When it comes to getting a clear idea of what’s going on inside a person’s body, few medical devices are as useful as a PET scanner. PET stands for Positron Emission Tomography, but simply put, it involves using radioactive positrons, or positively charged particles, to detect how parts of the body are functioning. An area of increased metabolic or chemical activity—such as the division of cancer cells—will show up on a colored image.
Most often PET scans are prescribed to see if cancer has spread or if a tumor is diminished, but they also are used to diagnose heart and neurological diseases. In fact, this type of imaging usually can detect changes in the body earlier than tests like CT scans or MRIs. That’s why it’s thought that PET scans might be able to spot brain conditions, such as Alzheimer’s disease, at an early stage.
But here’s the complication. Anyone who has had a PET scan knows that while it’s not an invasive procedure, it’s also not a particularly pleasant experience. Once your body is positioned within a large hole in the machine, while a scan is being done, you need to lie very still, often for as long as a half hour, sometimes even an hour, depending on what part of your body is being scanned.
Being forced to remain motionless for that long can be especially difficult for older people. It also measures brain activity in an artificial situation, when a person isn’t doing anything, including interacting with other people.
But what if you could make a PET scanner portable? What if a person could wear it?
Help from a helmet
That’s what Stan Majewski wondered. At the time, he was a physicist working for the Department of Energy (DOE) in Newport News, Virginia. He specializes in developing imaging and detector systems, so he was intrigued when he heard about a device invented by some colleagues in a DOE office in Upton, New York. They called it the RatCap, and it was a PET scanner worn on a rat’s head.
Majewski thought he could create something similar for humans. It could, he believed, have great potential in advancing research in brain disorders, like Alzheimer’s and Parkinson’s disease. So, he designed a helmet encircled by a ring of small, square PET detectors, then applied for a patent. He received one in 2011.
He started working on a prototype, and his project picked up momentum after he became a radiology professor at West Virginia University. Another professor at the university, Julie Brefczynski-Lewis, a neuroscientist, was visiting Majewski’s office when she noticed a drawing of a woman on a treadmill wearing an odd-looking helmet.
“What is this?” she asked him. When Majewski explained how it worked and what it could do, she committed to help make it happen.
With money awarded by the university, they moved ahead with the prototype. Then, in 2013, Majewski and Brefczynski-Lewis got a big boost from the BRAIN initiative announced by President Obama to develop innovative technologies that help explain how the brain functions. Along with collaborators at the University of California, Davis and the University of Washington, and a team at General Electric, they received a $1.5 million grant to determine what it will take to turn Majewski’s model into an effective treatment tool.
PET scans in motion
Brefczynski-Lewis, who has studied the effect of compassion on the human brain, is excited about what can be learned through brain scans of people in motion. Even allowing someone to sit up during the procedure can help stretch the range of research.
“If a person is seated, you can imagine them being able to tolerate the very long scans that are needed for research on conditions like Alzheimer’s or other neurological disorders," she says. “Just last week we were working with a woman in her 80s, and there’s no way she could have stayed still for 90 minutes, but she was able to sit in a chair and move her head and talk to us and be quite comfortable.”
That ability to engage a patient during a scan could make a big difference in diagnosing brain conditions, according to Brefczynski-Lewis. “Sometimes, early in Alzheimer’s you don’t see any difference, you don’t see any symptoms,” she explains. “But there’s a phase where if you tax them with high memory loads, you’re able to see the system react differently in an Alzheimer’s person versus someone who doesn’t go on to develop Alzheimer’s.”
Majewski and Brefczynski-Lewis say a portable PET scanner also could enable researchers to monitor brain activity while a person is laughing, exercising, experiencing stress, or even when the patient is immersed in a virtual reality setting. This could, for instance, help them better understand what’s going on in the brain of an autistic person in a social setting or a stroke patient doing rehab exercises.
There also could be an opportunity to study why some people have exceptional abilities, whether it’s a world-class athlete or a musical savant. The device, Brefczynski-Lewis says, could provide insight into what parts of the brain they access while they’re performing.
Another benefit of the portable helmet is that the level of radiation exposure is much lower, about one-tenth the level of a conventional PET scanner, because the detectors are so close to a person’s head. That’s why Majewski and Brefczynski-Lewis have named their device the AM-PET—the “A” is for ambulatory, the “M” for micro-dose.
Time to refine
But there are still hurdles to clear. The helmet can get heavy—during early testing, a bungee cord from the ceiling was attached to the device to lighten the weight on the patient wearing it. The challenge is to make it lighter without reducing the sensitivity of the detectors.
The researchers are also looking at ways to keep the movement of the helmet from affecting the resolution of the images it provides. That includes incorporating aspects of robotics, such as the ability to keep a camera on a robot stabilized no matter how much it moves.
“The idea is to be able to utilize that in the PET helmet so it takes into account the movement of a person’s body,” says Brefczynski-Lewis. “You want to compensate for motion so the helmet moves with the head, but you reduce resistance and that reduces the weight on the person.”
Another focus, she notes, is to continue to reduce the radiation levels. That would permit more scans to be done on a person, and perhaps enable doctors to use it on young children with neurological disorders.
Taking into account all the necessary fine-tuning and clinical testing, Brefczynski-Lewis estimates it could be another four or five years before the AM-PET can be used to treat patients. For now, they are applying for grants that could allow them to develop several different versions of their scanner. One to study Alzheimer’s would likely need to be different than one used to analyze the brain during more complex behavior, she says.
There’s even been discussion of a model that can be worn outside the lab. “We actually believe that a version of the helmet can be mounted to a backpack,” says Majewski. “The backpack would carry the weight.
“We call it the 'walk in the park' version.”