Anders Simonsen¹, Juan D. Sánchez-Heredia², Sampo Saarinen¹, Jan H. Ardenkjær-Larsen², Albert Schliesser¹, and Eugene S. Polzik^1
1Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark, ²Department of Health Technology, Technical University of Denmark, Kgs. Lyngby, Denmark

A new approach to MRI detection is reported, where an optomechanical transducer directly converts and amplifies the MR signal to amplitude modulation of laser light. The transducer, which is simultaneously a capacitor and an optical cavity, is connected directly in parallel to the receive coil. The mechanical Q-factor of the transducer is 1500, providing a 3 dB bandwidth of 1 kHz. We show here for the first time that this technology can be used to directly acquire a ¹³C MRI at 3T (32.13 MHz), and reconstruct it using the standard pipeline of a commercial MR scanner.

 

Hazal Yuksel¹, Lance DelaBarre², Djaudat Idiyatullin³, Julie Kabil⁴, Gregor Adriany³, Sung-Min Sohn⁵, Harish Krishnaswamy ¹, John Thomas Vaughan ⁴, and Michael Garwood^3
1Electrical Engineering, Columbia University, New York, NY, United States, ²Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, ³University of Minnesota, Minneapolis, MN, United States, ⁴Columbia University, New York, NY, United States, ⁵Arizona State University, Tempe, AZ, United States

Traditional MRI relies on the temporal separation of the receiver (RX) and transmitter (TX) to solve the problem of self-interference. Often, the TX signal is billions of times larger than the RX signal, and T/R switches are used so the TX does not saturate or destroy the RX. This leads to an inefficient method of acquiring imaging data for especially fast decaying signals. We propose a magnetic-free, PCB based circulator to remove the T/R switch and achieve simultaneous transmit and receive MRI. We present images of a phantom acquired with a continuous SWIFT sequence to validate the concept.

Ehsan Kazemivalipour^1,2, Alireza Sadeghi-Tarakameh^1,2, and Ergin Atalar^1,2
1Electrical and Electronics Engineering Department, Bilkent University, Ankara, Turkey, ²National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey

We propose a general analysis based on minimization of modal reflection coefficients, providing a simple tool for quantifying the performance of transmit array (TxArray) coils in terms of power efficiency. We investigate the performance of various dual-row birdcage TxArrays, with an additional degree of freedom to correct B1+-field inhomogeneities by adding RF shimming ability in the longitudinal-direction, together with simulations and experiments. The chosen structure of the TxArray allows the coil to act like degenerate birdcage coils. We demonstrate when TxArrays are properly designed, in some critical excitation modes such as circularly-polarized (CP) mode, the total reflection becomes negligibly small.

Lucia Navarro de Lara^1,2, Mohammad Daneshzand^1,2, Anthony Mascarenas³, Douglas Paulson³, Sergey Makarov^1,4, Jason Stockmann^1,2, Larry Wald^1,2,5, and Aapo Nummenmaa^1,2
1Radiology, A.A Martinos Center for Biomedical Imaging/MGH, Charlestown, MA, United States, ²Harvard Medical School, Boston, MA, United States, ³Tristan Technologies, San Diego, CA, United States, ⁴Department of Electrical and Computer Engineering, A.A Martinos Center for Biomedical Imaging/MGH, Worcester, MA, United States, ⁵HST/MIT, Cambridge, MA, United States

We investigate the feasibility of using small-diameter three-axis TMS coil as a basis for constructing a simultaneous stimulation and imaging array. We present an MR-compatible 3-axis TMS coil prototype comprising of three orthogonal coil X/Y/Z units. We assess the influence of the TMS coil element on the MRI images and measure the sound pressure levels with systematically varying the current amplitudes and coil orientation with respect to the magnetic field. Supported by simulations, we conclude that construction of a large-scale multichannel; system using such a 3-axis TMS elements as a basis appears feasible but the acoustic properties should be improved

Azma Mareyam¹, John E. Kirsch^1,2, Yulin Chang³, Gunjan Madan³, and Lawrence L. Wald^1,2
1Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, ²Harvard Medical School, Boston, MA, United States, ³Siemens Medical Solutions USA, Boston, MA, United States

We construct and test a prototype 64-channel brain array coil for 7T and compare it to a 32-channel coil of similar design.  Coil characteristics like signal to noise ratio, noise correlation matrix, and noise amplification (G-factor) for parallel imaging are described as well as and a comparison of the B1+ maps to assess birdcage coil efficiency and homogeneity. The coil was designed on a split-half former with a sliding top half to facilitate patient entry and utilizes a sliding birdcage coil for transmit

Natalia Gudino¹, Stephen J Dodd¹, Steve Li², and Jeff H Duyn^1
1LFMI, NINDS, National Institutes of Health, Bethesda, MD, United States, ²MIB, NIMH, National Institutes of Health, Bethesda, MD, United States

Optically controlled on-coil amplifiers have been presented for the practical implementation of pTx system at ultra-high field MRI. We present a new prototype that can transmit power to excite ¹H and X-nuclei. We show bench and MRI data with a dual-tuned on-coil amplifier implementation for ¹H and ³¹P excitation at 7T. We expect this technology can allow a simpler and more versatile implementation of a multinuclear multichannel hardware compared to the traditional multinuclear setup based on 50 Ω broadband voltage mode amplification.

Bruno Pinho Meneses^1,2, Jason Stockmann^3,4, and Alexis Amadon^1
1Neurospin/CEA-Saclay, Gif-sur-Yvette, France, ²Université Paris-Saclay, Saclay, France, ³Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States, ⁴Harvard Medical School, Boston, MA, United States

Using Singular Value Decomposition of optimal Stream Functions computed from a database of 100 B₀ fieldmaps, a 13-channel cylindrical optimized Multi-Coil Array for shimming of the human brain is built and tested in an experimental setup for field measurement at 7T. Such measurements are compared to expected performances, serving as proof of concept for this novel design methodology. Performance is compared to what would be achieved by matrix multi-coil array designs patterned on a cylinder.

Byeong-Yeul Lee¹, Xiao-Hong Zhu¹, Hannes M. Wiesner¹, Maryam Sarkarat², Sebastian Rupprecht³, Michael T Lanagan², Qing X Yang³, and Wei Chen^1
1CMRR, Radiology, University of Minnesota, Minneapolis, MN, United States, ²Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA, United States, ³Center for NMR Research, Neurosurgery, Pennsylvania State College of Medicine, Hershey, PA, United States

We present an innovative technique of tunable ultrahigh dielectric constant (tuHDC) ceramics incorporating RF coil(s) for MR imaging applications. The ceramic has a very high permittivity tunability of 2000-15000 by varying the ceramic temperature between few to 40 °C to achieve optimal performance at the nuclide Larmor frequency of interest, resulting in larger B₁ field and SNR improvements for ¹H MRI at 1.5T clinic scanner and  ¹⁷O MRSI at 10.5T human scanner. We found a large denoising effect in ¹⁷O MRSI, which further boosts the SNR gain. The technology should benefit for biomedical research and clinical diagnosis.

Vsevolod Vorobyev¹, Alena Shchelokova¹, Irena Zivkovic², Alexey Slobozhanyuk¹, Juan Domingo Baena³, Juan Pablo del Risco⁴, Redha Abdeddaim⁵, Andrew Webb^2,6, and Stanislav Glybovski^1
1Department of Nanophotonics and Metamaterials, ITMO University, Saint Petersburg, Russian Federation, ²Department of Radiology, C.J.Gorter Center for High Field MRI, Leiden University Medical Center, Leiden, Netherlands, ³Department of Physics, Universidad Nacional de Colombia, Bogota, Colombia, ⁴School of Exact Sciences and Engineering, Universidad Sergio Arboleda, Bogota, Colombia, ⁵Aix Marseille University, CNRS, Centrale Marseille, Institut Fresnel, Marseille, France, ⁶Stevens Research Center, Carle Foundation Hospital, Urbana, IL, United States

We present a new approach replacing high-permittivity water-based dielectric pads with a non-resonant low-cost artificial dielectric to improve MR image quality by modifying the interferences present in the radiofrequency field at 7T MRI. The artificial dielectric comprises a stack of metal patches printed on dielectric substrates. Numerical studies and imaging of a head-phantom with the proposed structure showed the same increase in the transmit radiofrequency field distribution at the area of interest as for conventional dielectric pads. The advantages of the new structure include ease of manufacture and long-term stability.