Sebastian A. Aussenhofer¹ and Andrew G. Webb^1
1C.J. Gorter Center for High Field MRI, Leiden University Medical Center, Leiden, South-Holland, Netherlands

Here, we present a totally new concept for an MRI coil, which uses reconfigurable conducting plasma rather than a fixed-geometry conductor. A plasma has many advantageous properties in terms of forming an MRI coil, including that the plasma can be turned on-and-off whenever needed (unlike a metal conductor which is always physically present), the resistance of the plasma decreases with increased current passing through the plasma, and the interactions between the precessing magnetization and the plasma can be manipulated by varying the relationship between the plasma frequency (_p) and the Larmor frequency (₀).

Mathieu Sarracanie^1,2, Cristen LaPierre^1,2, Najat Salameh^1,2, David E J Waddington^1,3, Thomas Witzel¹, and Matthew S Rosen^1,2
1MGH/A.A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States, ²Department of Physics, Harvard University, Cambridge, MA, United States, ³ARC Centre of Excellence for Engineered Quantum Systems, School of Physics, University of Sydney, Sydney, NSW, Australia

MRI is unparalleled in its ability to non-invasively visualize anatomical structure and function with high spatial and temporal resolution and a broad range of clinical contrasts. The vast majority of clinical scanners incorporate superconducting magnets operating at 1.5, 3 and more exceptionally at 7T. At 6.5mT, more than 450 times lower than clinical MRI scanners, we demonstrate 2.5×3.5×8.5mm3 resolution in the living human brain in 6 minutes. We contend that robust non-field-cycled low-field implementations of MRI (< 10mT) have the potential to make clinically relevant images and set new standards for a completely new category of affordable robust portable devices.

Clarissa Zimmerman Cooley^1,2, Jason P Stockmann^1,3, Mathieu Sarracanie^1,3, Matthew S Rosen^1,3, and Lawrence L Wald^1,2
1A. A. Martinos Center for Biomedical Imaging, Dept. of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, ²Harvard Medical School, Boston, MA, United States, ³Dept. of Physics, Harvard University, Cambridge, MA, United States

The development of a low-cost portable MRI scanner could facilitate imaging in sites with insufficient space, power, or funding for traditional scanners. To address this need, we previously demonstrated 2D encoding using a rotating, lightweight, inhomogeneous magnet. We now demonstrate the ability to add the missing 3rd direction of encoding using transmit array spatial encoding (TRASE). A TRASE coil consisting of a multi-birdcage coil and a Maxwell coil was designed to fit the geometrical constraints and rotate with the existing magnet to produce proof-of-concepts 3D images. The low-cost, portable scanner architecture is achieved by designing the magnet to only fit around the head, allowing the magnet to be low-field and inhomogeneous, and eliminating the need for gradient coils and gradient power amplifiers through the rotating SEM and TRASE methods.

Dan Spence¹ and Marco Aimi^2
1GE Healthcare, Waukesha, Wisconsin, United States, ²GE Global Research, Niskayuna, New York, United States

A custom MEMS (Micro Electro Mechanical System) switch has been developed to operate in an MR environment. This new switch greatly reduces the power dissipation and simplifies the decoupling design for RF coils. With a standoff voltage greater than 500V, a high isolation impedance, and small resistance, the new switch can directly replace the pin diode tank circuits used in MR coils. The unique features of this switch will enable the simplification of coils as they move to higher densities. Apart from decoupling, other uses of the switch include channel routing, dynamic tuning, T/R switch, and transmit coil applications.

Guido P. Kudielka^1,2, Christopher J. Hardy³, Pierre-André Vuissoz^1,4, Jacques Felblinger^5,6, and Anja C.S. Brau^7
1Imagerie Adaptative Diagnostique et Interventionnelle, Université de Lorraine, Nancy, Lorraine, France, ²GE Global Research, Munich, BY, Germany, ³GE Global Research, Niskayuna, NY, United States, ⁴U947, INSERM, Nancy, Lorraine, France, ⁵CIC-IT 1433, INSERM, Nancy, Lorraine, France, ⁶University Hospital Nancy, Nancy, Lorraine, France, ⁷GE Healthcare, Munich, BY, Germany

Impedance and Q-value of a MRI coil is dependent on its loading. Load changes due to motion can be measured by recording of the impedance change. In this work, we show, that on different positions of the body, respiratory and myocardial motion signals as well as flow profiles can be acquired by impedance change measurement and pulse wave velocity can be calculated. This additional physiological information could be acquired during the MRI examination. This technique has potential for sensor-less measurement of physiological data and motion for gating or triggering purposes, especially in environments where classical sensors do not perform well.

Kamal Aggarwal¹, Mazhareddin Taghivand¹, Yashar Rajavi¹, John Pauly¹, Ada Poon¹, and Greig Scott^1
1Electrical Engineering, Stanford University, Stanford, California, United States

High path loss and availability of wide bandwidth make mm-waves an ideal candidate for short range, high data rata communication. We propose a novel integrated chip solution for wireless MRI where-in the transceiver uses mm-wave (60GHz) as radio frequency carrier. ON-OFF keying (OOK) modulation for data transmission enables the transmitter to support data rates from 38Mbps to 2.45Gbps at a distance of 10cm while consuming 260µW to 11.9mW of DC power. Highly directional, linearly polarized, on-chip dipole antennas, placed orthogonally results in a significant reduction in cross-talk between multiple transceivers thus leading to a highly scalable solution for wireless MRI.

Kelly Byron¹, Pascal Stang², Shreyas Vasanawala³, John Pauly¹, and Greig Scott^1
1Electrical Engineering, Stanford University, Stanford, CA, United States, ²Procyon Engineering, CA, United States, ³Radiology, Stanford University, Stanford, California, United States

Wireless power transfer is a method that could be used to power wireless MRI coils, as well as send a synchronization signal for wireless coils. Our proposed system is capable of delivering power inside an MRI bore without degrading the image quality, due to our use of RF gating to stop power transmission during the MRI receive time, while continuing to power the load with a storage capacitor. We are also able to continuously send a synchronization tone with minimal impact on the image quality up to a 5-7W transmission threshold.

Daiki Tamada^1,2, Yosuke Yanagi³, Yoshitaka Itoh³, Takashi Nakamura^1,2, and Katsumi Kose^1
1Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki, Japan, ²RIKEN, Wako, Saitama, Japan, ³IMRA Material R&D., Ltd., Aichi, Japan

A magnet using a high critical temperature bulk superconductor is the new magnet for NMR/MRI. The bulk magnet gives a strong magnetic field without a liquid cryogen such as helium. However, there is a critical problem, which is the inhomogeneous magnetic field of the bulk magnet. To overcome this problem, the magnet structure was optimized using a finite element method. In addition to this, a single-layer shim coil was developed to compensate the residual inhomogeneity of the magnet. As the result, the 6.9 ppm (peak-to-peak) in  6.2  9.2 mm was achieved.

Jorge Fernandez Villena¹, Athanasios G. Polimeridis¹, Lawrence L. Wald^2,3, Elfar Adalsteinsson^1,3, Jacob K. White¹, and Luca Daniel^1
1Research Laboratory of Electronics, EECS, Massachusetts Institute of Technology, Cambridge, MA, United States, ²A.A. Martinos Center for Biomedical Imaging, Dept. of Radiology, Massachusetts General Hospital, MA, United States, ³Harvard-MIT Division of Health Sciences Technology, Cambridge, MA, United States

MARIE (MAgnetic Resonance Integral Equation suite) is an open-source software for fast EM analysis of MRI systems. It combines surface and volume integral equation formulations to exploit the characteristics of the different parts (coil array and body model), and applies sophisticated numerical methods to rapidly perform EM simulations to characterize the MRI design. Running on a GPU-accelerated windows desktop, MARIE solves complex scattering problems in ~2-3 min., port-parameter analysis of complex coils in ~3-5 min. per frequency, and a complete inhomogeneous body and coil system in ~5-10 min. per port. It includes a GUI for standard simulations, and scripts to develop more advanced analyses, such as ultimate intrinsic SNR/SAR on body models, fast coil design and optimization, or generation of patient specific protocols.

Christopher J Hasselwander^1,2, William A Grissom^1,2, and Zhipeng Cao^1,2
1Vanderbilt University Institute of Imaging Science, Nashville, TN, United States, ²Biomedical Engineering, Vanderbilt University, Nashville, TN, United States

Conventional commercial MR spectrometers are often limited in configurability, portability, scalability and cost. Software-defined radios (SDR’s) offer a low-cost and highly-flexible alternative, offering high-bandwidth direct RF signal synthesis and digitization with high bit depth. In this work we describe the use of a commercially-available SDR in educational NMR experiments, and in the generation of frequency-swept RF pulses for RF spatial encoding using the Bloch-Siegert shift. The SDR was shown to enable rapid development of simple NMR experiments, and to produce higher-quality frequency-swept pulses than a conventional spectrometer.