Ultrasound flies high but lays low following NASA budget cuts

Boosted into space March 8, the modified HDI 5000 built by ATL Ultrasound now waits for a crew capable of running it. Budget cuts have reduced the size of the crew of the International Space Station (ISS), sidelining research with the space-faring ultrasound scanner for a year or more.

"I would have preferred to fly it closer to when it would be used, because then we could have gotten more upgrades into it," said David S. Martin, senior scientist for ultrasound at NASA's Johnson Space Center in Houston.

There is another concern about having the scanner sit idle in space. The longer the unit orbits the earth, the greater the possibility that radiation or some other force will cause a malfunction. If something does go wrong, troubleshooters on earth will use ATL's UpLink remote system diagnostics program, which has been customized for space communications, to find the problem. Circuit boards have been located in easily accessible locations within the body of the scanner, so replacement parts, flown in on a future supply mission, could be swapped in, if necessary. Components would be taken from an identical backup unit or either of two training units on earth.

In the meantime, the space station project has provided some benefits here on the planet. Finding ways to reduce the system's volume by 80% and weight by 60% bodes well for ATL's efforts to construct powerful yet compact and lightweight scanners. Some of this achievement, however, was accomplished in ways not appropriate for terrestrial systems. Locked into an equipment rack, as it is in the Destiny research laboratory of the ISS, the box surrounding the electronics could be eliminated-as could the wheels. And not all of the reengineering has everyday applications. Developments to protect the electronics from radiation damage have limited application here, since cosmic rays, the source of this damage, never reach the earth.

HDI 5000 was preceded into space by other scanners flown on the U.S. space shuttle and Russian space station, Mir. These were relatively primitive. None offered phased array, color flow, or tissue Doppler imaging, according to Martin.

"They left some questions unanswered," he said.

The HDI 5000 now in orbit was designed to address those questions, including the effects of microgravity on blood flow, the heart, and other organs as well as a range of musculoskeletal and cardiovascular functions. The answers may be crucial in planning a mission to Mars, which could last two or more years.

"It is clear we have the hardware to go to Mars, but the major unknown factor is whether people will be able to function when they get there," said NASA ultrasound consultant Dr. Art Fleischer, who is chief of diagnostic sonography and professor of radiology and ob/gyn at Vanderbilt University Medical Center.

The data that will answer those questions were supposed to be streaming to earth soon after delivery of HDI 5000 into orbit. ISS was designed to support a seven-person crew, and one was to be a physician trained in the use of ultrasound. The crew size, however, has been limited to three; no more astronauts are allowed onboard than can be safely evacuated in case of an emergency. Plans to build a space lifeboat capable of returning a seven-person crew have been scrapped, leaving the three-person Soyuz capsule docked to ISS as the only means of escape. Ultrasound research projects, therefore, must wait until a trained operator is available.

The high-flying HDI 5000 might be called into service sooner in the event of a medical emergency. The system could be used to diagnose a range of injuries and ailments, including fractures, pneumothorax, abdominal trauma, musculoskeletal injuries, and appendicitis, according to Martin. But talking an astronaut not skilled in the use of ultrasound through an exam would be challenging.

"As a test, I trained a group of astronauts for two to three hours and then brought them back six months later to talk them through an exam," he said. "It cost me a lot of hair pulling."

On earth, ultrasound might not be the first-choice modality to study all the problems that could beset the ISS crew, especially fractures, but an injured or sick astronaut would have no other option. HDI 5000 is the only medical imaging device currently installed on ISS.

"We are fortunate to have the ultrasound unit up there," Martin said. "We may come up with a whole bunch of applications never thought about before."

© 2001 Miller Freeman Inc.
3/28/01, Issue # 1506, page 5.