Congcong Liu^1,2, Caiyun Shi¹, Jianguo Cui², Xin Liu¹, Hairong Zheng¹, Dong Liang¹, and Haifeng Wang^1
1Shenzhen Institutes of Advanced Technology,Chinese Academy of Sciences, Shenzhen, China, ²Chongqing University of Technology, Chongqing, China

Conventional Magnetic Particle Imaging (MPI) systems are expensive and bulky, and most of them use CPU and MPU as controllers. Field Programmable Gate Arrays (FPGAs) have recently become widely utilized as controllers in many systems for flexibility and speed. In this paper, we proposed an implementation scheme of a low-cost, small-volume MPI system based on FPGA architecture. The experimental results showed that the complete operation of the MPI system signal link could be realized by the low-cost FPGA-based control system (≤$200), and the distribution of the superparamagnetic iron oxide nanoparticles (SPION) could be imaged by the signal of the particle.

Ryan Hill¹, Elena Boto¹, Niall Holmes¹, Gillian Roberts¹, Jim Leggett¹, Zelekha Seedat¹, Molly Rea ¹, Tim Tierney², Stephanie Mellor ², Vishal Shah ³, James Osborne³, Gareth Barnes⁴, Richard Bowtell¹, and Matthew Brookes^1
1Sir Peter Mansfield Imaging Centre, University of Nottingham, Nottingham, United Kingdom, ²Wellcome Centre for Human Neuroimaging, UCL, London, United Kingdom, ³QuSpin Inc., Louisville, CO, United States, ⁴Wellcome Trust Centre for Neuroimaging, UCL, London, United Kingdom

We have a developed a wearable magnetoencephalography (MEG) system comprising 50, miniaturised optical pumped magnetometers (OPMs) fixed on an EEG-type cap. Large, bi-planar field and field-gradient coils sited inside a magnetically shielded room reduce the field around the head to < 1nT. This allows the subject to move their head during experiments without confounding the OPM signals. We report results from a simple finger abduction paradigm and a motor learning experiment in which a subject learns to play the ukulele. The results demonstrate the potential of OPM-MEG to overcome some limitations of neuroimaging investigations using fixed, cumbersome scanners.

Fred Tam¹, Benson Yang¹, and Simon J Graham^1,2
1Physical Sciences, Sunnybrook Research Institute, Toronto, ON, Canada, ²Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada

Building a flexible setup for parallel transmission (PTx) MRI research is still challenging. A commercial software defined radio device was tested for suitability in a revised setup. Software was developed to make the device generate radiofrequency (RF) bursts in response to triggers. Preliminary bench tests showed quick and reliable triggering, consistent amplitude and phase across channels, and successful runtime adjustment. An initial PTx MRI demonstration showed capability for RF shimming in echo planar imaging of a phantom. Further troubleshooting is planned to reduce observed phase jitter, but the setup is already capable of a range of PTx research applications.

Jin Jin^1,2,3, Zhentao Zuo^4,5, Mingyan Li², Ewald Weber², Aurelien Destruel², Feng Liu², Rong Xue^4,5, and Stuart Crozier^2
1Siemens Healthcare Pty Ltd, Brisbane, Australia, ²The University of Queensland, St Lucia, Australia, ³University of Southern California, Los Angeles, CA, United States, ⁴Institute of Biophysics, Chinese Academy of Sciences, Beijing, China, ⁵Sino-Danish College, University of Chinese Academy of Sciences, Beijing, China

RF shimming, by means of adjusting the relative amplitudes and phases of the independent transmit channels of a parallel transmit system, is widely used in ultra-high-field imaging to improve transmit homogeneity but has limited capabilities especially for large fields of view. This work designed and tested an 8-channel rotating transceiver array to provide more degrees-of-freedom for both transmission and reception. During transmission, the array achieved a uniform effective transmit magnetic field in a time-multiplexed fashion; during reception, the array provided more unique sensitivity profiles, facilitating higher image SNR. Parallel-imaging-like reconstruction was developed, assisted by a robust self-calibrated sensitivity estimation technique.

Ali Aghaeifar¹, Jiazheng Zhou¹, Feng Jia², Maxim Zaitsev², and Klaus Scheffler^1
1Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, ²Dept. of Radiology, Medical Physics, Medical Center University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany

Multi-coil shim setup is a popular choice for B₀ shimming. In contrast to conventional regular arrangement of the shim coils, one can effectively position the shim coil to match inhomogeneity distribution in the human brain. In this work, a comparison between regular and optimized arrangement of the local coils in a multi-coil shim setup is performed and the pros and cons of each design are evaluated.

Sebastian Gantz^1,2, Volker Hietschold³, Sergej Schneider^1,2,4, and Aswin Louis Hoffmann^1,2,5
1Institute of Radiooncology-OncoRay, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, Germany, ²OncoRay – National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany, ³Department of Radiology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany, ⁴Technische Universität Dresden, Carl Gustav Carus Faculty of Medicine, Dresden, Germany, ⁵Department of Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany

The targeting precision of proton therapy is expected to benefit from real-time MRI guidance. We developed a setup of a first prototype in-beam MRI scanner with a proton pencil beam scanning nozzle. Dipole magnets in the nozzle used for beam steering produce time-dependent magnetic fringe fields that may interfere with the MR image acquisition. In this study, we show that vertical beam steering shows no degradation of the MR image quality, whereas horizontal beam steering introduces severe ghosting artefacts in phase encoding direction. The origin of these artefacts is unraveled and strategies to eliminate or correct these artefacts are proposed.

Jixin Xia^1,2, Charlotte R. Sappo^1,3, William A. Grissom^1,3,4, and Xinqiang Yan^3,4
1Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, ²Department of Electrical Engineering, Vanderbilt University, Nashville, TN, United States, ³Vanderbilt University Institute of Imaging Science, Nashville, TN, United States, ⁴Department of Radiology, Vanderbilt University Medical Center, Nashville, TN, United States

Large RF chokes increase the inductance/resistance of the DC loop and thus lead to unwanted power dissipation and bulk. We theoretically analyzed the added coil loss induced by bridge inductors in AC/DC coils and found that large bridge chokes can be replaced by low-profile inductors with much smaller values, if the capacitance is adjusted to compensate the resonance frequency shift. This will reduce the footprint of AC/DC coils as well as the inductance/resistance and thus power dissipation, with a cost of slightly higher coil loss.

Michael Hock¹, Maxim Terekhov¹, Markus Johannes Ankenbrand¹, David Lohr¹, Theresa Reiter^1,2, Christoph Juchem³, and Laura Maria Schreiber^1
1Chair of Cellular and Molecular Imaging, Comprehensive Heart Failure Center (CHFC), University Hospital Wuerzburg, Wuerzburg, Germany, ²Department of Internal Medicine I, University Hospital Wuerzburg, Wuerzburg, Germany, ³Departments of Biomedical Engineering and Radiology, Columbia University, New York City, NY, United States

Spatio-temporal inhomogeneities of the static magnetic (B₀) field are a major limiting factor in cardiac magnetic resonance applications at 7T. A previously developed shim strategy was demonstrated to correct spatial myocardial B₀-field inhomogeneities in a preliminary in vivo implementation. To correct localized spots of B₀-inhomogeneities, third-order terms were found to be beneficial. Cardiac phase-specific shimming was evaluated in simulations based on the in vivo field map data, and optimal shim settings were shown to differ between cardiac phases. Future work will address the application of a shim averaged over all cardiac phases to each individual phase.

Michael Garwood¹, Michael Mullen¹, Naoharu Kobayashi¹, Lance delaBarre¹, Steven Suddarth¹, Djaudat Idiyatullin¹, John Strupp¹, Gregor Adriany¹, Jarvis Haupt¹, Alex Gutierrez¹, Taylor Froelich¹, Russell Lagore¹, Benjamin Parkinson², Konstantinos Bouloukakis², Mark Hunter², Mathieu Szmigiel², Mailin Lemke², Edgar Rodriguez-Ramirez², Robin de Graaf³, Chathura Kumaragamage³, Scott McIntyre³, Terry Nixon³, Christoph Juchem⁴, Sebastian Theilenberg⁴, Yun Shang⁴, Jalal Ghazouani⁴, Alberto Tannús⁵, Mateus José Martins⁵, Edson Vidoto⁵, Fernando Paiva⁵, Daniel Pizetta⁵, Maurício Falvo⁵, Diego Turibio⁵, Christian Bones⁵, Eduardo Falvo⁵, John Thomas Vaughan⁴, Julie Kabil⁴, Hazal Yüksel⁴, Harish Krishnaswamy⁴, Sung-Min Sohn⁶, and Ramon Gilberto Gonzalez^7
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, ²Victoria University of Wellington, Wellington, New Zealand, ³Yale University, New Haven, CT, United States, ⁴Columbia University, New York, NY, United States, ⁵Centro de Imagens e Espectroscopia por Ressonância Magnética, Universidade de São Paulo in São Carlos, São Carlos, Brazil, ⁶Arizona State University, Tempe, AZ, United States, ⁷MGH/Harvard, Boston, MA, United States

A multi-disciplinary team of researchers in a multi-institutional consortium have designed and are building an easily relocatable head-only 1.5T MRI scanner weighing only ~500 kg. The goal is to develop a radically new type of MRI scanner that will enhance brain research, and ultimately, enable the diagnosis of neurological diseases in underserved populations throughout the world where MRI scanners are currently unavailable. To image with this system, pulse sequences have been developed and implemented to generate images using a highly inhomogeneous B₀.

Christopher M. Collins^1,2, Ryan Brown¹, and Daniel K. Sodickson^1
1New York University School of Medicine, New York, NY, United States, ²Center of Advanced Imaging, Innovation, and Research (CAI2R)), New York, NY, United States

By adjusting the electrical permittivity of the material in the bath  and adding slots to the conductive ground for the ultrasound array in MR-guided focused ultrasound it is possible to go from a situation where the ultrasound array and associated fluid bath detrimentally affect the RF fields for MRI and prohibit effective imaging in the Region of Interest, to where they actually enhance it, thereby improving image quality.

Hans Hoogduin¹, Mark Gosselink¹, Giel Mens¹, Wim Prins², Tijl van der Velden¹, and Dennis Klomp^1
1UMCU, Utrecht, Netherlands, ²Philips, Best, Netherlands

Directional couplers are used to measure reflected waves from an eight channel PTx coil to detect head motion at 7T. The method doesn't require any changes to pulse sequences and has no time penalty. A general linear model is used to predict head motion from the signals measured at the couplers. 

Haopeng Han¹, Thomas Wilhelm Eigentler¹, Eckhard Grass^2,3, and Thoralf Niendorf^1,4,5
1Berlin Ultrahigh Field Facility (B.U.F.F.), Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany, ²IHP – Leibniz-Institut für innovative Mikroelektronik, Frankfurt (Oder), Germany, ³Institute of Computer Science, Humboldt-Universität zu Berlin, Berlin, Germany, ⁴Experimental and Clinical Research Center (ECRC), a joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular Medicine, Berlin, Germany, ⁵MRI.TOOLS GmbH, Berlin, Germany

Thermal Magnetic Resonance makes use of the physics of radio frequency waves applied at ultrahigh field-MRI. To achieve precise energy focal point formation, accurate thermal dose control and safety management, the transmitted RF signal amplitude and phase need to be supervised and regulated in real-time. In this work, a multi-channel power and phase supervision module was developed, evaluated and applied as an integral part of the Thermal MR hardware system. Preliminary experiments were conducted to demonstrate that the proposed module is suitable and essential for RF heating using a hybrid Thermal MR approach.

Devin Willey^1,2, Julia Bresticker^1,2, Trong-Kha Truong^1,2, Allen Song^1,2, Bruno Madore³, and Dean Darnell^1,2
1Brain Imaging and Analysis Center, Duke University, Durham, NC, United States, ²Medical Physics Graduate Program, Duke University, Durham, NC, United States, ³Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States

An integrated RF/wireless coil, used to wirelessly transmit data and acquire MR images, and small ultrasound-based sensors, used to monitor physiological motion and correct MRI artifacts, were combined to enable wireless transmission of  1-MHz ultrasound data acquired from the sensors. Experiments were performed to validate that the coil could wirelessly transmit ultrasound data 1) while taking MR images and 2) from inside and outside the bore to a computer. This integrated system improves the mobility of the OCM sensors, thereby enabling them to accompany patients throughout the hospital, and demonstrates the coil’s ability to transmit high-fidelity analog data while imaging.

Rafael Limgenco Calleja¹, Celine Jeyda Veys¹, and Michael Lustig^1
1Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA, United States

Low-to-mid field systems have nearly been abandoned for high-field, high-performance systems. However, recent improvements in MR hardware, algorithms and computation are stimulating a resurgence in interest of upgrading lower-end magnets to achieve high-performance at significantly lower cost, improved accessibility, portability and siting. Here, we look at upgrading a wrist/animal 1T permanent-magnet system. We integrate a simple B₀ array into a solenoid TRX coil for reducing B₀ through localized targeted shimming. We demonstrate potential for improved field homogeneity with simulations, and demonstrate homogeneity improvements using a 6-channel prototype array with negligible effects on the transmit field and received SNR.