540 - Bringing X-ray Imaging to Space: A Radionuclide-Based Approach for Inflight Diagnostics and Interventional Radiology

Purpose: Medical emergencies are a significant risk in commercial spaceflights and on long-duration missions. X-ray imaging, however, currently remains unused on missions due to size, weight, and electricity constraints on spacecrafts. We developed a lightweight, portable X-ray apparatus with a commercially-available, low-dose radionuclide source. After showing that the apparatus was able to successfully capture images of tungsten foil and cooked pork meat without an electrical power source, it was selected for Low-Earth Orbit launch on September 10, 2024 with the SpaceX Polaris Dawn mission, becoming the first X-ray apparatus to leave Earth. Here, we present our apparatus design and our findings from imaging subjects that are closer to what we would see in a hypothetical image-guided procedure: simulated human tissue and 0.032" stainless steel wire.

Materials and Methods: Commercially-available exempt-quantity radionuclides- Ba-133, Cs-137, Cd-109- were coupled with a digital camera using a phosphor screen to convert X-rays to visible photons. The experimental apparatus was built using commercially-available lens tube parts connected to the camera. Image subjects included raw pork meat, pork bone, and phantom fingers made with Knox gelatin with or without an embedded chicken bone. A segment of 0.032" stainless steel wire, similar to those used in interventional procedures, was imaged alone as well as threaded through the simulated human tissue. Radionuclide sources and imaging conditions were examined.

Results: Images captured with each of the three radionuclides demonstrated varying levels of contrast, which correlated with the emission spectrum of each radionuclide source. Imaging parameters were adjusted to optimize exposure. It was difficult to appreciate the granularity in the raw pork tissue and the Knox gelatin finger, but their boundaries were distinct. Bone and steel wire were very clearly visualized, demonstrating clear contrast whether embedded in simulated human tissue or imaged alone.

Conclusion: The study demonstrated that it is possible to create a compact, lightweight, low-power radionuclide-based X-ray imaging system. Further work is required to optimize the images, such as uniformity correction due to the low photon flux levels. While the images obtained are not of clinical diagnostic quality, they are radiographs and demonstrate a feasible path to a device for long-duration spaceflight. In addition to diagnostic radiology, inflight X-ray imaging is expected to enable minimally-invasive procedures and eventually cross-sectional imaging of humans in space.