Clarissa Zimmerman Cooley^1,2, Patrick C McDaniel^1,3, Jason P Stockmann^1,2, Sai Abitha Srinivas¹, and Lawrence L Wald^1,2,4
1Athinoula 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 Electrical Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States, ⁴Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA, United States

Access to MRI scanners is limited by cost, size, and siting requirements. Specialized low-cost, compact, portable systems could greatly increase accessibility worldwide and enable point-of-care MRI. We present a portable MRI scanner for human brain imaging based on a compact 122kg Halbach cylinder with a built-in readout field. Designing for a built-in encoding field reduces the size of the magnet, the overall system power-consumption, cooling requirements, and acoustic noise. The generalized reconstruction method accounts for non-linearities in the gradient fields. T1 and T2-weighted in vivo images are presented with a resolution of 2x2x7mm.

Thomas O'Reilly¹, Wouter Teeuwisse¹, Bart de Vos², and Andrew Webb^1
1C.J. Gorter Center for High Field MRI, Leiden University Medical Center, Leiden, Netherlands, ²Circuits and Systems, Delft University of Technology, Delft, Netherlands

We show the first 3D in-vivo images acquired from our custom-built 50 mT low-cost Halbach based portable MRI scanner. 3D Images of a knee were acquired with a ~2 mm isotropic resolution using a 3D turbo spin echo sequence in less than 12 minutes. Gradient non-linearity induced image distortions are minimal within the central ~10 cm of the magnet bore length, but require correction beyond this point. These results represent the latest step towards our goal of creating a fully portable MRI scanner targeting pediatric neuroimaging in the developing world for less than 30 000 euros.

Aaron R. Purchase¹, Gordon E. Sarty², Logi Vidarrson³, Keith Wachowicz¹, Piotr Liszkowski^4,5, Hongwei Sun¹, Jonathan C. Sharp¹, and Boguslaw Tomanek^1,6
1Department of Oncology, University of Alberta, Edmonton, AB, Canada, ²Department of Psychology and Division of Biomedical Engineering, University of Saskatchewan, Saskatoon, SK, Canada, ³LT Imaging, Toronto, ON, Canada, ⁴AGH University of Science and Technology, Krakow, Poland, ⁵MRI-Tech Sp. z o.o, Krakow, Poland, ⁶Institute of Nuclear Physics, Polish Academy of Sciences, Krakow, Poland

MRI is desired for monitoring bone and muscle deterioration in astronauts during long-term spaceflights and on the International Space Station (ISS). However, the magnet is generally too heavy to be transported to the ISS. Therefore, we designed a light (~10kg) magnet that allows transmit array spatial encoding (TRASE) MRI of the ankle on the ISS. The magnet is based on a sparse Halbach geometry with magnetic block-pairs. The positions of the block-pairs were optimized using a genetic algorithm. We intend to manufacture the magnet and test the entire MRI system on a Falcon 20 jet.

Jerome L. Ackerman^1,2, Shahin Pourrahimi³, Marcus Donaldson^1,2, Nadder Pourrahimi³, Julien Rivoire⁴, Julien Muller⁴, Hizami Murad⁴, Ouri Cohen⁵, and Isabela Choi^1
1Martinos Center, Dept of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, ²Department of Radiology, Harvard Medical School, Boston, MA, United States, ³Superconducting Systems, Inc., Billerica, MA, United States, ⁴RS2D, Mundolsheim, France, ⁵Memorial Sloan Kettering Cancer Center, New York, NY, United States

We developed an MRI scanner designed for limb scanning based on a novel conduction-cooled three-bore cryogen-free 1.5T magnet. The two outer bores accommodate the unscanned leg for enhanced patient comfort. We describe the issues relevant to this unique magnet and scanner, including our solution to the field instability problem common in conduction-cooled MRI magnets. By recording the field variation as a function of the phase of the cold head cycle, a compensating waveform may be played out via the numerically-controlled oscillator of the scanner to reduce the periodic field excursion from 25 Hz to about 1-2 Hz.

Dion Thomas¹, Petrik Galvosas¹, Paul D Teal², Freya G Harrison^3,4, Max Berry^3,5, Yu-Chieh Tzeng³, and Sergei Obruchkov^6
1School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington, New Zealand, ²School of Engineering and Computer Science, Victoria University of Wellington, Wellington, New Zealand, ³Centre for Translational Physiology, University of Otago, Wellington, New Zealand, ⁴Department of Surgery and Anaesthesia, University of Otago, Wellington, New Zealand, ⁵Department of Paediatrics and Child Health, University of Otago, Wellington, New Zealand, ⁶Robinson Research Institute, Victoria University of Wellington, Wellington, New Zealand

We have developed a new permanent magnet based single sided magnetic resonance system, which is suitable for relaxometry and diffusion measurement. Our design generates an external region of homogeneous B₀ field, a sweet spot, from which signal can be detected. The magnet has been optimised to have a larger penetration depth and higher B field strength than currently existing systems. We have found the system provides good homogeneity and field strength, making it useful for relaxometry. Additionally, we demonstrate it can be used for diffusion-T2 measurements, which will allow further biomedical applications.

Yaohui Wang¹, Qiuliang Wang¹, Jianhua Liu¹, Junsheng Cheng¹, Zhongbiao Xu², Zhifeng Chen³, and Feng Liu^4
1Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing, China, ²Department of Radiotherapy Cancer Center, Guangdong Provincial People's Hospital & Guangdong Academy of Medical Science, Guangzhou, China, ³School of Biomedical Engineering, Southern Medical University, Guangzhou, China, ⁴School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, Australia

7T whole-body MRI system has received comprehensive praises from the worldwide users, but some patients feel clautrophobic when doing the scanning at the long tunnel. This work proposed a ultra-short design scheme for the 7 T MRI magnet, which is nearly a half of the presented commercial system. In addition, the magnet operates at helium-off enviroment, which saves the precious coolant liquid helium and is also conveinent to maintain.

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 demonstrate the first in vivo imaging experiment with a multiphoton excitation technique at 1T. To produce multiphoton excitation, we built a secondary RF coil that produces an RF field, parallel to the $$$B_{0}$$$ field. Designed for kHz frequencies, this coil consists with two layers of traces in a spiral configuration on a printed circuit board (PCB). Adding this low-frequency coil to an Aspect 1T Wrist Scanner, we acquired gradient echo images with two-photon excitation of a human hand in vivo. 

Matthew A. McCready¹, William B. Handler¹, and Blaine A. Chronik^1
1Physics and Astronomy, Western University, London, ON, Canada

Delta relaxation enhanced magnetic resonance (dreMR) is a field-shifting quantitative molecular imaging method using activatable MR probes. The dreMR method may be used to produce images with signal proportional to concentration of contrast agent and eliminate signal due to unbound agent. In this work we outline a novel design method for dreMR coils, using an inner layer of windings determined by the boundary element method (BEM). This new design method produces a strong, highly homogeneous field shift which, when coupled with a 0.5T MRI system and activatable MR probes, can reliably image on a larger volume than previous designs.

Yongxian Qian¹, Bei Zhang¹, Shannon Haas¹, and Aaron R. Chidakel^2
1Radiology, New York University, New York, NY, United States, ²Endocrinology, New York University, New York, NY, United States

This study presents preliminary results supporting a new concept to build a wearable magnetic resonance spectroscopy (MRS) system for noninvasive blood glucose measurement in humans. Computer simulations, hardware buildings and subject studies demonstrated the promising of such a system.