MRI Engineering Team

National Institute Of Neurological Disorders And Stroke

Investigators

Linked publications, trials & patents

Abstract

For the 11.7T system, major technical developments are needed to allow transmission and detection of the required RF fields. For the initial human studies at 11.7T, we planned to use a general-purpose whole head coil for both transmission and reception. This single channel coil is the first setup for the initial safety testing required by the FDA. We concluded the optimization of the hardware model and its validation (Murphy-Boesch et al, 2025). EM field simulations were performed using commercial software (XFdtd, Remcom) and used to compare measured and simulated frequency response (s-parameters). In parallel to the implementation of the Tx/Rx head resonator to image human subjects, the MRIEngT is developing a 32 channel Rx array that fits inside a detunable version of the 500 MHz head resonator (now set as Tx only coil). The 24 coils on the posterior side of the array are matched and tuned. We optimized further the low noise amplifier (LNA) to fit a 4-channel board that host electronics for detuning and decoupling (Dodd and Gudino). These boards were also optimized and fully assembled. All coaxial connections are built with cable traps for connecting each coil to the receive electronics. The connection of the array to the electronics is in progress with careful optimization of element decoupling by the low input impedance amplifier. The coils were successfully detuned (=< -30 dB) by a novel circuit on the LNA board without DC connection to each coil. This hardware will allow imaging the human brain with higher sensitivity. Following the safety assessment of the the Tx/Rx head resonator, we expect a straightforward analysis of the safety of the 1Tx/32Rx RF setup. The MRIEngT has been developing on-coil RF amplification technology for multi-channel transmission (also called pTx). The MRIEngT is currently working on moving this technology to higher fields. The key component to achieve this, is the power field effect transistor (FET). The performance of this device is challenged by the stronger MRI field and frequency. The MRIEngT started investigating the possibility to improve transistor design beyond capabilities currently available with commercial devices. In parallel to the development of a new device, we continue testing the operation of commercial field effect transistors (FETs) in MRI fields up to 14 T (Setera and Gudino). We designed a chip and the PCB that will host it, to assess bench performance of different devices (all in same chip) as well as to analyze performance in the strong MRI magnetic field (Setera and Gudino). This is work in progress at NIST nano fabrication lab (project initiated and led by Gudino). Recently a tunable Tx chain based on on-coil amplification was presented to replace the conventional multinuclear MRI chain built with remote broadband amplification (Gudino, 2025). The new technology can reduce the layers of hardware required to image multiple X-nuclei and 1H in a single experiment by the implementation of a novel hardware control. Multinuclear imaging was successfully demonstrated at 7T MRI for 1H, 13C and 23Na with a single Tx tuned from optical control and Rx electronics tuned at each nucleus. Multinuclear coils were also tuned remotely. This technology is particularly interesting for the implementation of X-nuclei imaging in our 11.7 T head only MRI system where coil outer diameter is restricted by the limited bore space (Gudino, 2025). In parallel to the development of a pTx system with on-coil amplification, the team is developing a Tx coil for direct integration with the commercial pTx interface (Siemens 8-channel). We are currently analyzing different element decoupling strategies at 500 MHz to achieve high pTx performance while minimizing the complexity of the Tx array layout (Dodd and Gudino). Besides the development of RF hardware, the team has supported other non-RF projects. Recently, we have successfully developed the control and monitoring of a B0 insert coil (built by Resonance Research Inc, Boston, MA) to shift the static magnetic field up to 0.77 T inside a 4.7 T animal scanner to switch Iron-Rhodium microparticles (Dodd and Gudino). The switching of the particles from OFF to ON to OFF was visible in the MRI image through the change in T2* contrast. The result of this work is important toward the development of new contrast methods for in-vivo cell tracking (Dodd et al, 2025). For the 7T in the NMR Center, arterial spin labeling coils and setup were reengineered to accommodate the new Siemens TERRA system Two version of the labeling coil, Helmholtz and Maxwell configurations, were fully integrated with the MRI system as standard Tx coils in order to characterize transmit performance through B1 mapping. We continue the implementation of on coil-amplification to improve performance and safety. Lastly, a dual-tuned, 13C 1H head coil for 3T has been completed and integrated into a mechanical assembly for imaging of the human head on a Philips 3T MRI (Murphy-Boesch). The coil obtained IRB approval and has begun to be used for imaging patients. The MRIEngT also continued its support of the various groups the use MRI at NIH. It developed a variety of coils and RF interfaces for animal imaging and postmortem studies.