ISMRM 21st Annual Meeting & Exhibition 20-26 April 2013 Salt Lake City, Utah, USA

2707 -2719 Gradients & Shimming
2720 -2759 Arrays & Array Technology
2760 -2768 Specialized Systems & Devices
2769 -2771 Magnets
2772 -2796 Novel RF Coils
2797 -2802 High-Dielectric Materials in RF Imaging
2803 -2807 RF Simulations
2808 -2818 PET/MRI Systems Engineering
2819 -2842 Safety (Non-Contrast Agent)

Wednesday, 24 April 2013 (13:30-15:30) Exhibition Hall
Gradients & Shimming

2707.   The Effect of Magnet Flanges on Eddy Current Predictions
Dominic Michael Graziani1, Jean-Baptiste Mathieu1, and Seung-Kyun Lee1
1GE Global Research, Niskayuna, New York, United States

Eddy currents from an actively shielded transverse gradient coil were evaluated for the case where the eddy current surfaces are approximated by a coaxial cylinder, as well as a cylinder with flanges. The percent error in the predicted eddy current response in the imaging volume due to neglecting the magnet flanges was determined to be non-negligible, with an observed rms error of 6.9% and 15.8% with and without pre-emphasis respectively. These results have implications when designing gradient coils with an optimal eddy current response.

2708.   Preliminary Evaluation of a High Performance Gradient Coil for 3T Head Specialty Scanner
Jean-Baptiste Mathieu1, Seung-Kyun Lee1, Eric G. Budesheim1, Yihe Hua2, Jian Lin2, Christopher Immer1, Silke M. Lechner-Greite3, Joseph Piel1, John F. Schenck1, Matthew A. Bernstein4, John Huston4, and Thomas K. Foo1
1Diagnostics and Biomedical Technologies, GE Global Research, Niskayuna, NY, United States, 2Diagnostics and Biomedical Technologies, GE Global Research, China Technology Center, Pudong, Shanghai, China, 3Diagnostics and Biomedical Technologies, GE Global Research, Garching, Bavaria, Germany, 4Radiology Department, Mayo Clinic, Rochester, MN, United States

A head gradient prototype has been built. Its design enables high-performance imaging without compromise on patient ergonomics. Preliminary testing results on gradient efficiency, resistance, inductance, and eddy currents are presented. Data were compared to predictions and shows very good agreement. Next steps will include evaluation of peripheral nerve stimulation, and image quality. This work demonstrates substantial progress towards the development of a dedicated compact 3T head scanner.

2709.   Sinusoidal PatLoc Imaging Using Matrix Gradient Coils
Sebastian Littin1, Feng Jia1, and Maxim Zaitsev1
1Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany

The concept of PatLoc (parallel imaging technique using localized gradients) provides a method for parallel imaging by using nonlinear Spatial Encoding Magnetic fields (SEMs). Matrix gradient coils may allow one to generalize PatLoc encoding by using almost arbitrary SEM configurations. In this abstract we show how matrix gradient coils can be used to generate sinusoidal SEMs and demonstrate a possibility of image reconstruction over an extended field of view.

2710.   Design of a Low Joule Heating Gradient Coil Conductors
Yukinobu Imamura1, Mitushi Abe1, and Akira Kurome2
1Hitachi Research Laboratory, Hitachi,Ltd., Hitachi-shi, Ibaraki-ken, Japan, 2Hitachi Medical Corp., Kashiwa, Chiba, Japan

A computation code based on FEM was applied for calculation of current flow on gradient coil conductors. In the high frequency gradient fields (over 500Hz), eddy current appeared remarkably on wide conductors. We find narrow conductors can effectively reduce the eddy currents, and we confirmed the effect of heating suppression by the experiments.

2711.   AC Resistance Predictions Vs Experimentally Measured Values for a High Performance Head Gradient Coil
Silke M. Lechner-Greite1, Jean-Baptiste Mathieu2, Seung-Kyun Lee3, Bruce C. Amm4, Thomas K. Foo3, John F. Schenck3, Matthew A. Bernstein5, and John Huston5
1Diagnostics and Biomedical Technologies Europe, GE Global Research Europe, Garching n. Munich, Germany, 2Electromagnetics and Superconductivity Laboratory, GE Global Research, Niskayuna, NY, United States, 3Magnetic Resonance Imaging Laboratory, GE Global Research, Niskayuna, NY, United States, 4Biomedical and Electronic Systems Laboratory, GE Global Research, Niskayuna, NY, United States, 5Dept of Radiology, Mayo Clinic, Rochester, MN, United States

We report on AC resistance predictions and measurements of a head-only shielded gradient coil prototype consisting of asymmetric transverse gradients and a symmetric axial gradient. The AC resistances were simulated with finite element method software and measured experimentally on the available prototype of the head gradient. The simulations predicted the AC losses for individual gradient coil excitation with reasonable accuracy for X and Y.

2712.   Development of Gradient Coil Probes for Vertical Wide Bore Superconducting Magnets with Solenoid RF Coils and Optimized Planar Gradient Coils
Masabumi Horiga1, Kazunori Ishizawa1, and Katsumi Kose1
1Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki, Japan

We developed two large bore (30 and 40 mm diameter) gradient coil probes for a vertical wide bore superconducting magnet (4.74 T) with solenoid coils. The planar gradient coils were designed using the genetic algorithm, which optimized power consumption under the restriction that the linearity of the magnetic field gradients is less than 10% within the target volume (30 and 40 mm diameter sphere). The gradient probes were evaluated using a 3D lattice phantom and plant samples, which demonstrated the usefulness of the developed gradient probe.

2713.   Implementation of High-Performance Non-Linear O-Space Gradient Coil for Accelerated Neuroimaging
Leo K. Tam1, Gigi Galiana2, Andrew Dewdney3, William F.B. Punchard4, Kai-ming Lo4, Terence W. Nixon2, John Keiley4, Dana C. Peters2, and Robert Todd Constable2
1Biomedical Engineering, Yale University, New Haven, CT, United States, 2Diagnostic Radiology, Yale University, New Haven, CT, United States, 3Siemens AG Healthcare, Erlangen, Bavaria, Germany, 4Resonance Research, Inc., Billerica, MA, United States

An O-space imaging gradient head insert was installed and the first in vivo head images were taken with the system. Field purity was of primary concern during design and implementation, and it was found via simulation that up to 10% deviation in field shape was acceptable given appropriate inclusion of the generated field during algebraic reconstruction. The O-space non-linear imaging system promises an attractive paradigm for future neuroimaging studies.

2714.   Evaluation of an Independent Linear Model for MRI Acoustic Noise and Implications for Acoustic Noise Reduction
Ziyue Wu1, Yoon-Chul Kim2, Michael C.K. Khoo1, and Krishna S. Nayak2
1Department of Biomedical Engineering, University of Southern California, Los Angeles, California, United States, 2Deptartment of Electrical Engineering, University of Southern California, Los Angeles, California, United States

We evaluate an independent linear model for gradient-induced MRI acoustic noise on a clinical scanner and introduce a new method to synchronize the measured acoustic impulse responses of all three gradient axes, thus substantially improve the model’s acoustic noise prediction accuracy from >32% to <4% when combining sound from all three axes. We also examine differences in the measured transfer functions across different positions within the scanner bore, and discuss implications on the ability to perform general acoustic noise reduction by avoiding system resonance peaks.

2715.   Concurrent Magnetic Field Monitoring of EPI Time Series: Characterizing Encoding Field and Image Fluctuations Using Principal Component Analysis
Saskia Klein1, Lars Kasper1, Johanna Vannesjo1, Maximilian Häberlin1, Simon Gross1, Benjamin Dietrich1, and Klaas P. Prüssmann1
1Institute for Biomedical Engineering, ETH Zurich, Zurich, Switzerland

In fMRI, changes in image intensity are induced by signal fluctuations, e.g. related to the brain metabolism (BOLD). They can also be caused by gradient system instabilities and drifts, leading to confounds in time series analyses. We use concurrent magnetic field monitoring to characterize typical EPI trajectory fluctuations and B0-modulations over several days, and identify corresponding image artifacts using comparative PCAs. The standard deviations in the images are in the range of the BOLD effect, correcting for the non-reproducible fluctuations for fMRI seems highly beneficial.

2716.   Analysis of Measurement Precision in Continuous Magnetic Field Monitoring
Benjamin E. Dietrich1, David Otto Brunner1, Bertram J. Wilm1, Christoph Barmet1,2, and Klaas P. Pruessmann1
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland, 2Skope Magnetic Resonance Technologies, Zurich, Switzerland

Dynamic magnetic field monitoring with NMR probes enables the observation of the spatio-temporal magnetic field evolution during MR experiments. A recently proposed method based on time interleaved acquisition of sets of fast relaxing NMR probes allows scanner independent dynamic magnetic field monitoring even under strong gradients over arbitrary durations. Such continuous gradient field monitoring alleviates hence the limitation on resolution, acquisition duration and duty cycle of the approaches shown using a single coherence. The presented work assesses the precision of this method with regard to different field-probe-set configurations, gradient strengths, set alternation patterns, and re-excitation periods.

2717.   Matrix Shimming for Whole Body Gradient Coils
Derek A. Seeber1, Kevin Koch2, and Bernardo Ortega3
1Engineering, GE Healthcare, Florence, SC, United States, 2ASL, GE Healthcare, Waukesha, WI, United States, 3Engineering, GE Healthcare, Apodaca, NL, Mexico

A matrix array shim coil system was designed to be included into a widebore gradient coil consisting of 24 channels in a 6 circumferential by 4 axial coil matrix array. The matrix shim coil is designed from multi-layer Kapton circuit boards and is integrated into a gradient coil between the inner and outer gradient coil. Simulations from brain images were analyzed and demonstrate improved performance over a traditional 3rd order harmonic shim set.

2718.   Reliable in Vivo Shimming for Solving Shim Degeneracy and Incorporating System Constaints at High B0 Fields
Iulius Dragonu1, Nicoleta Baxan1,2, Markus Wick2, Jeff Snyder3, Franek Hennel2, Jürgen Hennig1, Dominik von Elverfeldt1, and Maxim Zaitsev1
1Dept. Radiology - Medical Physics, University Medical Center Freiburg, Freiburg, Germany, 2Bruker BioSpin MRI GmbH, Ettlingen, Germany, 3Dept. of Neurology, University Medical Center Freiburg, Freiburg, Germany

Discontinuities in the magnetic susceptibility generate induction fields which perturb the static B0 field. At high B0 fields the susceptibility difference effects are enhanced leading to potential shimming problems. The problem of finding the correct shim values can become ill-conditioned for very thin or off-centred volumes. In such cases, the required linear independence of shim functions is not maintained leading to shim degeneracy. In this work, we propose a new method for solving the shim degeneracy problem in order to calculate the correct shim values. In addition, this technique will optimize the shim currents taking into account the limitations of the maximum current available for each shim channel.

2719.   Active Magnetic Shielded Cancelling Coils for Direct Detection of MR Signals with an Atomic Magnetometer in Ultra-Low Field MRI
Takenori Oida1, Masahiro Tsuchida1, and Tetsuo Kobayashi1
1Department of Electrical Engineering, Graduate School of Engineering, Kyoto University, Kyoto, Kyoto, Japan

Optically pumped atomic magnetometers (OPAMs) do not require cryogenic cooling and allow us easily to measure extremely small magnetic fields including MR signals. Recently, an ultra-low field (ULF) MRI system with an OPAM has been attracted attentions. In this study, we proposed the active magnetic shielded cancelling coils for direct detection of MR signals with an OPAM. Results of magnetic field distribution analyses showed that the proposed active magnetic shielded coils could sufficiently reduce the magnetic field distortion caused by the cancelling coils, demonstrating their feasibility of direct detection of MR signals.


Wednesday, 24 April 2013 (13:30-15:30) Exhibition Hall
Arrays & Array Technology

2720.   Models of Parasitic Mutual Capacitance in Array Coils: Effects on Mutual Reactance, Resistance and Noise Correlation
Adam Maunder1, Mojgan Daneshmand1, Pedram Mousavi1, B. Gino Fallone2, and Nicola De Zanche2
1Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta, Canada, 2Oncology, University of Alberta, Edmonton, Alberta, Canada

Despite its impact on array coupling and design, especially for higher frequencies, capacitance between coils has not been studied quantitatively. The proposed capacitive coupling circuit model is shown to accurately predict simulated and measured impedance changes, as well as measured noise correlations. An important application is the reduction or elimination of both reactive and resistive coupling with appropriate adjustments of inter-element capacitance. This model includes mutual inductance and resistance, and quantifies the effect and amount of parasitic capacitive coupling.

2721.   Accurate Phased Array Modeling in the Presence of Coupling
Pei-Shan Wei1, Scott B. King1,2, Michael J. Smith2, Jarod Matwiy2, and Christopher P. Bidinosti3
1Departmentof Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada, 2National Research Council of Canada, Winnipeg, Manitoba, Canada, 3Department of Physics, University of Winnipeg, Winnipeg, Manitoba, Canada

An accurate modeling of a constructed coil contains resistive and mutual inductance coupling and preamplifier de-coupling information in realistic electromagnetic fields and is important for optimization of SNR and g-factor. Noise correlation analysis and current ratio of induced current relative to the primary current at different angular position representing different coupling have been used to evaluate the perturbation in the B/E- field distribution. Our results suggest that incorporating a preamplifier circuit into the coil model can accurately simulate decoupling and is suitable for phased array coil optimization.

2722.   An Automated Framework to Decouple PTx Arrays with Many Channels
Zohaib Mahmood1, Bastien Guérin2, Elfar Adalsteinsson1,3, Lawrence L. Wald2,3, and Luca Daniel1
1Dept of Electrical Engineering & Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2Martinos Center for Biomedical Imaging, Dept. of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts, United States, 3Harvard-MIT Division of Health Sciences Technology, Cambridge, Massachusetts, United States

In this paper we present an algorithm to automatically design a decoupling matrix for pTx arrays with many channels. The algorithm optimally selects the decoupling matrix based on the constraints defined on network such as reciprocity, passivity and the network being lossless. We show that our algorithm converges and the decoupling matrix achieves ideal decoupling. We explore various useful features of the decoupling network by analyzing L-curves and singular values. However the problem of realizing the optimal decoupling matrix using practical circuits is still open and is currently work in progress.

2723.   Noise Figure and Gain Comparison of GaAs and SiGe Semiconductors at High B0 Field Strength
Russell Lagore1, Al-Karim A. Damji1, Alan H. Wilman1, and Nicola De Zanche2
1Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada, 2Department of Oncology, University of Alberta, Edmonton, Alberta, Canada

Gallium Arsenide (GaAs) and Silicon Germanium (SiGe) semiconductor devices behave differently in terms of gain and noise figure as B0 field strength increases and orientation varies. SiGe devices are essentially immune to B0 field variation while the more common GaAs devices are highly sensitive.

16-Channel Tx Array and 32-Channel Rx Array for Brain MRI at 7T
Wei Zhao1, Boris Keil1, Jonnathan R. Polimeni1, James N. Blau1, Azma Mareyam1, Thomas Witzel1, Elfar Adalsteinsson2, and Lawrence L. Wald1,3
1A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States, 2Electrical Engineering and Computer Science, MIT, Cambridge, MA, United States, 3Division of Health Sciences and Technology, Harvard-MIT, Cambridge, MA, United States

Ultra-high field MRI can potentially improve diagnostic power using a coil setup consisting of a pTx array and a separate multi-channel Rx array. 32-channel receive arrays have been widely used in 7T brain MRI for improving sensitivity and parallel imaging performance. The use of simultaneous reception with multiple coils to speed-up encoding, has proven to be a requirement for obtaining high spatial resolution fMRI at 7T. Therefore, for improving the image quality of the pTx system, we combined a 16-channel transmit array and a 32-channel receive array with the ability for highly accelerated encoding and to perform parallel transmit excitations.

2725.   Potential and Probability of Inner Ear Magnetic Resonance Imaging at 7 T
Kyoung-Nam Kim1, Gyu Cheol Han2, Phil Heo1, Hongbae Jeong1, Suk-Min Hong1, Joshua Haekyun Park1, Myung-Kyun Woo1, Young-Bo Kim1, and Zang-Hee Cho1
1Neuroscience Research Institute, Gachon University, Incheon, Korea, 2Department of Otolaryngology-HNS, Gachon University, Incheon, Korea

The cochlear and the vestibular system play important roles in sound perception and maintaining the body equilibrium by sensing body movements and sending signals to the brain through mechanoelectric transduction. In order to use MRI for diagnosing inner ear diseases, improvement in the sensitivity of MRI and the development of an optimized special RF coil system and proper sequence protocol are needed. We presented preliminary results for visualization of the inner ear for the first time using only a customized RF coil and without the use of a contrast medium at 7 T.

2726.   Hybrid RF Coils for Inner Ear Imaging at 7 T MR
Kyoung-Nam Kim1, Phil Heo1, Gyu Cheol Han2, Hongbae Jeong1, Suk-Min Hong1, Myung-Kyun Woo1, Myung-Kyun Woo1, Joshua Haekyun Park1, Young-Bo Kim1, and Zang-Hee Cho1
1Neuroscience Research Institute, Gachon University, Incheon, Korea, 2Department of Otolaryngology-HNS, Gachon University, Incheon, Korea

To achieve ultra-structural magnetic resonance imaging (MRI) of inner ear, hybrid radiofrequency (RF) coils and their integrated RF circuitries was employed at 7 T MRI and targeted to allowing the feasibility of small anatomical imaging. The coil configuration of hybrid RF coils for inner ear MR imaging was consist of two parts of 8-channel volume transmit/receive (Tx/Rx) and planar type of dual 4-channel Rx-only coil for simultaneous RF signal acquisition at 7 T. In in-vivo inner ear MR imaging, the hybrid RF coils showed improvement of SNR in the inner ear included cochlear, semicircular canal, and other organs was achieved and thus coverage to allow adequate observation of the encompassed anatomy of inner ear.

2727.   Switchable Bilateral/Unilateral 7T Breast Coil Using Forced Current Excitation
Jiaming Cui1, Ivan E. Dimitrov2,3, Sergey Cheshkov2,4, Mary P. McDougall1,5, Craig R. Malloy2,4, and Steven M. Wright1,5
1Electrical and Computer Engineering, Texas A&M University, College Station, Texas, United States, 2Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, United States, 3Philips Medical systems, Cleveland, Ohio, United States, 4Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas, United States, 5Biomedical Engineering, Texas A&M University, College Station, Texas, United States

Breast imaging and spectroscopy are of interest at 7T. In this abstract, a 7T Forced Current Excited (FCE) bilateral breast coil, which can be electronically switched to unilateral excitation mode, was developed. The coil was designed to provide the large field-of-view needed for bilateral breast imaging, while allowing unilateral mode when higher excitation fields are needed. Extending the forced current approach to two Helmholtz pairs avoided any difficulties with mode splits due to coupling between the closely spaced coils. The coil was tested at a 7T scanner using phantoms, demonstrating highly effective mode switching and excellent homogeneity.

16-Channel Receive Array Insert for Breast Imaging at 7T
Samantha By1, Joseph Rispoli1, Jiaming Cui2, Sergey Cheshkov3,4, Ivan E. Dimitrov3,5, Craig R. Malloy3,4, Steve Wright1,2, and Mary P. McDougall1,2
1Biomedical Engineering, Texas A&M University, College Station, TX, United States, 2Electrical and Computer Engineering, Texas A&M University, College Station, TX, United States, 3Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, United States, 4Radiology, University of Texas Southwestern Medical Center, Dallas, TX, United States, 5Philips Medical Systems, Cleveland, OH, United States

B1 inhomogeneities associated with high fields make effective imaging and hardware design challenging. "Forced current excitation" (FCE) provides homogeneous excitation and ease of tuning, irrespective of asymmetric loading, but the necessary incorporation of transmission line lengths in the resonant structure decreases SNR. This work presents the combined use of a FCE transmit breast coil with a 16-channel receive array insert to increase the receive sensitivity while taking advantage of the benefits of FCE during transmission. Breast imaging results indicate an improvement in SNR of up to six times from the insert as compared to the FCE coil in T/R mode.

Uniform Bilateral Breast MRI at 7T with Dual Transmit and 30-Channel Receive
Michel Italiaander1, Ingmar Voogt1, Irene van Kalleveen1, Bertine L. Stehouwer1, Tijl van der Velde1, Peter R. Luijten1, Vincent Oltman Boer2, and Dennis W.J. Klomp1
1UMC Utrecht, Utrecht, Utrecht, Netherlands, 2University Medical Center Utrecht, Utrecht, Utrecht, Netherlands

In the detection of breast cancer strong T1 weighting in contrast-enhanced MRI is essential, requiring a high density of strong flip angles, that generally will be limited due to SAR constrains particularly at 7 Tesla. Therefore we propose the use of efficient quadrature surface arrays to maximize contrast-enhanced MRI efficiency at 7 Tesla in the breast (bilateral). With B1 compensating RF pulses in one dimension and B1 shimming in the second dimension uniform flip angles can be obtained. Combined with 30 receivers, we demonstrate uniform and strong T1 weighting in a volunteer and in a patient with breast cancer.

2730.   Design of a Receiver Array for MRI-Guided Transrectal Prostate Biopsy
Francesca Galassi1, John McGinley1, Mihailo Ristic1, Nandita M. deSouza2, and Djordje Brujic1
1Imperial College, London, UK, United Kingdom, 2Institute of Cancer Research, The Royal Marsden Hospital, London, UK, United Kingdom

MRI Transrectal prostate biopsy requires updating of the targeted lesions while tracking the biopsy needle. Reliable tracking and fast, high resolution imaging require an optimized receiver. A novel external receive coil was designed to ensure higher signal from the prostate and from markers placed into a probe. The design was based on volunteer subjects and optimised for use with an MRI compatible manipulator. The sensitivity of the coil and the RF field homogeneity were evaluated. The results indicated significant improvements in sensitivity over the region of interest, with consequent improvements in needle tracking and imaging of the targets.

2731.   Analysis of Geometrical Arrangement for a 64-Channel Cardiac Phased-Array Coil for 3T
Mark Schuppert1, Boris Keil2, Bastien Guérin2, Stefan Fischer1, Laura Maria Schreiber1, and Lawrence L. Wald2,3
1Section of Medical Physics, Department of Diagnostic and Interventional Radiology, Johannes Gutenberg University Medical Center, Mainz, Germany, 2Department of Radiology, A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, 3Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA, United States

We analyze several different geometrical arrangements of coil elements in a 64-channel phased-array cardiac coil for optimized SNR and g-factor values in the heart using magnetic field simulations (Biot-Savart law). The final coil pattern comprises 40 coil elements on the chest and 24 coil elements on the back each exhibiting a diameter of 75mm. Lateral arrangement of coil elements wrapping around the body is important and results in a homogeneous SNR distribution and low g-factor values in the heart simultaneously.

2732.   Wireless Phased Array Endorectal Coil for Prostate Imaging
Haoqin Zhu1, Mehran Fallah-Rad1, and Labros Petropoulos1
1R&D, IMRIS Inc, Winnipeg, MB, Canada

A novel wireless endorectal phased array coil design was presented. It has shown that this coil can greatly improve image quality in terms of SNR and signal penetration on the prostate gland by 7.5 fold in average with the combination of both wireless endorectal coil and 8 channel flex phased array coil. When compared with an external cabled 8 channel flex phased array coil only. In addition to the SNR improvements, the wireless phased array endorectal coil design is lightweight, enhances patient comfort and set up workflow and can be made to be a disposable device. Besides the significant improvement in SNR, the proposed phased array design of the coil provides significant coverage over the prostate gland.

2733.   SENSE Induced Correlations Are Used to Optimize RF Coil Design for Specific FcMRI Studies
Iain P. Bruce1, L. Tugan Muftuler2,3, and Daniel B. Rowe1,2
1Department of Mathematics, Statistics, and Computer Science, Marquette University, Milwaukee, Wisconsin, United States, 2Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin, United States, 3Department of Neurosurgery, Medical College of Wisonsin, Milwaukee, Wisconsin, United States

In fcMRI, a significant dependence is placed on developing models and processing operations to rid the acquired data of artifacts at the neglected expense of altering the statistical properties of the acquired data. The alleviation of artifacts at a fundamental level, when the data is first acquired, would provide an appreciable advantage for specific fcMRI studies. Optimal RF coil designs can be achieved by minimizing a cost function in which both the g-factor is reduced to lower the amplification of coil related noise in a ROI, and the correlation induced by SENSE reconstruction is minimized to avoid type-I&II errors.

2734.   A Flexible 4 Ch. Transmit / 16ch. Receive Auditory Cortex Array for HiRes fMRI at 7 Tesla
Gregor Adriany1, Scott Schillak2, Matt Waks2, Brandon Tramm2, Alard Roebroeck3, Elia Formisano3, Federico DeMartino3, Essa S. Yacoub1, and University of Minnesota University of Minnesota Vaughan1,2
1Center for MR Research, University of Minnesota, Minneapolis, MN, United States, 2Life Services LLC, Minneapolis, MN, United States, 3Maastricht University, Maastricht, Netherlands

A dedicated 7 Tesla coil array for bilateral high-resolution fMRI of the temporal lobe is presented. 4 transceiver and 12 receiver-only loop coils were realized within a slim FDM molded housing. Excellent decoupling between the transceiver and receiver arrays was achieved allowing for on coil preamplifiers.

2735.   A 3T Transmit and 16 Channel Receive Array Coil for Hand/Wrist Imaging
Shinya Handa1, Matthew Finnerty1, Craig I. Lawrie1, Tsinghua Zheng1, Xiaoyu Yang1, Joseph Herczak1, Hiroyuki Fujita1,2, John A. Carrino3, Filippo Del Grande3, Guarav K. Thawait3, and Sahar J. Farahani3
1Quality Electrodynamics, Mayfield Village, Ohio, United States, 2Department of Physics, Case Western Reserve University, Cleveland, Ohio, United States, 3Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University, Baltimore, Maryland, United States

A transmit and 16 channel receive array coil for hand/wrist imaging at 3.0 Tesla was constructed and tested. The coil consists of an elliptical 8 rung birdcage coil for transmitting and an array of 16 independent loops for receiving. Initial phantom and volunteer imaging results demonstrated that the coil had excellent image quality, coverage of FOV, and required significantly less transmit power than an existing receive only coil.

2736.   A Semi-Optimized Phased Array Coil Design for High-Resolution MRI of Cervical Spinal Cord
Nabraj Sapkota1,2, Josh Kaggie1,2, J. Rock Hadley2, and Eun-Kee Jeong2,3
1Dept. of Physics and Astronomy, University of Utah, Salt Lake City, Utah, United States, 2Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, United States, 3Dept. of Radiology, University of Utah, Salt Lake City, Utah, United States

In this work, a Cervical Spinal Cord (CSC)-dedicated 8-channel phased array coil is developed with its layout and the dimension optimized using computer simulation. The performance of phased array coil depends on its shape, size and number of elements. The sensitivity of a phased array coil depends on the magnetic field of the coil perpendicular to the static magnetic field. The magnitude and direction of the RF magnetic field (B1) in 3-dimensional space is calculated using the Bio-Savart’s law and the shape and size of the surface coil is optimized. MRI experiments are performed to confirm the numerical simulation.

2737.   Mixing Loops and Electric Dipole Antennas for Increased Sensitivity at 7 Tesla
Graham C. Wiggins1, Bei Zhang1, Martijn A. Cloos2, Riccardo Lattanzi1, Gang Chen1, Karthik Lakshmanan1, Gillian Haemer1, and Daniel Sodickson1
1Center for Biomedical Imaging, NYU Medical Center, New York, NY, United States, 2Center for Biomedical Imaging, New York University School of Medicine, New York, NY, United States

Analysis of the ideal current patterns corresponding to the Ultimate Intrinsic SNR show that for large objects at high field there can be a substantial contribution from electric dipole-like currents. For a body sized cylindrical phantom at 7T the Ultimate Intrinsic SNR for the center of the object is 23% higher for electric dipole-like (curl free) currents compared to loop-only (divergence free) currents, and is 54% higher if a combination of current patterns is allowed. Lesser but still substantial benefits are demonstrated in both simulation and experiment in a coil design combining loops and electric dipoles.

2738.   Multi-Turn Transmit Coil to Increase B1 Efficiency in Current Source Amplification
Natalia Gudino1 and Mark A. Griswold1,2
1Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States, 2Department of Radiology, Case Western Reserve University, Cleveland, OH, United States

A multi-turn transmit surface coil design is presented to improve B1 efficiency when driven by on-coil current source amplification. Benchtop and 1.5 T MRI experiments showed a three-fold increase in B1 at same amplifier output current and without increasing heat dissipation in the amplifier. This gain in B1 allowed the use of lower power rated FETs that present lower port capacitances which could improve the overall performance of the on-coil current source transmitter and its multiple-channel implementation.

2739.   Reducing SAR and Imaging Time at 7T Using RF Multiplexing and Transceiver Arrays at 7T
Hoby P. Hetherington1, Nikolai I. Avdievich1, and Jullie Pan1
1Neurosurgery, Yale University, New Haven, CT, United States

At 7T, decreasing T2, T2* and increasing SAR and T1 can limit the number of slices acquired or acquisition time. RF multiplexing enables coil dense transceiver arrays (more coils than independent RF channels) to be used; which improves SNR (more optimal coil size and number) and B1 homogeneity and coverage. RF multiplexing inherently generates simultaneous multiple bands of excitation for slice selective pulses. The aliasing generated by the multiple bands of excitation can be removed by deconvolution with the receiver sensitivity matrix to regenerate three independent slices, thereby reducing SAR and increasing imaging speed by acquiring three slices per excitation.

2740.   The Ultimate Local SAR in MRI
Yigitcan Eryaman1,2, Bastien Guérin3, Elfar Adalsteinsson4,5, and Lawrence L. Wald2,5
1Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA, United States, 2Martinos Center for Biomedical Imaging, Dept. of Radiology, MGH, Charlestown, MA, United States, 3Martinos Center for Biomedical Imaging, Dept. of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, 4Dept. of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States, 5Harvard-MIT Health Sciences and Technology, Cambridge, MA, United States

We calculated a lower bound for peak 10 g local SAR that can be obtained with an arbitrary transmit coil in a uniform cylindrical phantom. For that purpose we used cylindrical basis expansion to express an arbitrary EM field in the phantom. Then the optimum least square RF shimming or pTx pulse solutions are calculated for the cylindrical modes with an explicit constraint to minimize local SAR. To make this optimization computationally possible the local SAR matrices are compressed using the VOP method. The result is the trade-off (L-curve) between the excitation fidelity and the lowest possible local SAR afforded by an arbitrary transmit array. The ultimate L-curves can be used as a figure of merit for the SAR performance of modeled or constructed pTx coils.

2741.   Performance Comparison of Parallel Transmit Arrays for Body Imaging at 3 T Under Local SAR Constraint
Bastien Guérin1, Matthias Gebhardt2, Peter Serano1, Elfar Adalsteinsson3, Michael Hamm2, Josef Pfeuffer2, Juergen Nistler2, and Lawrence L. Wald1
1Radiology, Massachusetts General Hospital, Charlestown, MA, United States, 2Siemens Healthcare, Erlangen, Germany, 3Electrical Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States

Little theoretical work has been done optimizing pTx array geometries and number of Tx channels. We simulate eight 3T body pTx arrays with varying number and distribution of Tx channels. We design transverse and coronal RF shimming and 2-spoke pulses subject to local SAR constraint. We show that adding Tx channels improves the local SAR vs. fidelity tradeoff however at the cost of increased power. For arrays with at least 8 Tx channels per row, it is beneficial to add channels in the z-direction as opposed to only in the transverse direction, especially for imaging in the coronal orientation.

2742.   Closed-Loop Control for Transmit Array Matching
Giorgos Katsikatsos1 and Klaas P. Pruessmann1
1Institute for Biomedical Engineering, Zurich, ZH, Switzerland

A closed-loop controlled matching for Tx-arrays in ultra-high field has been implemented as an autonomous system to react to load changes in various stages of an MR experiment. Building blocks of the system are the L-matching networks, built from custom low-loss capacitors actuated by piezoelectric motors and controlled by an external computer. The feedback is provided by a network analyzer which triggers the re-matching procedure. The matching algorithm is based on previous knowledge about the matching circuit connected to the array and uses common objective functions to detect the best matching settings for arbitrary loads.

2743.   Computerised Tuning of an 8-Channel Cardiac TEM Array at 7T: An Integrated System Using Piezoelectric Actuators and Power Monitors
Graeme A. Keith1, Christopher T. Rodgers1, Aaron T. Hess1, Carl J. Snyder2, University of Minnesota University of Minnesota Vaughan2, and Matthew D. Robson1
1Oxford Centre for Clinical Magnetic Resonance Research, University of Oxford, Oxford, Oxfordshire, United Kingdom, 2Center for Magnetic Resonance Research, Minneapolis, MN, United States

A novel method for tuning and matching an eight channel cardiac RF array for parallel transmit at 7 Tesla is presented. Piezoelectric stepping motors were used to allow automation of the process and remove the need for tuning by hand. S11 profiles for each channel were gathered showing the ratio between reflected and forward power across all of 2-D tune/match space. For both a phantom and in vivo these plots show a clear peak where the maximum S11 occurs. Auto-tuning at 7T was used in vivo to quickly and effectively to maximise the B1+.

2744.   An Easily Integrated Multichannel Modulator for All Field Strengths
Neal Hollingsworth1, Katherine Moody2, Jon-Fredrik Nielsen3, Douglas C. Noll3, William A. Grissom4, and Steven Wright1
1Electrical Engineering, Texas A&M University, College Station, TX, United States, 2Biomedical Engineering, Texas A&M University, College Station, TX, United States,3Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States, 4Biomedical Engineering, Vanderbilt University, Nashville, TN, United States

Parallel transmit allows for acceleration of spatially selective RF pulses using multiple, independently modulated channels. We have developed an improved, stand alone, multichannel vector modulation system to support work with multi-dimensional RF transmit pulses. The modulators are integrated with an existing MRI system by connecting the RF input to the power amplifier and a digital trigger to them. Scaling to high channel counts is straight forward due to a modular design. Further, they can be used with systems at virtually all field strengths by replacing a simple filter located on a daughter board.

2745.   Coil Tuning with Piezoelectric Actuators Using the MRI Signal as the Optimization Parameter
Aaron T. Hess1, Carl J. Snyder2, Graeme A. Keith3, Christopher T. Rodgers3, Stefan Neubauer3, University of Minnesota University of Minnesota Vaughan4, and Matthew D. Robson3
1University of Oxford, Oxford, Oxon, United Kingdom, 2University of Minnesota - Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, 3University of Oxford Centre for Clinical Magnetic Resonance Research, Oxford, Oxon, United Kingdom, 4University of Minnesota - Center for Magnetic Resonance Research, Minneapolis, MN, United States

The effectiveness of using MRI signal from turbo flash images to tune and match a four element transmit receive transverse electromagnetic (TEM) coil is assessed. The complete range of the tune and match capacitors is assessed over a 30x32 grid using piezoelectric controlled actuators. The measure was repeated in four coil elements in a phantom and two subjects. The maximum MRI signal fell within -10 dB reflected/forward power (S11) for the four elements. We conclude that MRI is a suitable metric for tuning and matching a TEM coil but less sensitive around the optimum than the S11 metric.

2746.   Searching for the Optimal Body Coil Design for 3T MRI
Jinfeng Tian1, Lance DelaBarre1, John Strupp1, Jay Zhang2, Josef Pfeuffer3, Michael Hamm3, Juergen Nistler3, Kamil Ugurbil1, and University of Minnesota University of Minnesota Vaughan1
1Center for Magnetic Resonance, University of Minnesota, Minneapolis, Minnesota, United States, 2Cardiology, University of Minnesota, Minneapolis, Minnesota, United States,3Siemens Healthcare, Erlangen, Germany

Short RF wavelengths in high field MRI result in less homogeneous |B1+| field and severe SAR gradients in body. To investigate possible solutions, B1 and SAR contours were calculated for ten different 3T whole-body coils. Referenced to a high-pass birdcage body coil, new design permutations included multi-channeled TEM and loop arrays with elements distributed in x, y, and z. RF fields were configured by circular polarization and by B1 shimming. Results showed all arrays with B1 shimming could greatly improve the RF homogeneity while the TEM 2x8 array provides optimal performance based on |B1+| homogeneity, peak SAR and power efficiency.

2747.   Design, Evaluation and Application of a Six-Channel Transceiver Array Tailored for In Vivo Human Eye Imaging at 7.0 T
Andreas Graessl1, Michael Schwerter1, Maximilian Muhle1, Jan Rieger1,2, Celal Oezerdem1, Abdullah Ok1, Davide Santoro1, Darius Lysiak1,2, Oliver Stachs3, Soenke Langner4, Paul-Christian Krueger4, and Thoralf Niendorf1,5
1Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrueck-Center for Molecular Medicine, Berlin, Germany, 2MRI.TOOLS GmbH, Berlin, Germany, 3Department of Ophthalmology, University of Rostock, Rostock, Germany, 4Institute for Diagnostic Radiology and Neuroradiology, University of Greifswald, Greifswald, Germany, 5Experimental and Clinical Research Center, Berlin, Germany

In vivo imaging of the spatial arrangement of eye segments and their masses is an emerging MRI application and ultimately aims at performing MR image-based biometry. For this purpose, a six-element transceiver eye coil array (f=298 MHz) which uses loop elements is proposed. Our EMF simulations and experimental results indicate that the use of multiple surface coil transceiver loop elements yields an excellent SNR for eye imaging, affords uniform signal intensity across the eyes, and facilitates the depiction of anatomical details of the eye.

2748.   Improved 2D RF Shimming with a Local Detunable 8-Element Transmit/Receive Coil Array Using DREAM and SENSE at 3T
Christoph Leussler1, Peter Vernickel1, Christian Findeklee1, Daniel Wirtz1, Peter Börnert2, and Kay Nehrke1
1Philips Technologie GmbH, Hamburg, Germany, 2Philips Research Laboratory, Hamburg, Germany

A dual mode Tx/RX coil is presented. In a first mode, the coil acts as a receive only coil array in combination with the conventional transmit body coil. In the 2nd mode, the coil is used as local Tx/Rx array with the mentioned advantages. While in the first mode the required SENSE reference information is generated, this information is used to accelerate the acquisition of the B1+ maps based on the DREAM technique in the second mode. Using both modes sequentially, we obtain all information required for exact B1+ mapping and fast RF shimming.

2749.   An 8 Channel Transmit Recieve Helmet Coil with Dodecahedral Symetry
Gillian Haemer1, Martijn A. Cloos2, and Graham Wiggins1
1The Bernard and Irene Schwartz Center for Biomedical Imaging, NYU Medical Center, New York, NY, United States, 2The Bernard and Irene Schwartz Center for Biomedical Imaging, New York University School of Medicine, New York, NY, United States

We describe here an 8-channel Transmit-Receive (TxRx) array, consisting of 8 loop elements, placed with dodecahedral symmetry at a safe distance from the average human head. The design was modeled after a previously proposed coil (ref) which was designed to allow for full brain coverage as well as variation along all three directions, x, y, and z. It has been modified here to better fit around the head and to balance all areas of each element at a precise distance from the subject.

2750.   Simulation Study of a 4-Channel Ladder-Shaped Body Coil at 3T
Yoshihisa Soutome1, Yosuke Otake1, Masayoshi Dohata1, Hisaaki Ochi1, and Yoshitaka Bito1
1Central Research Laboratory, Hitachi Ltd., Kukubunji, Tokyo, Japan

We have designed a 4-channel body coil with ladder-shaped coils and demonstrated its characteristics at 3T using numerical simulations. The designed coil can increase bore size in the right-left and anterior-posterior directions because of the increase in space between nearest neighbor coils. The designed ladder-shaped coils were decoupled from each other very well. The designed body coil also showed good B1 uniformity of 7.6% in the region-of interest of 40 cm and the same transmission efficiency as the birdcage coil in the loaded condition. Simulation results suggest that the designed coil can be used as a multi-channel transmit body coil

2751.   RF Body Coil Symmetry as a Function of Cable Routing
Ed B. Boskamp1, Masahiro Fujimoto1, and Michael Edwards1
1GE Healthcare, Waukesha, WI, United States

In MRI systems, receive coil connectors are part of the patient cradle for easy access. The patient cradle and coil cables travel through the bore of the system, and thus through the RF body coil. The electric fields generated by the body coil induce voltages and currents in the shielding of this cable bundle. These common mode currents are usually stopped by applying baluns on the cable shield. This research investigates coil symmetry perturbation due to the presence and motion of the cable and baluns. FEM simulation and lab measurements were performed to study the effect.

2752.   Design Guidelines for Utilizing Co-Planar Shielded Loops at 7T
Joseph Vincent Rispoli1, Samantha By1, and Mary P. McDougall1,2
1Biomedical Engineering, Texas A&M University, College Station, Texas, United States, 2Electrical & Computer Engineering, Texas A&M University, College Station, Texas, United States

The need for RF shields increases with increasing field strengths in regards to handling patient safety concerns and optimizing coil stability. Through electromagnetic modeling and bench measurements, this work presents design guidelines for co-planar RF shields to reduce specific absorption rate while maintaining effective B1.

2753.   Simple and Accurate Determination and Visualization of True Quadrature Settngs on Commercial Multiple Channel Transmitters Using Anti-Quad
Steven M. Wright1, Ivan E. Dimitrov2,3, Sergey Cheshkov2, Mary P. McDougall4, and Craig R. Malloy2
1Electrical and Computer Engineering, Texas A&M University, College Station, TX, United States, 2Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, United States, 3Philips Medical Systems, Cleveland, OH, United States, 4Biomedical Engineering, Texas A&M University, College Station, TX, United States

In addition to B1 homogeneity, searching for the most efficient (true quadrature) B1+ is desirable for a number of applications, especially those that require high power, e.g. proton decoupled spectroscopy. This abstract discusses a simple method for calibration of the drive phases in a two channel transmit system. Setting the phases for reverse circular polarization (anti-quad) provides greater sensitivity for the validation of the phase calibration for ‘steering’ to a point of interest. In addition to its general applicability for coil calibration, this method may find application in steering the zero effective field needed for catheter-tracking based on reverse polarization.

2754.   Improving B1 Excitation in Head Apex by Combining Birdcage Coil with Crossed Dipole Elements
Karthik Lakshmanan1, Martijn A. Cloos2, Graham C. Wiggins1, and Ryan Brown1
1NYU, Newyork, Newyork, United States, 2New York University School of Medicine, Newyork, Newyork, United States

Circularly polarized volume coils have been for B1 excitation in head imaging at 7.0 Tesla. However the excitation in head apex produced by CP Volume coil is usually poor. In this work we improved the excitation in Head Apex by combining a crossed dipole Antenna pair with a Birdcage coil. With this setup we were also able to manipulate the excitation pattern in the center of the Head.

2755.   Baluns for UHF Transmit Arrays
Debra S. Rivera1,2 and Turner Robert2
1Univercity Medical Center, Utrecht, Netherlands, 2Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Saxony, Germany

For transmit elements, mismatch in phase or amplitude of signal delivered to the two sides of a coil element cause common-mode current losses. Using 3-port mixed-mode scattering parameters, the authors compare common-mode rejection (CMR) and insertion loss (IL) of lattice and wire-wound baluns. Transmit efficiency of the different baluns, and a through were compared for a 7T head transmit array. All baluns were tuned to CMR <-20 dB, and provided >20% improbed power efficiency, indicating the severity of common-mode losses for 7T. Transmit efficiency correlated with IL, favoring wire-wound baluns.

2756.   Effect of Number of RF Transmit Channels for RF Shimming in Partial Region
Yukio Kaneko1, Yoshihisa Soutome1, Hideta Habara1, and Yoshitaka Bito2
1Hitachi Ltd., Central Research Laboratory, Kokubunji, Tokyo, Japan, 2Hitachi Ltd., Hitachi, Ltd., Kokubunji, Tokyo, 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 for the entire region of the torso. However, the effect for a partial region of the torso in 3T has not yet been investigated. In this study, numerical simulation has been used to investigate the effect of the number of RF transmit channels for regional RF shimming in the torso region in 3T. The results show that 4-channel and 8-channel RF shimming can contribute to improving the B1 inhomogeneity in a partial region.

2757.   Transmit Array with Novel Shield and Fabrication Technique for Reducing Losses at UHF
Debra S. Rivera1,2, Thomas Siegert3, Carsten Koegler2,4, Andreas Schaefer2, Markus Nikola Streicher3, and Robert Turner2
1Univercity Medical Center, Utrecht, Netherlands, 2Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Saxony, Germany, 3Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Saxony, Germany, 4RAPID Biomedical, Rimpar, Germany

The authors present a 7T head transmit array made of interlocking printed circuit boards (PCBs). The two-stage prototyping process, focused on minimizing radiation losses and coil asymmetries. A transparent mesh shield was used which suppresses eddy-currents and allows line-of-sight to the region of interest. Data was collected with a cylindrical phantom for the hand-built prototype, and for the PCB array with two different shields. The greatest symmetry and power transmitted to the phantom was observed for the PCB array with the transparent shield. Anatomical phantom or brain data is projected to be available for the conference.

2758.   Comparison of 3 RF Head Arrays for 7T MRI
Jinfeng Tian1, Devashish Shrivastava1, Gregor Adriany1, John Strupp1, Scott Schillak2, Jay Zhang3, Kamil Ugurbil1, and University of Minnesota University of Minnesota Vaughan1
1Center for Magnetic Resonance, University of Minnesota, Minneapolis, Minnesota, United States, 2Virtumed, LLC, Minneapolis, Minnesota, United States, 3Cardiology, University of Minnesota, Minneapolis, Minnesota, United States

Previous research has demonstrated feasibility of 3D RF arrays in mitigating RF inhomogeneities for ultra-high field MRI applications. Three RF coil designs were simulated to investigate their relative |B1+| and SAR performance in 7T whole-head MRI. A 16-ch 2D TEM reference coil was compared to a 30-channel, 3D TEM array, and a 32 channel, 3D loop array. All coils were circularly polarized in this initial study by numerical simulation. The 3D loop array exhibited a higher |B1+| on the central trans-axial slice, together with higher mean SAR on all three central slices, and higher peak 1gram and 10gram SAR across the whole head. Advantages of these 3D arrays will be further explored through B1+ shimming models.

2759.   7 Tesla Body Imaging with TIAMO on Single-Channel Tx Systems
Stephan Orzada1,2, Stefan Maderwald1, Sören Johst1,2, Andreas K. Bitz1,2, Klaus Solbach3, and Mark E. Ladd1,2
1Erwin L. Hahn Institute for MRI, Essen, NRW, Germany, 2Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, NRW, Germany, 3High Frequency Engineering, Department of Electrical Engineering, University of Duisburg-Essen, Duisburg, NRW, Germany

In today’s high-field systems, severe problems regarding the homogeneity of the transmission field are encountered. Most of the methods proposed to tackle these problems are multichannel methods. Recently, Time-Interleaved Acquisition of Modes (TIAMO) has been proposed to cope with B1 inhomogeneity in ultra-high-field imaging. In this work we present a simple and inexpensive hardware setup which makes it possible to use TIAMO on any single-channel Tx system while making use of the vendor-provided single-channel RF safety system. We show that with this setup 7 Tesla spin echo imaging of the pelvis is possible without severe signal dropouts.


Wednesday, 24 April 2013 (13:30-15:30) Exhibition Hall
Specialized Systems & Devices

2760.   A Dedicated 1.5T NICU MR System
Wolfgang Loew1, Jean A. Tkach1, Ronald G. Pratt1, Barret R. Daniels1, Randy O. Giaquinto1, Stephanie L. Merhar1, Beth M. Kline-Fath1, Kim M. Cecil1, and Charles L. Dumoulin2
1Imaging Research Center, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, United States, 2Imaging Research Center, Cincinnati Children's Hospital, Cincinnati, Ohio, United States

In this abstract we present the development of a dedicated 1.5T neonatal MR system for Neonate Intensive Care Units (NICUs). This novel system utilizes a small footprint magnet with advanced imaging capabilities and a dedicated patient handling system. A systems overview is given including the workflow of the patient handling. Clinical relevant spectroscopy scans and an in-vivo imaging scan were acquired on neonates.

2761.   Development of a Portable Wrist MRI for Skeletal Age Assessment
Yasuhiko Terada1, Kazunori Ishizawa1, Shinya Inamura1, and Katsumi Kose1
1Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki, Japan

A portable wrist MRI system for skeletal age assessment without special RF shielding was developed. The system consisted of a small 0.3 T permanent magnet of 135 kg weight, which is readily portable and can be placed anywhere. Despite the small magnet gap (8 cm), the B0 and B1 homogeneities and the gradient nonlinearity were high over 8 cm × 8 cm × 4 cm diameter ellipsoidal volume. The portable system provided wrist images with high quality that are as reliable as those provided by a compact hand MRI system with a 0.3 T permanent magnet of 700 kg weight.

2762.   A Portable Low-Field System for Localized NMR Measurements
Mikayel Dabaghyan1, Eric Frederick2, Iga Muradyan3,4, Alan Hrovat1, Michael Hrovat1, Samuel Patz3,4, and Mirko I. Hrovat1
1Mirtech Inc., Brockton, MA, United States, 2Physics, University of Massachusetts, Lowel, Lowell, MA, United States, 3Radiology, Brigham and Women's Hospital, Boston, MA, United States, 4Harvard Medical School, Boston, MA, United States

Here we describe a system of monohedral permanent magnets that make up a part of a device for uni-lateral portable NMR. The magnets generate a focused region with a uniform magnetic field, located several centimeters above the surface of the magnet. The surface of the magnet is placed on the posterior portion of the chest allowing the homogeneous field region to be located inside the lung. The device can measure a proton signal, as well as that of hyperpolarized Xe, in order to measure lung density and ventilation respectively.

2763.   Reducing the Gradient Artefact in Simultaneous EEG-fMRI by Adjusting the EEG Cap Lead Configuration
Karen J. Mullinger1, Muhammad E.H. Chowdhury1, and Richard W. Bowtell1
1SPMMRC, School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom

EEG data recorded simultaneously with fMRI acquisition are contaminated by large voltages generated by the time-varying magnetic field gradients. Previous work suggested changing the EEG cap lead layout and cable bundle position could reduce the gradient artefact (GA). Here, through simulations and experiments, we show that a reduction of the GA can be achieved through the suggested modifications. Using a modified cap, we experimentally demonstrate significant reduction in the GA amplitude over the temple regions using a standard EPI sequence. Different lead configurations could be explored to minimise the GA for other electrodes depending on the cortical areas of interest.

2764.   A Compact Setup to Improve the Quality of EEG Data Recorded During fMRI
Sara Assecondi1,2, Paolo Ferrari1, and Jorge Jovicich1
1Functional Neuroimaging Laboratory, Center for Mind/Brain Sciences (CIMeC), University of Trento, Trento, Italy, 2School of Psychology, University of Birmingham, Birmingham, United Kingdom

We describe the setup for simultaneous EEG-fMRI experiments used in our institution with a 4T MR-scanner. In our laboratory a compact setup was devised, in which the EEG cables are shortened and the amplifiers placed closer to the MR (RX/TX) coil and stabilised on a wooden form-fitting extension moving with the MR-bed. We found that a careful design of the EEG-fMRI workplace, tailored to the laboratory-specific needs, not only improves the quality of EEG data during simultaneous EEG-fMRI, but might also have an impact on important aspects such as safety, ergonomics and reproducibility of the setup across sessions and laboratories.

2765.   Cost Efficient Small Animal Monitoring and Trigger Device for Clinical Scanners
Karl-Heinz Herrmann1, Norman Pfeiffer1,2, Ines Krumbein1, Lutz Herrmann2, and Jürgen R. Reichenbach1
1Medical Physics Group, Institute of Diagnostic and Interventional Radiology I, Jena University Hospital - Friedrich Schiller University Jena, Jena, Germany, 2Ernst-Abbe-Fachhochschule Jena, Jena, Germany

A cost efficient system to acquire a respiratory and cardiac monitoring signal for small animals like mice and rats is presented. The motion detection is based on a small pressure pad and the signal is converted and processed by an analog amplifier and filter circuit. The output in the range of Volts allows any kind of further visualization or sophisticated post-processing in hard- or software. Exemplarily the improved image quality of T2 weighted MR images are shown using the generated respiratory trigger in comparison to the untriggered images.

2766.   RF-Selective-Excitation for State Estimation of an MRI-Powered Motor
Christos Bergeles1, Panagiotis Vartholomeos1, Lei Qin2, and Pierre E. Dupont1
1Boston Childrens Hospital, Harvard Medical School, Boston, MA, United States, 2Dana-Farber Cancer Research, Harvard Medical School, Boston, MA, United States

MRI-powered motors may allow the design of interventional medical robots that are powered, imaged, and control by MRI-scanners. Closed-loop control of an MRI-powered motor is necessary for maximum energy transfer and stability. This abstract presents a real-time tracking methodology based on RF-selective excitation that allows closed-loop control of an MRI-powered motor.

2767.   in-vivo High Resolution Rat Brain Using a Temperature-Stable High-Temperature Superconducting Cryostat at 3 Tesla
In-Tsang Lin1, Hong-Chang Yang2, and Jyh-Horng Chen3
1Interdisciplinary MRI/MRS Lab, Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, 2Department of Physics, National Taiwan University, Taipei, Taiwan, 3National Taiwan University, Taipei, Taiwan

In this work, a compact temperature-stable high temperature superconducting (HTS) cryo-system for keeping animal rectal temperature at 37.4 ºC for more than 3 hours was successfully implemented. The proton resonant frequency (PRF) method was used to monitor the frozen effect. The signal-to-noise ratio (SNR) of the HTS surface coil at 77 K is higher than that of a professionally-made copper coil at 300 K with the same geometry and the SNR gain is 3.79 folds.

2768.   Phantoms for Ultra-Low Field MRI
John Arthur Benson Mates1, Michael A. Boss1, Hsiao Mei Cho1, Gene C. Hilton1, and Kent D. Irwin1
1National Institute of Standards and Technology, Boulder, CO, United States

We constructed phantoms for the characterization of ultra-low field (~100 uT) MRI systems and measured them at 132 uT, 1.5 T, and 3 T. The phantoms permit characterization of resolution, PD accuracy, and T1 accuracy. The phantoms can serve as common references and guide ultra-low field scanner development.


Wednesday, 24 April 2013 (13:30-15:30) Exhibition Hall

2769.   An Actively Shielded 3T MgB2 MRI Magnet Design
Michael A. Martens1, Tanvir Baig1, Mihai Cara1, Robert W. Brown1, David Doll2, and Michael Tomsic2
1Case Western Reserve University, Cleveland, OH, United States, 2Hyper Tech, Columbus, OH, United States

Superconducting MRI magnets are dominantly made with NbTi wire cooled below 4.2K using liquid helium. As helium costs have more than tripled in the last decade, there is a need for a cryogen-free conduction-cooled alternative. A key reason for pursuing MgB2 superconductor wire in the design of MRI magnets is its superior critical current compared to NbTi over a temperature range of 10-15K. We present a 3T whole body actively shielded main magnet design assuming second-generation multifilament MgB2 wire using an improved functional approach. Trade-offs for the reduction of any given parameter are analyzed.

2770.   A Novel Magnet Main Coil Design with Shimming Capability
Zhenyu Zhang1 and Weijun Shen1
1GE Healthcare, Florence, South Carolina, United States

A major constrain of MRI superconducting magnet design is the cost and it becomes increasingly important given the dynamics in global market. Shimming system, an essential subsystem in MRI magnets, is one of the areas where constant efforts have been put down to make it more cost-effective. In this paper, a novel magnet coil design scheme, which minimizes B0 inhomogeneity through micro-adjustments of main coil currents, is presented. This design could substantially reduce system cost in comparison to traditional designs such as a set of standalone shimming coils.

2771.   Measurements of the Magnetic Field Distribution in the High Tc Superconducting Bulk Magnet During the Magnetization Process
Daiki Tamada1,2, Takashi Nakamura1,2, and Katsumi Kose1,2
1Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki, Japan, 2RIKEN, Wako, Saitama, Japan

A high critical temperature superconducting bulk magnet is a novel magnet for magnetic resonance imaging which has the advantage of its compactness. However, it is a difficult to achieve a homogeneous magnetic field sufficient for MRI because of the complicated magnetization process. In this study, we clarified the magnetization process by measuring the magnetic field distribution of the bulk magnet using a phase method based on 3D spin echo sequences.


Wednesday, 24 April 2013 (13:30-15:30) Exhibition Hall
Novel RF Coils

2772.   Parallel Imaging and Acceleration in the Johnson Noise Dominated Regime
Cristen D. LaPierre1,2, Mathieu Sarracanie1,2, Lawrence L. Wald1,3, and Matthew S. Rosen1,2
1Department of Radiology, Mass General Hosptial, A.A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States, 2Department of Physics, Harvard University, Cambridge, MA, United States, 3Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA, United States

Parallel imaging in the Johnson noise dominated regime is a new regime; optimal parameters are not available in the literature. In this study, an eight-coil receive only array for 6.5 mT was constructed and SENSE was used to accelerate images. An 8 channel receive only array was constructed from 8 cm, 30 turn, 24 gage wire inductive coils. The correlation coefficient matrix was almost the identity matrix. SENSE with a reduction factor of 2 was simulated and then acquired and images were successfully reconstructed. Future work will attempt higher reduction factors and combine SENSE with random undersampling.

2773.   Detunable RF Coil for Arterial Spin Labeling at 7T
Myung-Kyun Woo1, Randall B. Stafford2, Suk-Min Hong1, Se-Hong Oh2, Young-Bo Kim1, Jongho Lee2, and Zang-Hee Cho1
1Neuroscience Research Institute, Incheon, Korea, 2Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States

Arterial Spin Labeling (ASL) at ultra-high field benefits from increased spin polarization and blood T1 and has potential to improve perfusion maps. However, one needs to overcome the challenges of increased specific absorption rate (SAR), B0 and B1 inhomogeneity. Particularly, SAR is an important hurdle for continuous or pseudo-continuous ASL due to the use of long RF labeling. To address this challenge, we have developed a new RF coil system that has separate labeling coils. This approach allows us to reduce SAR by removing RF for the control condition.

2774.   A Novel Four-Channel Phased Array Coil with a Special Shield for Cardiac Functional Imaging
Dasong Zhu1, Yuki Mori1, and Yoshichika Yoshioka1
1Biofunctional Imaging Lab, Immunology Frontier Research Center, Osaka University, Suita, Osaka, Japan

MRI is playing an increasingly important role in the evaluation of cardiovascular disease. How to improve signal-to-noise rate (SNR) of cardiac imaging is one of the important factors for cardiovascular research. Usually Transmit/receive arrays are used in the 1.5T, 3T and 7T MRI for decreasing RF inhomogeneities and increasing SNR. Strengthening the effect of transmitting radio frequent(RF) can improve SNR under the ruled specific absorption rate(SAR). In this work, a novel shield circuit is proposed to strengthen transmitting magnetic field(B1) and we got much higher SNR from our experiment results.

2775.   Soft Surface - EBG Structure to Improve the |H|/|E| Field Ratio of Stripline Coil for 7 Tesla MRI
Gameel Saleh1, Klaus Solbach1, Daniel Erni2, and Andreas Rennings2
1High Frequency Technique (HFT), University of Duisburg-Essen, 47048, Duisburg, Germany, 2General and Theoretical Electrical Engineering (ATE), University of Duisburg-Essen, and CENIDE - Center for Nanointegration Duisburg-Essen, 47048, Duisburg, Germany

In this paper, a multilayer offset EBG structure is introduced as a high surface impedance ground plane to maximize the magnetic field intensity inside the phantom, by suppressing the anti-phase currents on the metallic ground plane. The proposed structure works as a Soft surface with higher surface impedance in the longitudinal direction (like a perfect magnetic conductor PMC), and lower surface impedance in the transversal direction (like a perfect electric conductor PEC). The MRI strip-line coil backed by our EBG structure is successful in exhibiting a stronger H/E field ratio (amounts to 58 %) inside the phantom than the original design using a (PEC) ground plane for the coil.

2776.   Whole-Brain and Local Receive Arrays for Imaging Non-Human Primates
Kyle M. Gilbert1, Matthew R. DiPrimio1, Sarah Hughes1, Kathryn Y. Manning1, and Ravi S. Menon1
1Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada

A 16-channel whole-brain receive coil and 7-channel local receive coil was developed for imaging non-human primates. This coil system will allow for high-resolution imaging of the peripheral cortex with the ability to co-register to a whole-brain image. Performance metrics of the two coil arrays are provided.

2777.   Design of a Four-Channel Array Coil for Dual High-Resolution Rat Knee MR Imaging
Anne-Laure Perrier1, Jean-Christophe Goebel1, Astrid Pinzano2, Emilie Roeder2, Pierre Gillet2, Denis Grenier1, and Olivier Beuf3
1Creatis, Villeurbanne, France, 2PPIA, Vandoeuvre-les-Nancy, France, 3CREATIS, Villeurbanne, France

An equivalent electrical circuit of a four-channel NMR surface coil based on common conductor decoupling technique was proposed. The topology allowed good matching and good decoupling between elements without the use of additional low input impedance preamplifier and without additional capacitive network. The design of a four-channel surface coil with a particular wave-like topology for the simultaneous two rat knees imaging was realized at 300 MHz. The capacitor adjustments permit to obtain decoupling better than -17 dB between all element pairs. To our knowledge, this coil represents the first four-channel NMR surface coil based on common conductor not using the preamplifier decoupling technique. Performance of the coil was proved through the simultaneous HR-MRI of both knees joint of a rat. Voxel size of 49x49x98 µm3 was obtained for a 1h22min acquisition time.

2778.   A Whole-Brain 8-Channel Receive-Only Embedded Array for MRI and fMRI of Conscious Awake Marmosets at 7T.
Daniel Papoti1, Cecil Chern-Chyi Yen1, Julie Mackel1, Hellmut Merkle1, and Afonso C. Silva1
1NINDS, NIH, Bethesda, Maryland, United States

We have previously devised a helmet restraint system to allow MRI/fMRI experiments of conscious, awake marmosets in a completely non-invasive and comfortable manner. The present work describes the development of a whole-brain 8-channel receive-only surface array for conscious, awake marmosets. Improved SNR is obtained by placing the coil elements on the inner surface of the helmet, to minimize the distance between the array elements and the cortical brain surface. The coil elements are built using flat and flexible conductors and are connected to low input impedance preamplifiers. Results show excellent brain coverage, good coil-to-coil isolation and high sensitivity.

2779.   A PIN-Diode-Controlled Double-Tuned Birdcage Coil for 1H-Imaging and 31P-Spectroscopy on Mice
Maximilian N. Voelker1, Alexander M. Koenig1, Steve Braun1, Andreas H. Mahnken1, and Johannes T. Heverhagen2
1Diagnostic Radiology, Philipps University, Marburg, Hessen, Germany, 2University Institute of Diagnostic, Interventional and Pediatric Radiology, Inselspital, Bern University Hospital, Bern, Switzerland

A PIN-diode switched Birdcage coil for MRI on mice at 7T had been developed. PIN-diodes are used directly on the end rings of a high pass birdcage to add a second/parallel capacitor line to a 1H-tuned Birdcage coil. Therefore the resonance frequency can be changed between proton and phosphor frequencies. The intended usage is proton imaging and spectroscopy with phosphor spectroscopy as an Add-on. The coil is easy to match and tune and shows superior SNR to a 4-Ring-BC of similar size in proton imaging, but lower SNR on phosphor resonance mode.

2780.   Dedicated 8-Channel Transceive Array for Rat Head MRI at 9.4T
Yu Li1, Ewald Weber1, Ivan Hughes1, Stuart Crozier2, Peter Ullmann3, Johannes Schneider3, and Sven Junge3
1School of ITEE, The University of Queensland, Brisbane, Select, Australia, 2The University of Queensland, Brisbane, Select, Australia, 3Bruker BioSpin MRI GmbH Ettlingen Germany, Ettlingen, Germany

To benefit from the advantages of Parallel Excitation (PEX)/Transmit SENSE and Spatially Selective Excitation (SSE) imaging, a dedicated 9.4T phased-array for rat head MRI was developed. An 8-channel transceive array coil was modelled /simulated and a prototype was constructed and tested in a Bruker 9.4T Biospec MRI system. Preliminary experimental results presented herein demonstrate the potential of the work.

2781.   Simultaneous Dual-Nuclear 31P/1H MRS at a Clinical MRI System with Time-Sharing Second RF Channel
Eun-Kee Jeong1,2, Nabraj Sapkota3, Joshua Kaggie3, and Xian-Feng Shi4
1Radiology, University of Utah, Salt Lake City, UT, United States, 2Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, UT, United States, 3Dept. of Physics, University of Utah, Salt Lake City, UT, United States, 4Dept. of Psychiatry, University of Utah, Salt Lake City, UT, United States

This work presents a novel acquisition method that simultaneous measures both 31P and 1H MR spectroscopies at the exactly same sampling window within the same acquisition, at a clinical MRI system that is equipped with a time-sharing second RF channel. The high frequency 1H NMR signal is down-converted to the carrier 31P frequency, using additional RF components, which includes PIN-diode driven RF switches, preamplifier for 1H frequency, a precision synthesizer, a mixer, and low-pass filter, and measured at one of the 31P receive channels. The residual water signal is used to identify and correct the phase-error on both 1H and 31P spectra. Pulse sequence manipulates both spin systems within the same acquisition using time-shared RF transmission.

2782.   A Form-Fitted 3 Channel 31P, Two Channel 1H Transceive Coil for Calf Muscle Studies at 7 T
Elmar Laistler1,2, Sigrun Goluch1,2, Andre Kuehne1,2, Martin Meyerspeer1,2, Albrecht Ingo Schmid1,2, Jürgen Sieg1,2, Tim Herrmann3, Johannes Mallow3, Johannes Bernarding3, and Ewald Moser1,2
1Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria, 2MR Centre of Excellence, Medical University of Vienna, Vienna, Austria,3Institut für Biometrie und Medizinische Informatik, Otto von Guericke University, Magdeburg, Germany

We show first results with an 3ch 31P/2ch 1H RF coil providing both increased sensitivity and an enlarged sensitive volume, as compared to commonly available single surface coils. Together with the higher transverse magnetization available at 7T, this will enable measurements of muscle metabolism in the human calf with unprecedented accuracy.

2783.   Dual-Tuned Strip-Line Loop Array H1 / Birdcage Na23 RF Coil for 3T MRI
Seunghoon Ha1, Harry Friel2, Marijn Kruiskamp3, and Orhan Nalcioglu1,4
1Tu & Yuen Center for Functional Onco-Imaging, University of California Irvine, Irvine, California, United States, 2Philips Healthcare, Highland Heights, Ohio, United States, 3Philips Healthcare, Best, Netherlands, 4Department of Cogno-Mechatronics Engineering, Pusan National University, Pusan, Korea

The common scheme of using trap circuits for dual-tuned operation results in increased coil losses as well as problems in obtaining optimal tuning and matching at both frequencies. Against these reserved problems, the duel tuned RF coil combined with strip-line coils array and a birdcage coil has proven their performance at 7T. However, a loop coil generates more uniformed B1- field and has better coil sensitivity than a strip-line coil at 3T. In the study, we construct the dual coil combined with a H1 loop coils array and a Na23 birdcage coil as well as evaluate decoupling methods to solve inter loop coupling.

2784.   A Novel Double Tuned 4T 1H/17O Head Volume Coil
Jing-Huei Lee1, Mathew Norris1, Elizabeth M. Fugate1, Nikolai I. Avdievich2, and Hoby P. Hetherington2
1University of Cincinnati, Cincinnati, OH, United States, 2Yale University, New Haven, CT, United States

The development and implementation of the CMRO2 imaging approach based on high-field 17O magnetic resonance spectroscopic (MRS) imaging, combined with brief inhalation of17O-isotope-enriched oxygen gas, has received increased interest. However, the low sensitivity of 17O MR signal has limited the potential of this technique. In this work, we introduced a novel double tuned 1H/17O head volume coil, in which the 1H coil is driven in quadrature mode and the 17O coil utilizes phased array approach.

2785.   A Dual-Tune Sodium/Proton Tx/Rx 14-Channel Sodium and 2-Channel Proton Array Breast Coil at 7T
Xiaoyu Yang1, Shinya Handa1, Tsinghua Zheng1, Craig I. Lawrie1, Matthew Finnerty1, Joseph Herczak1, Hiroyuki Fujita1,2, Wolfgang Bogner3,4, Olgica Zaric3, Stefan Zbýn3, and Siegfried Trattnig3
1Quality Electrodynamics, Mayfield Village, OH, United States, 2Physics, Case Western Reserve University, Cleveland, OH, United States, 3Department of Radiology, Medical University Vienna, Vienna, Austria, 4Department of Radiology, Harvard Medical School, Boston, ma, United States

A Dual-Tune Sodium/Proton Tx/Rx 14-channel Sodium and 2-channel Proton Array Breast Coil at 7T was constructed and tested. The coil was built using nested approach without using lossy traps or PIN diodes. The coil has a three-layer structure. Initial volunteer imaging results demonstrated that the coil had promising image quality on both sodium and proton.

2786.   Comparison of Decoupling Schemes for a Three Channel 31P Array for the Human Calf Muscle at 7 T Using 3D Electromagnetic Simulation
Sigrun Goluch1,2, André Kühne1,2, Ewald Moser1,2, and Elmar Laistler1,2
1Center of Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria, 2MR Centre of Excellence, Medical University of Vienna, Vienna, Austria

NMR spectroscopy benefits from higher sensitivity, increased spectral resolution and shorter relaxation times at 7T. To gain sensitivity it is common practice to use phased arrays. This technique leads to mutual coupling between array elements. In this work we compare three different decoupling schemes for a three channel 31P array using 3D electromagnetic simulation.

2787.   A Four-Channel 1H/31P Dual-Tuned Transceiver Array for 7 Tesla Cardiac Spectroscopy
Hai Lu1, Xiaotong Sun1, Yu Shao1, Nouha Salibi2, Bernd Stoeckel2, Thomas Stewart Denney Jr.1, Ronald J. Beyers1, and Shumin Wang1
1Auburn University, Auburn, AL, United States, 2Siemens, Malvern, PA, United States

Early stages of heart failure are characterized by reduction in energy reserve with impairment of myocardial contractility and/relaxation. The Pcr/ATP ratio obtained from 31P MRS is a metabolic parameter to assess myocardial energetic reserves. In this study, we propose to develop a four-channel 1H/31P dual-tuned transceiver array for cardiac spectroscopy at 7 Tesla. A unique coil design was employed to achieve decoupling of neighboring coils at multiple frequencies simultaneously. Static B1 shimming with both phase and magnitude was further applied at 7T to ensure that no intensity fallout occurs in the heart region. Phantom test results confirmed the design principle.

2788.   Development and Performance Evalution of a Dual Tuned 23Na/1H Knee Coil
Gunthard Lykowsky1, Flavio Carinci1, Peter M. Jakob1,2, and Daniel Haddad1
1MRB Research Center, Würzburg, Bavaria, Germany, 2Department of Physics 5, University of Würzburg, Würzburg, Bavaria, Germany

Although sodium imaging has shown promising results for years, sodium MR is still intrinsically challenging because of the low sensitivity of the 23Na nucleus, low in vivo concentrations, fast transverse relaxation times and the requirement for dual tuned RF coils. Several dual tuning approaches with specific advantages and drawbacks have been proposed over the years, e.g. LC traps, PIN diodes or additional rungs. In this study we use an alternate rung concept to build a 1H/23Na quadrature birdcage and evaluate its performance in regards of SNR and B1 homogeneity.

2789.   Technology Development for Sub-0.3 Mm Voxel Functional Imaging of the Murine Forepaw Barrel Subfield at 400MHz (9.4T)
Phillip D. Bishop1, Jason W. Sidabras1, Andrzej Jesmanowicz1, Rupeng Li1, and James S. Hyde1
1Biophysics, Medical College of Wisconsin, Milwaukee, WI, United States

A 400 MHz (9.4 T) site-specific surface coil was developed to image the rat forepaw barrel subfield at the cortical column level for functional MRI BOLD studies. To pinpoint this activation to a specific cortical column, the signal-to-noise ratio (SNR) must be appreciably high with a very small voxel size. A low-noise-amplifier was used to overcome losses along the signal path. Images with resolution under 200 micron cubic are now possible. SNR values comparing different voxel sizes are tabulated and compared to the traditional Bruker Surface Coil.

2790.   RF Coil and Positioning Setup for IMCL Spectroscopy on the Mouse Calf
Dominik Berthel1, Michael Neumaier2, Titus Lanz1, Thomas Kaulisch2, and Detlef Stiller2
1Rapid Biomedical GmbH, Rimpar, Germany, 2In-Vivo Imaging Unit, Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach, Germany

Positioning the muscle fibers along the main magnetic field (B0) is important to obtain well-resolved and undistorted lipid MR-spectra. For qualified 1H-MR spectroscopy (1HMRS) of intra-myocellular lipids (IMCL) we present a positioning and fixation setup for the mouse calf combined with an optimized and highly sensitive two channel RF receive coil. By the use of this setup fast positioning of the in vivo objects are assured, incorrect voxel-positions will be avoided and so a high throughput of IMCL-studies can be achieved.

2791.   RF Coil Configuration Study for 7T High Resolution Na23 and H1 Animal MRI
Seunghoon Ha1, Se-Ho Lee2, Mark Jason Hamamura1, Keum-Shik Hong2, and Orhan Nalcioglu1,2
1Tu & Yuen Center for Functional Onco-Imaging, University of California Irvine, Irvine, California, United States, 2Department of Cogno-Mechatronics Engineering, Pusan National University, Busan, Busan, Korea

The high resolution multinuclear imaging in animal study has been highly demanded to research cancer therapies, neurodegenerative diseases and metabolic disorders. Although dual-tuned RF coil provide anatomical and functional MRI without subject’s repositioning issued from the use of two separate tuned RF coils, it causes SNR loss due to adding trap circuit or PIN diode. Against this reserved problems, we suggest the exchangeable single tuned RF coil configuration on the fixed couch frame without subject’s repositioning in the study. We prepare a dual tuned RF coil and two single tuned RF coils as well as evaluate SNR of separate coils with scanned animal MR images.

2792.   Circularly Polarized Coil for Traveling Wave MRI
Norman B. Konyer1,2, Alexey A. Tonyushkin3,4, Andrew J.M. Kiruluta3,4, and Michael D. Noseworthy1,2
1Imaging Research Centre, St. Joseph's Healthcare, Hamilton, Ontario, Canada, 2Electrical and Computer Engineering Dept., McMaster University, Hamilton, Ontario, Canada,3Radiology Dept., Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States, 4Physics Dept., Harvard University, Cambridge, MA, United States

Patch antenna is a typical choice for a transmit/receive probe for a traveling wave MRI (TW-MRI) on 7T preclinical scanners. We demonstrate an alternative circularly polarized coil that is more ideally suited for TW-MRI in systems, where the diameter-to-critical-wavelength ratio is small. The coil consists of two orthogonal loop-coils that are driven in quadrature. We used our coil for TW-MRI in a clinical 3T system to image a long dielectric rod filled with saline, and a bottle of saline adjacent to the rod. The SNR from this coil is significantly improved over previous linear coils developed for TW-MRI and tested on 3T system. With these improved coils, it is possible to apply far-field imaging concepts to a clinical 3T system.

2793.   A Bi-Planar Surface Coil for Parietal Lobe Imaging
Daniel Hernandez1, Marlon Perez1, and Soo Yeol Lee1
1Bio-medical Engineering, Kyung Hee University, Yongin-si, Gyeonggi-do, Korea

In a helmet-style head array coil consisting of loop-coil elements, some coil elements are nearly vertical to the z-axis making a blind region around the central axis of the loop coil. We propose a surface coil structure that consists of two parallel conductor planes to be placed vertically to the z-axis. We use the B1 components parallel to the conductor planes at one side of the coil. The vertical planar coil does not produce a blind region near it. Through phantom and human brain imaging experiments, we compared the imaging performances between a conventional loop coil and the proposed coil.

2794.   Flexible Magnetic Flux Guides for Magnetic Resonance Imaging
Patrick Bollgrün1, Dario Mager1, Michael Bock2, and Jan G. Korvink1,3
1Department of Microsystems Engineering, University of Freiburg - IMTEK, Freiburg, Germany, 2Department of Radiology, University Hospital Freiburg, Freiburg, Germany,3Freiburg Institute for Advanced Studies - FRIAS, University of Freiburg, Freiburg, Germany

In this work, a flexible magnetic flux guide which consists of a series of inductively coupled electric resonators on an elastic carrier structure is used to guide the magnetic flux created during signal reception in a magnetic resonance system and overcome unwanted geometric constraints on applications such as interventional MRI. An RF signal travels through the waveguide by inductive coupling between the individual resonators, thus transmitting the magnetic flux over a considerable distance even when the structure is bent. Magnetic resonance imaging was successfully performed, which indicates that such waveguides could become a valuable alternative to conventional receive coil arrangements.

2795.   High Temperature Superconductivity Coil Design for Low Field MRI
Daniel Gogola1, Ladislav Valkovic1, Tomáš Dermek1, Martin Škrátek2, Vladimír Juráš1, and Ivan Frollo1
1Department of Imaging Methods, Institute of Measurement Science, Bratislava, Slovakia, 2Department of Magnetometry, Institute of Measurement Science, Bratislava, Slovakia

It has been demonstrated that a receiving coil designed from HTS material with a dedicated preamplifier can significantly improve SNR of the obtained image at low fields, thus time-demanding signal averaging is no longer needed. From the obtained results, the HTS materials appear to be suitable materials for the construction of complex receiving coils for low field scanners and can also find utilization also in micro imaging at high field scanners.

2796.   First in vivo Imaging of the Mouse Brain at 4.7 T Using a Subcentimeter HTS Surface Coil
Simon Auguste Lambert1, Marie Poirier-Quinot1, Ludovic De Rochefort2, Jean-christophe Ginefri2, and Luc Darrasse1
1UMR 8081, IR4M, Univ Paris Sud, CNRS, Orsay, Paris, France, 2UMR 8081, IR4M, Univ Paris-Sud, Orsay, Paris, France

For field strengths of 4.7 T and above, cryocooled probes based on normal coil conductors at 30 K have been commercially developed and afford SNR gain factors of 2-4. Only few studies relate sensitivity improvement using superconducting coil above 3 T. A particularly challenging issue with HTS coils for in vivo applications at high field is the design of sub-centimeter coils in order to achieve SNR gains overcoming the limits of normal conducting cryocooled probes. This is the first report of in vivo imaging using a subcentimeter cryocooled HTS 6 mm mean diameter surface coil at 4.7 T.


Wednesday, 24 April 2013 (13:30-15:30) Exhibition Hall
High-Dielectric Materials in RF Imaging

2797.   Potential for a Single High-Dielectric Head Coil Former to Reduce SAR and Improve SNR in Brain for a Wide Variety of Coils at 7T
Christopher Michael Collins1 and Qing X. Yang2
1Radiology, New York University Medical Center, New York, NEW YORK, United States, 2Radiology, The Pennsylvania State University, Hershey, PA, United States

Using numerical simulations, we explore the potential of a high-dielectric head coil former to improve MRI at 7T. A helmet-shaped former consisting of several sections was modeled and dielectric properties were optimized in a manual process. The resulting former greatly improved transmit efficiency to the head for both a large volume array and a patch antenna. The ability to perform RF shimming array was not adversely affected by the presence of the high-dielectric former. The former also improved efficiency, homogeneity, and penetration depth of surface coils placed on its outer surface. Results thus far are promising and warrant further investigation.

2798.   Quasi-Static Traveling Wave Imaging on a Clinical 3T MRI System
Alexey A. Tonyushkin1,2, Norman B. Konyer3,4, Michael D. Noseworthy3,4, and Andrew J.M. Kiruluta1,2
1Radiology Dept., Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States, 2Physics Dept., Harvard University, Cambridge, MA, United States,3Imaging Research Centre, St. Joseph's Healthcare, Hamilton, Ontario, Canada, 4Electrical and Computer Engineering Dept., McMaster University, Hamilton, Ontario, Canada

Recent developments in ultra-high field MRI have allowed researchers to explore the traveling wave regime. Traveling wave MRI holds promise in a future to solve various RF transmission issues, however, the traveling wave approach is forbidden for clinical MR systems due to their much lower field, and therefore, hard-to-fulfill cut-off requirements. Here, we demonstrate a quasi-static field regime allowing traveling wave concept to be applied in 3T clinical system. We demonstrate MR images of phantoms and human leg with large field of view that are comparable to the ones obtained in ultra-high field scanners (>7T) using traveling wave approach.

2799.   Performance Evaluation of Parallel Travelling Wave MRI Using Microstrip Transceiver Arrays
Hong Shang1, Wei Bian1, Daniel B. Vigneron1,2, and Xiaoliang Zhang1,2
1UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco & Berkeley, CA, United States, 2Radiology&Biomedical Imaging, University of California San Francisco, San Francisco, CA, United States

Travelling Wave MRI is an emerging method for large FOV imaging at ultrahigh fields. In this work, we investigate parallel imaging performance in traveling wave MRI using simple microstrip transceiver arrays. The two-element arrays were placed orthogonally at the end of the bore of a 7 Tesla whole body MR scanner for excitation and reception. MR experiment was performed demonstrating sufficient spatial diversity of B1 fields of each transceiver channel and good quality of parallel accelerated images.

2800.   Transmit Strategies for Body Imaging at 3T - Comparing Multitransmit and Dielectric Shimming
Wyger M. Brink1 and Andrew Webb1
1Radiology, Leiden University Medical Center, Leiden, Netherlands, Zuid-Holland, Netherlands

High permittivity pads are shown to improve the B1 homogeneity to a level similar to that of an eight-channel system, however without the penalty of reducing the transmit efficiency. The best transmit setup for 3T body imaging is shown to be the two-channel system with high permittivity pads.

2801.   High Permittivity Solid Ceramic Resonators for High Field Human MRI
Sebastian A. Aussenhofer1 and Andrew Webb1
1Department of Radiology Leiden University Medical Center, CJ Gorter Center for High Field MRI, Leiden, South Holland, Netherlands

A dielectric resonator made from a high permittivity low loss barium strontium titanate has been designed to operate in degenerate quadrature HEM11 modes at 298.1 MHz (7 Tesla). The compact resonator was designed for high resolution imaging of human digits with a high filling factor and patient comfort. New methods of double tuning such a resonator to proton/fluorine are also presented.

2802.   Dramatic Improvement of Parallel Imaging with High Dielectric Material – Demonstration with Electromagnetic Field Calculations at 123 MHz
Zhipeng Cao1, Wei Luo2, Christopher T. Sica2, Sukhoon Oh3, Sebastian Rupprecht2, Giuseppe Carluccio3, Christopher Michael Collins3, and Qing X. Yang2
1Radiology, Pennsylvania State University, Hershey, PA, United States, 2Radiology, The Pennsylvania State University, Hershey, PA, United States, 3Radiology, New York University, New York City, NY, United States

A simulation analysis of the effect of high dielectric materials on receive efficiency and g-factor for a phantom within an 8-channel head sized array is performed using numerical calculations. Results indicate that strategic use of high dielectric materials can provide notable improvement in parallel imaging performance for a given sample with standard coil setup.


Wednesday, 24 April 2013 (13:30-15:30) Exhibition Hall
RF Simulations

2803.   Novel RF Resonator Using Microstrip at 3T
Hyeokwoo Son1, Ahryum Kim2, Jinyoung Choi1, Youngki Cho1, and Hyoungsuk Yoo2
1School of Electronics Engineering, Kyungpook National University, Daegu, Korea, 2School of Electrical Engineering, University of Ulsan, Ulsan, Korea

Magnetic Resonance Imaging (MRI) systems have good intrinsic SNR (signal-to-noise ratio) and are used an important instrument for diagnosis. Recently, transceive phased array coils using transmission lines in MRI systems have been studied for parallel imaging[1-3], RF shimming[4] and RF homogenization[5]. These coils are composed of several RF resonators that are independently controlled by adjusting the amplitude and phase of the excitation. Microstrip, one of most widely used transmission lines, is used to design a transceive array coil element. The RF resonators using microstrip operate at a Larmor frequency of 128 MHz (3T). In this paper, we introduce four different RF resonators and a slot loaded RF resonator shows better RF efficiencies than other three RF resonators.

2804.   Precomputed Green’s Functions for Fast Electromagnetic Simulation with Realistic Human Body Models
Jorge Fernandez Villena1, Amit Hochman2, Luis Miguel Silveira1, Elfar Adalsteinsson2,3, Lawrence L. Wald3,4, Jacob K. White2, and Luca Daniel2
1INESC ID Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento, Lisbon, Portugal, 2Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3Harvard-MIT Division of Health Sciences Technology, Cambridge, Massachusetts, United States, 4Department of Radiology, Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, United States

We propose a fast electromagnetic (EM) simulation of RF coils operating in the presence of realistic human body models (RHBM), based on frequency-domain integral equation methods. We introduce the RHBM Green’s functions (GF), which mimic the effect of the RHBM inside an EM field due to coil’s currents. This RHBM GF needs to be precomputed only once for a given complex body model, and then it can be combined with traditional Boundary Element Methods that only discretize the coil surface. This scheme generates smaller models that are very fast to solve, allowing for efficient coil design exploration.

2805.   Accurate Simulation of Signal and Noise in MRI Based on Electromagnetic Field Calculation and Bloch Simulation
Zhipeng Cao1, Christopher T. Sica2, Wei Luo2, Sukhoon Oh3, and Christopher Michael Collins3
1Radiology, Pennsylvania State University, Hershey, PA, United States, 2Radiology, The Pennsylvania State University, Hershey, PA, United States, 3Radiology, New York University, New York City, NY, United States

A method for generating simulated MR images (starting with knowledge of only pulse sequence, receiver bandwidth, and distributions of sample properties and field distributions through space) with realistic levels of noise is described and demonstrated with comparison to experimentally-measured SNR.

2806.   Efficient and Accurate Bloch-Based Simulation of Intra-Voxel Dephasing Using Multiple Isochomats and Magnetization Spatial Gradients
Zhipeng Cao1, Christopher T. Sica2, Giuseppe Carluccio3, and Christopher Michael Collins3
1Radiology, Pennsylvania State University, Hershey, PA, United States, 2Radiology, The Pennsylvania State University, Hershey, PA, United States, 3Radiology, New York University, New York City, NY, United States

A method for simulating intra-voxel dephasing in Bloch-based MRI simulation that is a hybrid of existing methods is introduced and compared to its predecessors. Results indicate much greater accuracy than either of the prior methods with little increase in computational resources.

2807.   A New Accurate FEM Based Optimization Method for Birdcage Coil Design at High Field Strength
Necip Gurler1, Fatih Suleyman Hafalir1, Omer Faruk Oran1, and Yusuf Ziya Ider1
1Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey

An accurate method and a software tool for the capacitance calculation of low-pass and high-pass birdcage coils using a Finite Element Method (FEM) based optimization algorithm is presented. For the verification of the algorithm, 8-leg low-pass and high-pass birdcage coils are constructed and capacitance values used in the experiments are compared with the capacitance values calculated using our algorithm and also with the capacitance values obtained by the widely used software BirdcageBuilder which is based on a lumped element circuit model. Results show that our algorithm is more accurate than the lumped element circuit models especially at higher frequencies.


Wednesday, 24 April 2013 (13:30-15:30) Exhibition Hall
PET/MRI Systems Engineering

2808.   An Optimum RF Shield for Simultaneous MRI-PET System
Changheun Oh1, Yeji Han1, and HyunWook Park1
1Electrical engineering, Korea Advanced Institute of Science and Technology, Daejeon, Daejeon, Korea

the coupling of RF noise between electronics in the PET system and RF coil of the MRI system can degrade the MR image quality. In addition, the center frequency of the RF coil may experience shifting due to the PET insert. In order to solve the RF noise coupling and frequency shifting problems, an appropriate RF shield should be used. For an MRI-PET fusion system with an add-on/off type PET insert, a gold-mesh tape shield is proposed for the RF coil in this study.

2809.   Computer Simulation and Experiments of RF Coil for Simulataneous MRI-PET System
Changheun Oh1, Yeji Han2, and HyunWook Park1
1Electrical engineering, Korea Advanced Institute of Science and Technology, Daejeon, Daejeon, Korea, 2Korea Advanced Institute of Science and Technology, Daejeon, Daejeon, Korea

In the integrated MRI-PET system, the coupling of RF noise between electronics in the PET system and RF coil of the MRI system, and frequency shifting of RF coil can be main problems that can deteriorate MR image quality. In this study, we propose an MRI-PET fusion system, which can simultaneously acquire MRI and PET images by using an add-on/off type PET insert, and a gold-mesh tape shield is used to improve the MR image quality.

2810.   Feasibility of PET Attenuation Characterization of MR Hardware Using 3D Data from a LINAC as Radiation Source
Stephan Biber1, Ralf Ladebeck1, David Faul2, and Yvonne Candidus1
1Siemens Healthcare Magnetic Resonance Imaging, Erlangen, -, Germany, 2Siemens Healthcare Molecular Imaging, Knoxville, TN, United States

With the introduction of integrated MR-PET systems both for preclinical animal studies as well as full sized human scanners, the question of PET attenuation originating from MR hardware (MR-HW) which is located between the patient and the PET camera, has been a topic of increasing interest for research. Prvious studies have identified mechanical structures for the patient table, the housings of local coils as well as the electronics and antenna structures within these housings as the major contributions to PET signal attenuation. This attenuation map needs to be included in the PET reconstruction. The goal of this paper is to evaluate the feasibility and the potential advantages of MR-HW attenuation correction based on 3D data coming from a LINAC instead of a CT, which has been used for measurement of hardware attenuation in earlier studies. The advantage of a LINAC based scan can be the reduced level of artifacts, as the LINAC provides a radiation beam with photons of much higher energy than the CT.

2811.   MR-Based Attenuation Mapping of the Pelvis Using 3D UTE DIXON at 3T
Christian Stehning1, Michael Helle2, Stefanie Remmele3, and Melanie Kotys-Traughber4
1Philips Research Europe, Hamburg, Germany, 2Philips Research Laboratories, Hamburg, Germany, 3Hochschule Landshut (FH), Landshut, Germany, 4Philips Healthcare, Cleveland, Ohio, United States

MR-based radiation therapy planning (RTP) and hybrid PET/MR systems require a complete segmentation of bone, soft tissue, and air for attenuation correction. Conventional MRI sequences cannot reliably differentiate between air and bone. While promising results for cortical bone were obtained with 3D ultrashort echo time imaging (UTE) in the knee and head, UTE bone imaging in the pelvis is more demanding due to the significantly larger FOV. A UTE Dixon sequence and reconstruction workflow is presented, which provides good in vivo image quality and reliable bone segmentation over a 400mm FOV. This is an integral component of emerging application such as MR-based therapy planning, and hybrid PET/MR systems.

2812.   Hardware Attenuation Correction in PET/MR Hybrid Imaging: Evaluation of µ-Maps for Local RF Coils
Daniel H. Paulus1, Harald Braun1, and Harald H. Quick1
1Institute of Medical Physics, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany

In hybrid PET/MR imaging local receiving RF coils, placed in the FOV, attenuate and scatter PET annihilation photons thus affecting PET quantification. Flexible RF surface coils are yet omitted in PET attenuation correction (AC), because they can vary in position and geometry. Several CT-based attenuation maps (µ-map) of the RF coil were used for PET AC to evaluate the effect of different parameters. Furthermore small shifts and rotations of the µ-map simulating misregistration or motion of the patient were analyzed. Depending on the PET reconstruction algorithm the shifts can cause artifacts or just a bias of the activity concentration.

2813.   Towards Simultaneous PET/MR Breast Imaging: Systematic Evaluation and Integration of an RF Breast Coil
Bassim Aklan1, Daniel H. Paulus1, David Fual2, Christian Geppert3, Eric E. Sigmund4, Amy Melsaether5, Evelyn Wenkel6, Harald Braun1, Susanne Ziegler1, and Harald H. Quick1
1Institute of Medical Physics, University of Erlangen-Nuernberg, Erlangen, Germany, 2Siemens Medical Solutions, New York, NY, United States, 3Siemens Medical Systems, New York, NY, United States, 4Department of Radiology for Biomedical Imaging NY Langone Medical Center, New York, NY, United States, 5Breast Imaging Section, Department of Radiology Medical Center, New York, NY, United States, 6Institute of Radiology, University Hospital Erlangen, Erlangen, Germany

Simultaneous PET/MR breast imaging requires the RF breast coil necessary for MR data acquisition to be located in the FoV of the PET detector thus attenuating PET signals and reducing PET quantification accuracy. Integration of a commercial 4-channel RF breast coil on an integrated PET/MR hybrid system resulted in local PET signal attenuation of 4-16% in systematic phantom experiments. Application and registration of a CT-based attenuation map of this coil resulted in successful attenuation correction (AC). First PET/MR studies in breast cancer patients demonstrate successful integration of the RF breast coil into the new application of PET/MR breast imaging.

2814.   MR-Based Attenuation Correction of Local Radiofrequency Surface Coils in PET/MR Hybrid Imaging
Daniel H. Paulus1, Harald Braun1, Bassim Aklan1, and Harald H. Quick1
1Institute of Medical Physics, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Bavaria, Germany

In simultaneous PET/MR imaging, local receiving RF coils are positioned in the FOV of the PET detectors and attenuate the PET signal. Flexible RF surface coils vary in position and geometry and are thus omitted in PET attenuation correction (AC). In a phantom experiment and a patient scan, local deviations of up to 15% in the PET emission images were observed, when the coil is omitted in PET AC. It is demonstrated that with CT-based AC of the RF coil, where markers were used for image registration of MR and CT, the PET signal attenuation could mostly be corrected.

2815.   MR Based Attenuation Correction Including Cortical Bone for PET/MR Hybrid Imaging
Bharath K. Navalpakkam1, Harald Braun2, Joachim Hornegger1, Torsten Kuwert3, and Harald H. Quick2
1Pattern Recognition Lab, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Bavaria, Germany, 2Institute of Medical Physics, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Bavaria, Germany, 3Clinic of Nuclear Medicine, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Bavaria, Germany

An MR-based attenuation correction approach for PET/MR that includes cortical bone information is proposed. An epsilon insensitive Support Vector Regression model is trained and validated on head regions for five patients. The reconstructed PET data is evaluated for the proposed approach (PETMRAC) against other approaches that include (PETboneAC) and disregard bone class (PETnoboneAC). For the complete brain, PETMRAC yielded a mean absolute error of 2.40±3.59%, 10.15±3.31% for PETnoboneAC and 3.96±3.71% for PETboneAC. For atlas segmented landmarks, the errors for the same were 2.16±1.77%, 11.03±2.26% and 4.22±3.91%, respectively. An initial result of an MR-based pseudo-CT for a whole-body application is illustrated.

2816.   MR-Compatibility of a SiPM-Based PET Detector Module Using HDMI for Analog Readout and Power Supply
Jonathan D. Thiessen1, Eric Berg2, Chen-Yi Liu1,3, Daryl Bishop4, Piotr Kozlowski5,6, Fabrice Retière4, Vesna Sossi6, Greg Stortz6, Christopher J. Thompson7, Xuezhu Zhang1, and Andrew L. Goertzen1,3
1Radiology, University of Manitoba, Winnipeg, Manitoba, Canada, 2Biomedical Engineering, University of California, Davis, Davis, California, United States, 3Physics & Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada, 4Detector Development Group, TRIUMF, Vancouver, British Columbia, Canada, 5Radiology, University of British Columbia, Vancouver, British Colubmia, Canada, 6Physics & Astronomy, University of British Columbia, Vancouver, British Columbia, Canada, 7McConnell Brain Imaging Centre, Montreal Neurological Institute, Montreal, Quebec, Canada

An MR-compatible PET detector module featuring a silicon photomultiplier coupled to a dual-layer LYSO scintillator crystal array and using an HDMI cable for supplying power and bias as well as transmitting analog signals was tested in a 7 T Bruker MRI. Performance of the PET detector was evaluated inside the MRI as was performance of the MRI with the PET detector present and operating. Given the limited interactions between the operating PET detector module and MRI, the current PET detector design appears to be a viable first step in creating an MR-compatible full-ring PET system.

2817.   Three Approaches to Phantom Fluid Selection for Simultaneous PET/MR Hybrid Imaging
Susanne Ziegler1, Harald Braun1, Philipp Ritt2,3, Carsten Hocke2, Torsten Kuwert2, and Harald H. Quick1
1Institute of Medical Physics, University of Erlangen-Nuremberg, Erlangen, Germany, 2Clinic for Nuclear Medicine, University Hospital Erlangen, Erlangen, Germany, 3Pattern Recognition Lab, University of Erlangen-Nuremberg, Erlangen, Germany

Simultaneous PET/MR hybrid imaging of fluid-filled phantoms can be problematic. Pure water can cause inhomogeneous RF excitation when imaging large sized phantoms at high field strength. Oil, as alternative fluid, does not mix well with the standard PET radiotracer 18F-FDG. In this study three different approaches of fluid and radiotracer selection were considered and systematically evaluated with respect to their usability for simultaneous PET/MR phantom imaging. Alternative fluids as a compromise for both imaging modalities and workarounds for improving the use of standard fluids are presented. Additionally an alternative radiotracer to 18F-FDG is proposed and evaluated in PET/MR measurements.

2818.   Simultaneous PET/MR with Continuous Table Motion: The Effect of Table Motion Speed on Image Quality
Harald Braun1, Susanne Ziegler1, and Harald H. Quick1
1Institute of Medical Physics, University of Erlangen-Nürnberg, Erlangen, Germany

In simultaneous whole-body PET/MR imaging, data is usually acquired in a multi-station (step-and-shoot) approach. In contrast, an acquisition paradigm with continuous table motion that was introduced recently allows for seamless whole-body coverage and greater flexibility in the planning workflow. To allow the use of continuous table motion acquisitions in clinical protocols, it must be evaluated which impact table motion speed has on MR and PET image quality. This was performed for the available MR protocols that support continuous table motion (FLASH 2D, FLASH 3D, TSE, HASTE, BLADE) and for PET imaging for several different table speeds.


Wednesday, 24 April 2013 (13:30-15:30) Exhibition Hall
Safety (Non-Contrast Agent)

2819.   The New EU Proposal Vs. 2004/40/EC - An MR Exposure Data Comparison
Jens Groebner1,2 and Michael Bock1
1Dept. of Radiology / Medical Physics, University Medical Center Freiburg, Freiburg, BW, Germany, 2Dept. of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, BW, Germany

The EU announced that the directive 2004/40/EC will be replaced by a proposal of the European Commission (EC). In this work the EC limit values and the 2004/40/EC’s limit values are compared to MR exposure data. 37 MR workers were asked to wear a field probe in the magnet room (up to 7T). Results show that the new limits (both peak and average) can be exceeded during routine work. With an optic/acoustic response system the EC’s proposal can help reducing transient effects like vertigo or magnetophosphenes.

2820.   Effect of 9.4 Tesla Sodium MR Neuroimaging on Vital Signs and Cognitive Performance in Healthy and For-Cause Volunteers
Ian C. Atkinson1, Wesley McClain1, Neil Pliskin2, and Keith R. Thulborn1
1Center for MR Research, University of Illinois at Chicago, Chicago, IL, United States, 2Psychiatry, University of Illinois at Chicago, Chicago, IL, United States

Current FDA guidelines classify MR devices operating at up to 8 Tesla as insignificant risk. Vital sign and cognitive performance data supporting the safety of performing non-proton MR imaging of the human brain at 9.4 Tesla in healthy and for-cause volunteers are presented. These data add to the growing body of results that suggest ultra-high field MR imaging can be safely performed up to 9.4 Tesla.

2821.   A Portable MR Exposure Monitoring System for B0 and DB/dt Up to 7T.
Jens Groebner1,2, Reiner Umathum2, and Michael Bock1
1Dept. of Radiology / Medical Physics, University Medical Center Freiburg, Freiburg, BW, Germany, 2Dept. of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, BW, Germany

The EU directive 2004/40/EC is currently under review and will be replaced in future. In this study a wireless MR exposure monitoring probe is presented for exposure monitoring. A magnetic field probe consisting of three Hall sensors and induction coils is worn at the head of a volunteer. The exposure data (B0, dB/dt, dB/dtrot+trans*) is recorded on a SD memory card. Six measurements were performed in the vicinity of a 7T MR system. The new limits would only be exceeded during measurements in a frequency range of 0.6-1Hz and if the ICNIRP definition of dB/dtrot+trans is used.*according to ICNIRP

2822.   Gradient Induced Heating on Thin Conducting Surfaces: Simulation and Experiment
Chad Tyler Harris1, William B. Handler1, and Blaine A. Chronik1,2
1Physics and Astronomy, Western University, London, Ontario, Canada, 2Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada

The ability to accurately calculate the induced current distribution, caused by gradient switching, over arbitrary thin conducting surfaces is extremely useful for the design and MR safety evaluation of medical devices and interventional robotics. In this abstract we present an integral method to calculate these induced currents. The method is applied to predict the average heating rate of a thin conductor and then extended to calculate the spatial distribution of power deposition over the conductor surface and subsequent spatially varying heating rate.

2823.   A Whole-Body RF Dosimeter for Independent SAR Measurement in MR Scanners
Di Qian1,2, AbdEl-Monem M. El-Sharkawy3, Paul A. Bottomley2,3, and William A. Edelstein1
1Radiology, Johns Hopkins School of Medicine, Baltimore, MD, United States, 2Electrical and Computer Engineering, Johns Hopkins University, Baltimore, MD, United States,3Radiology, Johns Hopkins University, Baltimore, MD, United States

We have developed an RF dosimeter for independent measurement of average whole-body RF exposure at 3T. The dosimeter includes an RF transducer with two tuned, orthogonal resistive loops and a lossless phantom. The loop impedances are adjusted so that the power deposited in the transducer is equivalent to that for an average human subject while minimizing B1-interference with the scanner. The deposited RF power is measured by sampling the current in the transducer loops. The dosimeter is tested on multiple GE, Philips, and Siemens MR systems, and can be used independent of make or model for a given MR frequency.

2824.   Influence of a Receive Coil on SAR and Temperature Increase at 3T: Simulations & Experimental Measurements
Sukhoon Oh1, Yeun-chul Ryu2, and Christopher Michael Collins1
1Center for Biomedical Imaging, School of Medicine, New York University, New York, New York, United States, 2Center for NMR Research, Radiology, College of Medicine, The Pennsylvania State University, Hershey, Pennsylvania, United States

In this study, we report the effect of a surface coil close to the subject on SAR and temperature increase. We observed notable effect on both SAR and temperature distribution near the surface coil.

2825.   SAR Safety Issues in Case of Partial Coil Loading
Peter Vernickel1, Christoph Leussler1, Daniel Wirtz1, and Ingmar Graesslin1
1Philips Research Laboratories, Hamburg, Germany

MR imaging demands an exact control of the SAR to ensure patient safety. Dedicated hard- and software is used to measure the complex coil currents I, coil quality factor Q, or reflection coefficient Sxx to ensure that the scan runs within allowed limits. However, uncertainties may exist when relying on the verification of one of the mentioned quantities, because this can lead to ambiguous results when characterizing the complex arrangement of coil and load. This abstract demonstrates an example for a situation in which measuring I, Q or S11 while slightly modifying arrangement of coil and load leads to misleading results for SAR monitoring.

2826.   RF-Heating Testing in 64 MHz RF-Laboratory System and 1.5 Tesla MRI – a Comparative Evaluation
Wolfgang Görtz1, Nicolas Fülle1, Gerrit Schönwald1, Susanne Matthey1, and Gregor Schaefers1
1MR:comp GmbH, Germany, Gelsenkirchen, NRW, Germany

RF-heating tests as described in ASTM F2182 have been performed in a 1.5 Tesla MR scanner and additionally in a 64 MHz RF laboratory workbench system. A comparison of the results of the detected temperature increases shows a good agreement between both systems. Based on this finding it can be concluded that the laboratory system is an alternative to usually used clinical MR systems for RF heating test on medical implants following ASTM F2182.

2827.   Uncertainties of Local SAR Determination in Parallel Transmission MRI
Frank Seifert1 and Bernd Ittermann1
1Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany

Local SAR prediction in pTX MRI based on real-time multi-channel driving voltage measurements with directional couplers are prone to model variations even when the ‘worst case’ values for different models a similar. Hence, when aiming to go beyond, i.e. below, ‘the worst case’ scenario for patient safety in pTx MRI, even the careful validation of simulation results including the variability ‘real life applications’ is already a challenging task.

2828.   Radiofrequency Heating During Head Imaging in a 3T Transmit Body Coil
Devashish Shrivastava1, Lynn Utecht1, Jinfeng Tian1, Rachana Visaria2, John Hughes1, and University of Minnesota University of Minnesota Vaughan1
1University of Minnesota, Minneapolis, MN, United States, 2MR Safe Devices, Burnsville, MN, United States

Radiofrequency (RF) heating during head imaging with a transmit body coil is unknown and a safety concern. To better understand this heating, the heating was simulated by solving the new, analytical generic bioheat transfer model (GBHTM) and the ‘gold standard’ empirical Pennes bioheat transfer equation in a digital pig with the pig head in the isocenter of a 3T, birdcage, transmit body coil. The simulations were validated by direct fluoroptic measurements in anesthetized swine. The GBHTM simulations as well as the measurements showed that in vivo temperatures may change significantly due to the power deposition from a body coil.

2829.   Using MR Thermometry for SAR Verification in Local PTX Applications
Klaus M. Huber1, Joerg Roland2, Johanna Schoepfer1, Stephan Biber2, and Sebastian Martius1
1Corporate Technology, Siemens, Erlangen, Germany, 2Healthcare, Siemens, Erlangen, Germany

Monitoring local and global SAR is one of the major challenges on the way to the clinical use of parallel TX arrays. Usually, SAR estimations are based on numerical simulations with 3D-EM-tools which are rather sophisticated and tend to deliver erroneous results in case of unprecise inputs. PRF-based MR thermometry might be a powerful tool to determine spatial temperature maps and thus cross-check SAR simulations. The motivation of this study is to examine the feasibility and quantitative accuracy of MR thermometry for SAR and temperature monitoring of local transmit antenna arrays based on existing hardware.

2830.   Effects of Tuning Condition, Head Size and Position on the SAR of a 9.4T Dual Row Array
Mikhail Kozlov1, Gunamony Shajan2, and Robert Turner1
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Saxony, Germany, 2Max Planck Institute for Biological Cybernetics, Tuebingen, Germany

For an already constructed 9.4T dual row array, excited in CP and other transmit modes, we investigated peak SAR averaged over 10 grams (SAR10g) for different tuning conditions, and different head positions with three scaling factors. For a given array, the tuning condition significantly affected SAR10g, while the influence on SAR10g of head position and scaling factor was relatively small.

2831.   A Fast Sampled Projection Method for Assessing Coil Configuration Impact on SAR
Amit Hochman1, Jorge Fernandez Villena2, Luis Miguel Silveira2, Elfar Adalsteinsson1,3, Lawrence L. Wald3,4, Jacob K. White1, and Luca Daniel1
1Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA, United States, 2INESC ID Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento, Lisbon, Portugal, 3Harvard-MIT Division of Health Sciences Technology, Cambridge, MA, United States, 4Department of Radiology, Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States

We propose a method for combining electromagnetic field solutions obtained for a small set of excitations so as to approximate the solutions for nearby excitations. This work is relevant for coil and excitation design.

2832.   EM and Thermal Validation of a Numerical Elliptical Birdcage at 3T
Mélina Bouldi1 and Jan M. Warnking1,2
1Grenoble Institut des Neurosciences - UJF, Grenoble, Rhône-Alpes, France, 2Inserm U836, Grenoble, Rhône-Alpes, France

Understanding the risks of overheating due to the presence of active implants requires a rigorous simulation of experimental conditions. We built a numerical elliptical birdcage model of the whole body transmit coil in a Philips Achieva TX® system, using the SEMCAD X software (Speag®). The resonator was tuned to 128MHz. The simulated current density distribution, B1 map and temperature changes qualitatively agree with the theoretically predicted and experimentally observed behavior. Quantitative differences remain. Our method of validation, permits to assess the validity of the resonator model, and paves the way for a realistic numerical elliptic resonator model.

2833.   Statistical Local SAR Analysis by Latin Hypercube Sampling for 11.7 Tesla Brain MRI
Yu Shao1, Peng Zeng2, Joseph Murphy-Boesch3, Jeff H. Duyn3, Alan P. Koretsky3, and Shumin Wang1
1Electrical and Computer Engineering, Auburn University, Auburn, AL, United States, 2Mathematics and Statistics, Auburn University, Auburn, AL, United States, 3LFMI/NINDS/NIH, Bethesda, MD, United States

Local specific absorption rate analysis is critical to the safety of high-field human MRI studies. In order to address the inter-subject variability in head dimensions and the variability in the relative position of the human body to the RF coil, applying the conventional Monte Carlo method would require a fairly large number of simulations. In order to dramatically improve the efficiency of statistical simulations, we propose a new approach based on the Latin Hypercube Sampling (LHS). The LHS can achieve the same accuracy with much smaller run size than conventional Monte Carlo sampling because it guarantees that the selected runs uniformly spread across the domain of each input variable. We demonstrate that with a few sampling points (17 samples), the expectation, the standard deviation and sensitivity to changes in conditions, such as the head geometry and its relative position, can be accurately computed when six random variables were considered. This approach appears uniquely suited for RF safety assessment.

2834.   Prediction of RF Burning: Mapping of High-SAR Areas Using a Low-RF Power Scan
Toru Yamamoto1 and Minghui Tang2
1Faculty of Health Sciences, Hokkaido University, Sapporo, Hokkaido, Japan, 2Graduate School of Health Sciences, Hokkaido Univrsity, Sapporo, Hokkaido, Japan

Prediction of the RF burning that may occur during an MRI examination is one of the key issues in MR safety. Although several methods have been developed for mapping the specific absorption rate (SAR), few practical methods for predicting RF burning have been demonstrated because of the difficulty in actualizing RF burning in a phantom study. In this study, we developed a method of mapping high-SAR areas using a low-RF power scan and demonstrated the prediction of RF burning in a phantom study using an elaborate setup of an RF resonant loop.

2835.   Local SAR Prediction Errors with Variation of Electrical Properties in the Head at 7T
Muhammad Hassan Chishti1, Zhangwei Wang2, and Desmond Yeo1
1GE Global Research Center, Niskayuna, New York, United States, 2GE Healthcare, Waukesha, Wisconsin, United States

The ability to accurately predict Specific Absorption Rate (SAR) is a key to patient safety during RF exposure in MR scans. SAR is highly dependent on accurate values of the tissues’ electrical properties. In this work, we investigate the errors in EM-modeling-based SAR prediction when incorrect electrical conductivity and relative permittivity values are applied. In the 7T human body model simulations performed, results show that the maximum deviation (from nominal) of the ratio of peak SAR10g to the whole head average SAR is -7.83% and occurs when both electrical conductivity and relative permittivity of the tissues are reduced by 20%.

2836.   Vascular Flow Effects on RF Heating of Passive Implants: The Use of a Flow Modified ASTM F2182 Phantom in a Siemens Tim Trio 3T Scanner
Alan Leewood1, David Gross1, Jeff Crompton2, Sergei Yushanov2, Orlando P. Simonetti3, and Yu Ding3
1MED Institute, Inc., West Lafayette, IN, United States, 2AltaSim Technologies, LLC, Columbus, OH, United States, 3The Ohio State University, Columbus, OH, United States

MR safety of electrically conductive passive implants is directly related to localized heating of tissue when the device is subjected to RF powered E-fields. Current MR Safety methodology relies primarily on experimental methods (ASTM F2182), which use a gel phantom and produce conservative estimates of temperature rise for vascular devices due to lack of blood-flow. Ultimately, this raises the issue that clinically indicated MRI scans may be inappropriately withheld from patients because RF heating concerns were based on inappropriately conservative test methods. This work is an investigation of the effects of including vascular flow on the cooling of passive implants.

2837.   A New Design of an Implanted Medical Lead to Reduce RF Heating in MRI
Rupam Kumar Das1 and Hyoungsuk Yoo1
1Department of Biomedical Engineering, School of Electrical Engineering, University of Ulsan, Ulsan, Korea

The RF coils in Magnetic Resonance Imaging (MRI) systems induce scattered electric field in the medical implant, and the principal bio effect is tissue heating. In this work, a noble design to reduce the scattered field has been proposed. In this proposed design, metal nails have been placed along the length of the medical lead. The scattered electric field is calculated near the lead tip at 64 MHz for a model implant by using Ansoft HFSS. By using this method, a significant decrease in the scattered electric field has been observed. Key Word : MRI,pacemaker,implantable device,lead,RF heating

2838.   Local SAR Investigations in the Presence of Conductive Media
Craig I. Lawrie1, Xiaoyu Yang1, Tsinghua Zheng1, Matthew Finnerty2, Shinya Handa2, and Hiroyuki Fujita2,3
1Quality Electrodynamics, LLC, Mayfield Village, Ohio, United States, 2Quality Electrodynamics, Mayfield Village, Ohio, United States, 3Department of Physics, Case Western Reserve University, Cleveland, Ohio, United States

The use of a local transmitter coil to reduce local SAR heating is evaluated with regards to MRI imaging in the presence of long conductive media. Simulation results indicate that a local transmitter coil has an SAR advantage due to both smaller electric fields and the ability to fine-tune geometric positioning.

2839.   Detailing RF Heating Induced by Coronary Stents at 7.0T Using Numerical EMF Simulations and Heating Experiments
Lukas Winter1, Davide Santoro1, Alexander Müller1, Wolfgang Renz1,2, Celal Özerdem1, Andreas Graessl1, Valeriy Tkachenko3, Jeanette Schulz-Menger3,4, and Thoralf Niendorf1,3
1Berlin Ultrahigh Field Faciltiy (B.U.F.F.), Max-Delbrück Center for Molecular Medicine, Berlin, Germany, 2Siemens Healthcare, Erlangen, Germany, 3Experimental and Clinical Research Center (ECRC), a joint cooperation between Charité Medical Faculty and Max-Delbrück Center for Molecular Medicine, Berlin, Germany, 4Department of Cardiology and Nephrology, HELIOS Klinikum Berlin-Buch, Berlin, Germany

This study examines RF induced heating, which potentially can be caused by an electrically conductive coronary stent in combination with RF fields applied at ultrahigh field (UHF) MR. EMF simulations, phantom experiments and MR thermometry were performed and show that in a careful evaluated setup, RF induced heating due to the presence of a coronary stent may not be significant versus the baseline heating induced by a cardiac optimized transmit/receive RF coil at 7.0T.

2840.   Contrast in Visualized Currents Using Reverse Polarization and Pre-Spoiling Twister Gradients
Christopher W. Ellenor1, Pascal P. Stang1, John M. Pauly1, and Greig C. Scott1
1Electrical Engineering, Stanford University, Stanford, CA, United States

In a simple phantom study, we compare the use of two techniques for the visualization of dangerous currents in implanted wires. The phantom is imaged using the reverse-polarization method, twister gradients, or a combination of the two, and the conspicuity of the current-carrying wire is determined by measuring image contrast. We find that gradient spoiling can achieve results similar to reverse polarization. We also employ a numerical model to attempt to extrapolate these results to 3T and 7T systems, where we find very similar results at 3T, and a reduction in effectiveness of reverse polarization at 7T.

2841.   Ink-Net: Safe 256 Channel EEG at 7T
Daniel G. Wakeman1, Boris Keil1, Bill McSwain2, Maria Ida Iacono1, Catherine Poulsen2, and Giorgio Bonmassar1
1A.A. Martinos Center for Biomedical Imaging, Harvard Medical School, Radiology, Massachusetts General Hospital, Charlestown, MA, United States, 2Electrical Geodesics, Inc., Eugene, OR, United States

We show safety testing of a new 256 channel EEG device at 7T. Previous studies have shown that high density EEG caps in high field strength MRI (3 & 7T can generate high SAR. We performed SAR simulations and Temperature measurements on a conductive phantom to test the risk of heating.

2842.   Recent Developments in Tattoo Removal Methods and Potential Implications for MRI Patient Safety
Michael C. Steckner1 and Emanuel Kanal2
1TMRU, Mayfield Village, OH, United States, 2Department of Radiology, University of Pittsburgh Medical Center, Pittsburgh, PA, United States

Laser based tattoo removal techniques are growing in popularity, but conductive ink constituents remain. Thus the MRI safety profile of tattoos may remain unchanged or even more complex. With the increasing number of tattoos and tattoo removals, caution is needed to identify all existing or partially removed tattoos, either decorative or cosmetic, during the patient screening process.