Metamaterial radiofrequency lens for magnetic resonance imaging

TL;DR

This paper introduces a metamaterial-based radiofrequency lens that enhances the penetration depth and signal-to-noise ratio of MR imaging, demonstrated through successful experiments on knee imaging at 1.5T.

Contribution

It presents a novel passive metamaterial device acting as a lens to improve RF field penetration in MRI, tested across different systems and configurations.

Findings

Increased penetration depth of MR coils demonstrated

Improved SNR in MR images with the lens

Potential application for safer, higher-quality breast imaging

Abstract

The purpose of this work is to test the ability of a new class of passive electromagnetic device to increase the penetration depth of phased arrays of surface coils for magnetic resonance (MR) imaging systems. This new device is based on the emerging technology of metamaterials and behaves like a lens for the radiofrequency magnetic fields. The presented device was tested in several 1.5-T MR systems from different companies in combination with different phased arrays. One of the authors was enrolled as volunteer for the experiments. In these experiments his knees were imaged by using a dual phased array. The device was placed between the knees to check that the penetration depth of the coils was improved by this passive device. In all the experiments the presented device was successfully tested and it was checked that the knees of the volunteer can be imaged at deeper distances and that the signal-to-noise-ratio (SNR) in the obtained MR images was improved by the presence of the lens. The presented device has proven to increase the penetration depth of MR phased arrays of surface coils. The lens was tested by means of the MR imaging of the knees but it can be used to image any pair of joints simultaneously by placing it between the joints. The positive results suggest the possibility of using the lens to image the female breast. This would make it possible to increase the SNR without higher fields, thus fulfilling the safety regulations governing the standard absorption rate (SAR).