ISMRM 24th Annual Meeting & Exhibition • 07-13 May 2016 • Singapore

Traditional Poster Session: Engineering

2126 -2168 RF Coils & Arrays
2169 -2208 MR Engineering Beyond RF Coils

Traveling wave MR using an array of regular RF resonators
Xinqiang Yan1,2 and Xiaoliang Zhang3
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.

Slotted-tube-resonator design for whole-body MR imaging at 14T
Jérémie Daniel Clément1, Arthur Magill2, Hongxia Lei3, Özlem Ipek3, and Rolf Gruetter4,5,6
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.

Design and construction of a triple-tuned RF probe for 23Na/31P/1H using traps
Arthur W. Magill1, Chang-Hoon Choi1, Yonghyun Ha1, and N. Jon Shah1,2
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).

13C RF coil combination for cardiac and abdominal human and pig studies
Steffen Ringgaard1, Rolf F Schulte2, James Tropp3, Carsten Kögler4, Titus Lanz4, Miguel A Navarro5, Jan Henrik Ardenkjaer-Larsen6,7, Fraser J Robb5, Hans Střdkilde-Jřrgensen1, and Christoffer Laustsen1
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.

Effect of the RF Shield on the Mutual Coupling Between Adjacent and Non-Adjacent Array Elements
Andreas Pfrommer1, Nikolai I Avdievich1, and Anke Henning1,2
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.

Tunable Defected Ground Structure for Decoupling Monopole Antenna Transmit/Receive Arrays in 7T MRI
Xinqiang Yan1,2 and William A. Grissom1,2,3
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.

New decoupling method for receiver arrays with small coils
Xueming Cao1, Elmar Fischer1, Oliver Gruschke2, Jan Korvink2, Jürgen Hennig1, and Maxim Zaitsev1
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.

Design of a forward view antenna for prostate imaging at 7 Tesla
Bart Steensma1, Dennis Klomp1, Nico van den Berg1, Peter Luijten1, Abe van der Werf2, and Alexander Raaijmakers1
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. 

Multi-Channel Helical-Antenna Inner-Volume RF Coils for Ultra-High-Field MR Scanners
Pranav S. Athalye1, Milan M. Ilic1,2, Pierre-Francois Van de Moortele3, Andrew J. M. Kiruluta4, and Branislav M. Notaros1
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.

A proton-free birdcage coil to enable zero-echo-time MRI without background signal
Markus Weiger1, David Otto Brunner1, Thomas Schmid1, Romain Froidevaux1, Manuela Barbara Rösler1, Simon Gross1, and Klaas Paul Pruessmann1
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.

Experimental Implementation of Array-compressed Parallel Transmission at 7T
Zhipeng Cao1,2, Xinqiang Yan1,3, and William A. Grissom1,2,3
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.

Array-compressed parallel transmit pulse design with optimized coil-channel assignments and coil pruning for simultaneous multislice and 3D reduced-field-of-view excitations
Zhipeng Cao1,2, Xinqiang Yan1,3, and William A. Grissom1,2,3
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.

A Cervical Spine Array Coil with Volume Transmitter at 7 Tesla
Tsinghua Zheng1, Matthew Finnerty1, Xiaoyu Yang1, Matthew Diprimio1, Luke Beery1, Paul Taylor1, Johanna Vannesjo2, Stuart Clare2, and Hiroyuki Fujita1,3,4,5
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.

Transceive surface array of dipole antennas for multi-transmit imaging at 3T
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. Raaijmakers1
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

A Mixed Dipole and Microstrip Transmit/Receive Array
Xinqiang Yan1,2, John C. Gore1,2,3, and William A. Grissom1,2,3
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.

A 7-Tesla Transmit with 32-Channel Receive-Only Array Head Coil for fMRI
Matthew Finnerty1, Derick Petrey1, Paul Taylor1, Luke Beery1, Tsinghua Zheng1, Xiaoyu Yang1, Hiroyuki Fujita1,2,3,4, Se-Hong Oh5, Ken Sakaie5, and Mark Lowe5
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.

Cost-Efficient 7ch Rx Shoulder Array for 7T UHF MRI Featuring External Switchbox Detuning
Stefan HG Rietsch1,2, Oliver Kraff1, Stephan Orzada1, Andrea Lazik3, and Harald H Quick1,2
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.

Design of RF Coils Mixing Elements of Dissimilar Radiation Pattern
Ian RO Connell1,2 and Ravi S Menon1,2
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.

A Hybrid 8 channel TR Dipole and 8 channel Rx Birdcage Body Coil Array for 7T
Jan Paska1,2, Martijn Cloos1,2, Gillian Haemer1,2,3, Bei Zhang1,2, and Graham C Wiggins1
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.

Analytical theory, circuit and numerical simulations to design a splittable degenerate birdcage for MSK applications.
Riccardo Stara1,2,3, Fabio Morsani2, Gianluigi Tiberi4,5, Maria Evelina Fantacci2,3, Massimo Marletta6, Virna Zampa6, Brian Rutt1, Alessandra Retico2, and Michela Tosetti5
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.

Optimized MRI RF Body Coil for Integration with In-bore Therapy or Biopsy System
Jiaqi Li1, Masahiro Fujimoto1, Amy Sue Meyers1, Qiong Zhang2, and Huaiyu Dong2
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.

A new monopole intravascular coil with three parasitic elements optimized for MRI 1.5 T
mohammad mohammadzadeh1,2 and alireza ghasempour Shirazi1
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.

Simulation, measurement, and optimization of a microcoil design for MR Microscopy at 9.4 T
Mohammad Mohammadzadeh1,2 and Mohammad Mohammadi2
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.

Increasing transmit coil efficiency without local transmit coils: a novel device for locally concentrating B1
Tracy Wynn1, Olli Friman1, and Randy Duensing1
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.

Evaluation of Spiral Extended Monopole Antenna Array with Individual Whields (SEMAS) at 7T
Myung Kyun Woo1, Chang-Ki Kang2, and Zang-Hee Cho3
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.

Printed Receive Coil Arrays with High SNR
Joseph Corea1, Balthazar P. Lechene1, Thomas Grafendorfer2, Fraser Robb3, Ana Claudia Arias1, and Michael Lustig1
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. 

An 8Tx/32Rx RF Coil for 7T UHF Body MRI
Stefan HG Rietsch1,2, Stephan Orzada1, and Harald H Quick1,2
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.

A 7T head coil with 16-channel dual-row transmit and 32-channel receive array for pTx applications and high SNR
Shajan Gunamony1, Jens Hoffmann1, Gregor Adriany2, Kamil Ugurbil2, and Klaus Scheffler1
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. 

End-Loaded Dipole Array for 10.5T Head Imaging
Russell Luke Lagore1, Lance DelaBarre1, Jinfeng Tian1, Gregor Adriany1, Yigitcan Eryaman1, and J. Thomas Vaughan1
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.

Interchangeable Patient-Specific Receive-Only Carotid Coils for Simultaneous Imaging with Radio Frequency Head Coils at 3 Tesla
Michael J Beck1, Dennis L Parker1, Bradley D Bolster, Jr.2, Seong-Eun Kim1, J Scott McNally1,3, Gerald S Treiman1,4,5, and J Rock Hadley1
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.

Electric-LC resonators decoupling approach for monopole antenna arrays at 7T
Xinqiang Yan1 and Xiaoliang Zhang2
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.

Improvement of B1+ Homogeneity and Reduction of Transmit RF Power Using 4-channel Regional RF Shimming in L-spine Imaging at 3T
Yukio Kaneko1, Kosuke Ito2, Masahiro Takizawa2, Yoshihisa Soutome1,2, Hideta Habara1,2, Yusuke Seki1, Tetsuhiko Takahashi2, Yoshitaka Bito2, and Hisaaki Ochi1
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.

A 6 Channel Transmit-Receive Coil Array for 7T Cervical Spine Imaging
Zidan Yu1,2, Bei Zhang1, Jerzy Walczyk1, Gang Chen1,2, and Graham Wiggins1
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.

RF coil design using circulant and block circulant matrix algebra
Sasidhar Tadanki1
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.

Inverse Design of Dielectric Pads based on Contrast Source Inversion
Wyger Brink1, Jeroen van Gemert2, Rob Remis2, and Andrew Webb1
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.

Improvement of B1+ Homogeneity along Z-Direction Using Top-Hat Dipole-Antenna pTX Array for Body Imaging at 7 Tesla
Suchit Kumar1, Joshua Haekyun Park2,3, Young-Seung Jo2,4, Jeong-Hee Kim2,3, Chulhyun Lee2, and Chang-Hyun Oh1,4,5
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.

3D-printed RF Probeheads for Low-cost, High-throughput NMR
R. Adam Horch1,2 and John C. Gore1,2
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.

Numerical Comparison of Stacked and Planar Coil Reception Arrays for Prostate MRI at 3 T
Jorge Chacon-Caldera1, Javier Uranga Solchanga1, Paulina Koziol1,2, and Lothar R Schad1
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. 

SNR simulations including coupled preamplifier noise
Matthias Malzacher1,2, Markus Vester3, Robert Rehner3, Christopher Stumpf1, and Patrick Korf1
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.

Transmission Line Resonator Segmented with Series Capacitors
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.

Design of quadrature-compensated double-tuned RF surface coil using trap circuits
Chang-Hoon Choi 1, YongHyun Ha1, Arthur W. Magill1, and N. Jon Shah1,2
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.

Copper plating of conductive silver ink coils for improved SNR performance
J. Rock Hadley1, Emilee Minalga1, and Dennis L. Parker1
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.

TMS positioning in MRI using NMR probes
Yi-Cheng Hsu1, Ying-Hua Chu1, Pu-Yeh Wu1, Shang-Yueh Tsai2, and Fa-Hsuan Lin1
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).

Frequency-agnostic inexpensive modular FDM receiver design
Edwin Eigenbrodt1 and Mary Preston McDougall2
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.

A Q-switch system for an MRI RF coil operating at 2.5 MHz.
Nicholas R. Payne1, Lionel M. Broche1, and David J. Lurie1
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.

Scalable, In-Bore Array Receiver Platform for MRI
Jonas Reber1, Josip Marjanovic1, David Otto Brunner1, Andreas Port1, and Klaas Paul Pruessmann1
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.

Miniaturized MRI System for Diagnosis of Samples of Low Physical Dimensions using Piezoelectric Receiver and Transmitter
Dhiraj Sinha1 and Shao Ying Huang1
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.

In vivo Concurrent Excitation and Acquisition MRI with Self-referenced Active Decoupling
Ali Caglar Özen1, Jan Korvink2, Ergin Atalar3, and Michael Bock1
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. 

Frequency Translation for 1H Decoupled Multichannel 13C Spectroscopy
Stephen Ogier1, Mary McDougall1,2, and Steve Wright1,2
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.

Proton Imaging at 4.7 T Using a Piezoelectric-based Automation System for impedance matching of Monolithic Transmission Line Resonators
Zhoujian Li1, Sajad Hosseinnezadian1, Genevičve Guillot1, Georges Willoquet1, Laurčne Jourdain1, Marie Poirier-Quinot1, Luc Darrasse1, and Jean-christophe Ginefri1
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.

Analysis of Eddy Currents for High Field RF Coil Design
Yu Li1, Fangfang Tang1, Bassem Henin1, Fabio Freschi1,2, Feng Liu1, and Stuart Crozier1
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. 

Wireless Probe Detection For Auxiliary Control Syncing
Jonathan Y Lu1, Thomas Grafendorfer2, Fraser Robb3, John M Pauly1, and Greig C Scott1
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.

Explorations of Non-Magnetic Amplifiers for MRI Applications
Sawson Taheri1, Pascal Stang2, John Pauly1, and Greig C. Scott1
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.

Spherical droplet design and adiabatic excitation for enhanced performance and flip angle control of NMR field probes
Jennifer Nussbaum1, Simon Gross1, David O. Brunner1, Christoph Barmet1,2, Thomas Schmid1, Benjamin E. Dietrich1, Markus Weiger1, and Klaas P. Pruessmann1
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.

Digital RF Current Sources for safer, adjust-free MRI scanners
Oliver Heid1, Juergen Heller1, Xiaoyu Yang2, and Hiroyuki Fujita2
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.

High Powered GaN HEMT devices for Low Powered Q-spoiling at 3T MRI
Jonathan Y Lu1, Thomas Grafendorfer2, Tao Zhang1, Kamal Aggarwal1, Fraser Robb3, John M Pauly1, and Greig C Scott1
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.

Monitoring of RF transmit signal in on-coil current-source switch-mode amplification
Natalia Gudino1, Jacco A de Zwart1, Qi Duan1, Peter van Gelderen1, and Duyn Jeff H1
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.

A hybrid-segmentation atlas method to construct the attenuation correction factor for human pelvic PET/MRI
Hiroshi Kawaguchi1,2, Tkayuki Obata2,3, Hiromi Sano2, Eiji Yoshida2, Mikio Suga4, Yoko Ikoma2, Yukari Tanikawa1, and Taiga Yamaya2
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.

Clinical-Scale, Stopped-flow 129Xe Hyperpolarizer Development
Aaron M. Coffey1, Panayiotis Nikolaou1, Kaili Ranta2, Iga Muradyan3, Matthew S. Rosen4, Samuel Patz3, Michael J. Barlow5, Boyd M. Goodson2, and Eduard Y. Chekmenev1
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.

RF field penetrability study of an electrically floating PET insert for simultaneous PET/MRI
Brian J Lee1,2, Ronald D Watkins1, Chen-Ming Chang1,3, and Craig S Levin1,4,5,6
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%.

Concept of an RF penetrable oval PET insert for MRI system: initial study of the shielding effect
Md Shahadat Hossain Akram1, Craig S. Levin2, Takayuki Obata1, Fumihiko Nishikido1, Eiji Yoshida1, and Taiga Yamaya1
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. 

Extension of the MR field-of-view with HUGE for MR-based attenuation correction in integrated PET/MR
Maike E. Lindemann1, Jan Ole Blumhagen2, and Harald H. Quick1,3
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.

T1-enhanced segmentation and selection of linear attenuation coefficients for PET/MRI attenuation correction in head/neck applications
Meher Juttukonda1, Bryant Mersereau1, Yi Su2, Tammie Benzinger2, David Lalush1, and Hongyu An2
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.

Investigation of systematic errors in NMR field probes
Spencer Baird Parent1, William Bradfield Handler 2, and Blaine A. Chronik2
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. 

Removing Gradient Induced Voltages from 12-lead ECGs acquired during DW-EPI and fMRI brain Imaging
Mikayel Dabaghayan1, Shelley Hua Lei Zhang1, Zion Tsz Ho Tse2, Charles L Dumoulin3, Ronald Watkins4, Wei Wang1, Jay Ward5, and Ehud Jeruham Schmidt6
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.  

STEREO-MC for Connected Spatiotemporal Excitation
Mohan Lal Jayatilake1, Christoph Juchem 2, Michael Mullen1, Gregor Adriany1, Robin de Graaf2, and Michael Garwood1
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. 

Planar-type multi-circular shimming for a 1.0 T permanent magnet
Ryota Yamada1, Makoto Tsuda1, Katsumi Kose1, and Yasuhiko Terada1
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.

COSI Measure - Open Source Multipurpose Measurement System
Lukas Winter1, Haopeng Han1, and Thoralf Niendorf1,2,3
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 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.

Comparison of ECG and Novel Ultrasound Triggering with Spatially Resolved MR-compatible Doppler for Cardio-vascular MRI.
Lindsey Alexandra Crowe1, Gibran Manasseh1, Aneta Chmielewski2, Thomas de Perrot1, Hajo Müller3, Rares Salomir1, and Jean-Paul Vallée1
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.

Rapid Eddy Currents Insensitive Field Map Estimation for Accurate B0 Shimming
Hai Luo1, Bin Wang1, Gaojie Zhu1, Wenzhou Wang1, Xiang Zhou1, Ziyue Wu1, and Leping Zha1,2
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.

Feasibility of Non-invasive Proton-Density Fat Fraction Evaluation using a Single-sided MR device
Vanessa L. Landes1, Eamon K. Doyle1,2, Pablo J. Prado3, John C. Wood1,2, and Krishna S. Nayak4
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 0şC and intervals of 4% PDFF for a 0 – 12% PDFF range at 23şC 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.  

A Combination of Radiomic Features from MRI and Ultrasound Appears to better predict presence of prostate cancer: Validation against whole mount pathology
Mahdi Orooji1, Mehdi Alilou2, Rachel Sparks3, Mirabela Rusu4, Nicolas Bloch5, Ernest Feleppa6, Dean Barratt7, Lee Ponsky8, and Anant Madabhushi2
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.

An initial experiment of "Flexible PET/MRI" for CNS tumors
Takuya Hinoda1, Yasutaka Fushimi1, Tomohisa Okada1,2, Ryusuke Nakamoto1, Yuji Nakamoto1, and Kaori Togashi1
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. 

Optimization of a switching circuit for a matrix gradient coil
Stefan Kroboth1, Kelvin J. Layton1, Feng Jia1, Sebastian Littin1, Huijun Yu1, Jürgen Hennig1, and Maxim Zaitsev1
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.

Semi-automatic multi-feature bone segmentation in the pelvic region using Dixon MRI images acquired in 2 minutes: a preliminary result
Yi Gao1,2,3 and Chuan Huang4,5
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.

Realistic Patient-Based E-Phantoms and Simulation of PET-MR Neuroimage Data
Bryant G. Mersereau1, Meher R. Juttukonda1, Hongyu An2, and David S. Lalush1
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.

Impact of spatio-temporal resolution on MR-based cardiac motion correction PET-MR
Camila Munoz1, Christoph Kolbitsch1,2, and Claudia Prieto1
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.

Bo and SAR calculation for a full-ring human head PET system integrated with an 8-element Birdcage coil at 3T
Md Shahadat Hossain Akram1, Takayuki Obata1, Mikio Suga2, Fumihiko Nishikido1, Eiji Yoshida1, and Taiga Yamaya1
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 Bo and SAR calculation of our hybrid system. Though there have noticeable changes in the Bo values, the SAR remains very low.

100% efficient motion corrected coronary MR angiography using a gradient echo sequence in a 3T PET-MR system
Camila Munoz1, Radhouene Neji2, Peter Weale2, Rene Botnar1, and Claudia Prieto1
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.

Real time tracking in the fringe field of a MRI scanner: a solution for more accurate MR guided breast biopsies
Ileana Hancu1, Robert Darrow1, Eric Fiveland1, Elizabeth Morris2, Dominic Graziani1, and Mauricio Castillo-Effen1
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.

NiftyWeb: web based platform for image processing on the cloud
Ferran Prados1,2, Manuel Jorge Cardoso1, Ninon Burgos1, Claudia Angela Michela Gandini Wheeler-Kingshott2,3, and Sebastien Ourselin1
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 (

About the application of the ICNIRP Guidelines for motion-induced electric fields in MRI
Luca Zilberti1, Oriano Bottauscio1, and Mario Chiampi2
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.

Ultra-Low-Field Spin Manipulation for Precise Flip-Angle and T$$$_1$$$-Determination
Kilian Wolfgang1, Frank Seifert1, Silvia Knappe-Grüneberg1, Jens Voigt1, Eva Al-Dabbagh1, and Isaac Fan1
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.

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