Editor’s note: Artemis I, an unmanned space mission on a trip around the Moon and back, launched on November 16, 2022. The highly anticipated spaceflight will be the first to test the new Orion spacecraft along with its ground and rocket systems. (Updated November 16, 2022)
The Artemis I mission is the first step in NASA’s plans to transport human crews to further explore the lunar surface and eventually establish a sustainable outpost on the Moon. The flight would also contribute to the preparatory work necessary for a mission to Mars. When it takes off from the Kennedy Space Center in Florida, Artemis will carry two mannequins strapped to its crew module. The mannequins are part of a project helped by a team of bioengineers from Duke University with support from the National Institute of Biomedical Imaging and Bioengineering (NIBIB).
Among the challenges facing human space exploration is the health risk posed by cosmic radiation. The mannequins, physical phantoms, were manufactured by a commercial supplier and originally designed for use in medical imaging testing or radiology practices. For the space mission, each ghost will be equipped with sensors to measure the radiation accumulated in various parts of the body that astronauts would absorb during such a space flight.
“Various anthropomorphic phantoms have been critical tools used to evaluate and adjust medical scans from X-rays to CT. These phantoms are particularly important as they represent human anatomy and therefore the impact of the images in the most relevant way,” said Behrouz Shabestari, Ph.D., director of NIBIB’s National Technology Centers Program and acting director of the Division of Health Informatics Technologies. “The Duke University team has honed its expertise in computational modeling and studying human tolerance to radiation dose from medical imaging and has now further put this expertise into analysis and study for the space program.”
Each ghost is a representation of the female anatomy. The researchers performed some radiation exposure experiments on a male ghost who was previously aboard the International Space Station. Each phantom is embedded with more than a thousand radiation sensors that will collect readings for precise organ locations, according to Duke University’s Center for Virtual Imaging Trials (CVIT) director Ehsan Samei, Ph.D., the Reed and Martha Rice Distinguished Professor of Radiology, Medical Physics, Biomedical Engineering, Physics, and Electrical and Computer Engineering at Duke University. CVIT researchers have been developing computational models of virtual humans for the past 19 years for medical imaging research.
The models are realistic, dynamic and diverse, and include detailed anatomies of a variety of different subjects: pediatric and adult, pregnant and non-pregnant. They also include cardiac and respiratory movements and can simulate any number of illnesses. “With enough realism, medical experiments can be conducted to determine whether or not an intervention is effective by testing it in a computational model,” Samei said. He added that this experiment uses female phantoms because female anatomy is more sensitive to radiation exposure than male anatomy and radiation exposure estimates for male astronauts can be based on data from female phantoms.
In addition to NASA, project collaborators include engineers from the German Aerospace Center, the Israeli Space Agency and CIRS. During the test flight, researchers equipped the ghost named Zohar with a vest that will be evaluated for its ability to protect the body from radiation absorption. The other ghost, Helga, will not be surrounded by a protective shield.
“When we are exposed to radiation, the damage is deposited directly in the organs, and different organs have different levels of radiosensitivity,” Samei said. “For example, breast tissue tends to be more radiosensitive, while muscles are not as radiosensitive. The brain is less radiosensitive than the heart. That is why it is essential for the study to track the radiation and where in the body it is deposited.”
Helga and Zohar are specifically made to include only definitions of the lungs and bones of the body. The Duke team created an interior map to define everything else. They used the virtual models developed as part of CVIT to determine where all the organs are, according to Paul Segars, Ph.D., associate professor of Radiology and deputy director of CVIT.
“We have a computer GPS map that indicates where each sensor is installed,” Segars said. “Our virtual definition of the organs provides the GPS, telling it the number of sensors to measure to compensate for the heart dose or to obtain the pancreas dose.”
NASA will use information on radiation doses to better understand the risks posed to astronauts and to design possible protective measures for space flights or prolonged stays on the Moon.
Radiation exposure is a danger that must be faced on long space missions. According to Samei, a mission to Mars would take about 36 months round trip. “The fact that we have so much charge around the Moon indicates how important radiation exposure is,” Samei said. The ghosts Zohar and Helga weigh as much as the human astronauts. “NASA will receive the most definitive assessment of the radiation dose received by astronauts that we can ever obtain and could never obtain from real astronauts.”
Duke University’s CVIT laboratory is part of a network of NIBIB-supported National Centers for Biomedical Imaging and Bioengineering. The Centers create critical and unique technology and methods that can be applied to a variety of basic, translational and clinical research. The CVIT team has been working with virtual phantoms for two decades and has more recently focused on designing anatomical maps for use in phantom models.
The research project is partially supported by NIBIB grant EB028744.
