Clarissa Zimmerman Cooley^1,2, Jason Stockmann^1,2, and Lawrence L Wald^1,2,3
1Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, ²Harvard Medical School, Boston, MA, United States, ³Harvard–MIT Division of Health Sciences and Technology, Cambridge, MA, United States

There is clear motivation for increasing the accessibility of MRI, particularly for brain imaging.  To address this, we present a portable tight-fitting MRI scanner with a geometry that is optimized for head.  We use a 35kg “Halbach-bulb” permanent magnet design that combines a Halbach sphere and Halbach cylinder.  The gradient coils are designed on the outer surface of the magnet, enabling a closer-fit B0 magnet.  The inhomogeneous B0 magnet results image distortion, which we correct using a generalized reconstruction algorithm that employs measured field maps. We present the full scanner system and in vivo 3D images with resolution 1.5mmx2.7mmx7mm. 

José Miguel Algarín¹, Elena Díaz², Pepe Borreguero¹, Fernando Galve¹, Daniel Grau², Juan Pablo Rigla², Rubén Bosch¹, José Manuel González², Eduardo Pallás¹, Miguel Corberán¹, Carlos Gramage¹, Alfonso Ríos², José María Benlloch¹, and Joseba Alonso^1
1I3M, CSIC, Valencia, Spain, ²Tesoro Imaging, Valencia, Spain

Here we present the first demonstration of dental imaging in a low cost MRI setup at sub-Tesla fields (260 mT). We show 3D reconstructions of a rabbit head and human teeth acquired in “DentMRI – Gen I” (Fig. 1(a)), a home-made special-purpose MRI scanner designed with the goal of demonstrating dental imaging at low field strengths. We use two variations of zero echo time (ZTE) pulse sequences (Fig. 1(b)): standard PETRA , and Double Radial Non Stop Spin Echo (DRaNSSE), which we have devised to address limitations we find with PETRA. We reconstruct images by Algebraic Reconstruction Techniques (ART).

Thomas K.F. Foo¹, Mark Vermilyea², Minfeng Xu², Anbo Wu², Yihe Hua², Wolfgang Stautner², Ye Bai², Justin Ricci², Doug Kelley³, John III Huston⁴, Yunhong Shu⁴, Matt A Bernstein⁴, Christopher Hess⁵, and Duan Xu^5
1GE Global Research, Niskayuna, NY, United States, ²GE Research, Niskayuna, NY, United States, ³GE Healthcare, Fairfax, CA, United States, ⁴Mayo Clinic, Rochester, MN, United States, ⁵University of California - San Francisco, San Francisco, CA, United States

A design for a lightweight, low-cryogen, head-only 7T MRI system was completed with its construction underway. This new 7T system is a dedicated brain scanner with 140 mT/m and 820 T/m/s gradients and weighs about 8 tons with 18 liters of liquid helium. The fringe field is similar to the 5 Gauss limits of a clinical whole-body 3T MRI scanner.

David A Feinberg^1,2,3, Peter Dietz⁴, Chunlei Liu^1,5, Kawin Setsompop⁶, Pratik Mukherjee^7,8, Lawrence L Wald^9,10,11, An T Vu^7,8, Alexander JS Beckett^1,2, Ignacio Gonzalez Insua⁴, Martin Schröder⁴, Stefan Stocker⁴, Paul H Bell¹², Elmar Rummert⁴, and Mathias Davids^9,10,13
1Helen Wills Neuroscience Institute, University of California, Berkeley, CA, United States, ²Advanced MRI Technologies, Sebastopol, CA, United States, ³Department of Cognitive Neuroscience, Maastricht University, Maastricht, Netherlands, ⁴Siemens Healthcare GmbH, Erlangen, Germany, ⁵Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, United States, ⁶Radiological Sciences Laboratory, Stanford University, Stanford, CA, United States, ⁷Radiology, University of California, San Francisco, CA, United States, ⁸San Francisco Veteran Affairs Health Care System, San Francisco, CA, United States, ⁹A.A. Martinos Center for Biomedical Imaging, Dept. of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, ¹⁰Harvard Medical School, Boston, MA, United States, ¹¹Harvard-MIT Division of Health Sciences Technology, Cambridge, MA, United States, ¹²Siemens Medical Solutions USA, Inc, Cary, NC, United States, ¹³Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Heidelberg, Germany

A Next-Generation 7T MRI scanner was designed to achieve higher performance in human brain imaging for the NIH BRAIN Initiative. The new 7T scanner introduces several innovative hardware designs including a PNS optimized asymmetric head gradient coil (Siemens Healthcare, Erlangen, Germany) with Gmax 200mT/m and Smax 900T/m/s. The scanner also includes 128-channel RF receiver and 16-channel transmit systems for all-in-one cumulative gains in performance. The resulting higher spatial resolution, sensitivity and image acceleration will enable in-vivo whole-brain mesoscale research on cortical layer and columnar circuitry and other brain structures.

Dimitri Welting¹, Edwin Versteeg¹, Ingmar Voogt², Joost van Straalen³, Martijn Heintges³, Marco Rietveld³, Jeroen C.W. Siero^1,4, and Dennis W.J. Klomp^1
1Radiology, University Medical Center Utrecht, Utrecht, Netherlands, ²Wavetronica, Utrecht, Netherlands, ³Prodive Technologies, Son, Netherlands, ⁴Spinoza Centre for Neuroimaging Amsterdam, Amsterdam, Netherlands

Here we propose a setup to boost spatiotemporal encoding for fMRI in the human brain using high dense receiver arrays (72ch) and fast gradients (6000T/m/s). Moreover, we demonstrate that the operation frequency of a high-end gradient amplifier can be increased to ultrasonic frequencies so to avoid unpleasant acoustic noise. By using this amplifier with 8 transceivers, 64 receivers and a 2-axis cooled gradient coil, a light weight setup is constructed for operation in a 7 Tesla MRI system for fMRI experiments in the human brain.

Jianshu Chi¹, Victor Han¹, and Chunlei Liu^1,2
1Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA, United States, ²Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA, United States

We are exploring in vivo brain imaging with two-photon excitation on a 3T scanner. To do that, we built a customized coil that is large enough to fit a standard birdcage transceiver coil inside of it. The resulting two-photon gradient-echo brain images excited using a 25.5 kHz z-axis RF were overall similar to standard single-photon images with equivalent parameters. Interestingly, we observed some slight differences in tissue contrast whose cause are being investigated.

Mathias Davids^1,2,3, Peter Dietz⁴, Gudrun Ruyters⁴, Manuela Roesler⁴, Valerie Klein^1,3, Bastien Guerin^1,2, David A Feinberg^5,6, and Lawrence L Wald^1,2,7
1Martinos Center for Biomedical Imaging, Boston, MA, United States, ²Harvard Medical School, Boston, MA, United States, ³Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany, ⁴Siemens Healthineers, Erlangen, Germany, ⁵Advanced MRI Technologies, Sebastopol, CA, United States, ⁶Brain Imaging Center and Helen Wills Neuroscience Institute, University of California, Berkeley, CA, United States, ⁷Harvard-MIT, Division of Health Sciences and Technology, Cambridge, MA, United States

PNS modeling was utilized during the design stage of a high-strength (Gmax = 200mT/m, Smax = 900 T/m/s) head gradient for 7T fMRI research. The design-stage preview of PNS thresholds and locations allowed alteration of the winding pattern to balance head and body stimulation. This process yielded significantly improved PNS thresholds and increased usability of the coil performance space. The results were validated using PNS experiments in a constructed coil.

Leanna Pancoast^1,2, Douglas Brantner^1,2, Roy Wiggins^1,2, Jerzy Walczyk^1,2, and Ryan Brown^1,2
1Center for Biomedical Imaging, NYU Grossman School of Medicine, New York City, NY, United States, ²Center for Advanced Imaging Innovation and Research, NYU Grossman School of Medicine, New York City, NY, United States

The temporal resolution in MRI can be too slow to track respiratory or bulk subject motion. Auxiliary sensors have been developed to track motion with high temporal resolution, but can require cumbersome cabling. In this work, we describe an MRI-compatible wireless accelerometer data acquisition platform and demonstrate proof-of-concept by correlating respiratory motion data with independent, ground-truth optical measurements.

Malte Laustsen^1,2,3, Mads Andersen⁴, Rong Xue^3,5,6, Kristoffer H. Madsen^2,7, and Lars G. Hanson^1,2
1Section for Magnetic Resonance, DTU Health Tech, Technical University of Denmark, Kgs. Lyngby, Denmark, ²Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark, ³Sino-Danish Center, University of Chinese Academy of Sciences, Beijing, China, ⁴Philips Healthcare, Copenhagen, Denmark, ⁵State Key Laboratory of Brain and Cognitive Science, Beijing MR Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China, ⁶Beijing Institute for Brain Disorders, Beijing, China, ⁷DTU Compute, Technical University of Denmark, Kgs. Lyngby, Denmark

Tracking and retrospective correction of high-resolution structural 3D-GRE images is accomplished with a slightly modified EEG cap and sampling system. Carbon wire loops added to the EEG cap allow for motion tracking using gradient-induced signals from native sequence elements, without the need for sequence modification, or electrode-skin contact, while requiring only a short calibration scan, and mounting of the cap. The motion estimates closely resemble estimates from interleaved navigators (mean absolute difference: [0.13,0.33,0.12]mm, [0.28,0.15,0.22]deg). Retrospective correction using carbon wire loops yield similar improvements to Average Edge Strength (12%) for images with instructed movement, and does not degrade images without motion.

Suma Anand¹ and Michael Lustig^1
1Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA, United States

Pilot Tone (PT) navigators are tones within the MR receiver bandwidth that are used to estimate subject motion. Unfortunately, PTs are bound to the Larmor frequency with a wavelength of 1-4.7m (7T to 1.5T), limiting their sensitivity to motion. We propose a new approach, Beat Pilot Tone (BPT), which overcomes this limitation using second order intermodulation in MR coil preamplifiers (preamps). Any two tones separated by the desired PT frequency are mixed at the preamp and digitized by the receiver. We demonstrate our approach at 2.4GHz, obtaining improved sensitivity (20x) compared to PT without reduction of image SNR.