Described in the journal NMR Biomedicine, the coil was specifically designed to image the entire body of a mouse. The animals are often subjected to MRI scans during preclinical studies, usually achieved by combining regions scanned with small coils with high sensitivity or long scans using large coils with low sensitivity. Both of these approaches can be problematic, however, with the small coils adding complexity and the large coils producing low-quality images. This prompted the researchers to search for an alternative solution.
The team, from St Petersburg’s ITMO University, was able to create a small MRI coil using a metastructure of brass telescopic tubes with copper plates as distributed capacitance. Its field distribution was measured experimentally and was found to be in close correlation with previously simulated results, producing image quality three times better than standard coils.
"We measured the signal-to-noise ratio in different parts of the image at different distances between the object and the coil,” said Mikhail Zubkov, a researcher at ITMO’s Laboratory of Nanophotonics and Metamaterials. “The obtained results were compared with mathematical simulation and experimental parameters of standard volume coils. It turned out that there is an optimal distance between the image and the coil, at which our coil provides the image quality three times higher than the standard one.”
Anna Khurshkainen, a graduate student at ITMO’s Laboratory of Nanophotonics and Metamaterials, added: "Standard coils are tuned to a particular frequency using non-magnetic capacitors. They introduce internal losses, reducing the signal-to-noise ratio. This is one of the main parameters used to determine the image quality in MRI.
“Since our coil is self-resonant, we do not need any capacitors. We can tune the coil by changing the geometric parameters. Also, new design allows us to optimise how the coil works, increase its sensitivity and image quality. Besides, the cost of raw materials is low, and the manufacturing technology allows us to adapt the method for various projects."
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