A portable MRI diagnostic scanner that can fit in a pickup truck bed and run on a hardware store generator is nearing reality at the University of Minnesota.

Researcher Michael Garwood and colleagues have been scanning lemons and water bottles with the device they invented. The resulting images are as clear as those from fixed MRIs using magnets that weigh several tons. Human trials could start as early as this summer if the scanner passes safety testing.

"There's no reason, no physics, that I can think of that says it's unsafe, but we have to go through that process because it's such a radically different kind of scanner," said Garwood, associate director of the U's Center for Magnetic Resonance Research.

The goal is to expand access to a diagnostic technology that has become essential but remains unavailable to people in remote or rural locations worldwide, he said. "We take it to the people rather than the people coming to the large medical centers."

MRI technology has existed for nearly a half-century, using powerful magnets that stimulate molecules in the body and radio waves to generate precise images. MRIs identify tumors, injuries and abnormalities in the brain and other parts of the body that help doctors decide on surgeries or other courses of treatment.

Typical MRI machines are large because of their power needs and the size of the magnets needed to generate strong magnetic fields. When Mayo Clinic installed the nation's first 7-tesla MRI scanner in 2017, it needed multiple trucks and a crane to drop the cylindrical device through a hole in the Rochester hospital's roof. (Tesla is a measure of magnetic field strength. An even larger 14-tesla scanner is under development in Europe.)

While some researchers are making MRI technology stronger and sharper, others are making it leaner. The typical scanner is a large, thick doughnut with a hole in the middle for patients. Recent innovations include thinner doughnut-shaped scanners that aren't as claustrophobic and mobile MRIs that can be moved around on semitrailer-truck trailers.

Other solutions include scanners that can be smaller because they focus on body parts. An Australian firm, Magnetica, is developing a machine the size of a household oven with a small hole for scanning arms or legs.

Garwood at first studied a smaller MRI for breast cancer screening, but abandoned the project because it was unlikely to replace low-cost mammograms in clinical care. Funding through former President Barack Obama's $5 billion brain initiative allowed the U research team to pivot toward a scanner that focused on the head.

The traditional MRI approach involves creation of a stable magnetic field with a large magnet, allowing for radio waves on a single frequency to map out human anatomy. A smaller magnet produces an unstable magnetic field by comparison, but Garwood's innovation is to use a cascade of multiple radio frequencies to produce the same imaging results.

Collaborators include imaging experts at Harvard, Yale and Columbia, electronic component experts in Brazil, and electrical superconductor experts in New Zealand. Their prototype looks like a throne with a half-dome magnet on top. The device sits on wheels and can roll through doorways — at least when the 800-pound magnet is detached and moved separately.

The approach involves complex and costly engineering, but theoretically this form of MRI could one day be cheaper in clinical care, Garwood said. The U's MRI prototype doesn't need as much power or the use of costly and increasingly rare liquid helium to cool down larger magnets.

Once safety standards are met, U researchers plan to work with underserved populations to test the benefits of the new MRI technology for diagnosis and brain research.