Xinqiang Yan^1,2 and Xiaoliang Zhang^3
1Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States, ²Radiology, Vanderbilt University, Nashville, TN, United States, ³Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, United States

In this study, we investigate the feasibility of using regular microstrip resonators as RF array elements for traveling wave parallel imaging. In the proposed microstrip array, electromagnetic decoupling between the array elements is sufficient for the practical use. Additionally, geometric factors and diverse B1 fields from individual array elements can be obtained in a relatively large area in the magnet bore. Furthermore, in non-accelerated imaging applications, this decoupled multi-channel traveling wave method could improve sensitivity of traveling wave MRI, which is currently a main issue for traveling wave MRI.

Jérémie Daniel Clément¹, Arthur Magill², Hongxia Lei³, Özlem Ipek³, and Rolf Gruetter^4,5,6
1CIBM-LIFMET, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, ²Forschungszentrum Jülich, Jülich, Germany, ³CIBM-AIT, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, ⁴LIFMET, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, ⁵Department of Radiology, University of Geneva, Geneva, Switzerland, ⁶Department of Radiology, University of Lausanne, Lausanne, Switzerland

The purpose of the study was to build a slotted-tube resonator for whole-body MR imaging at 14T. Flip angle maps were computed to assess the transmit field distribution in a phantom. A longitudinal coverage of 8 cm and flip angle homogeneity are observed and spin-echo images were acquired.

Arthur W. Magill¹, Chang-Hoon Choi¹, Yonghyun Ha¹, and N. Jon Shah^1,2
1Institute of Neuroscience and Medicine - 4, Forschungszentrum Juelich GmbH, Juelich, Germany, ²Department of Neurology, JARA, RWTH Aachen University, Aachen, Germany

Traps may be used to dual-tune an RF probe, either by splitting the resonance of a single tuned circuit, or by blocking coupling at the higher frequency when using a pair of resonant circuits. This work combines both methods to construct a triple-tuned probe consisting of a nested pair of loops. The inner loop incorporates two traps, one to prevent coupling to the outer loop, which is tuned to ¹H, and a second to simultaneously tune the loop to ²³Na and ³¹P. The probe is designed for use at 4T, with resonances at 45MHz (²³Na), 69MHz (³¹P) and 170MHz (¹H).

Steffen Ringgaard¹, Rolf F Schulte², James Tropp³, Carsten Kögler⁴, Titus Lanz⁴, Miguel A Navarro⁵, Jan Henrik Ardenkjaer-Larsen^6,7, Fraser J Robb⁵, Hans Stødkilde-Jørgensen¹, and Christoffer Laustsen^1
1MR Research Centre, Aarhus University, Aarhus, Denmark, ²GE Global Research, Munich, Germany, ³GE Healthcare, Fremont, CA, United States, ⁴Rapid Biomedical, Rimpar, Germany, ⁵GE Healthcare, Cleveland, OH, United States, ⁶GE Healthcare, Copenhagen, Denmark, ⁷DTU, Copenhagen, Denmark

We have developed and validated a dedicated coil system for human and large animal hyperpolarised 13C measurements. The system consists of an outer two-element transmit coil and an inner 16-element receive coil. It was validated by hyperpolarised experiments in two healthy pigs using a multi-echo spiral CSI sequence. The 13C metabolic images showed good SNR and there was low noise correlation between the receive elements. Hence, the coil system is promising for future human hyperpolarised examinations.

Andreas Pfrommer¹, Nikolai I Avdievich¹, and Anke Henning^1,2
1Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, ²Institute for Biomedical Engineering, UZH and ETH Zurich, Zurich, Switzerland

In this study we investigated the effect of an RF shield on the mutual coupling between adjacent and non-adjacent array elements in a simple model mimicking our previously developed cylindrical eight channel transceiver head array. Both numerical EM simulations and experimental measurements suggest that at 124 MHz and 400 MHz an RF shield can substantially decrease S₁₂ for non-adjacent-array elements.

Xinqiang Yan^1,2 and William A. Grissom^1,2,3
1Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States, ²Radiology, Vanderbilt University, Nashville, TN, United States, ³Biomedical Engineering, Vanderbilt University, Nashville, TN, United States

Radiative dipole and monopole coil arrays are increasingly used for ultrahigh ?eld MRI, but few decoupling methods have been proposed for radiative arrays. To overcome this problem, we propose a Tunable-Defected-Ground-Structure (TDGS) method to decouple monopole arrays at 7T. This concept was successfully validated by EM simulation, bench test and MR experiments. By using the TDGS method, the cross-talk between two closely-spaced monopoles was reduced from -7 dB to -25 dB. It was also found that the TDGS method had little effect on the original B₁ fields of the individual monopole elements.

Xueming Cao¹, Elmar Fischer¹, Oliver Gruschke², Jan Korvink², Jürgen Hennig¹, and Maxim Zaitsev^1
1University Medical Center Freiburg, Freiburg, Germany, ²Karlsruher Institut für Technologie, Karlsruher, Germany

In receiver coil arrays, the most commonly used decoupling methods are overlap together with low-input-impedance preamplifiers. But very small receiver coils can not be decoupled effectively with these two methods. A new decoupling method, which is helpful for receiver coil arrays with very small coils, is developed here. The coil arrays decoupled with this method have less noise correlation and better performance in highly accelerated imaging in the sample periphery.

Bart Steensma¹, Dennis Klomp¹, Nico van den Berg¹, Peter Luijten¹, Abe van der Werf², and Alexander Raaijmakers^1
1University Medical Centre Utrecht, Utrecht, Netherlands, ²Machnet B.V., Maarn, Netherlands

The forward view antenna has been introduced as a novel antenna for ultrahigh field imaging. This study has investigated its potential for prostate imaging where the antenna is placed between the legs, to contribute as an additional element of an existing dipole antenna transceiver array.  A significant increase in signal-to-noise ratio is expected because of the generally smaller distance towards the prostate from this side. Numerical simulations and in vivo scans show that signal-to-noise ratio in the prostate region increases as a result of adding the forward view antenna to the dipole antenna array. 

Pranav S. Athalye¹, Milan M. Ilic^1,2, Pierre-Francois Van de Moortele³, Andrew J. M. Kiruluta⁴, and Branislav M. Notaros^1
1Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, CO, United States, ²School of Electrical Engineering, University of Belgrade, Belgrade, Yugoslavia, ³Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States, ⁴Radiology Department, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States

RF coil design for human ultra-high-field scanners is an area of intense development, to address difficult challenges including RF excitation spatial heterogeneity and low RF efficiency. We present the development and testing of a novel category of multi-channel RF volume coil structures at both 7T and 10.5T based on a subject-loaded multifilar helical-antenna RF coil. Phantom data show excellent consistency between numerical simulations and experimental results with 4- and 8-channel helical-antenna coil prototypes. This design shows capability for multi-channel RF-transmit technology and parallel imaging. This work may help decide which coil structure should be used for future studies at 10.5T.

Markus Weiger¹, David Otto Brunner¹, Thomas Schmid¹, Romain Froidevaux¹, Manuela Barbara Rösler¹, Simon Gross¹, and Klaas Paul Pruessmann^1
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

MRI of tissues with very short T2s below 1 ms, such as bone, lung, or myelin is usually performed with 3D radial sequences with ultra-short or even zero TE. However, with these techniques also signals from hardware parts are detected, in particular from the RF coils. Especially the ZTE method is highly sensitive also to materials with extremely short T2 of tens of us. In this work, it is demonstrated how the undesired signal is avoided during coil design and production, presenting for the first time a birdcage coil which is virtually free of proton signal.

Zhipeng Cao^1,2, Xinqiang Yan^1,3, and William A. Grissom^1,2,3
1Vanderbilt University Institue of Imaging Science, Vanderbilt University, Nashville, TN, United States, ²Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, ³Radiology, Vanderbilt University, Nashville, TN, United States

With a constructed 8 channel transmit array and a tunable 2 channel-to-8 coil compression matrix, the array-compressed parallel transmit pulse design is demonstrated on 7T MRI through B1+ mapping and accelerated spiral excitation. Results showed more accurate excitation pattern can be achieved with the compression matrix hardware and compressed parallel transmit pulses than two-channel CP-mode pulses.

Zhipeng Cao^1,2, Xinqiang Yan^1,3, and William A. Grissom^1,2,3
1Vanderbilt University Insitute of Imaging Science, Vanderbilt University, Nashville, TN, United States, ²Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, ³Radiology, Vanderbilt University, Nashville, TN, United States

An improved array-compressed parallel transmit pulse design is proposed and validated to optimally connect transmit arrays with a large number of elements to a few transmit channels. It is further demonstrated to achieve better performance with array-compressed coil designs than conventional designs for multiband RF shimming for human brain imaging and 3D spatially selective excitation for human occipital lobe imaging.

Tsinghua Zheng¹, Matthew Finnerty¹, Xiaoyu Yang¹, Matthew Diprimio¹, Luke Beery¹, Paul Taylor¹, Johanna Vannesjo², Stuart Clare², and Hiroyuki Fujita^1,3,4,5
1Quality Electrodynamics, LLC, Mayfield Village, OH, United States, ²FMRIB Centre, Oxford University, Oxford, United Kingdom, ³Physics, Case Western Reserve University, Cleveland, OH, United States, ⁴Radiology, University Hospital of Cleveland, Cleveland, OH, United States, ⁵5School of Information and Electrical Engineering, the University of Queensland, Brisbane, Australia

A cervical spine array coil with a volume transmit coil for 7.0 Tesla was constructed and tested. The coil uses one partially shielded birdcage volume transmit coil for generating uniform excitation throughout the cervical spine region and an array of sixteen loop coils for receiving. Initial volunteer imaging demonstrated good coverage and uniformity along cervical spine.

Aidin Ali Haghnejad¹, Shaihan J. Malik², Francesco Padormo², Cornelis A.T. van den Berg¹, Peter R. Luijten¹, Dennis W.J. Klomp¹, Joseph V. Hajnal ², and Alexander J.E. Raaijmakers^1
1UMC Utrecht, Utrecht, Netherlands, ²King's College London, London, United Kingdom

The birdcage body coil at 3T has some considerable disadvantages. Most of all it has very large power requirements. The use of local transmit arrays severely reduces these power requirements. In this study, we intend to explore the use of dipole antennas as transceive surface array elements at 3T. Three designs are investigated after which a strongly meandering dipole antenna is selected. An array of eight of these element is used for prostate imaging at 3T in a 8ch. multi-transmit MRI system. Using 8x200W input power, 12 µT is achieved inside the prostate. Relatively homogeneous T2w images have been acquired

Xinqiang Yan^1,2, John C. Gore^1,2,3, and William A. Grissom^1,2,3
1Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States, ²Radiology, Vanderbilt University, Nashville, TN, United States, ³Biomedical Engineering, Vanderbilt University, Nashville, TN, United States

Dipole and microstrip coils produce different and somewhat complementary B1 patterns and hybrid E-field distributions. Based this observation, we developed a 16-channel transmit/receive array for 7T head imaging by interleaving dipole and microstrip elements. Mutual coupling among any elements is <-14 dB without including any other decoupling. Compared with 8-channel microstrip-only and dipole-only arrays, the proposed 16-ch dipole+microstrip array has a higher SNR gain and lower g-factor. No decoupling treatment is needed for the mixed dipole and microstrip array, so it can be used as a flexible transceiver array at ultrahigh field.

Matthew Finnerty¹, Derick Petrey¹, Paul Taylor¹, Luke Beery¹, Tsinghua Zheng¹, Xiaoyu Yang¹, Hiroyuki Fujita^1,2,3,4, Se-Hong Oh⁵, Ken Sakaie⁵, and Mark Lowe^5
1Quality Electrodynamics, LLC, Mayfield Village, OH, United States, ²Department of Physics, Case Western Reserve University, Cleveland, OH, United States, ³Department of Radiology, University Hospitals of Cleveland, Cleveland, OH, United States, ⁴School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, Australia, ⁵Imaging Institute, Cleveland Clinic, Cleveland, OH, United States

While fMRI at 7-Tesla can provide clinically relevant increases in functional sensitivity over 3-Tesla, it also typically uses visual and audio stimulation devices that require additional space accommodations inside the RF coil.  In order to accommodate a wider range of stimulus devices than possible with high filling factor designs, a head array coil utilizing a volume transmitter and 32 receive elements for 7-Tesla was constructed inside a versatile mechanical package to support fMRI and other applications.

Stefan HG Rietsch^1,2, Oliver Kraff¹, Stephan Orzada¹, Andrea Lazik³, and Harald H Quick^1,2
1Erwin L. Hahn Institute for MR Imaging, University of Duisburg-Essen, Essen, Germany, ²High Field and Hybrid MR Imaging, University Hospital Essen, Essen, Germany, ³Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany

MRI at 7T and above opens the field for high resolution human imaging for example in the shoulder. In order to improve a present setup consisting of an 8ch Tx/Rx shoulder coil using microstrip line elements with meanders, we present an additional low cost 7ch Rx loop coil and utilize a simple approach for detuning of this coil during transmit via a custom built 8ch Tx/Rx switchbox. With the additional 7ch Rx coil a factor of 2 in SNR can be achieved in the center of the humeral head in proton-density weighted images with a spatial resolution of 0.4x0.4x2.5 mm³.

Ian RO Connell^1,2 and Ravi S Menon^1,2
1Centre for Functional and Metabolic Mapping, Robarts Research Institute, London, ON, Canada, ²Department of Medical Biophysics, University of Western Ontario, London, ON, Canada

At ultra-high field (UHF), multi-channel radio-frequency (RF) arrays have found increasing utility in mitigating wave-like behaviour during transmission (1), while continuing to provide increases in sensitivity to MRI signal with densely filled conformal receive arrays (2).  In an effort to more efficiently excite spin populations, and increase sensitivity to the transverse magnetization during relaxation, work into mixing array elements of dissimilar radiation pattern has been demonstrated to better encapsulate UHF ideal current patterns (3). Application of our method - coupling matrix synthesis - is used to robustly decouple a sample of these array-types.

Jan Paska^1,2, Martijn Cloos^1,2, Gillian Haemer^1,2,3, Bei Zhang^1,2, and Graham C Wiggins^1
1Center for Biomedical Imaging, Department of Radiology, NYU School of Medicine, Newyork, NY, United States, ²Center for Advanced Imaging Innovation and Research (CAI2R), NYU School of Medicine, Newyork, NY, United States, ³The Sackler Institute of Graduate Biomedical Sciences, NYU School of Medicine, Newyork, NY, United States

A body array at 7T was optimized in simulation for potential hybrid elements, including dipoles, loops, and birdcage arrays. The optimal coil, consisting of 8 transmit/receive dipoles and an 8ch birdcage receive coil, was built and tested as proof of principle.

Riccardo Stara^1,2,3, Fabio Morsani², Gianluigi Tiberi^4,5, Maria Evelina Fantacci^2,3, Massimo Marletta⁶, Virna Zampa⁶, Brian Rutt¹, Alessandra Retico², and Michela Tosetti^5
1Stanford University, Stanford, CA, United States, ²Istituto Nazionale di Fisica Nucleare (Pisa), Pisa, Italy, ³Dipartimento di Fisica, Universita' di Pisa, Pisa, Italy, ⁴IMAGO7, Pisa, Italy, ⁵IRCCS Stella maris, Calambrone (Pisa), Italy, ⁶Dipartimento di radiologia diagnostica ed interventistica AOU, Pisa, Italy

The degenerate birdcage is not a common design for ultra-high field transmit array due to the technical difficulties in its construction, such as the interdependence of tuning and degeneracy on the value of capacitors. We present here a combination of an analytical theory, circuit simulations and numerical simulations to be used for an efficient design and construction of the degenerate birdcage at 7T. We demonstrate satisfactory performance in terms of decoupling, B₁⁺ homogeneity and B₁⁺ efficiency on the workbench and with scanner measurements on phantoms and human volunteers.

Jiaqi Li¹, Masahiro Fujimoto¹, Amy Sue Meyers¹, Qiong Zhang², and Huaiyu Dong^2
1GE Healthcare, Waukesha, WI, United States, ²GE Healthcare, Beijing, China, People's Republic of

An optimized MRI RF coil for integration with in-bore therapy or biopsy system is discussed. The RF coil is optimally designed into an open Ω shape to allow a much bigger room for therapy or biopsy system. Horizontal rails as well as coil support brackets are integrated with body coil. Such that, the in-bore treatment system can have bigger space and more power. The optimized design also separated HIFU or SWL sub-assembly from high voltage RF parts, which reduces EMI between those two, and safety issue due to liquid leakage from HIFU or SWL sub-assembly is also greatly reduced.

mohammad mohammadzadeh^1,2 and alireza ghasempour Shirazi^1
1ICT, University of applied science and technology, Tehran, Iran, ²Shahid Beheshti, Tehran, Iran

Monopole coil has a thin and flexible structure provides high-resolution MR images from the internal vessels such as aorta and coronary arteries. However, its SNR homogeneity decreases at higher Tesla MRI systems, leading to increasing the image artifact caused by the wall movement which is not fully compensated using the post processing algorithms. In this study, we introduced a monopole coil with tree parasitic elements and compared its ISNR (Intrinsic SNR) magnitude and distribution homogeneity to a conventional monopole coil with one parasitic element for MRI 1.5 T at 64MHz . We optimized the coil geometry using a fast genetic algorithm written in MATLAB and performed the simulation of the ISNR indices by Involving HFSS and MATLAB inside a saline phantom.

Mohammad Mohammadzadeh^1,2 and Mohammad Mohammadi^2
1ICT, University of Applied Science and Technology, Tehran, Iran, ²Nuclear Engineering, Shahid Beheshti, Tehran, Iran

MR micro coils provide high SNR images of the mass limited samples. To increase the coil sensitivity and then the image SNR, microcoils geometries are adapted to the sample dimension. However, differences between magnetic susceptibility of the coil conductor and its surrounding materials distorts the B0 magnetic fields homogeneity across the sample. In this study, we measured 2D  maps of a solenoid of 1mm diameter and compared them with the simulated results at 9.4 T. Considering the good agreement of the computed and measured maps, effects of the shimming and susceptibility matching processes were assessed in removing the B0 fields inhomogeneities. Simulated results verify that shimming coils are not able to fully cancel the B0 field inhemogenities but embedding the micro coils in susceptible materials will remove the B0 inhomogeneity completely.

Tracy Wynn¹, Olli Friman¹, and Randy Duensing^1
1Technology Architecture, Philips/Invivo, Gainesville, FL, United States

Bore size increases can contribute to decreased efficiency of transmit body coils, but modern protocols often increase the requirements for B₁ power. This paper describes a novel solution for concentrating B₁ power without the use of a traditional local transmit coil, based on the observation that roughly half of the transmit field from a traditional birdcage coil comes from the end rings. A dual-ring structure, modeled on a birdcage without rungs, was built and shown to enable head imaging with up to a 30% reduction in required RF input power. Uniformity was maintained.

Myung Kyun Woo¹, Chang-Ki Kang², and Zang-Hee Cho^3
1Electrical and Computer Engineering, Seoul National University, Seoul, Korea, Republic of, ²Neuroscience Research Institute, Incheon, Korea, Republic of, ³Seoul National University, Seoul, Korea, Republic of

This abstract is to propose and evaluate the Spiral Extended Monopole antenna Array with individual Shield (SEMAS) coil. This coil was compared with the original Monopole antenna Array (MA) coil and an Spiral Monopole antenna Array coil with no shield (SMA) coil. The SEMAS coil showed larger flip angle than the MA and SMA coils in the inferior areas of the brain and relatively uniform flip angles across the brain.

Joseph Corea¹, Balthazar P. Lechene¹, Thomas Grafendorfer², Fraser Robb³, Ana Claudia Arias¹, and Michael Lustig^1
1UC Berkeley, Berkeley, CA, United States, ²GE Healthcare, Stanford, CA, United States, ³GE Healthcare, Aurora, OH, United States

Extremely thin, lightweight, and flexible receive arrays can be achieved by the use of printed electronics. Coil arrays printed layer-by-layer from solution have shown potential to deliver a comfortable customized fit for many patients. However, relatively low SNR and poor mechanical robustness prevented these devices from performing to their full potential. Here we offer SNR within 3% of a traditionally made coil by using high quality polymeric films as dielectric layers in capacitors, high conductivity inks, and a mechanically robust fabrication processes using fewer printed layers and stronger connections. Using these techniques shoulder and elbow images of a volunteer were obtained. 

Stefan HG Rietsch^1,2, Stephan Orzada¹, and Harald H Quick^1,2
1Erwin L. Hahn Institute for MR Imaging, University of Duisburg-Essen, Essen, Germany, ²High Field and Hybrid MR Imaging, University Hospital Essen, Essen, Germany

In order to allow for improved SNR and higher acceleration during image acquisition in the body at 7T, we present a coil with 8Tx/Rx microstrip line elements with meanders and 24Rx loop elements. This coil comprises 8 building blocks each consisting of one Tx/Rx element and 3 overlapping loops which are actively detuned during transmit. With about -19 dB reflection and an average decoupling of more than -30 dB, the SNR can be boosted by about 21% in the abdomen. Evaluation of g-factors as well as in vivo images of healthy volunteers in both abdomen and heart show promising results.

Shajan Gunamony¹, Jens Hoffmann¹, Gregor Adriany², Kamil Ugurbil², and Klaus Scheffler^1
1Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, ²Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States

Transmit elements arranged in multiple rows are beneficial in extending longitudinal coverage and achieve whole brain excitation at ultra-high field strengths. Furthermore, studies have shown that dual-row arrays produce less local SAR. Receive arrays shaped to the contours of the anatomy improves the signal-to-noise ratio (SNR) of the image. In this work, we develop a 2x8 transmit array for spin excitation in combination with a 32-channel high sensitive receive array for human brain imaging at 7T. Critical coil performance parameters like transmit efficiency and SNR were evaluated. 

Russell Luke Lagore¹, Lance DelaBarre¹, Jinfeng Tian¹, Gregor Adriany¹, Yigitcan Eryaman¹, and J. Thomas Vaughan^1
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States

The feasibility of human head imaging at 10.5T is demonstrated by the successful acquisition of in vivo porcine head images. This is achieved with an 8-element end-loaded dipole array resonant at 10.5T (447MHz). This dipole array is compared in terms of transmit efficiency and signal-to-noise ratio to a high-pass birdcage coil and loop array at 3T, 7T, and 10.5T. All coils share identical dimensions and element count. While both transmit arrays have comparable SNR performance at 7T, the dipole array is inferior in terms of transmit efficiency compared to the loop array and birdcage coil at all field strengths examined.

Michael J Beck¹, Dennis L Parker¹, Bradley D Bolster, Jr.², Seong-Eun Kim¹, J Scott McNally^1,3, Gerald S Treiman^1,4,5, and J Rock Hadley^1
1Utah Center for Advanced Imaging Research, Salt Lake City, UT, United States, ²Siemens Healthcare, Salt Lake City, UT, United States, ³University of Utah Department of Radiology, Salt Lake City, UT, United States,⁴University of Utah Department of Surgery, Salt Lake City, UT, United States, ⁵Veterans Affairs Department of Surgery (VASLCHCS), Salt Lake City, UT, United States

We developed interchangeable carotid coils that can image simultaneously with clinical head coils. Both 7 and 9 channel carotid coils were built to demonstrate the interchangeability concept.  SNR results show that the 7 channel coil has ~4x the SNR and the 9 channel coil has ~3x the SNR of the commercial neck coil at the carotids.  The carotid coils image simultaneously with a head coil providing greater coil sensitivity at the carotid bifurcation and extending total coverage from the carotid bifurcation to the circle of Willis.

Xinqiang Yan¹ and Xiaoliang Zhang^2
1Key Laboratory of Nuclear Analysis Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China, People's Republic of, ²Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, United States

Induced current elimination (ICE) method could efficiently reduce the element coupling in monopole and dipole arrays, and ultimately improve their SNR and parallel imaging performance. Nevertheless, in current ICE method, the decoupling element has possible effect on the original B₁ field, leading to dark spots at the areas near decoupling elements. To address such effects, we introduce a new structure, electric-LC (ELC) resonator, for decoupling monopole arrays.  Based on the simulation and experimental results, ELC resonators could also effectively reduce the coupling of monopoles and meanwhile have less influence on the original B1 fields of the elements.

Yukio Kaneko¹, Kosuke Ito², Masahiro Takizawa², Yoshihisa Soutome^1,2, Hideta Habara^1,2, Yusuke Seki¹, Tetsuhiko Takahashi², Yoshitaka Bito², and Hisaaki Ochi^1
1Research and Development Group, Hitachi Ltd., Tokyo, Japan, ²Healthcare Company, Hitachi, Ltd., Chiba, Japan

The B₁⁺ inhomogeneity in a human body increases as the strength of a static magnetic field increases. Previous studies showed the effect of the number of RF transmit channels in RF shimming. However, the effect for a partial region of the lumbar spine in a sagittal plane has not yet been investigated. In this study, the effect of the number of RF transmit channels for regional RF shimming in the lumbar spine region was investigated. The results show that 4-channel RF shimming can contribute to improving B₁⁺ homogeneity and reducing the transmit RF power more than 2-channel RF shimming.

Zidan Yu^1,2, Bei Zhang¹, Jerzy Walczyk¹, Gang Chen^1,2, 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, ²The Sackler Institute of Graduate Biomedical Sciences, New York University School of Medicine, New York, NY, United States

The cervical spine presents a challenging target for 7T RF coils. In this work, we describe a 6 channel transmit-receive cervical spine coil constructed like a cervical collar, wrapping around the back of the neck. In-vivo experiments demonstrate higher transmit efficiency, better B₁⁺ uniformity in the transverse plane and equivalent SNR compared to a RAPID Biomedical cervical spine coil.

Sasidhar Tadanki^1
1Electrical and Computer Engineering, Worcester Polytechnic Institute, Worcester, MA, United States

In this work a simple, efficient method to designing a transmission line volume resonator coil for MR applications is presented. A multiconductor transmission line is represented as a multiport network using its port admittance matrix. Closed form solutions for port resonant mode frequencies are calculated by solving the eigenfunctions of the port admittance matrix using block matrix and circulant block matrix algebra. Detailed analysis and simulated results are presented and compared with standard published results. A dual-tuned surface coil is developed to demonstrate the efficacy of the proposed method.

Wyger Brink¹, Jeroen van Gemert², Rob Remis², and Andrew Webb^1
1Radiology, Leiden University Medical Center, Leiden, Netherlands, ²Circuits and Systems, Delft University of Technology, Delft, Netherlands

The design of passive dielectric pads can be an exhaustive procedure with many degrees of freedom to address. In this study we developed a constrained inverse design approach based on the contrast source inversion method. The procedure can yield design guidelines efficiently, enabling automated design of dielectric pads.

Suchit Kumar¹, Joshua Haekyun Park^2,3, Young-Seung Jo^2,4, Jeong-Hee Kim^2,3, Chulhyun Lee², and Chang-Hyun Oh^1,4,5
1Department of Biomicrosystem Technology, Korea University, Seoul, Korea, Republic of, ²Korea Basic Science Institute, Cheongju, Chungcheongbuk-do, Korea, Republic of, ³Industrial Technology Institute, Korea University, Sejong City, Korea, Republic of, ⁴Department of Electronics and Information Engineering, Korea University, Seoul, Korea, Republic of, ⁵ICT Convergence Technology Team for Health&Safety, Korea University, Seoul, Korea, Republic of

In ultra-high field (UHF), body imaging suffers from B1 inhomogeneity due to shorter wavelength. A range of new RF coil designs has been proposed to overcome this problem. But, B1 inhomogeneity in the coronal plane still exists due to limited coverage. In this work, a novel design of an 8-channel top-hat dipole antenna with parallel transmission is proposed to improve B1+ homogeneity along Z-direction. B1⁺ field distribution and SAR field were simulated in FDTD solver. Comparison with original dipole antenna array confirms the improved B1⁺ homogeneity in proposed design.

R. Adam Horch^1,2 and John C. Gore^1,2
1Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States, ²Department of Radiology & Radiological Sciences, Vanderbilt University, Nashville, TN, United States

3D printing is demonstrated as a new means to fabricate complete RF probeheads for solution-state NMR. Current 3D printing methods yield mm-scale RF coils with integral sample chambers for self-contained NMR probes, and 3D-printed microcoils are imminent given ongoing advances in technology. The unique properties of 3D printing enable facile construction of potentially thousands of coils at low cost, giving way to dense coil arrays for high-throughput NMR and novel coil geometries.

Jorge Chacon-Caldera¹, Javier Uranga Solchanga¹, Paulina Koziol^1,2, and Lothar R Schad^1
1Computer Assisted Medical Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany, ²Department of Medical Physics and Biophysics, Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Krakow, Poland

Prostate MRI is commonly performed using endorectal coils which are invasive. This is done since body planar arrays are not sensitive enough for prostate imaging. Increasing sensitivity of an array for deep structures in the body is not trivial. In this study, we extended the traditional stacked figure-8 and single loop quadrature pair to add more single loop coils and enhanced the sensitivity at the depth of the prostate without increasing the field over a larger lateral area. We compared these arrays to classical planar approaches and found a factor 1.35 increase in maximum localized |B₁^-| using numerical simulations. 

Matthias Malzacher^1,2, Markus Vester³, Robert Rehner³, Christopher Stumpf¹, and Patrick Korf^1
1Friedrich-Alexander University Erlangen-Nuremberg, Erlangen, Germany, ²Computer Assisted Clinical Medicine, University Heidelberg, Medical Faculty Mannheim, Mannheim, Germany, ³Siemens Healthcare GmbH, Erlangen, Germany

Using reciprocity, available SNR from a receive coil array can be calculated by maximizing B₁- at the target voxel for unit input power. However, for strongly coupled or lightly loaded coil elements, the noise figure degradation due to coupled preamplifier noise becomes significant. It is shown here that this effect can be modeled by power loss in a resistive attenuator at each coil port. Thus, it is now possible to simulate any coil configuration, including those where coil coupling cannot be neglected.

Vitaliy Zhurbenko¹, Vincent Boer ², and Esben Thade Petersen ^2
1Technical 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

Transmission line resonators are often used as coils in high field MRI. Due to distributed nature of such resonators, coils based on them produce inhomogeneous field. This work investigates application of series capacitors to improve field homogeneity along the resonator. The equations for optimal values of evenly distributed capacitors are presented. The performances of the segmented resonator and a regular transmission line resonator are compared.

Chang-Hoon Choi ¹, YongHyun Ha¹, Arthur W. Magill¹, and N. Jon Shah^1,2
1Institute of Neuroscience and Medicine-4, Research Centre Juelich, Juelich, Germany, ²Faculty of Medicine, Department of Neurology, JARA, RWTH Aachen University, Aachen, Germany

A novel double tuned (¹H/²³Na) butterfly/loop surface coil using LCC traps was designed whereby the sodium mode was operated in a quadrature. The performance of this coil was evaluated on a 4T whole-body scanner and compared with a single-tuned butterfly and a loop coil. Images obtained by the quadrature-compensated double-tuned RF coil were more uniform in each slice and the SNRs were slightly higher over the selected ROIs compared to those from the reference coils.

J. Rock Hadley¹, Emilee Minalga¹, and Dennis L. Parker^1
1Radiology, University of Utah, Salt Lake City, UT, United States

This work tests how much loop conductivity and SNR is improved with copper plating of the silver ink trace.  Coils made with a silver ink base and different amounts of copper plating were compared against solid copper. This work demonstrates that copper plating of silver ink coils is possible and it indicates that significant improvements in coil trace conductivity can be achieved.  Consequently, the SNR performance of silver ink coils that have been plated with copper improves over silver ink coils without plating.

Yi-Cheng Hsu¹, Ying-Hua Chu¹, Pu-Yeh Wu¹, Shang-Yueh Tsai², and Fa-Hsuan Lin^1
1Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan, ²Institute of Applied Physic, National Chengchi University, Taipei, Taiwan

We propose a method and a system to precisely place the TMS coil inside the MRI using NMR probes.The positioning can be completed in 0.1 s with high translation (0.015 mm) and rotation precision (0.0047°) as well as low bias (~0.8 mm in 50 mm FOV).

Edwin Eigenbrodt¹ and Mary Preston McDougall^2
1Texas A&M University, College Station, TX, United States, ²Biomedical Engineering, Texas A&M University, College Station, TX, United States

Here we describe a six channel inexpensive FDM receiver, agnostic to the nuclei of interest or magnetic field strength, implemented straightforwardly using off-the-shelf products, portable, and easily used in conjunction with any system with a single trigger line. The architecture is straightforwardly scalable to 16 channels at a cost of approximately $1300 per channel. This work describes the receiver architecture and the capabilities are demonstrated by acquiring six channel images from a previously reported mouse array coil, two-channel 13C spectra, and comparing the SNR of the receiver to the Varian Inova system.

Nicholas R. Payne¹, Lionel M. Broche¹, and David J. Lurie^1
1Bio-Medical Physics, University of Aberdeen, Aberdeen, United Kingdom

RF coil ringing following an excitation pulse is particularly problematic at low frequency and can prevent the measurement of signals from short-T2 samples or tissues; this issue can be addressed by Q-switching. A Q-switch circuit, designed to operate at 2.5 MHz and reduce the dead-time of an RF coil following an RF pulse, is described. The resulting reduction in coil dead-time allows signal to be detected earlier and RF pulses to be spaced closer together. MOSFETs are used in our design to isolate RF from the DC control system and the circuit can be inductively coupled to any RF coil. The device was found to reduce the duration of coil ringing by a factor of five.

Jonas Reber¹, Josip Marjanovic¹, David Otto Brunner¹, Andreas Port¹, and Klaas Paul Pruessmann^1
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

With the number of RF receive channels cable routing and data handling becomes and increasing problem in particular for demanding applications requiring high acquisition duty cycles and bandwidths. To overcome this we present an MR acquisition platform that is capable of acquiring MR signal in-bore and scales its data handling ability with the number of channel. Furthermore the system provides ample, configurable real-time computational power for advanced in-line data processing and low-latency applications.

Dhiraj Sinha¹ and Shao Ying Huang^1
1Engineering Product Development, Singapore University of Technology and Design, Singapore, Singapore

  An MRI system at small physical dimensions can be developed using a piezoelectric-microcantilever system with the capability of sensing  magnetic fields in the range of microtesla to picotesla at room temperature conditions . The RF magnetic field induces voltage in the piezoelectric material which is amplified by the microcantilever which also filters out the signal around its resonant frequency. The cantilever vibration is measured using an optical detection system or by using capacitance to impedance converter. A thick block of piezoelectric material is used as a transmitter in order to replace the transmitting coil.

Ali Caglar Özen¹, Jan Korvink², Ergin Atalar³, and Michael Bock^1
1Dept. of Radiology - Medical Physics, University Medical Center Freiburg, Freiburg, Germany, ²Institute of Microstructure Technology, Karlsruhe Institute of Technology, Karlsruhe, Germany, ³Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey

MRI with Concurrent Excitation and Acquisition (CEA) was shown to be feasible by achieving 80 dB analog isolation between transmit and receive coils using an active decoupling method. In this work, active decoupling system was upgraded using pick-up coils for simultaneous recording of the transmit signals. Preliminary results for MRI of a human wrist are represented and discussed. 

Stephen Ogier¹, Mary McDougall^1,2, and Steve Wright^1,2
1Electrical and Computer Engineering, Texas A&M University, College Station, TX, United States, ²Biomedical Engineering, Texas A&M University, College Station, TX, United States

Frequency translation is a technique that uses radiofrequency mixers to convert the received signal from one nucleus to another.  This technique can be used to adapt ¹H array receivers for use with other nuclei, such as ¹³C.  This facilitates the use of arrays with less sensitive nuclei, which will benefit greatly from the SNR enhancement arrays provide.

Frequency translation has been shown to provide a flexible means of adapting receivers for use with other nuclei without signal degradation or corruption.

Zhoujian Li¹, Sajad Hosseinnezadian¹, Geneviève Guillot¹, Georges Willoquet¹, Laurène Jourdain¹, Marie Poirier-Quinot¹, Luc Darrasse¹, and Jean-christophe Ginefri^1
1Laboratoire d'Imagerie par Résonance Magnétique Médicale et Multi-Modalités, Université Paris-Sud, Orsay, France

We have implemented a piezo-motor based automation system for contactless impedance matching of a monolithic Transmission Line Resonator (TLR) operating at 4.7 T. The automation system successfully achieved inductive matching to more than -30dB of the TLR inside the magnet and no artifacts was observed on the image of a rectangular box-shaped water phantom. A second image, acquired in the same condition but in the presence of another piezo-motor fixed on a side of the sample revealed that the close proximity of the piezo-motor to the sample brings B1-field inhomogeneity.

Yu Li¹, Fangfang Tang¹, Bassem Henin¹, Fabio Freschi^1,2, Feng Liu¹, and Stuart Crozier^1
1School of ITEE, The University of Queensland, Brisbane, Australia, ²Department of Energy, Politecnico di Torino, Torino, Italy

Eddy currents are inevitably induced in the electrically conductive surroundings including the magnet cryostat vessel, RF coil, RF shield and other peripheral metallic structures.  This results in image distortion and artefacts. In order to control eddy currents, some studies have also discussed the issue of eddy currents on magnet cryostat vessel and RF shields. In this work, the eddy currents on a 12 channel micro-strip RF array head coil for 7T MRI were analysed and compared with that of a slotted, double-sided copper RF shield. A preliminary approach is proposed to reduce the eddy current effect, without compromising RF performance. 

Jonathan Y Lu¹, Thomas Grafendorfer², Fraser Robb³, John M Pauly¹, and Greig C Scott^1
1Dept of Electrical Engineering, Stanford University, Stanford, CA, United States, ²Advanced Coils, GEHC Coils, Stanford, CA, United States, ³GE Healthcare, Aurora, OH, United States

We aim to demonstrate methods to wirelessly probe the MRI transmit state without access to the internal MRI hardware itself. We demonstrate two forms of RF pulse detection during a scan with simple magnetic field probes: 1) an electrical link undergoing peak detection and 2) an optical link. We process this signal as an external hardware interrupt into a microcontroller, which can be easily used to bias a coil between receive and transmit mode. Such a setup can be useful in future wireless receive coils.

Sawson Taheri¹, Pascal Stang², John Pauly¹, and Greig C. Scott^1
1Stanford University, Stanford, CA, United States, ²Mountain View, CA, United States

Broadcast amplifier pallets offer a low-cost solution in creating MR compatible non-magnetic transmit array systems capable of operating in both 1.5T and 3T B₀ fields. We developed a locally deployable PTx array utilizing readily available broadcast amplifier pallets. The conversion of a conventional slow-gated, non-linear FM band (88-108MHz) 1kW pallet to a fast-gated, linear non-magnetic amplifier targeting transmit array deployment in both 1.5T and 3T B₀ fields is demonstrated.

Jennifer Nussbaum¹, Simon Gross¹, David O. Brunner¹, Christoph Barmet^1,2, Thomas Schmid¹, Benjamin E. Dietrich¹, Markus Weiger¹, and Klaas P. Pruessmann^1
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland, ²Skope Magnetic Resonance Technologies, Zurich, Switzerland

To measure the spatiotemporal magnetic field evolution during MR procedures for image reconstruction and real-time field control, best field probe performance is desired. We propose improved field probes with 19F spherical droplet samples formed and positioned with gelled deuterium oxide.  It is shown that these spherical samples have an isotropic k-space range and thus de-phase less along the capillary than the common probes. Furthermore, with BIR-4 adiabatic plane rotation pulses the flip angle can be perfectly adjusted, opening a new realm of field monitoring methods.

Oliver Heid¹, Juergen Heller¹, Xiaoyu Yang², and Hiroyuki Fujita^2
1Corporate Technology, Siemens AG, Erlangen, Germany, ²Quality Electrodynamics, Mayfield Village, OH, United States

We propose direct digital RF switch mode current sources to eliminate image artifacts due to B₁ field amplitude errors without time consuming transmitter calibration and adjustment. In difference to all known linear analog or switch mode RF amplfiers our proposal maintains high efficiency under modulation, and thus provides sufficent average RF power even at low flip angles, e.g. in FLASH sequences. We thus avoid significant, safety critical transmitter oversizing as in conventional MRI scanners.

Jonathan Y Lu¹, Thomas Grafendorfer², Tao Zhang¹, Kamal Aggarwal¹, Fraser Robb³, John M Pauly¹, and Greig C Scott^1
1Electrical Engineering, Stanford University, Stanford, CA, United States, ²Advanced Coils, GEHC Coils, Stanford, CA, United States, ³GE Healthcare, Aurora, OH, United States

We examine different power depletion mode GaN HEMT devices for use in low power MRI Q-spoiling at 3T. These devices range in their on-resistance and off-capacitance, yielding different blocking impedances. We prototyped FET based Q-spoiling surface coils and compared SNR performances with conventional PIN diode Q-spoiling coils. Our coils enable Q-spoiling when unpowered providing a good safety feature. We tested the robustness of the FET devices in the coils by running fast spin echo sequences at 3T. The SNR performances of our FET based coils are comparable with conventional PIN diode coils without the high current draw.

Natalia Gudino¹, Jacco A de Zwart¹, Qi Duan¹, Peter van Gelderen¹, and Duyn Jeff H^1
1Advanced MRI section, LFMI, NINDS, National Institutes of Health, Bethesda, MD, United States

We demonstrate a new on-coil current-source switch-mode amplifier and communication setup for 7T imaging, which allows monitoring of the RF phase, frequency and amplitude at the amplifier output. This information is made available through a single optical signal per amplifier, making it a practical approach for safety monitoring and fast calibration of on-coil amplifier technology for parallel RF transmission.

Hiroshi Kawaguchi^1,2, Tkayuki Obata^2,3, Hiromi Sano², Eiji Yoshida², Mikio Suga⁴, Yoko Ikoma², Yukari Tanikawa¹, and Taiga Yamaya^2
1Human Informatics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan, ²Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan,³Research Center for Charged Ion Therapy, National Institute of Radiological Sciences, Chiba, Japan, ⁴Center for Frontier Medical Engineering, Chiba University, Chiba, Japan

The current attenuation correction method for human pelvic PET/MRI contains several problems such that the attenuation due to bone is not considered and a specific MR imaging, intended for attenuation correction only, is needed. In this study, we proposed a method to generate the distribution of attenuation correction factors with considering the bone attenuation using diagnostic T1-weighted MRI for pelvic PET/MRI scanning. The proposed method is the hybrid of the tissue segmentation based on Gaussian mixture model and the non-liner registration of tissue probability to a subject image. The simulation results showed that attenuation correction using the proposed hybrid method reduced the error on PET image than the conventional method.

Aaron M. Coffey¹, Panayiotis Nikolaou¹, Kaili Ranta², Iga Muradyan³, Matthew S. Rosen⁴, Samuel Patz³, Michael J. Barlow⁵, Boyd M. Goodson², and Eduard Y. Chekmenev^1
1Radiology, Vanderbilt University Institute of Imaging Science, Nashville, TN, United States, ²Southern Illinois University, Carbondale, IL, United States, ³Brigham & Women's Hospital, Boston, MA, United States,⁴Harvard University, Cambridge, MA, United States, ⁵University of Nottingham, Nottingham, United Kingdom

We report on the development of a first and second generation ¹²⁹Xe hyperpolarizers, capable of producing high (~25-90%) ¹²⁹Xe hyperpolarization at high Xe densities (up to 2000 Torr partial pressure), suitable for clinical and materials MRS/MRI applications.

Brian J Lee^1,2, Ronald D Watkins¹, Chen-Ming Chang^1,3, and Craig S Levin^1,4,5,6
1Radiology, Stanford University, Stanford, CA, United States, ²Mechanical Engineering, Stanford University, Stanford, CA, United States, ³Applied Physics, Stanford University, Stanford, CA, United States, ⁴Physics, Stanford University, Stanford, CA, United States, ⁵Electrical Engineering, Stanford University, Stanford, CA, United States, ⁶Bioengineering, Stanford University, Stanford, CA, United States

We have developed a RF-penetrable PET insert for simultaneous PET/MRI and investigated the RF-penetrability with MR experiments and electromagnetic simulations. We have shown that the RF field from the MR body coil penetrates through the inter-module gaps and the ends of the PET insert. We found that ~60% of the RF field transmitted through the ends contributes to the B1 magnitude while the RF field entering through the gaps improves the uniformity provided the ends are also opened. The simulations also show that either shortening the length/height of the modules, or widening the gaps enhances the RF-penetrability by ~16%.

Md Shahadat Hossain Akram¹, Craig S. Levin², Takayuki Obata¹, Fumihiko Nishikido¹, Eiji Yoshida¹, and Taiga Yamaya^1
1Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan, ²School of Medicine, Stanford University, Stanford, CA, United States

A prototype of a novel oval shape PET insert for simultaneous body imaging with the MRI systems has been proposed in this study. The smaller prototype has the minor axis and major axis of 14 cm and 21 cm. 16 copper shielded boxes are positioned on the periphery of the oval frame. The shielding boxes were kept floating to let the RF field penetrate through the gaps in between the 16 modules. To get the required RF field distribution inside the oval PET, the gaps between the shielded modules were varied by doing assumptions following the conformal electric phase angle methods. B1 maps and GRE and SE images were taken and they have a good agreement with the results for without shielding materials. We have found a reduced RF field value with increased noise in the FOV which is mostly due to shielding materials. The images of GRE and SE have shape distortions due eddy currents. 

Maike E. Lindemann¹, Jan Ole Blumhagen², and Harald H. Quick^1,3
1High Field and Hybrid MR Imaging, University Hospital Essen, Essen, Germany, ²Siemens Healthcare GmbH, Erlangen, Germany, ³Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany

In quantitative PET-imaging, it is essential to correct the attenuation of photons in tissue. In combined PET/MR-imaging the attenuation correction (AC) is based on MR-data and subsequent tissue class segmentation. The MR-FOV is limited due to B0-inhomogeneities and gradient nonlinearities. Therefore, the AC-map is truncated and reconstructed PET-data are biased. HUGE (B0-Homogenization using gradient enhancement), which determines an optimal readout gradient to compensate gradient nonlinearities, is evaluated in phantom experiments and applied to MR-imaging of volunteers. The extension of the MR-FOV for MR-based AC showed an improvement of PET-quantification in integrated PET/MR-imaging by reducing the truncated areas of the AC-map.

Meher Juttukonda¹, Bryant Mersereau¹, Yi Su², Tammie Benzinger², David Lalush¹, and Hongyu An^2
1Joint Department of Biomedical Engineering, The University of North Carolina at Chapel Hill and North Carolina State University, Chapel Hill, NC, United States, ²Mallinckrodt Institute of Radiology, Washington University, St. Louis, MO, United States

We propose a mapping-based, quantitative T₁ method with patient-specific thresholding for tissue segmentation and assignment of continuous-valued LACs for soft tissues and bone. The proposed method utilizes images from a dual flip angle, dual echo UTE-MR acquisition to segment air, bone, GM, WM, CSF, fat and soft tissue. A conversion from MR relaxation rate R₁ is then utilized to derive continuous-valued LACs to major tissues in the head/neck. The method has been validated in PET data from 23 subjects and has been shown to outperform the vendor UTE method in PET reconstruction accuracy.

Spencer Baird Parent¹, William Bradfield Handler ², and Blaine A. Chronik^2
1Medical Biophysics, Western University, London, ON, Canada, ²Physics and Astronomy, Western University, London, ON, Canada

Using finite elements methods, an investigation of the systematic errors in magnetic field NMR probes is investigated. A NMR field probe is modeled and the field broadening and field offset is investigated as a function of the susceptibility of epoxy. It is shown that susceptibility matching the epoxy drastically reduces field broadening with a minimal effect on field offset. Additionally the effect of air bubbles present in cured epoxy is modeled and the results show that for certain critical regions of the probe the presence of an air bubble can be disadvantageous to the quality of the field probe. 

Mikayel Dabaghayan¹, Shelley Hua Lei Zhang¹, Zion Tsz Ho Tse², Charles L Dumoulin³, Ronald Watkins⁴, Wei Wang¹, Jay Ward⁵, and Ehud Jeruham Schmidt^6
1Radiology, Brigham and Womens Hospital, Boston, MA, United States, ²Engineering, University of Georgia, Athens, GA, United States, ³Radiology, Cincinatti Childrens Hospital Medical Center, Cincinatti, OH, United States, ⁴Radiology, Stanford University, Stanford, CA, United States, ⁵E-Trolz Inc., North Andover, MA, United States, ⁶Radiology, Brigham and Womens Hospital, Newton, MA, United States

We developed a technique to restore the ECG signals distorted by MRI gradient-induced voltages (GIV) acquired during fMRI and DW-EPI brain imaging sequences. Brain EPI sequences produce the largest ECG artifacts, presenting a large challenge to GIV removal. We used a theoretical equation with 19 parameters, which characterized the GIVs at each ECG electrode based on the simultaneously recorded gradient waveforms.  A rapid training sequence permitted computing the equation coefficients, followed by real-time gradient-induced voltage removal during imaging. FIR notch filters were subsequently applied to remove some residual spikes. The method succeeded in removing most GIVs, excluding artifacts at the beginning and end of imaging periods, which resulted from amplifier non-linearity.  

Mohan Lal Jayatilake¹, Christoph Juchem ², Michael Mullen¹, Gregor Adriany¹, Robin de Graaf², and Michael Garwood^1
1Center for Magnetic Resonance Research, University of Minnesota, Minnesota, MN, United States, ²Department of Radiology and Biomedical Imaging, Yale University School of Medicine, New Haven, CT, United States

A highly uniform magnetic field (B0) is typically required to generate MR images. In the original STEREO (for STEering REsonance over the Object) method, spatial variations in B0 are compensated by adjusting pulse amplitudes and frequencies in a temporal manner. Here we present a novel design of a limited set of well-defined multi-coil (MC) arrays that can optimize magnetic field distortions across the object of interest. 

Ryota Yamada¹, Makoto Tsuda¹, Katsumi Kose¹, and Yasuhiko Terada^1
1Institute of Applied Physics, University of Tsukuba, Tsukuba, Japan

A multi-circular shim coil (MCSC), which consists of a set of localized circular current coils, provides the flexibility to design and produce linear and higher-order magnetic fields that compensate for a given B₀imhomogeneity both statically and dynamically. However, the concept of the MCSC has currently been realized only for cylindrical base geometries. Here we translated the concept of the MCSC to a biplanar geometry, and a planar-type MCSC was designed and fabricated for an open, 1.0 T permanent magnet system. We concluded that the planar MCSC is a useful devise to achieve field homogeneity with reasonable accuracy.

Lukas Winter¹, Haopeng Han¹, and Thoralf Niendorf^1,2,3
1Berlin Ultrahigh Field Facility (B.U.F.F.), Max Delbrück Center for Molecular Medicine, Berlin, Germany, ²Experimental and Clinical Research Center (ECRC), a joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular Medicine, Berlin, Germany, ³MRI.TOOLS GmbH, Berlin, Germany

Cost effective open source imaging (COSI) is a collaborative initiative currently building an affordable low field open source MR scanner with the technical documentation available at www.opensourceimaging.org. As part of this initiative COSI Measure has been developed in order to automatically map the static magnetic field. COSI Measure is an open source multipurpose 3-axis system for ~3000€, which can be equipped with other field mapping probes like electromagnetic field sensors, used for 3D printing / CNC machinery application or other applications, that require programmable submillimeter movement and sensor readouts in space and time.

Lindsey Alexandra Crowe¹, Gibran Manasseh¹, Aneta Chmielewski², Thomas de Perrot¹, Hajo Müller³, Rares Salomir¹, and Jean-Paul Vallée^1
1Division of Radiology, Faculty of Medicine, Geneva University Hospital, Geneva, Switzerland, ²University of Toronto, Hospital for Sick Children, Toronto, ON, Canada, ³Division of Cardiology, Geneva University Hospital, Geneva, Switzerland

A new cardiac MRI triggering method is sought for cases of ECG signal complications due to pathology, or for fetal imaging. We propose feasibility of triggering to carotid ultrasound using an MRI compatible probe using spatially resolved Doppler compared to gold standard ECG. Retrospective processing using Metric Optimized Gating (MOG), is also included for comparison. Imaging modalities were compatible and the positioning of the US probe stable and patient friendly. Phase contrast flow and cine images were successfully obtained in healthy volunteers with ECG, Doppler triggering and MOG.  Image quality is highly comparable and accurate functional parameters accessible.

Hai Luo¹, Bin Wang¹, Gaojie Zhu¹, Wenzhou Wang¹, Xiang Zhou¹, Ziyue Wu¹, and Leping Zha^1,2
1AllTech Medical Systems, Chengdu, China, People's Republic of, ²AllTech Medical Systems, Cleveland, OH, United States

3D dual echo gradient echo sequence is commonly used to obtain the field map for B0 shimming. The maps contain the true B0 fields mixed with eddy currents induced magnetic field changes averaged over the echo time difference, which compromise the shimming accuracy. A calibration sequence with alternating gradient polarities is proposed to measure the eddy currents term. Quadratic surface fitting is then applied to produce smooth eddy currents calibration maps over the full imaging volume containing only the first and second order components. The actual rapid in-vivo shimming sequence runs later, using the calibration maps to remove the eddy currents influences during the post-processing, with partial Fourier acquisition on phase encoding and slice encoding directions to reduce the scan time. The fast method provides means of eddy currents insensitive shimming, as well as reduced sensitivity to motion.

Vanessa L. Landes¹, Eamon K. Doyle^1,2, Pablo J. Prado³, John C. Wood^1,2, and Krishna S. Nayak^4
1Biomedical Engineering, University of Southern California, Los Angeles, CA, United States, ²Cardiology, Children's Hospital Los Angeles, Los Angeles, CA, United States, ³One Resonance, LLC, San Diego, CA, United States, ⁴Electrical Engineering, University of Southern California, Los Angeles, CA, United States

We investigate the use of a magnet with flat field isosurfaces over 4 cm for assessment of proton density fat fraction (PDFF). We experimentally demonstrate a correlation between PDFF and apparent T2 in phantoms. Apparent T2 measurement variability is low enough to produce invertible curves of T2 vs. PDFF in intervals of 2% PDFF for a 0 – 17% PDFF range at 0ºC and intervals of 4% PDFF for a 0 – 12% PDFF range at 23ºC in milk and cream mixtures. The long-term goal is to use this device for in-vivo clinical applications, such as measurement of intra-hepatic and intra-muscular fat.  

Mahdi Orooji¹, Mehdi Alilou², Rachel Sparks³, Mirabela Rusu⁴, Nicolas Bloch⁵, Ernest Feleppa⁶, Dean Barratt⁷, Lee Ponsky⁸, and Anant Madabhushi^2
1Biomedical Engineering, CenteCase Western Reserve University, Cleveland, OH, United States, ²Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States, ³Centre for Medical Image Computing, University College of London, London, United Kingdom, ⁴Albany, NY, United States, ⁵Boston Medical Center, Boston, MA, United States, ⁶Lizzi Center for Biomedical Engineering, Riverside Research, New York, NY, United States, ⁷University College London, London, United Kingdom, ⁸University Hospital Case Medical Center, Cleveland, OH, United States

To evaluate whether the combination of computer extracted or radiomic image parameters from two complementary modalities, MRI-TRUS can enable better prediction of presence of prostate cancer compared to either modality individually. We considered 12 slides who underwent MRI, TRUS prior to radical prostatectomy. Deformable co-registration methods were used for spatially aligning the pre-operative in vivo MRI and ultrasound with the ex vivo whole mount radical prostatectomy specimens to establish the ground truth for cancer extent on the imaging. It yielded the best separability between cancer and non-cancer regions with an Area under the operating characteristic curve of 0.88.

Takuya Hinoda¹, Yasutaka Fushimi¹, Tomohisa Okada^1,2, Ryusuke Nakamoto¹, Yuji Nakamoto¹, and Kaori Togashi^1
1Radiology, Graduate school of Mediine, Kyoto University, Kyoto, Japan, ²Human Brain Research Center, Graduate school of Mediine, Kyoto University, Kyoto, Japan

“Flexible PET (fxPET)”, a dual-head mobile DOI-TOF PET system with MR compatibility, is a newly developed device which enable us to examine the positron-emission tomography. In this first trial of the central nervous system (CNS), we tried to confirm the clinical feasibility of the fxPET with a 1.5T MRI scanner. The result of this study showed that fxPET have clinical feasibility in comparison with PET-CT. PET/MRI is an emerging modality. PET/MRI can provide us useful metabolic information to MRI images. 

Stefan Kroboth¹, Kelvin J. Layton¹, Feng Jia¹, Sebastian Littin¹, Huijun Yu¹, Jürgen Hennig¹, and Maxim Zaitsev^1
1Medical Physics, University Medical Center Freiburg, Freiburg, Germany

A matrix gradient coil consisting of 84 small coil elements was designed and constructed at our institution. Driving each coil element with an individual amplifier is impractical due to the high current requirements. To resolve this limitation, groups of coil elements can be connected in series and driven by a limited number of amplifiers. Such grouping configurations are obtained for one or several target fields. In the latter case, the configurations need to be switched with a switching circuit. We propose an algorithm to minimize the number of necessary switches to reduce the complexity and cost of this circuit.

Yi Gao^1,2,3 and Chuan Huang^4,5
1Biomedical Informatics, Stony Brook Medicine, Stony Brook, NY, United States, ²Applied Mathematics and Statistics, Stony Brook Medicine, Stony Brook, NY, United States, ³Computer Sciences, Stony Brook Medicine, Stony Brook, NY, United States, ⁴Radiology, Stony Brook Medicine, Stony Brook, NY, United States, ⁵Psychiatry, Stony Brook Medicine, Stony Brook, NY, United States

In simultaneous PET-MRI, attenuation correction is still a major hurdle due to the high attenuation of the bones and the lack of MR signal in conventional sequences. So far, several approaches have been proposed for bone attenuation correction, including bone segmentation and direct bone imaging. However, almost all available bone segmentation literatures focused on the head, which is arguably one of the easier regions because of its smaller field-of-view (FOV) requirement and the absence of major motion artifacts. Direct bone imaging is another promising approach which is accomplished by using zero-TE imaging, but its application in the body is challenging due to the larger FOV requirement and current instrumentation limitation such as peak B1. Recent research has demonstrated that PET quantitation can be largely improved even by assigning a fixed bone attenuation value (0.120 cm-1) to all bones. In light of this, we developed a technique that is able to produce good bone segmentation in the pelvic region using a 2-minute 6-echo DIXON MRI acquisition.

Bryant G. Mersereau¹, Meher R. Juttukonda¹, Hongyu An², and David S. Lalush^1
1Joint Department of Bioengineering, The University of North Carolina at Chapel Hill and North Carolina State University, Chapel Hill, NC, United States, ²Mallinckrodt Institute of Radiology, Washington University in St. Louis, St. Louis, MO, United States

Acquired PET-MR datasets can be problematic to build due to the high logistical and monetary cost associated with recruiting and scanning patients. We propose a new electronic PET phantom (E-phantom) platform to streamline the PET-MR research process. The proposed platform is shown to produce results consistent with acquired PET data reconstructed on manufacturer software and to provide high configurability and flexibility as a simulation tool.

Camila Munoz¹, Christoph Kolbitsch^1,2, and Claudia Prieto^1
1Department of Biomedical Engineering, King's College London, London, United Kingdom, ²Division of Medical Physics and Metrological Information Technologies, Physikalisch-Technische Bundesanstalt, Berlin, Germany

MR-based PET motion correction has been shown to improve image quality in cardiac PET-MR imaging. Here we present a numerical simulation study analysing the impact of temporal and spatial resolution of motion fields on the final image quality of myocardial perfusion PET scans in order to find the most efficient parameters yielding accurate cardiac motion compensation in the shortest possible scan time. Results show that cardiac motion correction is important for accurate assessment of myocardial lesions and that temporal resolution of the motion fields can be strongly optimised without losing diagnostic accuracy, reducing the total exam time in PET-MR imaging.

Md Shahadat Hossain Akram¹, Takayuki Obata¹, Mikio Suga², Fumihiko Nishikido¹, Eiji Yoshida¹, and Taiga Yamaya^1
1National Institute of Radiological Sciences, Chiba, Japan, ²Chiba University, Chiba, Japan

Simultaneous PET/MRI system has attracted much because of its both functional and anatomic imaging capability. In our laboratory, we have developed a human head-size PET/RF-coil integrated modality to be used with existing clinical 3T MRI system (Siemens Magnetom Verio). Eight PET detector modules are integrated with a cylindrical 8-element Birdcage RF coil for simultaneous PET and MRI imaging. In the design each detector has been integrated in between two coil elements. RF interference to PET detector circuits affects PET performance. Also noise generated from PET circuits affects MR image quality. For proper simultaneous operation, PET circuits in each detector-module were installed inside a copper-shielded box. But shielding materials very close to RF coil elements and close to imaging region adversely affects MR imaging quality. In this study we performed B_o and SAR calculation of our hybrid system. Though there have noticeable changes in the B_o values, the SAR remains very low.

Camila Munoz¹, Radhouene Neji², Peter Weale², Rene Botnar¹, and Claudia Prieto^1
1Department of Biomedical Engineering, King's College London, London, United Kingdom, ²MR Research Collaborations, Siemens Healthcare, Frimley, United Kingdom

Respiratory motion remains a challenge for coronary MR angiography at 3T. Here we propose an inline 2D translational motion correction scheme using an image-based navigator. Low-resolution navigators are acquired at each heartbeat by spatially encoding the start-up echoes of an ECG-gated gradient echo sequence, allowing for 100% scan efficiency. Results from healthy volunteers show that motion correction improves visualization of the right and left anterior descending coronary arteries. The proposed scheme potentially allows for performing a comprehensive diagnosis of coronary artery disease by acquiring both diagnostic and motion information from MR, that can also be used to correct PET data.

Ileana Hancu¹, Robert Darrow¹, Eric Fiveland¹, Elizabeth Morris², Dominic Graziani¹, and Mauricio Castillo-Effen^1
1GE Global Research Center, Niskayuna, NY, United States, ²Memorial Sloan Kettering Cancer Center, New York City, NY, United States

Many factors contribute to the inaccuracy of MR-guided breast biopsies. Significantly, the lack of real-time visualization of tool advancement towards the biopsy site increases their duration and rate of false negatives. In this work, a novel approach for instrument tracking, relying on the spatial variation of the magnetic field, and using a set of 3 axis accelerometers/gyroscopes/magnetic field sensors, is presented. One dimensional tracking with 1.3mm rms error was demonstrated in the fringe field of a 3T magnet.

Ferran Prados^1,2, Manuel Jorge Cardoso¹, Ninon Burgos¹, Claudia Angela Michela Gandini Wheeler-Kingshott^2,3, and Sebastien Ourselin^1
1Translational Imaging Group, Medical Physics and Biomedical Engineering, University College London, London, United Kingdom, ²NMR Research Unit, Queen Square MS Centre, Department of Neuroinflammation, UCL Institute of Neurology, University College London, London, United Kingdom, ³Brain Connectivity Center, C. Mondino National Neurological Institute, Pavia, Italy

This work proposes a new way to publicly distribute image analysis methods and software. This approach is particularly useful when the software code and the datasets cannot be made open source. We leverage the use of Internet and emerging web technologies to develop a system where anyone can upload their image datasets and run any of the proposed algorithms without the need of any specific installation or configuration. This service has been named NiftyWeb (http://cmictig.cs.ucl.ac.uk/niftyweb).

Luca Zilberti¹, Oriano Bottauscio¹, and Mario Chiampi^2
1Istituto Nazionale di Ricerca Metrologica, Torino, Italy, ²Dipartimento Energia, Politecnico di Torino, Torino, Italy

This contribution reports the results of an extended survey, in which the exposure indexes provided by the current Guidelines dealing with motion-induced fields in MRI environments have been computed. The analysis is carried out through numerical simulations, using detailed human models that experience realistic exposure conditions (motion trajectories and MRI scanners). Besides identifying some critical situations (where the exposure indexes may be exceeded), the research puts in evidence some degree of freedom in the evaluation procedure, which might lead to inconsistences between different assessment approaches.

Kilian Wolfgang¹, Frank Seifert¹, Silvia Knappe-Grüneberg¹, Jens Voigt¹, Eva Al-Dabbagh¹, and Isaac Fan^1
1Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany

Two distinct methods for precise flip angle determination for hyperpolarized rare gas samples are presented and were performed in ultra low magnetic field environment ($$$\approx\,\mu$$$T). The repetitive coherent excitation method is rather fast and allows for preserving most of the initial polarization whereas the incoherent excitation method is time consuming but determines the relaxation parameters $$$T_1$$$ and $$$T_2^\star$$$ inherently.