Illustration of a biological object placed on the metasurface resonator. Credit: Advanced Materials
A new wire-array metasurface placed between the biological object and scanning bed of a standard magnetic resonance imaging (MRI) machine could eventually increase scan resolution or scan speed and protect patients from potentially dangerous tissue heating caused by the MRI’s electrical field (Adv. Mater., doi: 10.1002/adma.201504270). The metasurface resonator—an artificial periodic structure—was designed and experimentally tested by an international team of researchers from Russia, Australia and the Netherlands. Their demonstrations show enhancement of the radio frequency magnetic field by subwavelength near-field manipulation with the metasurface resonances, with improvements to scanner sensitivity, signal-to-noise ratio (SNR) and image resolution.
MRI scans are a valuable diagnostic for health care providers, but their usefulness depends on the image quality. An MRI scan can also be uncomfortable for patients, lasting anywhere from 15 to 60 minutes. Faster scans with the same image quality as a standard MRI procedure, or higher-resolution images from a normal-length scan, would not only improve the patient’s experience, but also reduce hospital wait times for the scanner.
The metasurface resonator consists of an array of metallic wires, with the length of each wire tuned to match half a wavelength at the MRI’s operating frequency. To test the metasurface, the researchers placed the array in the scanning bed’s water chamber and placed an ex vivo fish—the biological test subject—on top. MRI scans with the metasurface add-on produced either higher-resolution images of the fish over the standard scanning time, or a 50 percent faster scan with standard MRI resolution, all while maintaining a “safe” temperature for the fish.
Coauthor Yuri Kivshar said in a press release: “This is the first real demonstration of the practical potential of metamaterials for MRI imaging enhancement and scanning time reduction.” The technology is patent-pending and is being co-developed by MediWise Ltd., U.K.