A life lesson many have learned: bigger is not always better. As technology began taking drastic leaps forward 20 years ago, manufacturers of all kinds were looking to “go bigger.” Luckily for physicist Matthew Rosen, that trend has ran out of steam for the most part.
Rosen is the director of the Low-field MRI and Hyperpolarized Media Laboratory at Massachusetts General Hospital.
“The focus of my lab is to deconstruct the MRI scanner,” said Rosen.
Typical MRI scanners are powered by a superconducting magnet that generates a magnetic field of 1.5 or 3 T. These instruments often must be housed in specially designed rooms, as they are incredibly sensitive to external vibration, including nearby motors, pumps, elevators, and even vehicles passing near a building. Given their attributes, typical MRI scanners are pricey—usually $3 million and up, which is why they are primarily found in imaging clinics, not smaller hospitals or doctor’s offices.
However, low-field MRI scanners that operate at 0.064 T are gaining popularity. These less powerful portable options come with a much less hefty price tag—between $50,000 and $100,000. As radiologists discover the new technology and the benefits of a smaller instrument, the conversation inevitably turns to contrast agents. With conventional MRIs, doctors commonly inject patients with a contrast agent based on the heavy metal gadolinium to enhance image quality. For gadolinium to be effective with low-field MRI, Rosen said a doctor would have to administer 1,000 times more than the amount approved by the FDA.
Needing an alternative, Rosen and his collaborators turned to superparamagnetic iron oxide nanoparticles (SPIONs) as a possible contrast agent for low-field MRI. In a study, recently published in Science Advances, healthy lab rats were scanned with Rosen's homemade ultralow field (ULF) MRI (0.0065 T), then injected with SPIONs and rescanned. A comparison of pre- and post-injection images shows a striking difference, with kidneys, livers, and other organs glowing brightly following administration of SPIONs.
SPIONs are already approved by the FDA for treating some people who suffer from anemia. In this case, though, the team was attracted to them for a different reason.
“SPIONs essentially amplify low magnetic fields," said University of Sydney physicist David Waddington, who is the lead author of the study. “SPIONs are 3,000 times more magnetic than conventional MRI contrast agents.”
And while SPIONS will still need to be approved by the FDA for use as contrast agents, Rosen says doctors can use them now "off label" with low-field MRI since they have been deemed safe for other treatments.
Waddington and colleague/co-author Zdenka Kuncic are also investigating the use of specially coated SPIONs that could allow MRI to be used for detecting malignant tumors.