由 John R. Fischer
, Staff Reporter | November 11, 2019
A new and "intelligent" metamaterial used in MR scans may save on cost and time for scans, while expanding safety and accessibility to them.
For less than $10, researchers at Boston University have developed a magnetic metamaterial designed to raise the signal-to-noise ratio of scanners tenfold, to produce images with greater quality in shorter amounts of time.
"We discovered that this special type of metamaterial can interact with radio waves or more generally speaking, electromagnetic waves, in a self-adaptive way," Dr. Xin Zhang, a professor in the College of Engineering at Boston University, told HCB News. "The 'intelligent' metamaterial serves to enhance the magnetic component of the electromagnetic wave in a designated fashion. Importantly, MR employs magnetic fields and radio waves to obtain images for disease diagnosis and characterization. Therefore, we sought to develop and validate the idea to harness nonlinear metamaterial to improve the performance of MR."
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Raising the SNR enhances the quality of an MR image. The most direct way of doing this is to increase the magnetic field of the machine. But increasing the magnetic field raises the complexity and costs of a scan, as well as potential risks to the patient due to the higher radiation emitted heating up the tissue and implanted devices.
Composed of an array of helical resonators closely packed with a passive sensor, the "intelligent" metamaterial is placed beside the body part that the scan is targeting. It selectively raises low-energy emissions from the body and turns itself off during millisecond bursts of high-energy transmission. The tenfold amplification improves the quality of the image and reduces scan time, saving the patient money. Its ability to turn itself off when energy is high enables it to spare patients from overexposure to radiation and allows clinicians to increase the energy returned to the MR system.
The technology is based on previous metamaterial composed by its developers that consisted of simple copper wiring and plastic. It is the simplicity of these materials that makes the metamaterial low cost.
The current prototype is a flat, thick layer that the researchers plan to adapt into a flexible, ultra-thin MR enhancement sheet. In addition to shortening scanning time, the hope is that the product will decrease waiting periods in the U.S. and other countries such as India, where waiting times are as long as a year and can put patient survival at risk.
"Currently, MR achieves high-quality images using contrast agents, advanced radiofrequency RF+ surface coils, and hardware design. In addition, the development of advanced pulse sequences and, more recently, artificial intelligence (AI) enables increasingly rapid image acquisition. Our technique using intelligent metamaterials is synergistic with all of these approaches to further improve the performance of MRI and decrease the scanning time," said Zhang. "Intelligent metamaterials can seamlessly be employed in conventional clinical MR systems without modifying the current configurations of the clinical systems to any significant degree."
The "intelligent" metamaterial was developed with the support of the National Institute of Biomedical Imaging and Bioengineering.
The findings from the project were published in the journal, Advanced Materials