Helmar Waiczies¹, Jan Rieger¹, Andreas Graessl², Andreas Pohlmann², Matthias A. Dieringer^2,3, and Thoralf Niendorf^2
1MRI.TOOLS GmbH, Berlin, Germany, ²Berlin Ultrahigh Field Facility (B.U.F.F.), Max Delbrück Center for Molecular Medicine, Berlin, Germany, ³3Working Group on Cardiovascular Magnetic Resonance, Experimental and Clinical Research Center (ECRC), Berlin, Germany

A dual-tuned ¹H/¹⁹F birdcage coil with high B₁⁺homogeneity for animal research at a clinical 3T-System has been constructed. The simulated B₁⁺ fields and the measured B₁⁺ maps were found to be in good agreement, including anatomical coverage, B₁⁺ distribution and B₁⁺ efficiency. The acquired ex vivo images showed superb sensitivity for ¹⁹F MRI as well as high spatial resolution for ¹H MRI. This work demonstrates the feasibility of a double tuned birdcage coil tailored for ¹H/¹⁹F MR in small rodents using a clinical 3T MR system. The proposed RF coil provides high homogeneity and sensitivity for very low concentrations of ¹⁹F. This progress may serve to enhance the capabilities of ¹⁹F MR based cell tracking in small rodents and benefits translational research en route to ¹⁹F MR in large animals or even humans.

James Tropp^1
1Engineering, GE Healthcare Technologies, Fremont, CA, United States

We have calculated the rates of radiation damping as a function of probe detuning, by numerical solution of the Bloch-Kirchhoff equations.

Lian Xue¹, Zungang Liu¹, Changwu Hu¹, Kuan Zhang¹, Erzhen Gao¹, QY Ma¹, Nikolaus M Szeverenyi², Rebecca Theilmann², and William Bradley^2
1Time Medical Systems, Inc., San Diego, CA, United States, ²Radiology, Univ. of California, San Diego, San Diego, CA, United States

A clinically useful 10 cm diameter high temperature superconductor (HTS) surface coil was designed, constructed, and tested for wrist imaging performance on a 1.5 Tesla scanner. The cryostat was constructed of fiberglass and had a liquid nitrogen hold time of 5 hrs and a vacuum hold time of 4 weeks. Comparison of this coil’s performance with a commercial 10 cm room temperature copper coil demonstrated a greater than 2 fold improvement in SNR. This receive coil has an active detuning circuit that can be used in future array coils designs.

Alexander J.E. Raaijmakers¹, Abe van der Werf², Hugo Kroeze¹, Peter R. Luijten¹, Cornelis A.T. van den Berg³, and Dennis W.J. Klomp^1
1Radiology, UMC Utrecht, Utrecht, Utrecht, Netherlands, ²Machnet B.V., Roden, Netherlands, ³Radiotherapy, UMC Utrecht, Utrecht, Netherlands

Helix antennas are a commonly used type of antenna in communication technology. They emit a circularly polarized wave with high directivity. For MRI, the helix antenna has the unique property to transmit or receive along the longitudinal axis of the scanner. This unique property enables the coverage of regions that are otherwise hard to address, particularly at higher field strengths. For example, the helix antenna can be used to recover B1 at the apex of the head. For prostate imaging, the helix antenna can be used to increase sensitivity by placing the coil between the legs, along the longitudinal axis.

Reina Ayde¹, Anne-Laure Perrier¹, Jean Dahdah², Raphael Sablong¹, Lionel Duvillaret², Gwenael Gaborit^2,3, and Olivier Beuf^1
1University of Lyon 1, CREATIS - CNRS UMR 5220 – INSERM U1044, Villeurbanne, Rhone-Alpes, France, ²Kapteos, Rhone-Alpes, France, ³University of Savoie, IMEP-LAHC UMR 5130, Rhone-Alpes, France

The use of metallic coaxial cables in Magnetic Resonance Imaging could induce local high Specific Absorption Rate (SAR). Optical fiber link could be a promising alternative to coaxial cables for MRI to ensure patient safety. Here, the conversion of the Radio-Frequency magnetic field into an electric signal by electro-optic effect was demonstrated and characterized. A waveguide crystal is used together with an endoluminal coil to demonstrate the ability of such transducer to perform a deported characterization of Radio-Frequency magnetic field at 3T. The results show a good agreement with theoretical values and a minimum magnetic detectable field of pT order.

Irena Zivkovic¹ and Klaus Scheffler^1,2
1High Field MRI, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, ²Center for Integrative Neuroscience, Universuty of Tuebingen, Tuebingen, Germany

It is a big challenge to produce as homogeneous as possible B1+ field with single channel antenna in traveling wave configuration. For that purpose, we proposed a new and very simple antenna concept. Antenna is entirely made of copper and without any lumped elements. By small changes in geometry different RF excitation patterns can be produced. We presented design that produced as homogeneous as possible B1+ field in sagittal, coronal and transversal planes. The second proposed design produced B1+field pattern in lower brain and neck region.

Zungang Liu¹, Changwu Hu¹, Erzhen Gao¹, Ronald Tse¹, QY Ma¹, Nikolaus M Szeverenyi², and William G Bradley^2
1Time Medical Systems, Inc., Shanghai, China, ²Radiology, Univ. of California, San Diego, CA, United States

A preliminary HTS volume knee coil was designed to improve the image quality of a low field MRI system. The coil is cooled by liquid nitrogen with a very low nitrogen boil-off rate. Knee images were obtained and compared to a commercial copper coil.

Ying-Hua Chu¹, Yi-Cheng Hsu¹, Shang-Yueh Tsai², and Fa-Hsuan Lin^1,3
1Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan, ²Institute of Applied Physics, National Chengchi University, Taipei, Taiwan,³Department of Biomedical Engineering and Computational Science, Aalto University, Espoo, Finland

We propose a new approach to improve the isolation of NMR signals originating from the field probe and from the imaging object without using an independent transceiver. We use an RF coil (Tx loop) to pick up the RF energy during RF transmission to the field probe inside an RF shield. During RF reception, the Tx loop is detuned such that the NMR signal from the imaging object will not be picked up by the Tx loop and the field probe can remain isolated inside the RF shielding. This design is empirically demonstrated by an one-channel prototype system.

Joseph Murphy-Boesch¹, Qi Duan¹, Steve Dodd¹, Natalia Gudino¹, Shumin Wang², and Jeff Duyn^1
1National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States, ²Department of Electrical and Computer Engineering, Auburn University, Auburn, AL, United States

An inductive birdcage resonator with 24 meshes has been assembled for imaging of the head in the confined space of an 11.7T head-only MRI system. To reduce radiative losses and de-tuning by the head, the resonator was suspended within its cylindrical shield with no direct RF connections. Four-port connection to the coil was effected using inductive couplers with balanced drive to further reduce E-fields. Bench sensitivity and field uniformity are similar to a 7T coil. Power testing using a custom phantom yielded differential temperature increases that can be used to validate EM simulations.

Riccardo Stara¹, Simone A. Winkler², Ronald D Watkins², Alessandra Retico³, Michela Tosetti⁴, and Brian K Rutt^2
1Dipartimento di Fisica, Università di Pisa, Pisa, Italy, ²Department of Radiology, Stanford University, Stanford, CA, United States, ³Istituto Nazionale di Fisica Nucleare, Pisa, Italy, ⁴IRCCS Stella Maris, Pisa, Italy

B₁⁺ shimming and parallel transmission can benefit from an increased number of transmit channels and from 3D segmentation. However, one of the remaining challenges in RF coil designs for parallel transmission is the decoupling between coil elements. We present a novel transmission line element used in a modular two-row 16-channel transmit array design. The proposed element employs cylindrical shielding to provide intrinsic geometric decoupling, without any additional hardware. The proposed 16-channel array can be configured for 8-channel single-row and 16-channel two-row mode using two Butler matrices. Numerical simulations and preliminary experiments show improved decoupling performance and B₁⁺/E performance.

Hai Lu¹, Ziyuan Fu², and Shumin Wang^2
1Auburn University, Auburn, Alabama, United States, ²Auburn University, Alabama, United States

Multi-channel transceiver arrays are highly desired for 7 Tesla MRI due to the lack of volume transmitters. We developed a 16-channel transceiver array for equine joint MRI at 7T by splitting the single-channel power input equally into 16 coil elements. The design and implementation details are discussed. Actual imaging results further demonstrate the feasibility of the design.

Roberta Kriegl^1,2, Jean-Christophe Ginefri¹, Marie Poirier-Quinot¹, Luc Darrasse¹, Ewald Moser^2,3, and Elmar Laistler^2,3
1Laboratoire d'Imagerie par Résonance Magnétique Médicale et Multi-Modalités (IR4M), Université Paris Sud, Orsay, Essonne, France, ²Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Vienna, Austria, ³MR Center of Excellence, Medical University of Vienna, Vienna, Vienna, Austria

A novel transceiver array composed of monolithic transmission line resonators, fabricated on flexible substrate, for MRI at 7 T is presented. Individual array elements are mutually decoupled via overlapping annexes; inductive matching and fine-tuning using pick-up loops in over-coupled mode was implemented. The decoupling and parallel imaging performance of the array was assessed in bench and MRI experiments in terms of transmission S-parameters, noise correlation values and GRAPPA g-factors, comparing planar and bent array configuration. It is shown that the developed array may be form-fitted to non-planar samples without degrading its performance.

Joshua D Kaggie^1,2, K Craig Goodrich¹, Seong-Eun Kim¹, Michael J Beck¹, Dennis L Parker^1,2, Robb Merrill¹, Travis A Abele³, Richard Wiggins³, and J Rock Hadley^1
1Utah Center for Advanced Imaging Research, Radiology, University of Utah, Salt Lake City, UT, United States, ²Physics, University of Utah, Salt Lake City, UT, United States, ³Neuroradiology, University of Utah, Salt Lake City, UT, United States

This work developed a small animal system that could acquire good in vivo 100μm isotropic resolution images of a guinea pig cochlea on a 3T clinical MR system. The system used improved gradients, RF coils, and animal holder/monitoring equipment when compared to a standard clinical magnet. FLASH imaging was used to assess the quality of the system. Gadolinium increased the SNR and contrast of the cochlea during FLASH imaging. The small animal system obtained good 100μm isotropic resolution images of the cochlear chambers in a scan time of only 33 minutes.

Jarek Wosik^1,2, Kurt H. Bockhorst³, Krzysztof Nesteruk⁴, Dhivya Ketharnath¹, Tan I-Chih⁵, and Ponnada A Narayana^3
1Electrical and Computer Engineering, University of Houston, Houston, Texas, United States, ²Texas Center for Superconductivity, University of Houston, Houston, Texas, United States, ³Health Science Center, University of Texas, Houston, Texas, United States, ⁴Polish Academy of Sciences, Institute of Physics, Warsaw, Poland, Poland, ⁵Center for Molecular Imaging, University of Texas, Houston, Texas, United States

We report on assessment of achievable SNR gain due to reduction of thermal noise by cooling receiver coil made out of copper or superconducting materials. High field MRI 300 MHz receiver probe with tuning/matching and decoupling circuitry was used. The coil was fabricated by patterning double-sided thin superconducting YBCO film on 0.4 mm thick sapphire substrate and comprises of two split rings rotated 180 deg. versus each other. Our main interest in this work is in identification all losses limiting SNR, such as rf losses from coil, body, cryostat and tuning/maching/decoupling circuitry and in discussion on the probe performance optimization.

Gang Chen¹, Martijn Cloos¹, and Graham Wiggins^1
1The Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, United States

At high field, electric dipole antennas are seeing increasing use. When placed close to a relatively high dielectric material such as the body the self-resonant length shortens somewhat, but for 7T head imaging this still comes out to an inconvenient length of 40 cm or more. We describe here a modified monopole antenna where the ground plane is replaced by a strip of conductor. These are arranged in an 8 element array which allows alternating monopoles to be driven from opposing ends of the array, which extends excitation into inferior brain regions while also providing diverse B1 profiles along Z.

Bart L. van de Bank¹, Stephan Orzada², Miriam W. Lagemaat¹, Andreas K. Bitz^2,3, and Tom W.J. Scheenen^1,2
1Radiology, Radboud University Medical Center, Nijmegen, Netherlands, ²Erwin L. Hahn Institute, University Duisburg-Essen, Essen, Germany, ³Medical Physics in radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany

A dedicated 31P birdcage coil was designed, validated and constructed as an insert for an 8 channel, multi-transmit, octagonal shaped, 1H coil to enable homogeneous excitation and acquisition of 31P compounds combined with 1H multi-transmit capabilities to asses metabolic processes in-vivo at 7T.

Fabian Vazquez¹, Oscar Marrufo², Sergio E Solis¹, and Alfredo O Rodriguez^3
1Dep Phys, FC UNAM, Mexico, DF, Mexico, ²Dep Neuroimage, INNN-MVS, DF, Mexico, Mexico, ³Dep Elec Ing, UAM Iztapalapa, Mexico, DF, Mexico

Travelling wave magnetic resonance imaging (twMRI) offers an approach to acquire larger fields-of-view images at 7T or greater. Images have two main problems: inhomogeneous acquisition due to the physical restriction in coaxial waveguide at 7T, and added noise in parallel-plate waveguide (PPWG) at 3T. We measured the signal phase added by a PPWG in twMR images at 3T, using a transmission circular coil and other one for reception tuned at 128 MHz. Phantom images were acquired with the PPWG in clinical scanner at 3T. The phase shift information was used to improve the image quality and results compared.

Wei Luo^1,2, Yang Qing¹, and Christopher M. Collins^3
1Radiology, Pennsylvania State University, Hershey, PA, United States, ²Engineering Science & Mechanics, Pennsylvania State University, University Park, PA, United States, ³Radiology, New York University, New York, NY, United States

A simple hybrid coil-HPM design using a simple loop coil and a high-permittivity material (HPM) disc was optimized at 3T using PSO/FDTD method including the consideration on HPM location, geometry, material properties, MRI coil location, and coil geometry for the first time. The coil efficiency of the optimized hybrid design was better than the one produced by the optimized single loop coil at any depth in a lossy sphere, particularly by an average increase of 87% and 22% at the center and superficial regions, respectively. The performance of this simple hybrid design encourages us to expect more improvement with a more sophisticated design.

Manushka V. Vaidya^1,2, Christopher M. Collins^1,2, Ryan Brown¹, Daniel K. Sodickson^1,2, and Riccardo Lattanzi^1,2
1Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, United States, ²Sackler Institute of Graduate Biomedical Sciences, New York University School of Medicine, New York, NY, United States

We performed simulations and experiments to evaluate the benefits of placing shielded dielectric discs between adjacent coil elements in a 4-element transmit/receive array surrounding a uniform cylindrical dielectric phantom at 7 T. Our results showed that array performance is improved in the presence of suitably-configured dielectric discs. In particular, the B1 homogeneity improved by ~27% and the transmit efficiency and SNR at the center improved by ~5%. The proposed array design performs better than, and is based on different physical principles than, conductive shields placed above or completely surrounding the coil elements.

Riccardo Lattanzi^1,2, Manushka V Vaidya^1,2, Giuseppe Carluccio¹, Daniel K Sodickson^1,2, and Christopher M Collins^1,2
1The Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, United States, ²The Sackler Institute of Graduate Biomedical Sciences, New York University School of Medicine, New York, NY, United States

Cushions of high-permittivity material (HPM) placed between radiofrequency (RF) coils and the object can enhance transmit and receive performance. We investigated in simulation the signal-to-noise ratio (SNR) gain when covering the inside of a receive array uniformly surrounding a dielectric sphere with a continuous 1 cm layer of HPM (εr = 500). The SNR gain was positive for every voxel when the array had at least 32 coils (average ~ 10%, maximum ~ 30%). Our results suggest that using a thin encircling layer of HPM could be a practical method to improve performance of receive head arrays at 3T.

Wyger Brink¹ and Andrew Webb^1
1Radiology, Leiden University Medical Center, Leiden, Zuid-Holland, Netherlands

This work investigates, in particular, the origin of the distinct left-right asymmetry in the B₁⁺ field typically observed in the head at 7 T.

Qi Duan¹, Jeff H. Duyn¹, Natalia Gudino¹, Jacco A. de Zwart¹, Peter van Gelderen¹, Daniel K. Sodickson^2,3, and Ryan Brown^2,3
1AMRI, LFMI, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States, ²The Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, United States, ³NYU WIRELESS, Polytechnic Institute of New York University, New York, United States

In order to predict wavelength effects on MRI performance and tissue heating at high field, a generic recipe for an inexpensive and nontoxic phantom with biologically-relevant dielectric properties was developed. The recipe includes deionized water, NaCl, sucrose, and benzoic acid. 117 samples were prepared with a range of NaCl and sucrose concentrations, and their dielectric properties were measured and fitted to a three-dimensional polynomial. Nonlinear relationships between sucrose and NaCl concentrations and measured dielectric properties were observed, and strong interactions were found between individual component concentrations in determining dielectric properties.

Andreas Rennings¹, Keran Wang¹, Le Chen¹, Friedrich Wetterling², and Daniel Erni^1
1General and Theoretical Electrical Engineering (ATE), University of Duisburg-Essen, Duisburg, NRW, Germany, ²Faculty of Engineering, Trinity College, Dublin University, Dublin, Ireland

We present a simple model and used it for electromagnetic simulations to get physical inside to the dielectric padding approach. Furthermore we determined the best suited values for the pad permittivity and the cross-sectional-planes with best and worst coefficient-of-variation (CoV) for the |B1+| profile.

Riccardo Lattanzi^1,2, Manushka V Vaidya^1,2, Giuseppe Carluccio¹, Daniel K Sodickson^1,2, and Christopher M Collins^1,2
1The Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, United States, ²The Sackler Institute of Graduate Biomedical Sciences, New York University School of Medicine, New York, NY, United States

Previous work has shown that transmit efficiency and signal-to-noise ratio (SNR) can be improved by placing pads of high-permittivity material (HPM) between the radiofrequency coil and the sample. We employed dyadic Green’s functions for multi-layered spherical geometries to calculate the ultimate intrinsic SNR and the SNR of a 32-element loop array surrounding uniform spheres with different radii. Ultimate performance limits did not change, but could be approached more closely by the finite array with HPM added between the coil and the object. For a head-sized sphere, the SNR advantage was larger at 1.5T and 3T compared to higher B0 values.

Clarissa Z Cooley^1,2, Jason P Stockmann^3,4, Cris LaPierre^2,4, Thomas Witzel², Feng Jia⁵, Maxim Zaitsev⁵, Pascal Stang^6,7, Greig Scott⁷, Yang Wenhui⁸, Wang Zheng⁸, and Lawrence L Wald^2,9
1Electrical Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States, ²Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, ³Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts, United States, ⁴Department of Physics, Harvard University, Cambridge, MA, United States, ⁵Department of Radiology – Medical Physics, University Medical Centre Freiburg, Freiburg, Baden-Württemberg, Germany, ⁶Procyon Engineering, San Jose, CA, United States, ⁷Electrical Engineering, Stanford University, Stanford, CA, United States, ⁸Department of Electromagnetic Detection and Imaging Technology, Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing, China, ⁹Harvard Medical School, Boston, MA, United States

A low-cost, open-interface classroom MRI scanner is demonstrated. The scanner was used in an undergraduate lab course to interactively teach the concepts of free induction decay, flip angle measurement, B0 shimming, gradient echo, spin echo, 1D projection, and 2D as well as 3D MR imaging. An open library of GUIs, pulse sequences, and reconstruction codes is being developed in MATLAB to help build a user base.

André Guillou^1,2, Gregory Petitmangin², Roger Abächerli³, Laurent Bonnemains¹, and Jacques Felblinger^1
1Inserm U947 (IADI), Nancy, Lorraine, France, ²Schiller, Wissembourg, Alsace, France, ³Schiller, Baar, Zoug, Switzerland

As the ECG in MRI is disturbed by MR gradient swithings, hall sensors are used as input for gradient artifact reduction tools (as adaptive filtering), to provide clean ECG trace. Placed in the MR bore, this sensor was found to give additional information about respiration and heart pulse. We explored the possibility to use these data for patient monitoring during cardiac MRI.

Huijun Yu¹, Frank Huethe², Sebastian Littin¹, Feng Jia¹, Jürgen Hennig¹, and Maxim Zaitsev^1
1Dept. of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany, ²Dept. of Clinical Neurology and Neurophysiology, University of Freiburg, Germany

We present a hardware design of multi-channel switches for a dedicated matrix gradient coil. The switching system is used to control the combination of the matrix coil elements. The system consists of a controller and a number of analog switches. The analog switches are designed to be placed in the immediate vicinity of the matrix coil elements inside the magnet bore. A timer circuit in combination with a current source charges the bootstrap capacitor periodically and generates the power supply for the floating driver output circuit. The realized setup for switching high currents switched correctly following the coil setting code. Due to its modular design, the number of channels can be customized in future systems by choosing the appropriate number of analog switches.

J. Thomas Vaughan¹, Lance DelaBarre¹, Jinfeng Tian¹, Sungmin Sohn¹, Devashshish Shrivastava¹, Gregor Adriany¹, and Kamil Ugurbil^1
1CMRR - Dept. of Radiology, University of Minnesota, Minneapolis, MN, United States

To safely and successfully image the whole human at 10.5T, new RF methods and technologies must be developed. This abstract outlines and shows results for the first steps toward 10.5T MRI.

Hong Shang¹, Timothy Skloss², Cornelius vonMorze¹, Lucas Carvajal¹, Mark Van Criekinge¹, Peder E.Z. Larson¹, Ralph Hurd³, and Daniel B. Vigneron^1
1Radiology and Biomedical Imaging, UCSF, San Francisco, California, United States, ²GE Healthcare, Wisconsin, United States, ³GE Healthcare, California, United States

A specialized magnetic carrier was constructed to supply a suitable magnetic field(> 50 G) to preserve the polarization during hyperpolarized sample transfer, especially for hyperpolarized C-13 urea. It improved the SNR measured in the MR scanner by 2 fold for C-13 urea in our experimental tests.

Nicolai Spicher^1,2, Christopher Brumann¹, Markus Kukuk¹, Mark E. Ladd^2,3, and Stefan Maderwald^2
1University of Applied Sciences and Arts Dortmund, Dortmund, Germany, ²Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany, ³Division of Medical Physics in Radiology, German Cancer Research Center Heidelberg, Germany

The Eulerian Video Magnification approach is used in this work for color amplification of video data to offer an alternative to the conventional contact-based hardware for peripheral pulse triggering or monitoring units in MR scanners; the triggering is obtained by contactless video analysis. Two different test scenarios, one inside the scanner room of a 7T scanner and one inside the scanner bore during MR measurements at 3T, are shown. The results of the algorithm bear good resemblance with the measured pulse oximeter logs. The validation of real-time feasibility remains to be done.

Brian J. Soher^1
1Radiology, Duke University Medical Center, Durham, NC, United States

The dynamic flow of MR data from scanners to external computers during data acquisition is complicated by the hierarchical study/series organization of data acquisition and processing and by the variety of hardware, software and network infrastructures inherent to MR platforms. These and other issues slow application prototyping. We introduce a platform/OS independent software package, called RTView, that simplifies dynamic data transfer through the use of the Python programming language and standard network communication protocols known as XML-RPC. We demonstrate the use of the RTView platform for streaming real-time multinuclear 31P MR spectroscopy data off a 3T Siemens Trio.

Michael Werner Eder¹ and Volker Rasche^2
1University Hospital Ulm, Ulm, BW, Germany, ²University Hospital Ulm, BW, Germany

For evaluating dynamic cardiac MR imaging sequences a advanced heart simulator has been built. The phantom uses a polyvinyl alcohol (PVA) based tissue model and is able to simulate heart beat and breathing motion. The device is specially designed to fit into a clinical environment. No modifications of the MRI system are required that could cause the loss of approval. As the phantom feeds trigger signals directly over the physiology board all evaluated sequences can be transferred directly to clinical examination without the need of sequence reprogramming. Its design allows the use of cardiac anterior and posterior dedicated receiver coils.

Giulio Gambarota^1,2, Pierre-Antoine Eliat³, Johanne Bezy-Wendling^1,2, and Hervé Saint-Jalmes^1,2
1Université de Rennes 1, LTSI, Rennes, F-35000, France, ²INSERM, UMR 1099, Rennes, F-35000, France, ³PRISM - Biosit CNRS UMS 3480, INSERM UMS 018, Rennes, F-35000, France

The field of MRI is rapidly moving towards more quantitative approaches. In this context, virtual phantoms that would provide a reference signal could be useful for quantification purposes in MRI. The aim of the present study was i) to implement a dedicated experimental set-up to generate MR images of virtual phantoms ii) to test its temporal stability and signal linearity. This approach is here referred to as Virtual Phantom (ViP) MRI. MR images of virtual phantoms were generated using a stand-alone, independent unit. Thus, ViP MRI can be performed on MR scanners from different vendors.

Qiyue Li¹, Zhiwei Chen¹, Zhiping Yan², and Zhong Chen^1
1Department of Electronic Science, Xiamen University, Xiamen, Fujian, China, ²Chenggong Hospital Affiliated to Xiamen University, Xiamen, Fujian, China

Mobile devices are playing a more and more important role in daily life. However, there was no useful application on mobile devices to help NMR researchers handle their data. To meet the needs, a free iPad application, Touch NMR, designed for basic NMR data processing is introduced. The software system can process FID data of Agilent, Bruker and JEOL formats. It can accomplish basic NMR data operations: FFT, manual/automatic phase correction, automatic baseline correction, referencing, peak picking, integration and so on. Besides 1D data, DEPT spectra edit, T1/T2 fitting, and 2D spectrum with projections in the two dimensions can also be accomplished in Touch NMR. In addition, the application takes full advantage of multi-touch technology and gives users a better experience.

Sherman Xuegang Xin^1,2 and Christopher Michael Collins^1
1Bernard and Irene Schwartz Center for Biomedical Imaging, New York University School of Medicine, New York, NY, United States, ²Biomedical Engineering, Southern Medical University, Guangzhou, Guangdong, China

The inverse method in computational electromagnetic calculation has its particular advantage, that is, the source electromagnetic field can be specially designed from the targeted field, which can be designed exactly. However, it is difficult to directly use inverse method for the human body in the high-field MR environment, where the complicated coil-tissue interaction must be considered. A new methodology, i.e. hybrid inverse/FDTD method, which has not been reported previously to the best of the authors’ knowledge, was proposed here for goal-oriented RF source field design loaded with human body at high-field MRI.

Zhoujian Li¹, Georges Willoquet¹, Marie Poirier-Quinot¹, Luc Darrasse¹, and Jean-christophe Ginefri^1
1Imagerie par Résonance Magnétique Médicale et Multi-Modalités (IR4M), UMR8081 CNRS, Univ. Paris Sud, Orsay, France

An automation system based on a piezoelectric motor that offers high resolution displacement is developed to automatically tune and match miniature monolithic coils used in MR microscopy. Tuning is done by approaching a dielectric slice to shift down the resonant frequency and matching is achieved by inductive coupling to a pick-up loop. The piezo-motor is driven by a dedicated board, which communicates with control software for automation. The resolution achieved by the developed system allows automatic matching and tuning with respect to specified matching level and target frequency with configurable tolerance.

Wyger Brink¹ and Andrew Webb^1
1Radiology, Leiden University Medical Center, Leiden, Zuid-Holland, Netherlands

This work presents a numerical approach using an integral equations method to model the effect of a dielectric shim in the RF field. By including body loading effects explicitely into the Green's function, the problem complexity is reduced to the interactions within the dielectric shim.

Adnan Trakic¹, Limei Liu¹, Hector Sanchez Lopez¹, Luca Zilberti², Feng Liu¹, Ewald Weber¹, and Stuart Crozier^1
1The School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD, Australia, ²Divisione Elettromagnetismo, Istituto Nazionale di Ricerca Metrologica, Torino, Italy

This novel study evaluates the induced electric field and current densities due to the rotation of the patient in a static magnetic field produced by the split superconducting magnet of a realistic MRI-Linear Particle Accelerator (LINAC) system. It was found that rotating the patient in the radial orientation relative to the magnet gap with periods larger than about 15.3 seconds would not exceed the ICNIRP exposure limits. This new research provides useful insights into the safe use of the MRI-LINAC technology and optimal orientations of the patient during image-guided treatment.

Aleksandar Nacev¹, Edward Anashkin¹, Juan Pablo Rigla Perez², Jose Maria Benlloch Baviera², Mario Urdaneta¹, Azeem Sarwar¹, Pavel Stepanov¹, Irving Weinberg¹, and Stanley Thomas Fricke^3
1Weinberg Medical Physics, Bethesda, MD, United States, ²Institute for Instrumentation in Molecular Imaging (I3M), Valencia, Spain, ³Children's National Medical Center, Washington, DC, United States

An inexpensive MRI device that can image solid structures with short T2 times was developed by adding gradient coils, pulse sequences, and a GUI to a 0.34T commercial spectrometer. Gradient coils were created by hand winding or additive manufacturing. The 3D-printed coils produced a homogenous gradient and minimized acoustic noise. The GUI was created so that custom pulse sequences could be programmed, data gathered, and images reconstructed. Custom pulse sequences were encoded in C including: gradient echo pulse sequence; spin echo pulse sequences; and three dimensional volume acquisitions. Images were obtained under one second with 50 micron resolution.

Irena Zivkovic¹ and Klaus Scheffler^1,2
1High Field MRI, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, ²Center for Integrative Neuroscience, University of Tuebingen, Tuebingen, Germany

Many techniques have been developed to improve magnitude and homogeneity of B1+ field at high field MRI. In order to manipulate B1+ field, we have designed one cell metamaterial (MM) plate. When proposed material was placed between RF transmit coil and phantom, B1+ magnitude and homogeneity significantly improved. Measured results show over 100% increase of B1+ magnitude in specific area in the case when box monopole antenna was used as a transmitter. When small loop antenna was used as a transmitter, there was zero B1+ field without MM plate and significant B1+ when MM plate was inserted.

Yi-Cheng Hsu¹, Koos C. J. Zevenhoven², Ying-Hua Chu¹, Juhani Dabek², Risto J. Ilmoniemi², and Fa-Hsuan Lin^1,2
1National Taiwan University, Taipei, Taiwan, ²Department of Biomedical Engineering and Computa of Biomedical Engineering and Computational Science, Aalto University, Finland

We propose the rotating sample acquisition (RSA) to achieve efficient ultra-low-field MRI (ULF-MRI). Specifically, the sample rotates in the instrument and we measure ULF-MRI signals without any phase encoding. The concomitant field artifacts can be minimized because only frequency encoding is used. Using empirical data, we demonstrate that RSA is more efficient than conventional Fourier encoding when only three SQUID sensors are used. The RSA method holds promise for a portable imaging system using no phase encoding gradients and few NMR signal detectors.

Patrick Vogel^1,2, Steffen Lother^1,2, Martin A. Rückert¹, Walter H. Kullmann³, Peter M. Jakob^1,2, Florian Fidler², and Volker C. Behr^1
1Experimental Physics 5 (Biophysics), University of Würzburg, Würzburg, Bayern, Germany, ²Research Center for Magnetic Resonance Bavaria e.V., MRB, Würzburg, Bayern, Germany, ³Institute of Medical Engineering, University of Applied Sciences Würzburg-Schweinfurt, Schweinfurt, Bayern, Germany

This abstract describes the first setup of a bimodal Magnetic-Particle-Imaging/Magnetic-Resonance-Imaging tomograph and shows the first results.

Christopher Sica¹, Sebastian Rupprecht¹, Wei Luo², Jeff Vesek³, Raffi Sahul⁴, Seongtae Kwon⁴, Michael Lanagan², Dan Nguyen³, and Qing Yang^1
1Radiology, Penn State College of Medicine, Hershey, Pennsylvania, United States, ²Engineering Science and Mechanics, Penn State University, Pennsylvania, United States, ³Radiology, Hershey Medical Center, Hershey, Pennsylvania, United States, ⁴TRS Technologies, State College, Pennsylvania, United States

Previously, we explored the use of dielectric pads containing water and barium titanate beads to enhance imaging of the cervical spine. One drawback to that approach was the volume of dielectric required for enhancement. In this work, we quantify the performance of a ultra high dielectric constant (uHDC) package containing monolithic blocks of relative permittivity ~800. This package is reduced in volume relative to our previous configuration. SNR gains of 20 – 40% were observed on discs C1 – C4. Gains of about 10% were found on C5, and a slight loss on C6. Average reduction of system power was 64.18%.

Bing Wu¹, Qingyu Dai¹, Xuelian Lu¹, and Jiabin Yao^1
1GE healthcare, Beijing, Beijing Municipality, China

A rapid and robust method for determining the location of floating anterior coil array is proposed, hence allowing automatic selection of the proper coil element in real time scan. In vivo experiments have been proposed for verification. This method may be combined with standard system scout scan and adds little or no additional scan time.

Nelly A. Volland^1,2, J. Rock Hadley^1,2, Eugene G. Kholmovski^1,2, Nassir F. Marrouche², and Dennis L. Parker^1,2
1Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, United States, ²Comprehensive Arrhythmia Research & Management Center, University of Utah, Salt Lake City, Utah, United States

Purpose: A catheter-mounted expandable loop (CAMEL) balloon RF coil for cardiac applications was developed and evaluated. Methods: The coil inductive flexible loop was sandwiched between two balloons to protect the coil from fluids. The inner balloon was inflated with saline to expand the coil and reduce the susceptibility mismatch between the inner balloon volume and phantom solution. Results and conclusion: A balloon CAMEL coil prototype was successfully constructed. MR images were acquired at 3T in a saline phantom. The SNR with in the coil sensitive volume was over 20 times the SNR of the external coils currently commercially available.

Angelo Galante¹, Allegra Conti², Cinzia De Luca², Vittorio Pizzella³, Gian Luca Romani³, Raffaele Sinibaldi², Marcello Alecci⁴, Piero Sebastiani⁵, Antonello Sotgiu⁵, and Stefania Della Penna^3
1MESVA, Department of Life, Health & Environmental Sciences, L'Aquila University, L'Aquila, AQ, Italy, ²Department of Neuroscience and Imaging, University of Chieti, CH, Italy, ³Institute of Advanced Biomedical Technologies, University of Chieti, CH, Italy, ⁴MESVA, Department of Life, Health & Environmental Sciences, L'Aquila University, AQ, Italy, ⁵ITA S.r.l., AQ, Italy

Results from a new hybrid MEG-MRI system, working at 8.9mT without prepolariztion pulses, are presented. When scaled to a full size system, suitable for human imaging, they give indications that this approach allows faster imaging and better spatial resolution if compared to other existing devices based on SQUID parallel imaging in the kHz range and prepolarization pulses.

Teo Stanescu^1,2, Jason Marle³, Tony Tadic¹, Jeff Winter⁴, Michael Sweitzer³, and David Jaffray^1,2
1Radiation Physics, Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada, ²Radiation Oncology, University of Toronto, Toronto, Ontario, Canada, ³Varian Medical Systems, Palo Alto, CA, United States, ⁴IMRIS, Minnetonka, MN, United States

Numerical simulations and experiments were performed to quantify the magnetic field decoupling between sub-components (i.e. linear accelerator gantry, patient couch assembly and 1.5T MR) for an MR-guided linac system.

Yusuf A Bhagat¹, Po-Hsiang Lai¹, Xu Zhu¹, Insoo Kim¹, and Zhouyue Pi^1
1Emerging Technology Lab, Samsung R&D Institute America, Richardson, Texas, United States

This educational review draws attention to birdcage volume resonators as a simple alternative to phased-array receive coils for high-resolution microstructural imaging of the human wrist. The value of quadrature volume coils for transmit-receive (Tx-Rx) applications is better realized at ultra-high fields (7T) due to lack of body Tx coils. Here, by virtue of examples, we discuss the design of birdcage resonators for wrist imaging at 3T and 7T. Further, we highlight their utility for specific absorption rate-compliance, patient setup for improved tolerance and a rapid spin-echo based technique for high-quality imaging of trabecular (spongy) bone microstructure.

Sachiko Yamaguchi-Sekino¹, Yoshio Machida², Toshio Tsuchihashi³, Haruo Isoda⁴, Takeshi Noguchi⁵, and Toshiharu Nakai^6
1National Insitiute of Occupational Safety and Health, Japan, Kawasaki, Kanagawa, Japan, ²Tohoku University, Graduate School of Medicine, Miyagi, Japan,³Department of Radiology, Nippon Medical School Hospital, Tokyo, Japan, ⁴Nagoya University, Graduate School of Medicine, Aichi, Japan, ⁵National Institute for Material Science, Ibaraki, Japan, ⁶NeuroImaging & Informatics, National Center for Geriatrics and Gerontology, Aichi, Japan

In order to evaluate the potential risk to MR scanners and consider patient safety under large earthquakes, we have performed a survey study to investigate damages in MR scanners caused by Great East Japan Earthquake. It was confirmed that the extent of damage was significantly different between seismic scale (SS) 5 and SS over 6. Logistic regression analysis suggested that anchoring for MR facilities reduced the occurrence of quake-induced damages in MR scanners. And significant decrease in machine damages was observed in the group of base isolation structure for medical facilities compared with earthquake-proof structures.

Michael Martens¹, Tanvir Baig¹, Zhen Yao¹, Charles Poole¹, Robert Deissler¹, Robert Brown¹, David Doll², and Michael Tomsic^2
1Department of Physics, Case Western Reserve University, Cleveland, Ohio, United States, ²Hyper Tech Research Inc., Columbus, Ohio, United States

A 7T conduction-cooled MRI whole-body magnet design using Nb3Sn superconductor is found for a current density of 179.95 A/mm2, a maximum peak field on a bundle of 11.59T, and operating at 8K. The high current density on wire allowed by the larger peak field helps to reduce the superconductor volume in comparison with high field NbTi magnet designs. Although the present manufacturing cost of Nb3Sn is higher than NbTi, the wire volume reduction and the 99% decrease in liquid helium usage may make Nb3Sn conduction cooled magnets a viable alternative for ultra-high field magnet systems.

Shin-ichi Urayama¹, Yasuyuki Terao², Osamu Ozaki², Hitoshi Kitaguchi³, Shinya Kawashima², Takashi Hase², Ken-ichi Sato⁴, and Hidenao Fukuyama^1
1Human Brain Research Center, Kyoto University, Kyoto, Kyoto, Japan, ²Kobe Steel, Ltd., Kobe, Japan, ³National Institute for Materials Science, Ibaraki, Japan, ⁴Sumitomo Electric Industries, Ltd., Osaka, Japan

Because of recent deficit of liquid helium, helium-free MRI magnets with high temperature superconducting (HTS) materials have been expected as one of the solutions. We have developed a 3T HTS-MRI system for human brain research with Bi-2223 tapes and showed its feasibilities at 1.5T. However, in spite that we succeeded energizing to 3T three times, sequencial abnormal events were happened for longer than ten minutes during the ramp-down at the third trial to 3T. Here, we show these unique events specific to HTS magnets.

Longzhi Jiang¹, Yihe Hua², Liya Ma³, Sung Moon¹, Jun Li², Kishore Mogatadakala¹, and Tim Havens^1
1Global MRI, GE Healthcare, Florence, SC, United States, ²GE Global Research, Shanghai, China, ³GE Healthcare, Beijing, China

The dynamic coupling between gradient coil and magnet has generated image quality issues at low frequencies and limited operational duty cycle at medium and high frequencies due to induced magnet Joule heating. With the combined demand for high patient through-put and high performance gradient coils in high field MRI systems, numerous researchers have attempted to develop both improved simulation capability and experimental apparatus to understand the Joule heating induced helium boil-off. However, to the authors’ best knowledge, the effects of dynamic coupling induced Joule heating is not yet fully understood. In this study, a novel experimental apparatus was devised to understand gradient coil induced magnet heating under different gradient coil mounting conditions. The apparatus included a whole body magnet with hermetically sealed cooling system having very limited helium volume and a gradient coil with minimum interaction. This paper demonstrates consistent correlation between the full mechanical-electro-magnetic coupling model and the experimental results. Furthermore, 100% operational duty cycle has been achieved for clinical protocols.

Joshua D. Trzasko¹, Shengzhen Tao¹, Yunhong Shu¹, Armando Manduca¹, and Matt A. Bernstein^1
1Mayo Clinic, Rochester, MN, United States

The gradient fields used for spatial encoding in clinical MRI are never truly linear over the imaging FOV. As standard MRI signal models presume gradient linearity, reconstructed images exhibit geometric distortion unless gradient deviations are properly accounted for. Geometric distortion is typically corrected via image-domain interpolation. Although this approach is straightforward, it does not account for the effects of finite sampling, undersampling, or noise, and may degrade spatial resolution. In this work, we propose a correction strategy that accounts for gradient nonlinearity during – rather than after – k-space to image reconstruction, and lessens the tradeoff between geometric accuracy and spatial resolution.

Gerald B Matson^1,2 and Hui Liu^1
1Center for Imaging of Neurodegenerative Diseases, Department of Veterans Affairs, San Francisco, California, United States, ²Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, California, United States

The imperfect fidelity of MRI gradient systems results in altered k-space trajectories, which can result in image degradation. Under the assumption that the gradient system is linear and time invariant, accurate measurement of the MRI gradient impulse response function (GIRF) can be used to predict the actual output gradient waveform as opposed to the requested waveform. In this study we demonstrate a simple sample and coil arrangement can be used to obtain GIRFs of high precision that can accurately predict gradient output waveforms. This capability could potentially be used to predict actual k-space trajectories for improved fidelity of image reconstruction.

Trong-Kha Truong¹, Dean Darnell¹, and Allen W Song^1
1Brain Imaging and Analysis Center, Duke University, Durham, NC, United States

Multi-coil shimming with localized shim coils can effectively shim high-order B₀ inhomogeneities, but requires an additional shim coil array outside or inside the RF coil, which compromises the shimming performance and/or SNR. To address these limitations, we recently proposed a new concept that enables parallel RF excitation/reception and B₀/B₁ shimming with a single coil array, thus maximizing both the SNR and shimming performance, and demonstrated its feasibility in phantom experiments. Here, we further validate it in vivo by demonstrating its ability to perform parallel reception and localized B₀ shimming in the human brain at 3T, specifically for distortion correction in DTI.

Fangfang Tang¹, Hector Sanchez Lopez¹, Fabio Freschi², Feng Liu¹, Yu Li¹, and Stuart Crozier^1
1School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, Queensland, Australia, ²Politecnico di Torino Corso Duca Degli Abruzzi, Department of Energy, Torino, Italy

In order to study the influence on gradient coils of different track widths and frequencies, 30 split and shielded, whole-body x-gradient coils were designed. The track width was set from 1mm to 30mm with an increment of 1mm. The 30 designed split x-gradient coils were analyzed to study the interaction between the coils and the metallic surroundings, which took into account the skin and proximity effects. This study provides very valuable information which will guide coil engineers to choose the optimal wire track on regards the MRI coil applications.

Trevor Paul Wade^1,2, Andrew Alejski¹, Janos Bartha¹, Dina Tsarapkina¹, R. Scott Hinks³, Graeme C. McKinnon³, Brian K. Rutt⁴, and Charles A. McKenzie^2
1Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada, ²Medical Biophysics, The University of Western Ontario, London, Ontario, Canada, ³GE Healthcare, Waukesha, WI, United States, ⁴Radiology, Stanford University, Stanford, CA, United States

A symmetric, folded gradient, was designed for human brain imaging, with a target gradient strength of 80 mT/m and slew rate of 2900 mT/m/s. This design should limit forces and torques leading to a quieter coil with better eddy-current performance. The ultra-short design allows for human brain imaging without the need for shoulder cut-outs. The insertable coil was built using litz wire for transverse axes and hollow copper for Z to facilitate cooling. It was successfully interfaced with a clinical scanner and its electrical and imaging performance was characterised.

Simone Angela Winkler¹, Andrew Alejski², Trevor Wade², Charles McKenzie², and Brian K Rutt^1
1Dept of Radiology, Stanford University, Stanford, California, United States, ²Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada

We present a new wave-based framework for understanding acoustic noise in MR gradient coils, and propose two new concepts for acoustic noise reduction. Results of this wave-based coupled structural-acoustic modeling, as well as experimental measurements, demonstrate that the addition of an impedance matching “horn” and an absorbing end cap both act to decrease acoustic noise inside the gradient coil. Simulation results show mean sound pressure level reductions of 2 dB for horn and end cap, and 3 dB for both used in combination. Experimental results show mean SPL reductions of 4 dB for horn and 9 dB for end cap.

Hongpyo Lee¹, Sung-Min Gho¹, Eunhae Joe¹, Joonsung Lee^2,3, and Dong-Hyun Kim^1
1Electrical and Electronic Engineering, Yonsei University, Sin-chon dong, Seoul, Korea, ²Nanomedical Research Center, Yonsei University, Sin-chon dong, Seoul, Korea, ³SIRIC, Yonsei University, Sin-chon dong, Seoul, Korea

In this abstract, we introduce an in vivo volumetric shim strategy which can be performed in a very short time using an intermediate space conversion idea. Linear shimming and high-order shimming approaches are presented.

Hector Sanchez-Lopez¹, Fangfang Tang¹, and Stuart Crozier^1
1School of Information Technology & electrical Engineering, The University of Queensland, Brisbane, QLD, Australia

This study aims to present a robust guideline to design a 500 mm transversal and 620 mm axial gap split x-gradient coil to be installed in a hybrid Linac-MRI scanner. The target torque (force) was varied from 0 to 15 Nm (15N) while the changes on slew rate, achieved net torque (force), peak current density, average power loss in the coil and cryostat and stored magnetic energy were observed. We found a nearly zero torque (force) coil capable to produce more than 200 T/m/s, and 33 µT/mA.

Hector Sanchez-Lopez¹, Fangfang Tang¹, and Stuart Crozier^1
1School of Information Technology & electrical Engineering, The University of Queensland, Brisbane, QLD, Australia

This study aims to present a robust guideline to design a 500 mm transversal and 620 mm axial gap split x-gradient coil to be installed in a hybrid Linac-MRI scanner. The methodology is divided in two parts: selection of the optimal shielding strategy (this work) and torque/force balancing. Four shielding approaches are studied in order to determine the most suitable for torque balancing and high coil performance. We found that coils designed using the minimizations of the magnetic energy in the whole system are the most suitable for torque/force balancing, optimal pre-emphasis, high slew rate and lower power loss.

Peter T. While¹, Markus V. Meissner¹, and Jan G. Korvink^1,2
1Department of Microsystems Engineering (IMTEK), Laboratory for Simulation, University of Freiburg, Freiburg im Breisgau, Baden-Württemberg, Germany,²Freiburg Institute for Advanced Studies (FRIAS), University of Freiburg, Freiburg im Breisgau, Baden-Württemberg, Germany

High-resolution NMR microscopy demands strong gradient fields. Power dissipation in micro-gradient coils is a primary concern and must be controlled carefully to avoid over-heating the system or the sample and to maximize the duty cycle. In this work, a recently reported method for designing minimum power gradient coils that accounts for the subsequent means of fabrication is applied to the design of a 3-axis biplanar micro-gradient system. A survey of results is presented, comparing coils designed for x-, y- and z-gradients, using both the standard and the new approach, and contrasting the merits of building using tracks or wires.

Michael Stephen Poole¹, Clemente Cobos Sanchez², and N Jon Shah^1,3
1INM-4, Forschungszentrum Jülich, Jülich, Germany, ²Ingeniería en Automática, Electrónica, Arquitectura y Redes de Computadores, Universidad de Cádiz, Cadiz, Spain, ³Department of Neurology, RWTH Aachen, Aachen, Germany

In this work we describe a method by which the temperature of gradient coils, designed with arbitrary geometry using the inverse boundary element method, can be simulated. The method requires tuning of the thermal parameters of the coil and its support. This simulation method should aid the coil design process by allowing the thermal performance of multiple coil designs to be estimated without construction.

Rahul Dewal¹, Zhipeng Cao², Sebastian Rupprecht³, and Qing X. Yang^1,3
1Bioengineering, Penn State College of Medicine, Hershey, PA, United States, ²Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States, ³Radiology, Penn State College of Medicine, Hershey, PA, United States

The B₀ field inhomogeneity artifacts near the air-tissue interfaces in animal and human brains at high field are difficult to remove with standard active shim coils as the associated gradients are high-order and highly localized. Several passive and localized active shimming methods have been proposed to deal with this problem but have high calibration or hardware requirements. Here, a synergistic shimming system that simultaneously optimizes the linear active shim coil settings and passive shim element configuration is demonstrated via application to an in vivo mouse brain. This synergistic shimming approach is expected to be extensible to high-field human MRI systems.

Gerrit Schultz¹, Feng Jia¹, and Maxim Zaitsev^1
1Dept. of Radiology - Medical Physics, University Medical Center Freiburg, Freiburg, Germany

Cylindrical gradient coils are typically designed on three different layers having different radii. As a consequence, the x- and y- gradients or, in case a magic angle gradient system is constructed, all three gradient coils may be designed to be similar, but they are not identical. Identical designs are desirable to further reduce the differences of the coil properties such as switching speed or maximum gradient strength. MR acquisitions would potentially profit from such an approach, and, with identical designs, also the optimization and fabrication of gradient systems may be facilitated. In this abstract, gradient system designs are proposed that consist of such identical gradient coils.

Elliot Charles Smith¹, Hector Sanchez Lopez¹, Michael Poole², and Stuart Crozier^1
1ITEE, The University of Queensland, Brisbane, Queensland, Australia, ²Institute of Neuroscience and Medicine, Jülich, Jülich, Germany

In this work we validated the feasibility of design and analysis of a coil which excites only certain eigenmodes in a surrounding structure. The work validated previous theoretical results.

Yu-Chun Chang^1,2, Martin Eschelbach¹, Nikolai Avdievitch¹, Klaus Scheffler¹, and Anke Henning^1,3
1Max Planck Institute of Biological Cybernetics, Tuebingen, Baden-Wuerttemburg, Germany, ²Graduate School of Neural & Behavioural Sciences, University of Tuebingen, Tuebingen, Baden-Wuerttemburg, Germany, ³Institute for Biomedical Engineering, University and ETH Zurich, Switzerland

A method for characterising a gradient system is introduced. This is a parametric method and thus the system has an analytic form. It is fast and requires only one measurement in each gradient direction and can thus be completed in minutes. It can also be extended to characterise the shim system. Monitoring the B0 field is done using a 16 channel field camera. The predicted model is compared to measured data.

Shengzhen Tao¹, Joshua D. Trzasko¹, Jeffrey L. Gunter¹, Seung-Kyun Lee², Ek T. Tan², Yunhong Shu¹, Kaely B. Thostenson¹, and Matt A. Bernstein^1
1Mayo Clinic, Rochester, MN, United States, ²GE Global Research, Niskayuna, NY, United States

Standard strategies to correct image distortion due to gradient non-linearity are based on a parameterization of the gradient field. The correction coefficients are predetermined and the same set of coefficients is applied to all systems in the field. In this work, we develop a simple method to measure and fit the gradient correction on a per-system basis using the Alzheimer’s Disease Neuroimaging Initiative phantom. A 3D spherical harmonic approximation of the distortion is determined and used for correction. The proposed method does not require detailed knowledge of gradient system and can be used in a variety of settings.

Derek A. Seeber¹, Kevin Koch², and Dirk Beque^3
1GE Healthcare, Florence, SC, United States, ²Applied Science Lab, Milwaukee, WI, United States, ³GE Reseach, Munich, Germany

A 27 cm diameter phantom was placed inside a 3T system consisting of a gradient coil with a 24 channel matrix shim array in a 6x4 array and was used to shim the phantom. The phantom studies demonstrate a 3 times reduction in frequency spread as compared with gradient only shimming across the entire phantom. Slice by slice shimming is shown to further reduce the frequency spread by an additional factor of 2 over a global shim. The low induced gradient voltages in the shim coils and fast switching times demonstrate a potential for dynamic shimming in the future.

Anna-Katinka Bracher¹, Erich Hell², Johannes Ulrici², and Volker Rasche^1
1Internal Medicine II, University Hospital of Ulm, Ulm, BW, Germany, ²Sirona Dental Systems, HE, Germany

Center-Out imaging sequences like UTE are very sensitive to trajectory imprecision in waveform and to k-space shift due to system delays. In this article an automatic delay correction method is introduced to determinate the delays by direct measurement of the echo peak shift. Therefore a conventional UTE imaging sequence is combined with an additional pre-phasing gradient to shift k-space center along the rising slope of the readout gradient. Furthermore the signal acquisition is started in front of k-space origin to acquire a partial echo for echo peak detection.