A team of researchers in the Martinos Center for Biomedical Imaging at Massachusetts General Hospital has developed a low-cost, portable MRI scanner, reporting the device in the journal Nature Biomedical Engineering on November 23. In a recent conversation, lead author Clarissa Zimmerman Cooley gave us the lowdown on the new and wildly innovative scanner. Here is what we learned.
The work addresses the need for greater accessibility with MRI
Undergoing an MRI scan in your doctor’s office or in the back of an ambulance might never have seemed possible before. The new technology opens the door to these and other scenarios by sidestepping several of the major requirements of conventional MRI, including the use of a full-body magnet with cryogenic cooling.
“We wanted this to be a truly portable, low-cost device that could be used for new applications and in locations where MRI was previously unavailable,” Cooley says. “It was never the goal to compete with the performance of conventional scanners. The device was meant to be a low-cost, point-of-care alternative for detecting brain abnormalities that are visible at a lower field strength and at lower resolution.”
Among the team’s strengths in the study: good old-fashioned ingenuity
One of the major innovations with this work was the use of a compact array of magnet “cubes” arranged around the head instead of the large superconducting magnet found in conventional MRI scanners. This design significantly reduced the scanner’s size and power and cooling needs. But because the magnetic field it generated was nonuniform, the scheme led to distortions in the resulting images. The researchers found a clever way to correct for this, devising an image reconstruction strategy incorporating magnetic field maps showing the spatial distribution of the field patterns measured in the scanner.
Cooley explains: “In traditional scanner designs, the main magnet is highly homogeneous, and a gradient coil system is used to spatially encode the image. In our close-fitting magnet design, it is difficult to create a homogenous field. Instead, we aimed to use the field variation of the inhomogeneous magnet to our advantage—essentially turning a bug into a feature.”
The new scanner is the result of reimagining how we do MRI
While much of technology development today is geared toward achieving higher, “better” resolution with MRI, the Martinos researchers set their sights on resolution that is simply “good enough” to obtain the formation you need.
“There are many cases where high-field MRI scanning is not feasible and lower-resolution images are sufficient for answering the clinical question,” Cooley says. “You don’t necessarily need a 3T scanner to see hydrocephalus, for example. These are the types of applications where our scanner could really make a difference.”
Also, because the scanner is portable and relatively inexpensive, small clinics around the world will have the option of operating their own MRI scanner onsite. Hospitals can benefit as well. For example, in cases where moving a patient presents a risk, researchers can wheel the scanner into the patient’s room for scanning.
Ultimately, the technology represents a paradigm shift in MRI, a fundamental reshuffling of how we think about imaging patients. “Portable devices such as ours will allow us, for the first time, to bring the MRI scanner to the patient,” Cooley says. “This will open up a host of new possibilities in diagnostics and monitoring.”
Work continues in readying the scanner for clinical implementation
Having described and demonstrated the technology, the researchers are now developing it further to enable real-world application. For example, electromagnetic interference (EMI) has always been one of the greatest concerns with MRI; it is why conventional scanners are permanently sited in shielded rooms. For true portable imaging, the researchers are integrating EMI detectors into their scanner to mitigate such interference. This will provide greatly improved image quality when the scanner is operated at point-of-care locations where installation of shielded rooms isn’t practical.
EMI mitigation isn’t the only advance the researchers are pursuing. Cooley says, “We are also excited to begin work on a point-of-care MRI scanner specially designed for neonatal patients in the neonatal intensive care unit (NICU). The transport and scanning of sick neonates are logistically difficult and can even be dangerous. The availability of a bedside MRI scanner in the NICU could have tremendous benefits for diagnostics and monitoring of neonatal brain injury.”
In the image above: the Center’s Clarissa Zimmerman Cooley, Jason Stockmann and Larry Wald with an earlier generation of the portable scanner in 2016.