In recent years, researchers have been striving to develop MRI machines that use much smaller permanent magnets made of the alloy often found in desk toys. These machines produce fields roughly 1/25th as strong as a standard MRI magnet, which one would have been far too weak to glean a usable image.
However, thanks to better electronics, more efficient data collection, and new signal processing techniques, multiple groups have imaged the brain in low fields, albeit with lower resolution than standard MRI. The result is scanners small enough to roll to a patient’s bed and possibly cheap enough to make MRI accessible globally.
According to an article in Science, machines mark a technological triumph. Kathryn Keenan, a biomedical engineer at the National Institute of Standards and Technology who is testing a Hyperfine scanner, says, “Everyone that comes through is super impressed that it even works.” Some say the scanners could also transform medical imaging.
“We’re potentially opening up a whole new field,” says Kevin Sheth, a neurologist at the Yale School of Medicine who has worked extensively with the Swoop but has no financial interest in Hyperfine. “It’s not a question of ‘Is this going to happen?’ It’s going to be a thing.”
The development of portable MRI scanners like the Swoop could revolutionize medical imaging. MRI sets the gold standard in medical imaging and has been used to image soft tissues for decades. If doctors suspect people have had a stroke, developed a tumor, or torn cartilage in the knee, they’ll likely prescribe an MRI. However, MRI scanners employ a magnetic field to twirl atomic nuclei in living tissue, specifically the protons at the heart of hydrogen atoms, so that they emit radio waves.
To generate the field, a standard scanner employs a large, powerful superconducting electromagnet that pushes a machine’s cost to $1.5 million or more, pricing MRI out of reach for 70% of the world’s population. Even in the United States, getting an MRI may require days of waiting and a midnight drive to some distant hospital. The patient must come to the scanner, not the other way around.
The Swoop from Hyperfine is the first low-field scanner to win U.S. Food and Drug Administration (FDA) approval to image the brain, and physicians are putting it through clinical studies at Yale New Haven and elsewhere. Other devices are close behind.
However, Andrew McDowell, a physicist and founder of the consulting firm NeuvoMR, LLC, cautions that it’s not clear there’s a market for a low-field scanner with its lower resolution. “The real challenge is to convince doctors to start using it,” he says. “That’s very difficult because they’re very conservative for good reasons.”