By Ms. Mallory Roussel (USARIEM)March 24, 2017
NATICK, Mass. (March 24, 2017) -- Scientists from the U.S. Army Research Institute of Environmental Medicine, or USARIEM, have been involved since 2010 in developing a computer program to create full-body, complete-anatomy avatars of individual warfighters, which would make an impact on military medicine throughout the U.S. Army.
They succeeded in making avatars a reality in 2016.
USARIEM researchers have now also developed computer software to create virtual X-ray images of their avatars, allowing them to better customize avatars to warfighters' physical makeup.
According to Dr. Gary Zientara, a mathematical modeler and avatar expert, this technology is the key to designing future software to produce avatars that best model individuals' body composition and internal anatomy, regardless of gender, shape or size.
"USARIEM's avatars are created by morphing standard, gender-specific anatomy figures to fit the body scans acquired from individuals," said Zientara, of USARIEM's Biophysics and Biomedical Modeling Division, or BBMD.
"When creating avatars, the virtual X-ray software plays a special role. By simulating two whole-body X-rays acquired by using high-energy and low-energy rays, the software can compose a dual-energy X-ray absorptiometry, or DXA, scan. DXA scans are a common and useful research tool at USARIEM, as well as other clinical medical centers and research sites, because they can take a comprehensive snapshot of a person's exact breakdown of bone, fat tissue and muscle mass. For USARIEM's avatar software, information from DXA scans can aid in managing Soldier nutrition requirements, directly contributing to Soldier readiness."
When X-rays interact with muscle, fat, organs and bones, they collide with many atoms along the way. With denser tissues like bone, the X-ray transfers all of its energy to the matter and it gets absorbed. That is why bones are easier to see in X-rays. Softer organ tissue only absorbs some of the X-ray energy, and the rest is scattered. That is what ends up producing the 2-D X-ray photographs of our bones, with denser organs like lungs and muscles darkening the film.
According to Zientara, the virtual X-ray software is able to replicate the actions of an X-ray by knowing the X-ray energy, the distance X-rays travel through various tissues and how much the X-ray beam is absorbed or scattered as it goes through organs and bones. Besides 2-D X-ray photographs, however, Zientara can also sample the virtual X-ray software data from different angles of the body, creating computed tomography, or CT, scans from the avatars.
"The ability to compute CT scans from avatars opens new state-of-the-art medical applications the Army could use in the field," Zientara said. "While X-rays are good for observing bone, we can use CT scans to take detailed pictures of the body from multiple angles in order to study soft tissues in the body, such as the brain, liver or abdominal organs. In a field hospital setting, for example, surgeons could use CT scans of avatars to study what is hidden beneath the flesh and tissue of the patient."
USARIEM's BBMD is working with Professor Steven Heymsfield from the Pennington Biomedical Research Center at Louisiana State University to further enhance USARIEM's avatar software. Using Heymsfield's data collected from body scans and DXA scans of hundreds of adult volunteer subjects, Zientara can modify the avatar internal anatomy so there are fewer differences between actual DXA scans and DXA scans computed from USARIEM's virtual X-ray software.
"USARIEM's avatars are currently created at a lower spatial resolution," Zientara said. "This can lead to minor distortions in the avatar body scans, compared to the photographic quality X-rays we may remember if we have had a broken bone in the past."
To solve this problem, Zientara is hoping to transfer the avatars to a supercomputer at the Department of Defense High Performance Computing Center. The higher resolution of a supercomputer would allow Zientara to create avatars that better model the shapes and contents of body anatomy.
USARIEM is capable of constructing male avatars, with hundreds already made. While the current software can morph standard anatomy into a body scan to create an avatar for any person, Zientara is working on developing software to accommodate female, gender-specific anatomy to construct female avatars.
"Simulating medical imaging using the avatars not only aids USARIEM's avatar development, but it also demonstrates the principle clearly and visually that the avatars can be employed for a wide range of Army simulation studies, reducing risk, costs and implementation time compared to the past," Zientara said.