Vanderbilt engineers have received a $1.4 million NIH grant to work toward a compact, silent, less expensive and potentially portable MRI device.
The team, led by William Grissom, associate professor of biomedical engineering, will develop new hardware, including low-field radio frequency transmission coils and amplifiers, and software that will together translate signals measured from the body into images of anatomy. And they’ll use new spatial encoding approaches that are completely different from those found on conventional clinical MRI scanners.
“The time is right to do this kind of work,” Grissom said. “Computational and electronic technologies have advanced so much over the last 40 years and become cheap enough that we can now look at whether we can get clinically useful images from less expensive and more portable magnets.”
A significant component of the cost of an MRI system has been the massive, superconducting magnet to produce a strong radiofrequency current and the bulky system required to keep it cool. The magnet for a 3-Tesla scanner, for example, weighs more than 12,000 pounds; Grissom’s team will use a 47.5 millitesla magnet.
“That is 100 times weaker than normal research magnets,” he said. “Rather than weighing tons we are looking at a few hundred pounds.”
Progress in the machining of magnets, designing the RF pulses that lead to signals coming from the body, and methods for encoding those signals across space to form an image have created the potential for new configurations. It is much like taking the advancements developed for a race car and using them to upgrade a regular car, Grissom said.
“The high-performance car is a good analogy,” he said.
The project builds on earlier work by the Grissom lab at the Vanderbilt University Institute for Imaging Science in coil design, spatial encoding using radiofrequency field gradients, and radiofrequency pulses. A key advancement in this project is to replace the type of gradient fields used by the scanner by taking advantage of the Bloch-Siegert shift, a phenomenon that has historically been viewed as a nuisance in magnetic resonance. In this project, it will be used to match up signals received from the body to their location of origin, and form images.
The gradient fields used now are problematic in many ways: they are loud and induce peripheral nerve stimulation, compromising patient comfort; and they require bulky cooling systems and customized amplifiers. All of that represents up to 30 percent of the cost of a clinical scanner.
A very low-field human 47.5 millitesla scanner the team built is already installed and working at VUIIS. In this project, it will be used as a testbed for the new hardware and software for silent and lower cost imaging methods. Although the NIH grant targets brain imaging, such a scanner can be used for any part of the human body, Grissom said.
The successful completion of this project, he said, “will enable silent, low-cost and more portable MRI systems, leading to a substantial reduction in the cost of imaging and improved patient compliance and comfort.”
