ACR Bulletin

Covering topics relevant to the practice of radiology

Patient Care Among the Stars

Researchers at the University of Southern California are working to provide patients with the best imaging care possible — even in space.
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One of the reasons I personally enjoy research is because of the joy that comes from a surprising result or discovery — and, as a physician, figuring out how it might be used to help my patients.

—John Choi, MD, PhD
May 19, 2023

Caring for patients is the goal of all physicians. With technological advancements sending humans to the moon and beyond, patient care must adapt as well, and radiologists must be able to provide imaging care — even in a spaceship.

But how will this be accomplished? Researchers from the Keck School of Medicine at the University of Southern California (USC) are planning an experiment to determine the best way to use radiation to help provide imaging care during spaceflight.

The Bulletin talked to the leader of the USC research team, John Choi, MD, PhD, an integrated IR/DR resident physician at the Keck School of Medicine, to find out more.

What sparked the idea for this experiment?

Prior to joining the program at the Keck School of Medicine at USC, I was fortunate to have worked at NASA’s Jet Propulsion Laboratory, and through an aerospace industry colleague I was introduced to an emergency medicine physician, who is now a NASA astronaut candidate, Anil Menon, MD. Through our conversations, the idea of radiology using ambient radiation came up, but I did not follow up further. Much later, while looking for a research project to pursue as a resident, I remembered the idea and was introduced to an anesthesiologist and PhD working in the field of space medicine. Together, we proposed the experiment for a launch opportunity, and we are very grateful to have been selected to potentially fly! Looking back, it was helpful to have those conversations with people from outside of my own field who motivated a new line of thought.

How long has X-ray imaging in space been a concern for astronauts?

According to one source, it was considered during the 1980s for a predecessor design of the International Space Station (ISS), but the idea was ultimately abandoned.1 Since then, X-ray imaging in space has not been a reality, due to the size, weight and power limitations aboard a spacecraft. Current space radiology is limited to the use of ultrasound, first implemented on the ISS in 2001 (a Philips ATL HDI-5000 weighing approximately 480 pounds).2,3 That system was upgraded in 2011 to a GE Vivid Q, weighing approximately 11 pounds, and there was a demonstration in 2021 of a handheld device, the Butterfly iQ, weighing less than 5 pounds.4,5,6 By comparison, a “portable” CT scanner, a CereTom, is advertised as weighing approximately 1,000 pounds and requiring 1.3 kilowatts (kW) of peak power. 7 For perspective, the ISS is characterized as providing up to 30 kW of power for use by all payloads, and a typical CT scanner alone might need more than 25 kW.8

Can you explain the process of harnessing radiation in space?

Using ambient radiation is a way to simplify our experiment for launch into space, and a starting point to begin the process of making in-flight X-ray imaging a reality. To give an analogy, we want to take photos using outdoor sunlight instead of using a flash or indoor lighting. This has analogous limitations, some of which would be deal-breakers for medical applications. However, just as photography started with extremely limited technologies, like pinhole cameras, our justification is that space radiology needs to start somewhere. The basic idea is to use an intensifying screen, as is used for analog X-ray film, to convert ionizing radiation into visible light, which is then captured by a digital camera, taking advantage of advances in digital camera technology. We want to answer the question of whether there is enough ambient radiation in space to generate a visible light signal and characterize the background noise level for our detection system. The next steps would be to capture an image containing spatial information and continue to iterate toward clinical usefulness.

Together, we proposed the experiment for a launch opportunity, and we are very grateful to have been selected to potentially fly!

—John Choi, MD, PhD

If successful, how will this specific experiment benefit future space missions such as the eventual trip to Mars?

The main motivation is that a human spaceflight mission measured in years, such as to Mars, will require medical capabilities onboard the spacecraft. To us, that includes diagnostic radiology, which we believe is an essential step of modern medicine for proper diagnosis. Although ultrasound is important, X-ray modalities would still be necessary for certain conditions that might occur in space. As an example, a case of left internal jugular venous thrombosis was reported aboard the ISS.9 This was diagnosed with an ultrasound scan and treated with anticoagulation, all aboard the ISS, an example of space radiology and in-flight medicine. However, if the thrombus had been within the pulmonary arteries, a pulmonary embolism, a CT would have been the proper exam for diagnosis rather than ultrasound.

What have been the biggest challenges in this experiment? Has anything surprised you during the preparation?

The biggest challenge has been the process of launching an experiment into space. This is not unique to our experiment, but universal for all space-related endeavors. The playing field was significantly changed by the advent of private commercial space entities, and the field will continue to evolve. I think the most surprising thing is the positive reception this project has received so far. In particular, I would like to thank the radiology department at USC, which has been extremely supportive — especially the chair at the time, Robert K.W. Ryu, MD, and my team of co-residents and collaborators. This project wouldn’t have been possible without all of them. I hope that means there are more radiologists who believe improving space radiology is a worthy goal and are willing to help make it a reality. Overcoming the challenges of patient care in space will require a community and not just one person, group or institution.

How will this endeavor benefit patient care on Earth?

As necessity is a driver of invention, the limitation of resources in space will likely result in X-ray-based medical technologies that consume less power and, consequently, use lower levels of ionizing
radiation. This would likely reduce the carbon footprint of radiology equipment and reduce patient exposure to ionizing radiation. In addition, I am sure there will be other unintended benefits. One of the reasons I personally enjoy research is because of the joy that comes from a surprising result or discovery — and, as a physician, figuring out how it might be used to help my patients. I hope that will be the case for space radiology as well.


1. Barratt MR, Baker ES, Pool SL. Principles of Clinical Medicine for Space Flight. Published 2008, Springer Publishing, pp 181-207.

2. NASA, Marshall Space Flight Center. Human Research Facility Rack 1. Fact sheet number FS-2001-02-43-MSFC. Release date February 2001. Accessed April 6, 2023.

3. Dr’s Toy Store, product description. Philips HDI 5000 Ultrasound Machine. Accessed April 6, 2023.

4. GE Healthcare press release. GE Healthcare’s Vivid q Cardiovascular Ultrasound System Selected for Use by NASA. Release date July 6, 2011. Accessed April 6, 2023.

5. Butterfly Network press release. The Butterfly iQ Catches a Ride on the SpaceX Dragon to Space. Release date June 3, 2021. Accessed April 6, 2023.

6. Butterfly Network System Specifications. Accessed April 6, 2023.

7. NeuroLogica CereTom Elite Product Features. Accessed April 6, 2023.

8. NASA. External Payloads Proposer’s Guide to the International Space Station. Accessed April 18, 2023.

9. Auñón-Chancellor SM, Pattarini JM, Moll S, Sargsyan A. Venous Thrombosis During Spaceflight. N Engl J Med. 2020;382(1):89–90. doi: 10.1056/NEJMc1905875.

Author Alexander Utano  editorial assistant, ACR Press