Reducing RF-Induced Heating of DBS in 3 T MRI Using Dual-Role Receive Arrays as Wireless Resonators: A Simulation Study

A Novel Lead Construct to Reduce MRI-Induced RF Heating: Construction, In Vitro Validation, and In Vivo Predictions.

OBJECTIVE Magnetic resonance imaging (MRI) of patients with active implantable medical devices is restricted by radiofrequency (RF) heating of conductive leads. Our goal was to develop and validate resistively tapered cylindrical (RTC) leads that intrinsically suppress RF heating. METHODS Two-segment RTC wire prototypes (RTC1, RTC2) were fabricated by thin-film physical vapor deposition to create axial conductivity discontinuities. The transfer functions for both were measured and validated with in vitro heating experiments at 1.5 T along 12 trajectories and benchmarked against a uniform conductivity control wire. Calibrated transfer functions were combined with electromagnetic simulations of 210 clinically realistic deep brain stimulation (DBS) trajectories in an anatomically detailed full-body model to predict in vivo heating, with a commercial DBS lead included for comparison. RESULTS Gel phantom experiments showed the RTC wires cut peak RF-induced temperature rise at the tip by $>$60% versus the control wire in vitro, lowering the mean heating from 3.67 to 1.43. The in vivo predictions using the transfer function methodology showed a $>$20% reduction in the mean tip heating vs. the uniform conductivity wire ($p< 0.001$) and a 20-fold lower peak heating compared to a commercial DBS lead under identical exposure conditions. CONCLUSION Axial conductivity tapering markedly attenuates MRI-induced RF heating without requiring significant changes to lead geometry. SIGNIFICANCE Conductivity-tailored leads provide a practical path toward inherently MRI-compatible AIMDs, potentially expanding diagnostic imaging access for millions of patients.

Birth of the Coil: another Milestone towards a fully reproducible low-field MRI scanner for head-imaging

This work presents an open-source, optimized solenoid head coil tailored for the 50 mT open-source scanner (OSII ONE v2.1), set the basis for a fully reliable and reproducible component for the open-source OSII ONE MRI scanner.

Inductively Coupled Wireless Coils for Magnetic Resonance Imaging: A Review.

This review elaborates on the inductive coupling mechanism of ICWCs, the derivation of the SNR formula, potential causes of g-factor reduction, and recommendations for fabrication methods, providing a reference for the innovation of MRI RF coil technology and the clinical translation of ICWCs.

A Wireless Volumetric Metamaterial Resonator for Breast MRI

High-performance breast magnetic resonance imaging (MRI) remains limited by the availability, geometry, and cost of dedicated receive coils. In contrast, spine coils are widely installed in MR scanners globally but provide insufficient sensitivity for anterior breast tissue. Here, we report a wireless volumetric metamaterial resonator (VMR) that converts a standard built-in spine coil into a scalable breast MRI receiver platform without modifying the scanner hardware. The VMR consists of axially stacked coaxial resonant rings that support a co-rotating collective mode, producing a centrally concentrated RF magnetic field within the enclosed imaging volume. Leveraging distributed capacitance in the coaxial cable, gap-engineered geometric tuning, and PIN-diode-based self-detuning, the VMR enables size scalability, electric-field confinement, and transmit-receive compatibility, as validated through bench measurements and 3.0 T MRI experiments. Three VMR prototypes spanning small, medium, and large breast-equivalent volumes were designed and evaluated using electromagnetic simulations, bench measurements, and phantom MRI experiments. Compared with a commercial 16-channel breast coil, the VMR-augmented spine coil achieved more than 4-fold higher central SNR and reduced spatial non-uniformity from approximately 70% to 20% within the target imaging region. Under SENSE parallel imaging at acceleration factors of 2-4, the VMR-augmented spine coil maintained an average 4-fold higher central SNR than the commercial coil for three sizes. These results establish the VMR as a passive, scalable hardware strategy for improving breast MRI performance using existing clinical scanner infrastructure.

A Method for Optimization of a Cylindrical Metasurface for Traveling-wave MRI Applications

SAR validation of RF coils and implants in a B0‐free RF safety laboratory

Abstract Background As MRI continues to advance toward higher field strengths, RF safety assessment has become more complex. Accurate estimation of specific absorption rate (SAR) is essential for evaluating both hardware and implant safety, yet thermometry and simulation‐only approaches face limitations. In addition, these evaluations are typically performed within the MR scanner, where failures or excessive loading can damage the transmit chain and result in costly repairs and scanner downtime. To overcome these challenges, alternative experimental approaches that enable direct and controlled SAR validation outside the MR environment are needed. Purpose This study demonstrates direct SAR validation of RF hardware and implants in a dedicated B0‐free RF safety laboratory. The work aims to establish direct SAR measurement as a practical and accurate alternative for quantitative safety verification while expanding the range of tools available for MR hardware evaluation beyond the constraints of the scanner environment. Methods Hardware assessments were conducted in the safety lab equipped with a 16‐channel broadband RF amplifier system (45–450 MHz), a 100 dB shielded Faraday cage, automated 3D and 1D motion systems, and a high‐precision SAR probe. For coil validation, direct SAR mapping was performed on a custom‐built parallel transmit (pTx) coil and a commercial single‐channel RF coil at 447 and 297 MHz, respectively, and results were compared with electromagnetic simulations. Transfer function (TF) validation for a directional DBS electrode at 128 MHz was performed in a rectangular electric‐field generator, whose field distribution was first validated using the SAR probe. The same probe was then used to compare measured SAR with TF‐based SAR predictions, providing a direct quantitative validation of the TF method. Results Measured SAR distributions showed strong quantitative agreement with simulations across all experiments. For the 8‐channel pTx head coil at 447 MHz, the normalized root‐mean‐square error (NRMSE) across four excitation patterns was below 13%. For the commercial single‐channel head coil at 297 MHz, plane‐wise comparisons across axial, coronal, and sagittal slices yielded an average NRMSE value of 7.18%, demonstrating spatial consistency between measured and simulated fields. The electric‐field generator used for DBS transfer function (TF) validation exhibited 3.68% NRMSE relative to simulation, confirming accurate field reproduction. SAR measurements using the same probe further showed close agreement with TF‐based SAR predictions across all seven lead trajectories, confirming both the accuracy and broadband applicability of the direct SAR method. Conclusion Direct SAR measurement provides a reliable and quantitative approach for validating RF coil and implant safety, matching the accuracy of conventional scanner‐based thermometry and simulation methods. Conducting these measurements in a B0‐free RF safety laboratory further simplifies and accelerates the process by eliminating magnetic field constraints and the waiting periods required for the setup to return to thermal equilibrium in thermometric techniques. This configuration provides an efficient and controlled platform for systematic SAR validation across a wide range of MR frequencies.