SMuK 2023 – scientific programme

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ST: Fachverband Strahlen- und Medizinphysik

ST 2: Medical Imaging Concepts

ST 2.1: Talk

Tuesday, March 21, 2023, 17:00–17:15, ZEU/0146

Metamaterials for Magnetic Resonance Imaging — •Dennis Philipp — Fraunhofer Institute for Digital Medicine MEVIS, 28359 Bremen, Germany

Electromagnetic metamaterials (MTMs) offer manifold degrees of freedom in MRI applications. Most prominently, field homogeneity improvement and signal-to-noise ratio (SNR) enhancement are typical use cases. However, passive MTMs also have some drawbacks such as transmit field (Tx) deformations. Here, we pave the way towards dynamic and active MTMs, which overcome some of the open problems. Bluetooth-controlled, reconfigurable MTMs for signal-to-noise ratio (SNR) enhancement in MRI are presented. These metasurfaces allow to be wirelessly interfaced and tuned during an MRI scan by means of a digital capacitor (DCAP), which is connected to a low-power microcontroller with BLE capabilities. Two prototypes are manufactured, one of which is a metasurface with adjustable resonance frequency, and the second one is dynamically tunable at the meta-atom (unit cell) scale. It includes multiple DCAPS and, thus, is the first wirelessly reconfigurable MTM for MRI that offers field shaping capabilities, adjustable FoV, focal regions, sequence sync., and active Tx detuning. A MTM arrangement that encloses a volume "metaBox" is shown to yield a significant and volume-homogeneous SNR enhancement in 3T MRI. Due to the integration of non-linear components, the structure self-detunes in Tx whilst being resonant in Rx. Fine-tuning capabilities are included in two different prototypes via (i) a manually trimmable capacitor and (ii) a BLE controlled DCAP.