Fridtjof Nansen and Roald Amundsen).
The crew carried an X-ray system that featured an ultraportable, wireless digital X-ray generator. They received four hours of training and took X-ray images of their bodies before and during the orbital flight.
The images included a phantom object that served as a control, a smartwatch, hands, forearms, chests, abdomens, and pelvises.
All the X-ray images were independently evaluated by radiologists on Earth, who found that the scans were all of a similar high quality suitable for diagnosis.
As expected, the greatest difficulty wasn't obtaining the X-ray images, but positioning the patient, detector, and X-ray source and keeping them still long enough to obtain a good image.
The hands and arms were the easiest parts to image cleanly because they are easy to keep still. The images of the chest, abdomen, and pelvis proved more difficult to obtain; they were slightly lower in quality than the hand and arm images, but still above the threshold for diagnostic use.
The technology is likely not going to be limited to diagnostic use on humans, either.
As the images of the smartwatch showed, a portable X-ray machine could be used to inspect spacecraft equipment and other mission-critical hardware for hidden damage, which the researchers refer to as non-destructive testing.
There are still some limitations to be addressed. In-flight imaging time imposed a limit on the number and variety of X-ray images that could be obtained, and real-time telehealth may be unavailable for future spaceflight missions.
The researchers suggested AI-assisted analysis could eventually help astronauts assess image quality and identify potential medical problems on missions where expert radiologists on Earth are too far away to provide immediate support.
In addition, the apparatus sustained damage when the crew returned to Earth, although it remained functional. For future missions to the Moon and Mars, a more robust, rugged system may need to be developed.
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As humans prepare for those historic journeys, the ability to diagnose illnesses and injuries without relying on Earth becomes ever more important.
This research represents a critical step towards providing the fundamental medical tools that those future explorers will need as they boldly venture beyond Earth and out into the Solar System that awaits.
The findings have been published in Radiology.
This article was fact-checked by Carly Cassella and edited by Rebecca Dyer. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.