Joint Annual Meeting ISMRM-ESMRMB 2014 10-16 May 2014 Milan, Italy

1276-1304 MR Engineering: RF & Other
1305-1343 Array Coils & Systems
1344-1358 Non-Array RF Coils, Dielectrics & Waves
1359-1381 RF Modelling & Safety
1382-1395 Gradients, Shims, Magnets & Field Monitoring
1396-1409 PET-MRI Engineering & Methods
1410-1437 Applications of Ultra-High Fields

MR Engineering: RF & Other

Monday 12 May 2014
Traditional Poster Hall  16:30 - 18:30

1276.   A Wireless Digital Capacitor Module for Tuning Receive Coil Arrays
Arne Reykowski1 and Randy Duensing1
1Invivo Corporation, Gainesville, Florida, United States

This paper presents a novel approach for tuning RX coil arrays using wireless digital programmable capacitors. This hardware is intended for research to improve coil tuning strategies and improve combined SNR beyond the currently accepted limits. The ability to change tune settings in the absence of a cable connection or the need to touch the hardware should greatly improve the accuracy of repeated SNR measurements.

1277.   Optical power transmission can help to build receive coils without coaxial cables
Jens Höfflin1, Elmar Fischer2, Oliver Gruschke1, Jürgen Hennig2, and Jan G Korvink1,3
1Lab of Simulation - Department of Microsystems Engineering, University of Freiburg - IMTEK, Freiburg, Germany, 2Medical Physics - Department of Radiology, University Medical Center Freiburg, Freiburg, Germany, 3Freiburg Institute for Advanced Studies - FRIAS, University of Freiburg, Freiburg, Germany

We present the use of optical power transmission as a possibility to power electronic components like an LNA inside the magnet without needing to use copper cables. The use of switching DC-to-DC converters inside high magnetic fields is evaluated, and SNR measurements are presented to compare the performance of different receive coil setups.

1278.   23Na Magnetic Resonance Spectroscopic Imaging (MRSI) on a High-Density 3d-cell culture on chip (3D-KITChip)
Andreas Neubauer1, Michaela Ruttorf1, Raffi Kalaycian1, Jan Sachs1, Cordula Nies2, Stefan Giselbrecht2, Eric Gottwald2, and Lothar Schad1
1Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Baden-Wuertemberg, Germany, 2Institute for Biological Interfaces-1, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Baden-Wuertemberg, Germany

In this study we present a setup capable to monitor changes in ionic concentration gradients in vitro. The main parts of the setup are a three dimensional cell culture, a completely MR-compatible bioreactor and a 23Na surface coil. In a pilot study we performd a 23Na CSI experiment to show that we are able to resolve a non varying reference compartment from a compartment with varying physiological parameters.

1279.   Harnessing Embedded Linux and Python for Stand-Alone MRI Applications
Pascal P Stang1,2 and Greig Scott2
1Procyon Engineering, San Jose, CA, United States, 2Electrical Engineering, Stanford University, Stanford, CA, United States

Advances in RF electronics, high-speed data converters, and multi-core processors have long fueled high-end MRI techniques such as parallel imaging and real-time scanning, yet these same technology advances can also be leveraged to benefit small-scale MR. We present a compact stand-alone MRI console powered by embedded Linux and programmed in Python to investigate the potential of such a platform to deliver modern performance and versatility for NMR/MRI applications constrained in size, power, cost, or user interface. Potential applications include desktop scanners, chemical spectroscopy and relaxometery, RF ablation control, and interventional device safety monitoring.

1280.   Web-interactive sharing of medical images and processing algorithms: the WISDM framework
Jeremy F Magland1 and Felix W Wehrli1
1Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States

WISDM is an open source software allowing web browser-based sharing of medical imaging data stored on any internet-connected computer. Users may interactively browse raw, intermediate, and resulting image arrays. In addition, processing algorithms written in a variety of scripting languages (MATLAB/Octave, C/C++, and Python) may be browsed on-line, and even edited and executed by authorized users. The framework has been used within the authors' institution to manage imaging data and processing pipelines for two imaging laboratories and allows multiple researchers to process and interact with a common pool of data from any operating system without downloading datasets or installing software.

1281.   BirdcageBuilder Mobile: New Functionality and Portability for a Standard MR Engineering Tool
Giuseppe Carluccio1, Chih-Liang Chin2, and Christopher Michael Collins1
1Bernard and Irene Schwartz Center for Biomedical Imaging, New York University School of Medicine, New York, New York, United States, 2Merck Sharp & Dohme, Singapore, Singapore

Birdcage coils are the most commonly used-volume coils in MRI for their ability to provide homogeneous circularly polarized fields inside their volume with a quadrature channel excitation. One of the most used tools by RF coils designers is BirdcageBuilder, a software which provides the values of the capacitors needed to make the coil able to resonate. In this work we extend the functionality and portability of the software by designing a version which can run on common mobile devices for easy access anywhere coils are constructed, and provide all resonant frequencies of the coil as designed.

1282.   Actively shielded bias magnetic field tuning coil for optically pumped atomic magnetometer toward direct MR signal detection 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

Recently, optically pumped atomic magnetometers (OPAMs) have been developed and allow us easily to measure extremely small magnetic fields. An ultra-low field (ULF) MRI system with an OPAM has been attracted attentions in recent years. In this study, we proposed an actively shielded bias magnetic field tuning coil toward direct detection of MR signals with an OPAM. Results of magnetic field distribution analyses demonstrated that the active shield could reduce the magnetic distortion caused by the bias tuning coil and the actively shielded bias magnetic field tuning coil was feasible to detect MR signals directly with an OPAM.

1283.   Very low field imaging of laser-polarized noble gases
Yuan Zheng1, Gordon D Cates2, John P Mugler2, William A. Tobias2, and G Wilson Miller2
1University of Virginia, Charlottesville, VA, United States, 2University of Virginia, VA, United States

We built an inexpensive low field MRI system and implemented a novel design of transverse gradient coils. We presented images of hyper-polarized He-3 and Xe-129 phantoms. Our system can also be expanded for small animal and even human lung imaging.

1284.   Phase Coherent Multi-Channel Synthesizer of Transmit Pulses at Larmor Frequencies up to 512 MHz
Andrzej Jesmanowicz1
1Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin, United States

The method of multi-channel RF pulse creation is presented here by the use of a set of independent wave-form synthesizers. They can operate directrly at Larmor frequency as high as 512 MHz. Up to 16 channels with absolute phase coherency can supply pulses to transmit amplifiers of scanners operating at magnetic fields up to 12 Tesla.

1285.   Comparison of analog and digital transceiver systems for magnetic resonance imaging
Seitaro Hashimoto1, Katsumi Kose1, and Tomoyuki Haishi2
1University of Tsukuba, Tsukuba, Ibaraki, Japan, 2MRTechnology Inc., Tsukuba, Ibaraki, Japan

Analog and digital transceivers for MRI systems were critically evaluated under identical experimental conditions. The MRI experiments were performed using a 4.74-Tesla vertical-bore superconducting magnet and a high-sensitivity gradient coil probe. 3D spin-echo images of a kumquat were acquired with and without using a gain-stepping scan technique to extend the dynamic range of the receiver systems. The acquired MR images clearly demonstrated that nearly identical image quality was obtained for both transceiver systems, but DC and ghosting artifacts were obtained for the analog transceiver. We therefore concluded that digital transceivers have several advantages over the analog transceivers.

1286.   A Generalized Concept for Preamplifier Decoupling
Enrico Pannicke1,2, Roland Müller2, Oliver Speck3, Ralf Vick1, and Harald E. Möller2
1Institute for Medical Engineering, Otto-von-Guericke-University Magdeburg, Magdeburg, Saxony-Anhalt, Germany, 2Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Saxony, Germany, 3Biomedical Magnetic Resonance, Otto-von-Guericke-University Magdeburg, Saxony-Anhalt, Germany

Preamplifier decoupling is a valuable technique in the development of multi-channel receiver array coils. Although well established, there is currently no simple rule available to design a proper network with desired properties. A suitable equation can be derived utilizing the concept of impedance transformations. With this concept, the robustness of the coil against varying loading conditions of the coil was investigated as a further property of the circuit.

1287.   Near-Magnet Power Amplifier with built-in Coil Current Sensing
Klaus Solbach1, Ashraf Abuelhaija1, and Samaneh Shooshtary1
1RF Technology, University Duisburg-Essen, Duisburg, Germany

A new concept of a near-magnet PA is presented which operates without circulator/isolator but closely cooperates with the coil to allow control of the coil current. The concept features a voltage probe at the PA output and a tuned transmission line connecting the coil. The probe voltage is proportional to the coil current which allows control of the coil current under mismatch and mutual coupling from other coils in an pTx array without extra pick-up loop. The function is demonstrated by an experimental set-up creating a wide range of load impedance by varying the coil distance to a phantom.

1288.   Stability Test of Near-Magnet Power Amplifier
Kabir Hasanzadeh1, Klaus Solbach1, and Samaneh Shooshtary1
1RF Engineering, University Duisburg-Essen, Duisburg, NRW, Germany

In this work a method to test the Stability of Near-Magnet Power Amplifier (DUT) is explained and the test results are presented. The method includes a bench stability test which employs an electronic circuit designed to realize reflection coefficients with variable magnitude and phase, which is implemented using the concept of the laod-pull. The mutual effect between the antennas around the coil have also been tested to confirm the stability of the DUT in such situations. Results show that although the DUT is stable for all the situations, but the output power is depended on the variation of the load.

1289.   Sensing of Birdcage Rung Currents for Detection of Anomalous Loading
Christopher Ellenor1, Pascal Stang1,2, John Pauly1, and Greig Scott1
1Electrical Engineering, Stanford University, Stanford, CA, United States, 2Procyon Engineering, San Jose, CA, United States

A birdcage coil is fitted with optically coupled current sensors on each of its rungs. This tool gives new, rapid and realtime information about the spatial distribution of current in the coil under different loading conditions. The detection of anomalous loading conditions may be indicative of certain RF safety hazards such as resonant wire coupling or strong coupling to tissue through the bore wall, leading to burns. Phantom experiments are conducted and distortion of the rung current pattern due to anomalous loading is observed.

1290.   Modeling PIN Diode Temperature Rise in High Induced Current MR Receive Coils
Robert Caverly1, Ronald Watkins2, and William E Doherty3
1Villanova University, Villanova, PA, United States, 2Department of Radiology, Stanford University, Stanford, CA, United States, 3Microsemi, Lowell, MA, United States

A new electrothermal SPICE-based model that predicts both electrical and thermal behavior of PIN diodes used in high field, high power MR imaging is described. The model accurately predicts the temperature rise in blocking applications and is fully compatible with industry-standard simulators such as SPICE as well as it variants. Knowledge of the temperature rise in PIN protection diodes is important because failure rates of these devices dramatically increase if temperatures exceed approximately 150 oC, with a potential loss of patient and equipment protection

1291.   14T Dual-tuned RF Probes for 13C/1H MRI Using Common-Mode Differential-Mode (CMDM) Method
Hong Shang1, Xiaoliang Zhang1,2, Yiran Chen1, Subramaniam Sukumar1, Peder Larson1, Daniel B Vigneron1,2, and Duan Xu1,2
1Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, United States, 2UC Berkeley/UCSF Joint Bioengineering Program, San Francisco, CA, United States

Double-tuned radiofrequency (RF) coils are critical for multinuclear MR applications, with advantage of image co-registration of proton anatomic images and multinuclear metabolic images, and B0 shimming using proton channel for low natural abundance heteronuclear MRSI. In this work, a 14T double-tuned surface coil was built based on the CMDM method, which has been proposed for designing double-tuned RF coils with better decoupling between channels and was demonstrated to provide excellent performance and easy implementation at 7T. Bench tests and phantom imaging were performed and demonstrated excellent decoupling between the two channels, efficient impedance match, and independent tuning.

1292.   Independent active decoupling circuit for RX coil on MR systems without active decoupling capabilities (0.2T) or with connecting issues (3T).
Thomas Feuillet1,2, Herve Saint-Jalmes3,4, Marie-Jose Seurin2, Michele Zani5, Alejandro Bordelois6, and Olivier Beuf1
1Université de Lyon, CREATIS ; CNRS UMR 5220 ; INSERM U1044 ; INSA-Lyon ; Université Lyon 1, Villeurbanne, France, 2SARL Cirma, Marcy l'Etoile, France, 3LTSI ; INSERM U1099, Université Rennes 1, Rennes, France, 4CRLCC, Centre Eugene Marquis, Rennes, France, 5Agilent Technologies, Oxford, United Kingdom, 6CBM, Universidad de Oriente, Santiago, Cuba

Some MR systems do not provide an active decoupling bias signal to RX coil and use only passive and/or geometrical decoupling. An external circuit which independently generates an active decoupling signal for RX coils for any MR system was developed. The circuit was tested on a 0.2T system with no active decoupling, and at 3T to demonstrate its interest when an additional dedicated RX coil is designed and its connection is unknown or third part coil is not allowed. Results were considered at both fields and were comparable to reference decoupling methods, in terms of delays, SNR and B1 uniformity.

1293.   Design of Flanged RF Shield for Mitigation of RF and Gradient Coil Interactions
Muhammad Hassan Chishti1, Jean-Baptiste Mathieu1, Joseph E Piel1, Desmond T.B. Yeo1, Christopher J Hardy1, Dominic Graziani1, and Seung-Kyun Lee1
1GE Global Research Center, Niskayuna, New York, United States

Radio-frequency (RF) shields mitigate undesired interactions between gradient coils and RF transmit coils. RF losses in gradient windings can lower the Q of the RF coil and result in increased power requirements. In this work, we present full-wave electromagnetic modeling and analysis of an end-flanged shield for use with an asymmetric head gradient coil. Differences in B1 maps with and without the flanged shield indicate that flanged shield is effective in ameliorating RF field leakage to the gradient coils. Bench measurements also show that Q of the RF coil improved from 50 (without flanged shield) to 185 (with flanged shield).

1294.   Regional Faraday shielding for improved dynamic hyperpolarized 13C MRI
Cornelius von Morze1, Galen D Reed1, Hong Shang1, Hsin-Yu Chen1, Lucas Carvajal1, James Tropp2, Daniel B Vigneron1, and Peder EZ Larson1
1Dept. of Radiology & Biomedical Imaging, UCSF, San Francisco, CA, United States, 2GE Healthcare, Fremont, CA, United States

We investigated the use of regional Faraday shielding to help prevent loss of hyperpolarized 13C magnetization due to premature excitation during tracer delivery and recirculation about a primary region of interest. The value of this approach was demonstrated in simulations and hyperpolarized phantom experiments.

1295.   Cross-Validation of Magnetic Resonance Elastography by Continuous Acoustic Vibration and Ultrasound Elastography by Acoustic Radiation Force Impulse: a Phantom Study
Mikio Suga1,2, Riwa Kishimoto2, Atsuhisa Koyama1, Tetsuya Wakayama3, Takayuki Obata2, and Hiroshi Tsuji2
1Chiba University, Chiba, Chiba, Japan, 2National Institute of Radiological Sciences, Chiba, Chiba, Japan, 3GE Healthcare Japan, Tokyo, Japan

For noninvasive evaluation of biomedical tissue elasticity, magnetic resonance elastography (MRE) and ultrasound elastography (USE) using acoustic radiation force impulse (ARFI) have become common for use in clinical practice. However, USE-ARFI has not yet been compared with MRE. In this study, the quantitativity of MRE and USE-ARFI (VTTQ) measurement was evaluated by polyacrylamide phantoms. There was strong correlation between MRE and rheometer, and VTTQ and rheometer. VTTQ with 4 MHz convex probe showed higher standard deviation, and VTTQ and MRE showed different depth dependency. Therefore, we should consider of the properties of each method.

1296.   Construction and Use of a Micro Resolution Phantom for Small Bore MRI
Samuel Barnes1, Naomi Santa Maria1, and Russell Jacobs1
1Biology, Caltech, Pasadena, CA, United States

Despite their usefulness in quality assurance of high resolution small bore systems, resolution phantoms with feature sizes of 100um are not commercially available. This works describes the design, manufacture, and use of resolution phantoms with features in the 100um to 500um range. These can be easily designed using CAD software and manufactured using laser drilling techniques. This provides a custom cost effective solution for labs to perform testing on new or existing sequences.

1297.   A resistive heating system for homeothermic maintenance in small animals.
Stuart Gilchrist1, Philip D Allen1, John S Beech1, Veerle Kersemans1, Paul Kinchesh1, Boris Vojnovic1, and Sean C Smart1
1Gray Institute for Radiation Oncology and Biology, Department of Oncology, University of Oxford, Oxford, United Kingdom

Anaesthesia is usually required for the immobilisation of animals for imaging. This induces a heat loss that must be artificially offset. It is commonplace for warm fluids (piped liquids or circulating air) to be used to provide this heat but these systems require significant space in which to circulate. We demonstrate a resistive heating system that creates no discernible artefacts in MR images or spectroscopy, and which requires no additional space as it embedded within the animal support cradle.

1298.   Development of an MRI method for awake mouse imaging using soft immobilization and a fast MR acquisition procedure
Shunsuke Kusanagi1, Kazunari Kimura1, Makoto Hirakane1, Shigeto Iwamoto1, Rikita Araki2, Sosuke Yoshinaga1, and Hiroaki Terasawa1
1Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan, 2Bruker Biospin K.K., Yokohama, Kanagawa, Japan

Mouse MRI studies facilitate the elucidation of the pathogenic mechanisms underlying various diseases and the appropriate medical treatments, due to the remarkable advances in mouse genetic technology. It is difficult to acquire accurate MR images when an imaging target moves in the scanner, and thus treatment with anesthesia and fixing apparatuses are usually required. However, the brain activation profiles were reportedly affected by anesthesia. To exclude the unfavorable anesthetic effects, we successfully developed an easy-to-operate method for awake mouse brain imaging, which uses softer immobilization with clothes for mice and a fast MR acquisition procedure, without surgery and training.

1299.   Noncontact physiological measurements using video recording inside an MRI scanner
Shang-Yi Yang1, Hsaio-Hui Huang1, Chi-Wei Liang1, Shang-Yueh Tsai2, and Teng-Yi Huang1
1National Taiwan University of Science and Technology, Taipei, Taiwan, Taiwan, 2The Graduate Institute of Applied Physics, National Chengchi University, Taipei, Taiwan, Taiwan

This study attempts to use video recording as a tool for physiology monitoring in an MRI scanner. During a cardiac cycle, facial skin blood perfusion changes alter optical path of ambient light emitted to the subject¡¦s face. Using a conventional digital camera to capture the changes of the reflected light and using ICA analysis to remove other sources in light, we identify that this method is feasible in a low-light MRI bore. This method is an optic-based technique which avoids the problem associated with switching gradient system.

1300.   MR-compatible normobaric gas mixer for hypercapnic vasoreactivity studies on humans
L. Lamalle1,2, J.-B. Menut3, S. Vergès4, J. M. Warnking5,6, and A. Krainik7,8
1Inserm — US 17, Grenoble, France, 2Université Grenoble Alpes — UMS IRMaGe, Grenoble, France, 3SMTEC, Sport & Medical Technologies S.A., Nyon, Switzerland, 4Université Grenoble Alpes — Laboratoire HP2, Grenoble, France, 5Inserm — U836 (Équipe 5), Grenoble, France, 6Université Grenoble Alpes — Grenoble Institut des Neurosciences, Grenoble, France, 7Université Grenoble Alpes — Faculté de Médecine, Grenoble, France, 8CHU de Grenoble — Unité IRM, Grenoble, France

A normobaric gas mixer was developed to allow MR-based hypercapnic vasoreactivity studies on humans. It operates safely close to the magnet and can be remotely computer controlled. Hypercapnic episodes with FiCO2 less than 10 % can be programmed to chain in succession for prescribed numbers of MR scanner trigger events. Device performance is demonstrated in a cerebral BOLD block-designed fMRI experiment.

1301.   3D printing of MRI compatible components: Why every MRI research group should have a low-budget 3D printer
Karl-Heinz Herrmann1, Clemens Gärtner1, Martin Krämer1, Daniel Güllmar1, and Jürgen R. Reichenbach1
1Medical Physics Group, Institute of Diagnostic and Interventional Radiology I, Jena University Hospital - Friedrich Schiller University Jena, Jena, Germany

The capabilities of a current low budget 3D printer was evaluated by designing and building a mouse head fixation custom fitted to a dedicated recieve coil. While the low budget 3D printing technology has not yet outgrown some inherent problems like warping due to thermal stresses, it was possible to build a fully functional multipart mouse head fixation. The printing material Polylactic Acid (PLA) is fully MRI compatible as even its susceptibility is close to biological tissue. We therefore consider a low budget 3D printer a quite useful assessory for MRI labs.

1302.   Evaluation of an MR compatible head fixation device using a custom-made 3D printed frame in combination with a thermoplastic head mask
Daniel Güllmar1, Karl-Heinz Herrmann1, Clemens Gärtner1,2, Nico Banz3, Thomas G Wendt3, and Jürgen R Reichenbach1
1Medical Physics Group, Institute of Diagnostic and Interventional Radiology I, Jena University Hospital - Friedrich Schiller University Jena, Jena, Germany, 2Medical Engeneering and Biotechnology, University of Applied Sciences, Jena, Germany, 3Department of Radiotheraphy and Radiooncology, Jena University Hospital - Friedrich Schiller University Jena, Jena, Germany

Head fixation using a custom-made frame in combination with a thermoplastic head mask was evaluated in terms of repositioning accuracy as well as degree of immobilization. In back-to-back scans regular fixation using clamps performed equally well compared to mask fixation. Repositioning accuracy using mask fixation was found to be very high (< 0.2mm, < 0.2°). Under heavy motion the degree of immobilization did not exceed 1.5 mm in translation and 1.5° in rotation. The approach can be used to acquire MR scans which require minimal head motion during very long scan times (e.g. DTI, fMRI, Perfusion, high-res anatomy scans).

1303.   An MRI Compatible Surface Scanner
Oline V. Olesen1,2, Jakob Wilm1,3, Andre van der Kouwe2, Rasmus R. Jensen1, Rasmus Larsen1, and Lawrence L. Wald2
1DTU Compute, Technical University of Denmark, Lyngby, Denmark, 2Athinoula. A. Martinos Center for Biomedical Imaging, Dept. of Radiology, Massachusetts General Hospital, Massachusetts, United States, 3Department of Clinical Physiology, Nuclear Medicine & PET, Rigshospitalet, University of Copenhagen, Denmark

We present the hardware design of an optical surface scanner for in-bore applications. It is the first remote structured light scanner that transmits projected patterns onto the subject and captures their images through optical fiber bundles. MPRAGE and EPI images of a phantom were acquired with simultaneous surface scanning. The system design was shown to be MRI compatible and functional on the Siemens mMR Biograph. This technology could be used for monitoring and markerless tracking of surfaces e.g. real-time motion correction feedback without the use of MR navigators or optical markers.

1304.   Imaging in a Rotating Frame: MRI without B0 Gradients
Steven M Wright1, Brian J Bass1, and John C Bosshard1
1Electrical and Computer Engineering, Texas A&M University, College Station, TX, United States

Spatial encoding with reduced reliance on Bo gradients has always been an interest for specialized applications. Some investigators have demonstrated entirely replacing gradient encoding in one direction and rotating a receiver coil at very high rates to create a virtual array for RF spatial encoding. Here we demonstrate early results from a novel planar imaging technique for MR imaging that uses no gradients at all, performing all spatial encoding by a combination of RF encoding and rotating the object. The specific interest here is the development of a simple, low-cost imaging system that is robust to magnetic field homogeneity.


Array Coils & Systems

Monday 12 May 2014
Traditional Poster Hall  16:30 - 18:30

1305.   Four Channel Transceiver Array for Functional Magnetic Resonance Spectroscopy in the Human Visual Cortex at 9.4 T
Andreas Pfrommer1, Nikolai Avdievich1, and Anke Henning1,2
1Dept. of High-Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Tübingen, Baden-Württemberg, Germany, 2Institute for Biomedical Engineering, University and ETH Zürich, Zürich, Switzerland

RF coils for functional magnetic resonance spectroscopy at ultra-high field strength must be designed with high SNR, high transmit efficiency and optimized to guarantee SAR safety. With numerical EM simulations we compared two possible 4 channel RF coil setups for the application in the human visual cortex. It turned out that overlapping loop elements can provide 12.5 % more B1+ /√SAR(10g) than without overlap for this particular case. Based on the simulation we have constructed a tight fit 4-channel transceiver head phased array. We could reach a B1+ of 63 µT in a 12.4x12.4 mm² sized voxel in the visual cortex region in a human head-and-shoulder phantom.

1306.   Evaluation of ICE and capacitive decoupling methods using in 8-channel loop array coils at 7T
Xinqiang Yan1,2, Xiaoliang Zhang3,4, Chuangxin Ma2, Long Wei2, and Rong Xue1
1State Key Laboratory of Brain and Cognitive Science, Beijing MRI Center for Brain Research, Insititute of Biophysics, Chinese Academy of Sciences, Beijing, Beijing, China,2Key Laboratory of Nuclear Analysis Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, Beijing, China, 3Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, United States, 4UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco, California, United States

In this study, two eight-channel transmit/receive volume-type loop array coils were built for human head imaging at 7T by using the ICE decoupling method and capacitive decoupling method, respectively. We have conducted research on comparison between these arrays in terms of S-parameter matrix, SNR and parallel imaging capability. Compared with the capacitively decoupled array, the ICE-decoupled array has better isolation between adjacent coil elements, higher SNR at periphery area and better parallel imaging capability. Additionally, ICE decoupling method is more robust that decoupling loops do not need to be retuned for different loads.

1307.   High SNR bilateral breast MRI with a dual transmit, 26-channel receive RF coil with simultaneous 31P CSI at 7 tesla
Tijl A. van der Velden1, Michel Italiaander2, Wybe J.M. van der Kemp1, Alexander Schmitz1, Kenneth Gilhuijs1, Peter Luijten1, Vincent O Boer1, and Dennis W.J. Klomp1
1Radiology, University Medical Center Utrecht, Utrecht, Utrecht, Netherlands, 2MR Coils, Drunen, Netherlands

Synopsis: Strong T1-weighted, high resolution dynamic contrast enhance MR images are key in the detection of breast cancer. Combined with phospholipid detection using 31P Chemical Shift Imaging (CSI), the earlier alterations in metabolism can be obtained using a novel decoupling loop a bilateral breast coil was designed for uncompromised 1H and 31P MR(S)I at 7 tesla enabling increased spatial and temporal resolution with the 26 1H receiver channels integrated in the coil. We demonstrate high spatial and temporal resolution imaging and 31P CSI in patients with breast cancer.

1308.   Comparison of three different microstrip transmit elements for use in multichannel Tx/Rx body coils at 7 Tesla
Stephan Orzada1, Klaus Solbach2, Mark E. Ladd1,3, and Andreas K. Bitz1,3
1Erwin L. Hahn Institute for MRI, Essen, Germany, 2Institute of Microwave and RF Technology, University of Duisburg-Essen, Duisburg, Germany, 3Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany

In this study three different elements are compared regarding their suitability for large-diameter, multi-element body coils at 7T: the centrally-fed microstrip line2 (MSL), the centrally-fed microstrip line with meanders3, and a new design where the meanders of the aforementioned element are loaded with a dielectric to eliminate the end capacitors. Comparison is done through simulations and phantom experiments on the single elements. The element with dielectrically loaded meanders shows a more focused sensitivity then the MSL or the meander element terminated with capacitors, which might be beneficial for parallel transmit and parallel reception.

1309.   Optimization of B1 field homogeneity along the longitudinal direction for 7T MTL resonators by using a multi-row design
Xinqiang Yan1,2, Xiaoliang Zhang3,4, Chuangxin Ma2, Long Wei2, and Rong Xue1
1State Key Laboratory of Brain and Cognitive Science, Beijing MRI Center for Brain Research, Insititute of Biophysics, Chinese Academy of Sciences, Beijing, Beijing, China,2Key Laboratory of Nuclear Analysis Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, Beijing, China, 3Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, United States, 4UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco, California, United States

In this work, we used a double-row microstrip transmission line (MTL) array by varying the termination capacitance distribution to generate more homogeneous B1+ field along longitudinal direction. The coupling between elements of adjacent rows was reduced by using the induced current compensation decoupling method. Full-wave electromagnetic modeling was used to study and compare the performances of the new design and the conventional MTL resonator. The B1+ homogeneity improvement along longitudinal direction was obvious and this new design has also paved the way for similar designs for human imaging.

1310.   A hybrid dielectric/birdcage double tuned volume resonator for high field MRI
Sebastian Arnold Aussenhofer1, Paul de Bruin1, and Andrew Webb1
1Radiology, C.J. Gorter Center for High Field MRI LUMC, Leiden, Select, Netherlands

This work describes a new principle to build double tuned volume resonators for high field human imaging by combining a dielectric HEM mode resonator with a birdcage coil. The dielectric resonator acts as the proton transceiver (298 MHz at 7T); the birdcage acts as the sodium transceiver (79 MHz at 7T). By inserting the birdcage into the dielectric coil a double tuned volume coil can be constructed if each of the birdcages rungs is proton frequency trapped. The homogenous B1 fields of the two resonators are preserved in the joint setup. A resonator was constructed to acquire high resolution proton and sodium images of the human wrist.

1311.   An 8 channel Transceiver phased array coil combined with a Surgical Robot for an MR assisted Robotic surgery.
Seunghoon Ha1, Haoqin Zhu1, and Labros Petropoulos1
1Research and Development, IMRIS Inc, Minneapolis, MN, United States

To fully utilize Robotic assisted surgery in MR, it is imperative that the RF coil design should be fully integrated with a Head Fixation Device. The combination of the RF coil, HFD, and Robotic surgery introduces clinical requirements and needs that cannot be satisfied with the design of a traditional RF coil that is targeted for diagnostic MR Imaging. In this study, we propose an new eight channel transceiver array coil that is seamlessly integrated with an MR safe HFD and an MR safe Robot by minimizing peak and average SAR, inside the surgical field containing the RF field outside the robot and optimizing image quality and SNR using EM simulation results and verifying the results with measurements on a prototype coil.

1312.   Comparison of RF Resonators Using Microstrip for Human Head at 3T
Hyeok-Woo Son1, Young-Ki Cho1, and Hyoungsuk Yoo2
1Kyungpook National University, Daegu, Korea, 2University of Ulsan, Ulsan, Korea

16-channel head coils using a variety of RF resonators were tested on study participants at 3 Tesla, and the penetrated RF magnetic fields were compared amongst four different RF resonators in a spherical phantom. we proposed using a 16-channel coil with a SIR with four arms, and we compared it to other RF resonators based on microstrip transmission lines. The 16-channel coil provided better B1+ fields and can be effectively controlled for parallel imaging in 3 Tesla MRI systems. 16-channel head coils using the SIR with four arms for parallel imaging could be used in hospitals for higher quality imaging.

1313.   A novel design approach for planar local transmit/receive antennas in 3T spine imaging
Johanna Schöpfer1, Klaus Huber1, Stephan Biber2, Sebastian Martius1, and Helmut Greim2
1Corporate Technology, Siemens AG, Erlangen, Germany, 2Healthcare Sector, Siemens AG, Erlangen, Germany

The human spine is one of the most frequently imaged body parts in clinical MRI. The imaging performance can be restrained by SAR restriction, B1+-inhomogeneities or insufficient B1+-peak values. In the following an optimized local transmit antenna structure for spine imaging is presented which offers reduced SAR values, improved B1+-inhomogeneity and reduced power requirements in comparison to examination with the body coil antenna. Following EM-simulations, the antenna structure was manufactured and successfully integrated, showing significant potential for future work in 3T MRI imaging with local transmit coils.

1314.   Design and Implementation of Flexible Printed Receive Coils Arrays
Joseph Russell Corea1, Anita Flynn1, Galen Reed1,2, Peter Shin2, Greig Scott3, Ana Claudia Arias1, and Michael Lustig1
1Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, California, United States, 2Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California, United States, 3Electrical Engineering, Stanford, Stanford, California, United States

Creating receive coil arrays using ultra-high quality components is the standard method of fabrication for arrays today. However, concessions can be made trading off excess quality factor for a more conformable device using screen printed materials. This is possible because in clinical scanners, the system is body noise dominated so lowering the quality factor of the coil does not necessarily lower the signal-to-noise ratio of the image. Here we discuss the implications of using printed materials for creating receive coil arrays and include a demonstration of a 4-channel fully printed prototype on different areas of a volunteer.

1315.   A 64-Channel Cardiac Receive-Only Phased Array Coil for Cardiac Imaging at 3T
Mark Schuppert1, Boris Keil2, Bastien Guerin2, Stefan Fischer1, Robert Rehner3, Lawrence L. Wald2,4, and Laura M. Schreiber1
1Section of Medical Physics, Department of Radiology, University Medical Center of the Johannes Gutenberg University, Mainz, Germany, 2A.A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, 3Siemens AG, Healthcare Sector, Erlangen, Germany, 4Harvard Medical School, Boston, MA, United States

A 64-channel cardiac receive-only phased array prototype coil was built. We show its use for accelerated imaging (tGRAPPA, acceleration factors R = 3, 5, 7, and 8) in comparison to a 38-channel commercial coil setup (Body 18/Spine 32 Tim coils). Compared to the commercial coil setup, the achieved center SNR with the 64-channel coil was 6% less using optimally combined complex data in phantom measurements. Nonetheless, at R = 7 mean noise amplification in phantom measurements was 50% less with the new coil. In vivo image quality was superior with the 64-channel cardiac phased array coil at R=5 and R=7.

1316.   Non-resonance 16-element transceiver array for human head imaging at 7T
Yong Pang1 and Xiaoliang Zhang1,2
1Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, United States, 2UC Berkeley/UCSF Joint Bioengineering Program, CA, United States

Decoupling issue is a challenging problem in transceiver array designs at high fields. The Non-resonance RF method (NORM) using traveling wave provides a promising way to alleviate this problem and also has multi-frequency excitation and reception capability. In this work, a 16-element transceiver NORM array for 7T human head imaging is modeled and simulated using FDTD method. The unmatched decoupling and excellent g-factors were achieved, indicating the feasibility of parallel imaging using the proposed NORM array. The same NORM array is able to perform multinuclear excitation and detection, such as C13 and P31, which is verified by FDTD simulation.

1317.   A Double-Row Transmit Array with Broadband Sheath-Wave Damping for 7T Human Head Imaging
Roland Müller1, Andreas Schäfer1, Debra S. Rivera1, Robert Turner1, and Harald E. Möller1
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany

Goal of the project was to design an eight-element, double-row, transmit RF array coil for imaging of human heads at 7T. Both rows should be tuned independently using the reflected power minimization approach. At high fields, the common mode problem is presenting a source of loss as well as a potential safety issue. This was addressed by a PCB based 3D coil structure. The combination of balanced feeding, balanced feed lines and resistor-bypassed line shield gaps was sufficient to eliminate sheath waves and hand effects. No conventional traps were required. A good longitudinal coverage of B1+ field can be shown.

1318.   Effects of Co-Planar Element Shielding on Array Performance at 7T
Samantha By1, Joseph V. Rispoli1, Ivan Dimitrov2,3, Sergey Cheshkov2,4, Craig Malloy2,4, Steven M. Wright1,5, and Mary Preston McDougall1,5
1Biomedical 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, 4Radiology, University of Texas Southwestern Medical Center, Dallas, TX, United States,5Electrical and Computer Engineering, Texas A&M University, College Station, TX, United States

At higher field strengths, shielding of RF coils to mitigate radiation losses becomes increasingly necessary. In an array configuration, however, shielding individual elements can be complex, particularly when the elements are overlapped for geometric decoupling. This work presents the benefits of a co-planar shielding configuration of the elements of an overlapped array at 7T. Compared to the unshielded array, the shielded array provided a 39% improvement in mean SNR throughout the entire phantom, an average decrease in mean g-factors for all three views of 8.9%, and a lower power setting required to produce a 90 degree tip angle.

1319.   Replacing Individual Baluns with Quarter Wavelength Baluns in Multi-Channel Arrays
Thomas Grafendorfer1, Greig Scott2, Paul Calderon3, Fraser Robb4, John Pauly2, and Shreyas Vasanawala5
1Advanced Coils, GEHC Coils, Stanford, CA, United States, 2Electrical Engineering, Stanford University, CA, United States, 3Engineering consultant, Stanford Radiology, CA, United States, 4Advanced Coils, GEHC Coils, OH, United States, 5Radiology, Stanford University, CA, United States

Baluns and cable traps are widely used in coil arrays to prevent common mode currents on cables and feeding lines that can severely impact coil performance. But this approach is often done in a trial and error fashion; arbitrarily moving and adding Baluns until the coil somehow works. Here we show a more controlled approach, where ground loops formed by cables are purposely set to hold certain resonance frequencies. In that case individual Baluns can be replaced with quarter wavelength Baluns, which is noting else than shorting individual cable shields together at the right location.

1320.   Four Element Endorectal Array Coil for Improved Sensitivity in Human Prostate Imaging
Ronald D Watkins1 and Kim Butts Pauly1
1Radiology, Stanford University, Stanford, CA, United States

We have designed, built, and tested a miniature four element linear surface coil array for high resolution imaging of human prostate. The prototype coil has demonstrated a factor of 2 increase in SNR near the array, over a single coil equal to the size of the array. In addition it is possible to perform parallel imaging with this array.

1321.   Design of a 96-Channel Bilateral Prone Breast Array for High Performance Parallel MRI
Mike J Smith1 and Scott B King1
1National Research Council of Canada, Winnipeg, Manitoba, Canada

We investigate SNR and parallel imaging limits of prone positioned MR breast imaging by evaluating different 96-Channel receive array coils. We show that the 96-Channel array has SNR and g-factor capabilities that allow 3x faster breast MRI than currently available with 16-Channel coils.

1322.   An eight-channel transmit/receive phased-array head coil with an ICE decoupling method at 7T
Xinqiang Yan1,2, Xiaoliang Zhang3,4, Chuangxin Ma2, Long Wei2, and Rong Xue1
1State Key Laboratory of Brain and Cognitive Science, Beijing MRI Center for Brain Research, Insititute of Biophysics, Chinese Academy of Sciences, Beijing, Beijing, China,2Key Laboratory of Nuclear Analysis Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, Beijing, China, 3Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, United States, 4UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco, California, United States

In this work, an eight-channel transmit/receive loop array with induced current elimination (ICE) decoupling method was built and investigated to demonstrate its feasibility and robustness for human head imaging at 7T. This array has been validated through bench tests and in-vivo human head MR imaging experiments. Isolation between the adjacent loop elements is better than -25dB by employing this new design. The ICE-decoupled array also shows excellent parallel imaging capability that the average g-factor of human head in the sagittal plane was as low as 1.14 when acceleration factor achieves 4.

1323.   An 8-Channel Integrated Balun Phased Array (IBPA) for Small Anatomical Features
Wolfgang Loew1, Randy O. Giaquinto1, Brynne Williams1, J. Matthew Lanier1, Christopher Ireland1, Ronald Pratt1, and Charles Dumoulin1
1Imaging Research Center, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States

A 3 Tesla 8-channel receive phased array for small anatomical features is presented in this abstract. The array uses a novel coil design integrating a balun into each coil element. Coupling and matching was assessed through network analysis. High-resolution imaging experiments were performed on a phantom and human fingers confirming high image quality and proof of concept.

1324.   Prototype 8-Channel Parallel Transmit Body Array in a Clinical 3T System
Wei Luo1,2, Christopher T. Sica1, YeunChul Ryu3, Yang Qing1, and Christopher M. Collins4
1Radiology, Pennsylvania State University, Hershey, PA, United States, 2Engineering Science & Mechanics, Pennsylvania State University, University Park, PA, United States,3Samsung, Korea, 4Radiology, New York University, New York, NY, United States

A prototype of an eight-channel transmit array which can be inserted into a commercial 3T system above the patient bed and used with commercial receive-only arrays was designed and implemented based on our previous studies. This design benefits from the signal-to-noise ratio offered by the commercial receive-only array and restricts the geometry and placement of the array elements. Here, we report progress on this prototype, including its implementation, preliminary shimming result on phantom, and its very first in vivo images.

1325.   An Optimized 8-Channel Helmet Array for Head Imaging at 6.5 mT
Cristen D LaPierre1,2, Lawrence L Wald1,3, and Matthew S Rosen1,2
1Department of Radiology, 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 Science and Technology, Cambridge, MA, United States

A low-field imager offers a potentially transportable and rapidly deployable human imaging system without many of the system requirements of typical scanners. The aim of this study was to construct an 8-channel receive-only helmet array for imaging the human brain. The helmet was 3D printed. Coils consisted of 4x12 cm and 4x14 cm loops, each with 30 turns of 24 AWG copper wire. Geometric decoupling between nearest neighbors was at least -30 db while next nearest neighbors was -6 dB. Future work will compare parallel imaging to incoherent random undersampling and SENSE.

1326.   Performance comparison of a form fitted coil array vs. a quadrature birdcage coil for 31P MRS studies in the human calf at 7T
Sigrun Goluch1,2, Andre Kuehne1,2, Ewald Moser1,2, and Elmar Laistler1,2
1MR Center of Excellence, Medical University of Vienna, Vienna, Vienna, Austria, 2Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria

This work compares the performance of a 3 channel transceive 31P surface coil with a comparable sized 16-leg birdcage for the application in 31P localized spectroscopy experiments in the human calf at 7T with 3D electromagnetic simulation. B1+ as well as SNR calculation for a comprehensive investigation is presented for both designs, showing higher B1+ and SNR in the regions of interest for the surface coil, while as expected the birdcage exhibits better homogeneity. Since the ROIs are small voxels the advantage of better homogeneity is of minor importance compared to high sensitivity in terms of B1+ and SNR.

1327.   Inverse RF Array Head Coil Design for MRI-LINAC System
Yimeng Wang1, Yu Li1, Feng Liu1, Ewald Weber1, Hector Sanchez Lopez1, and Stuart Crozier1
1School of ITEE, University of Queensland, Brisbane, Queensland, Australia

This paper focuses on the theoretical inverse design of cylindrical head RF phased array coils applied in the Magnetic Resonance Imaging Linear accelerator (MRI-Linac) system. A MRI-Linac system is the combination of cancer detection and real time, image guided radiotherapy. In this work, a RF phased-array coils with gaps are designed. Those gaps provide easy access for the accelerator without any disturbance, and multiple receiver coils can realize the fast imaging requirements. The simulation results show that homogeneous magnetic field within a given region of interest (ROI) can theoretically be achieved by the new designed coil.

1328.   Spatial Normalization Can Morph RF Coils into Geometries Optimized for fcMRI Studies in Specific Brain Regions
Iain P Bruce1, L Tugan Muftuler2,3, and Daniel B Rowe1,2
1Mathematics, Statistics and Computer Science, Marquette University, Milwaukee, WI, United States, 2Biophysics, Medical College of Wisconsin, WI, United States, 3Center of Imaging Research, Medical College of Wisconsin, WI, United States

Many degenerative brain disorders are commonly associated with specific regions of the brain that are often off-center and can reside within aliased regions prior to a SENSE reconstruction. While a conventional array of rectangular coils may generate the most uniform magnetic field sensitivities throughout the brain, the human brain is not symmetric, and such sensitivities may not be optimal for fcMRI studies in all regions. This study proposes an approach of using spatial normalization together with an iterated conditional modes algorithm to morph an array of rectangular coils into a geometry that is more optimal for a specific ROI.

1329.   Numerical analysis of a four channel array with intrinsically dual tuned single element antennas providing a congener resonant behavior for combined 23Na/1H MRI at 7T
Jan Taro Svejda1, Daniel Erni1, and Andreas Rennings1
1General and Theoretical Electrical Engineering (ATE), University of Duisburg-Essen, Duisburg, NRW, Germany

An intrinsically dual tuned single element antenna providing a congener resonance behavior is utilized within a four channel setup for combined 23Na and 1H MRI at 7T. The antenna is based on the composite right-/left-handed transmission line technique with short circuited line terminations. The array shows a homogeneous B1-field distribution for both resonances while the specific absorption rate is evenly distributed along the antennas.

1330.   Static shim optimization of 7T dual row arrays
Mikhail Kozlov1, Nicolas Boulant2, and Robert Turner1
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Saxony, Germany, 2CEA, DSV, I2BM, NeuroSpin, UNIRS, Saclay, France

1331.   Cartesian Feedback Configuration with Direct RF Signal Injection for Power Amplifier Linearization at 1.5T MRI
Jonathan Y Lu1, Pascal P. Stang1, John M. Pauly1, Marta G. Zanchi2, and Greig C. Scott1
1Dept of Electrical Engineering, Stanford University, Stanford, CA, United States, 2School of Medicine, Stanford University, Stanford, CA, United States

We demonstrate a modified version of Cartesian feedback, an RF power amplifier linearization technique, for use at 1.5T. In this feedback configuration, the MRI RF signal is directly injected at a point in the feedback loop that allows us to eliminate the initial down-converter needed to convert the MRI signal to baseband or intermediate frequency. Amplifier linearization is important especially in multichannel transmit where unpredictable coil loading conditions can affect amplifiers in the stage before, while this particular arrangement allows appreciable components savings and simplification in architecture when multiple coils are used.

1332.   B1+ distortion by residual currents in decoupled Receive arrays
Ed B Boskamp1 and David M Goldhaber1
1Engineering, GE Healthcare, Waukesha, WI, United States

Whole body RF transmit coil B1+ uniformity distortion due to residual currents in receive arrays is being studied. Complex arrays may be decoupled from B fields at first glance, but currents can still be induced in the copper traces by E fields and by B fields in loops that are not apparent but do exist due to parasitics. Proper placement of the blocking networks is crucial to minimize currents in the array and thus B1+ distortion.

1333.   Simultaneous Deep-local Hyperthermia and 1.5T MR Imaging – an Experimental Systems Interactions Study
Matthew Tarasek1, Tomas Drizdal2, Ruben Pellicer2, Wouter Numan2, Paolo Togni2, Gyula Kotek2, Gerard van Rhoon2, Maarten Paulides2, and Desmond Yeo1
1MRI, GE global research, Niskayuna, NY, United States, 2Erasmus Medical Center, Netherlands

The MRlabcollar was designed as a magnetic resonance (MR)-compatible array for simulation guided conformal radiofrequency (RF) hyperthermia treatment of head and neck (H&N) tumors. Here we present a comprehensive characterization of interactions between the MRI scanner and MRlabcollar to analyse MR image quality, especially with simultaneous operation of both RF sub-systems. We characterize image SNR, the relative B1+ uniformity, B0 distortion due to placement of the array, and phase-difference MR thermometry (MRT) maps acquired during RF transmit from the array. Results show that concurrent heating and imaging is feasible with no significant adverse effects on image quality.

1334.   Analysis of Gain and Noise Relationship in RF Feedback Power Amplifier Linearization for Use at 1.5T MRI
Jonathan Y Lu1, Pascal P. Stang1, John M. Pauly1, Marta G. Zanchi2, and Greig C. Scott1
1Dept of Electrical Engineering, Stanford University, Stanford, CA, United States, 2School of Medicine, Stanford University, Stanford, CA, United States

We analyze the possibility of improving noise in an RF Cartesian feedback system, a power amplifier linearization technique, for use at 1.5T MRI. This involves reducing the amount of attenuation in the feedback path without changing the open loop gain of the system and would entail essentially moving the RF input location in our feedback loop. While gain was reduced, we observed a reduction in noise for the same output voltage. This suggests that by driving a closed loop system with reduced gain at higher input power, we could achieve a linear output with reduced noise.

1335.   Investigating interactions between a TMS system and a novel MR device for concurrent TMS/fMRI experiments
Lucia Isabel Navarro de Lara1,2, Christian Windischberger1,2, Jürgen Sieg1,2, Ewald Moser1,2, Elmar Laistler1,2, and Andre Kuehne1,2
1Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Vienna, Austria, 2MR Center of Excellence, Medical University of Vienna, Vienna, Vienna, Austria

A dedicated 7-channel MR coil was built for concurrent TMS/fMRI Studies. The developed hardware can be placed under the TMS due to the ultra-slim design in the middle, ensuring efficient TMS stimulation and performing a very high SNR at a target depth up to 6 cm. With these satisfactory results, it had to be shown that the functionality of neither the novel MR head coil or the TMS system when working in combination was affected. The possible interactions of the dedicated MR coil on the TMS device and vice versa were the focus of this work.

1336.   A method to calculate the noise factor of the receive coil matching network
Xueming Cao1, Elmar Fischer1, Jan G Korvink2, Jürgen Hennig1, and Maxim Zaitsev1
1Department of Radiology, University Medical Center Freiburg, Freiburg, Germany, 2Institute of Microsystem Technology, Freiburg, Germany

In ordinary MRI experiments using local receive coil, major noise sources in signal reception are the sample and the preamplifier. However, as the sizes of individual coil elements becomes smaller, noise contribution from the coil matching network needs to be taken into account. Here, we present a method to calculate the noise factor of coil matching network. Approximations are also developed to allow the estimation of a coil matching network noise factor on the RF bench. Based on the calculations, a method to reduce the coil matching network noise factor is presented.

1337.   New matching networks for coil and preamplifier
Xueming Cao1, Maxim Zaitsev1, Jürgen Hennig1, Jan G Korvink2, and Elmar Fischer1
1Department of Radiology, University Medical Center Freiburg, Freiburg, Germany, 2Institute of Microsystem Technology, Freiburg, Germany

Based on the assumption that the sample and preamplifier are the dominant noise sources for MRI, the coil loop is matched to 50 Ohm through a coil matching network and the preamplifier is noise matched to 50 Ohm too, through another matching network. However, with receiving coils in an array becoming increasingly smaller, the noise contributed from their matching networks cannot be neglected. Here we present two methods to simplify the coil and preamplifier matching networks, therefore their noise contribution is reduced

1338.   Automatic matching of transmit arrays with optically controlled capacitors
Giorgos Katsikatsos1 and Klaas Paul Pruessmann1
1Institute for Biomedical Engineering, ETH Zurich, Zurich, Zurich, Switzerland

A closed-loop controlled matching for Tx-arrays for a 7T scanner 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, 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.

1339.   A Fully Integrated Automatic Tune and Match System for an 8-Channel Transmit/Receive Cardiac TEM Array at 7T: Initial Results in a Phantom and Volunteers
Graeme A Keith1, Christopher T Rodgers1, Aaron T Hess1, Carl J Snyder2, J Thomas Vaughan2, and Matthew D Robson1
1Oxford Centre for Clinical Magnetic Resonance Research, University Of Oxford, Oxford, Oxfordshire, United Kingdom, 2Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, United States

Results in both a saline phantom and in humans are presented for an auto-tune system using piezoelectric actuators and MATLAB control. The system was implemented on an 8-channel pTx cardiac TEM array for use at 7T. A rigorous performance evaluation algorithm was run on the phantom and found that in the majority of cases the S11 was significantly improved by the system. The system was then employed on human subjects, and it was found that it could successfully tune on a person in a maximum of 6 minutes. The system is now in routine use in our lab.

1340.   Single Configuration of Coil and High-Permittivity Material Improves Performance for a Wide Range of Subjects
Christopher M. Collins1 and Qing X. Yang2
1Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, United States, 2Radiology, The Pennsylvania State University, PA, United States

Using numerical simulations, we explore the potential of a single high-permittivity receive head coil former to improve performance of a large encircling transmit array at 7T for six different human subjects with a wide range in size and morphology. This is important to demonstrate the possibility of incorporating HPMs into arrays for high-throughput, high performance MRI. The ability to perform RF shimming with the large volume array was not adversely affected by the presence of the high-dielectric former in any of the subjects and the former greatly improved efficiency and homogeneity of the transmit array for all subjects.

1341.   Improvement of parallel imaging using high permittivity material (HPM) - demonstration with liver imaging at 3T
Zhipeng Cao1, Wei Luo2, Sebastian Rupprecht3, Christopher Sica3, Michael Lanagan2, Christopher M. Collins4, and Qing X. Yang3
1Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States, 2Engineering Science and Mechanics, Penn State University, University Park, PA, United States, 3Radiology, Penn State University, Hershey, PA, United States, 4Radiology, New York University, New York, NY, United States

Experimental demonstration of using HPM to improve parallel imaging on liver imaging at 3T. The HPM resulted in smaller g-factor loss and more SNR preservation with high data undersampling factors.

1342.   Approaching Ultimate SNR: Comparison of Composite and Surface Coil Arrays
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

It has been shown that at high MRI frequencies current patterns other than those provided by surface coils are required to approach the ultimate SNR. SNR improvements in realistic arrays become limited due to noise from coils and matching networks in large arrays. Arrays of three orthogonal coils are naturally decoupled, provide complementary sensitivities and allow the use of larger, body loss dominated, coils. Simulations of large 18-, 36- and 54-element arrays composed of composite and surface coils are compared in terms of SNR and parallel imaging performance. Noise contributions from the coil, matching networks and preamplifiers are included for a realistic comparison.

1343.   Active optical-based decoupling circuit for receiver endoluminal coil
Reina Ayde1, Raphael Sablong1, Gwenael Gaborit2,3, Lionel Duvillaret3, Anne-Laure Perrier1, and Olivier Beuf1
1CREATIS - CNRS UMR 5220 – INSERM U1044, University of Lyon 1, Villeurbanne, Rhone-Alpes, France, 2IMEP-LAHC UMR 5130, University of Savoie, Rhone-Alpes, France,3Kapteos, Rhone-Alpes, France

The use of metallic coaxial cables in MRI could induce local high Specific Absorption Rate. Optical fiber link could be an alternative to coaxial cables to ensure patient safety. In order to assure a complete optical endoluminal receiver coil, an optical system for decoupling the receiver coil was made. The MRI for a phantom of ionized water was taken with three endoluminal coils with different decoupling system: classical, optical and without decoupling system. The SNR and the uniformity of signal distribution were studied and compared. The results show that the decoupling system works perfectly and does not induce field inhomogeneity.


Non-Array RF Coils, Dielectrics & Waves

Monday 12 May 2014
Traditional Poster Hall  16:30 - 18:30

1344.   A susceptibility matched endorectal coil design suited for the MRS examination of the rectal wall
Jean-Marie Verret1,2, Frank Pilleul3,4, Cécile Rabrait2, and Olivier Beuf1
1Université de Lyon; CREATIS; CNRS UMR 5220; Inserm U1044; INSA-Lyon; Université Lyon 1, Villeurbanne, France, 2General Electric Healthcare, Buc, France, 3Hospices Civils de Lyon; Département d’imagerie digestive; CHU Edouard Herriot, France, 4Centre Léon Bérard - Centre de Lutte contre le Cancer, France

A susceptibility matched endorectal coil was tested and compared against a classical endorectal coil design. For different phantom angulations, it enabled a significant decrease (~30%) of the FWHM of spectra acquired on in vitro NMR tubes. These promising results and the restricted FWHM observed suggest the interest of this new coil for the acquisition of in vivo spectra especially for the characterization of the colorectal cancer.

1345.   Endoluminal MRI coils for mice rectal wall assessment
Hugo Dorez1, Raphaël Sablong1, Laurence Canaple2, Sophie Gaillard1, Driffa Moussata3, and Olivier Beuf1
1Université de Lyon, CREATIS CNRS UMR 5220 – INSERM U1044 – INSA Lyon 1, Villeurbanne, Rhône-Alpes, France, 2Institut de Génomique Fonctionnelle de Lyon, Université de Lyon 1, UMR 5242 CNRS, Ecole Normale Supérieure de Lyon, Lyon, Rhône-Alpes, France, 3Service hépato-gastroentérologie, Hospice Civil Lyon Sud, Pierre-Bénite, Rhône-Alpes, France

The purpose of this project research is to assess mice rectum wall using MRI combined with endomicroscopy and conventional endoscopy. Endoluminal MRI coils with active decoupling circuit were developed and characterized on phantoms. Then, in-vivo examination was finally done on mice (c57 black6j). Endoluminal coils improve significantly the local SNR compared to body mice volume birdcage coil. Rectal wall layers are better visualized due to improved spatial resolution achieve with SNR gain. This study shows the feasibility to use small endoluminal coils for mice rectal wall assessment and opens perspectives to better understand rectal pathologies.

1346.   Double-Resonant 13C/1H Coil System for {1H} 13C in vivo NMR Spectroscopy on a 7-T Whole-Body MR Tomograph
Tanja Platt1, Andreas Korzowski1, Reiner Umathum1, and Peter Bachert1
1Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Baden-Württemberg, Germany

13C NMR spectroscopy enables a noninvasive quantification of various metabolites in vivo (without or with an enrichment of 13C) and takes advantage of high B0 and of 1H-decoupling. The aim of this study was to design, implement and test a surface coil system for in vivo 1H-decoupled 13C NMR spectroscopy on an experimental 7-T whole-body MR tomograph. The use of a transmission line resonator concept with special frequency selective filter circuits ensures sufficient electromagnetic decoupling for both frequencies (13C, 1H). The resulting coil system allows among other applications the acquisition of high resolution 1H-decoupled 13C NMR spectra in vivo.

1347.   A variable diameter resonator for high field proton and sodium musculoskeletal MRI
Sebastian Arnold Aussenhofer1, Paul de Bruin1, and Andrew Webb1
1Radiology Leiden University Medical Center, C.J. Gorter Center for High Field MRI, Leiden, South-Holland, Netherlands

A variable-diameter birdcage resonator has been constructed for sodium imaging of the knee at 7 Tesla (78.85 MHz) in order to optimize sensitivity for different patient sizes. Anatomical proton data are acquired using two microstrip lines (tuned to 298 MHz) mounted on the inside of the shield of the variable diameter birdcage. The diameter of the birdcage can be varied between 13.5 and 18 cm. Co-registered proton and sodium images have been acquired from three volunteers ranging from a large male subject to a small female one.

1348.   Novel RF-coil assembly to simultaneously investigate fMRI and electrophysiology in non-human primates in a large bore vertical magnet
Jozien Goense1,2, Michael Beyerlein2, Jens Hoffmann2, Gunamony Shajan2, Thomas Steudel2, Klaus Scheffler2,3, Nikos Logothetis2,4, and Hellmut Merkle5
1University of Glasgow, Glasgow, United Kingdom, 2Max-Planck Institute for Biological Cybernetics, Tuebingen, Germany, 3University of Tuebingen, United Kingdom, 4University of Manchester, United Kingdom, 5National Institutes of health, MD, United States

RF-coil design for combined electrophysiology and fMRI in non-human primates is challenging because any coil design needs to be sufficiently open to allow for electrode access to the brain. Patch antennas allow for a more open design, but since our bore is too small for a 300 MHz traveling wave, we developed an open quadrature transmit coil/antenna placed in-situ. The transmit coil/antenna is capable of producing a sufficiently homogenous B1 field. This device can be used alone in transceiver mode or in combination with dedicated receive arrays which allow for maximum flexibility while maintaining a very high SNR.

1349.   A Circularly-Polarized Dual Litz RF Coil for High-Throughput Eight Whole Mouse Head Samples
Dung Minh Hoang1, Evelyn B Voura1, and Youssef Zaim Wadghiri1
1Radiology, NYU - School of Medicine, New York, New York, United States

In this work, we aimed to increase the throughput of ex vivo samples during overnight unattended sessions by designing a coil and setup accommodating up to eight whole mouse heads. Using our single channel MRI installation equipped with a gradient insert with a 60-mm diameter spherical volume (DSV), we considered a design based on the use of commonly accessible off-the shelf supplies and ease of sample preparation. Among the various structures examined, a dual litz structure electrically-fed through the mid-point of the rung proved to be the most electrically balanced and homogeneous coil throughout the length of the rung.

1350.   A target-field design of open multi-purpose coil for musculoskeletal MR imaging at 3T
Rui Zhang1, Qunzhi Chen2, Hongyang Yuan3, Wenchao Cai4, Kai Zhao4, Jue Zhang1,2, Xiaoying Wang2,4, and Jing Fang1,2
1College of Enigneering, Peking University, Beijing, Beijing, China, 2Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, Beijing, China, 3Department of Radiology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States, 4Department of Radiology, Peking University First Hospita, Beijing, Beijing, China

MRI plays an important role in diagnosing the diseases of musculoskeletal tissues at different body parts. In this study, based on the target-field method, we proposed a kind of open multi-purpose RF coil with three-plane structure for musculoskeletal MR imaging with satisfied homogeneity and high SNR. The design can meet the need of various body parts and provide large joint movement region for dynamic evaluation. The imaging results have demonstrated the effectiveness and advantage of this proposed design. In the near future, it is believed that the coil can be applied for real-time imaging of joint movement under dynamic situations.

1351.   Ladder-design volume coil with good uniformity and signal to noise for hyperpolarised 13C investigations of animals on a 3T clinical system
Deborah K. Hill1,2, Craig Cummings1, Jessica K. R. Boult1, Matthew R. Orton1, Yuen-Li Chung1, Thomas R. Eykyn1,3, Martin O. Leach1, David J. Collins1, and Rafal Panek1
1CR-UK and EPSRC Cancer Imaging Centre, The Institute of Cancer Research and Royal Marsden NHS Trust, Sutton, Surrey, United Kingdom, 2Department of Circulation and Medical Imaging, NTNU, Trondheim, Sør-Trøndelag, Norway, 3St Thomas Hospital, Kings College London, London, United Kingdom

Signal enhancement by Dynamic Nuclear Polarisation of 13C makes it possible to conduct real-time measurements of low concentration metabolites in vivo. Implementation of preclinical work on clinical systems for DNP studies is attractive, but severely limited by surface coils when moving from subcutaneous to orthotopic and genetically modified models. We describe and characterise a custom-made 13C volume ladder-design coil; the coil shows superior SNR and B1 homogeneity in both phantom studies and in vivo in mice when compared to a typical surface coil.

1352.   Design of a detachable rat head coil for MRI-guided stereotaxic interventions
Jijun Han1, Fulang Qi1, and Bensheng Qiu1
1Department of Electronic Science and Technology, University of Science and Technology of China, Hefei, Anhui, China

A detachable head coil with an aperture for MRI-guided stereotaxic rat brain surgery was proposed in this study. The distribution of B1 field was evaluated with numerical calculation. The design of the detachable RF head coil is capable of not only producing the homogenous B1 field, but also providing a free operation path for interventional instruments, which will enable MRI-guided stereotaxic neurosurgery of the rat in vivo.

1353.   Current limited superconducting RF coils
Christopher Stumpf1, Tobias Frank1, Markus Vester2, Sebastian Martius3, Robert Rehner2, Rainer Engelbrecht1, and Lorenz-Peter Schmidt1
1Institute of Microwaves and Photonics, University of Erlangen-Nuremberg, Erlangen, Bavaria, Germany, 2Healthcare Sector, Siemens AG, Erlangen, Bavaria, Germany,3Corporate Technology, Siemens AG, Erlangen, Bavaria, Germany

Superconducting self-resonant RF coils can be used in MRI as receive coils to raise the image SNR. Those coils distort the TX magnetic field if they are not detuned. A new method is presented to passively detune self-resonant HTS coils without Q-factor reduction by inserting a taper into the coil structure. Measurements of RF current in the loop at varying absorbed powers show that the current is limited to a maximum value. By reducing the trace width of the taper the maximum current value is reduced and the distortion of the TX field due to induction is decreased.

1354.   A large volume HEM dielectric resonator for musculoskeletal applications at ultra high field
Sebastian Arnold Aussenhofer1 and Andrew Webb1
1Radiology Leiden University Medical Center, C.J. Gorter Center for High Field MRI, Leiden, South-Holland, Netherlands

A water-based dielectric resonator operating in the quadrature HEM mode has been designed and constructed for imaging the human knee at 7 Tesla. The continuous current distribution throughout the resonator results in an extremely simple design of a water-filled annulus connected to the scanner through two impedance matching networks. High resolution images of the knee at sub-millimeter resolution have been acquired in less than 4 minutes using this resonator.

1355.   RF Field Enhancement at 0.5T to 1.5T with Ultra High Dielectric Constant Material (uHDC)
Christopher Sica1, Sebastian Rupprecht1, Wei Luo2, Raffi Sahul3, Seongtae Kwon3, Michael Lanagan2, and Qing Yang1,4
1Radiology, Penn State College of Medicine, Hershey, Pennsylvania, United States, 2Engineering Science and Mechanics, Penn State University, Pennsylvania, United States,3TRS Technologies, State College, Pennsylvania, United States, 4Neurosurgery, Penn State College of Medicine, Hershey, Pennsylvania, United States

Previous studies have established the benefits offered by dielectric materials at 3T and 7T, including reduced B1+ inhomogeneity and SAR, and increased transmit efficiency and SNR. We explored the application of dielectrics to field strengths of 1.5T and below. Utilizing simulation, the effects of ultra high dielectric constant material (up to εr = 28000) were examined with a block of uHDC material within a phantom at 0.5T, 1T, 1.5T, and 3T. We demonstrated a 2 to 3-fold enhancement in B1 at all field strengths studied, and that lower fields require higher permittivity for enhancement. Experimental results are presented at 1.5 and 3T utilizing available uHDC materials.lower case Greek epsilon

1356.   Single and Multiple Coaxial Inputs to Excite a Cylindrical Waveguide for Traveling Wave MRI at 21.1 T
Jose A Muniz1,2, Smriti Sagaram1,3, Jens T Rosenberg1,2, and Samuel Colles Grant1,2
1National High Magnetic Field Laboratory, The Florida State University, Tallahassee, FL, United States, 2Chemical & Biomedical Engineering, The Florida State University, Tallahassee, FL, United States, 3Electrical & Computer Engineering, The Florida State University, Tallahassee, FL, United States

In traveling wave MRI, propagating RF fields are excited through an antenna located at a distance to a given sample such that excitation and detection in MRI can be induced in the far field [1-3]. In this project, traveling wave MRI at ultra-high field is implemented using a concentric waveguide composed of a dielectric filled inner cylinder and an outer copper cylinder with dimensions similar to the magnet bore of a vertical 21.1 T ultra-wide bore magnet. Uniquely, this waveguide is excited by coaxial inputs at single and multiple points.

1357.   SNR Enhancement by Free Local Resonators for Traveling Wave MRI
Xiaoliang Zhang1,2, Yong Pang1, and Daniel B Vigneron1,2
1Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, United States, 2UC Berkeley/UCSF Joint Bioengineering Program, San Francisco, CA, United States

One of drawbacks of traveling wave MRI is its relatively low signal-to-noise ratio (SNR) due to the use of far fields in excitation and reception. In this work, we present and investigate a method based on free local resonator to improve MR SNR in traveling wave MR. In vivo imaging in rats performed using the proposed free local resonator method at 7T shows a significantly SNR gain over the traditional traveling wave MR.

1358.   Accurate and fast longitudinal RF magnetic field profiling for 7T traveling-wave MRI systems
Thorsten Liebig1, Jan Taro Svejda1, Hongyi Yang1, Andreas Rennings1, Juerg Froehlich2, and Daniel Erni1
1General and Theoretical Electrical Engineering (ATE), University of Duisburg-Essen, Duisburg, NRW, Germany, 2Laboratory for Electromagnetic Fields and Microwave Electronics (IFH), ETH Zurich, Zurich, ZH, Switzerland

We propose an adaptive, fast and accurate scheme for tailoring the RF magnetic field along the bore of a 7T traveling-wave MRI system. The setting consists of a periodic arrangement of quadrature fed resonant CRLH metamaterial ring antennas that are perfectly apt to excite, mold, and dump the propagating TE11 mode within the cylindrical bore. We have achieved narrow field profiles for larynx illumination while tackling the inverse problem using efficient electromagnetic simulations in conjunction with a direct (weighted) least-squares solution. This localized traveling-wave approach has the potential to act as a non-resonant head coils supporting uniform high-resolution brain imaging.


RF Modelling & Safety

Monday 12 May 2014
Traditional Poster Hall  16:30 - 18:30

1359.   Flip Angle Inhomogeneity Constrained pTx Pulse Design for Minimum Peak Local SAR
Mihir Pendse1, Simone Winkler2, and Brian Rutt2
1Department of Electrical Engineering, Stanford University, Stanford, CA, United States, 2Department of Radiology, Stanford University, CA, United States

This work introduces a new minimum SAR spokes-based pTx pulse design algorithm using a spokes trajectory that achieves a desired flip angle inhomogeneity (FAI) threshold while minimizing peak local SAR. Several realistic scan situations are modeled including the use of slightly inaccurate E-field maps for SAR matrix computation to represent patient/body model mismatch and enforcing a constraint on computation time for the optimization. Simulated L-curves show that for four different cases our proposed method achieves equal or lower SAR at low values of FAI compared to prior approaches for SAR-constrained pTx pulse design.

1360.   Transmit field fitting at 9.4 T using analytical solutions to Maxwell's equations
Michael Stephen Poole1, Desmond H Y Tse1, Arthur W Magill1, and N Jon Shah1,2
1INM-4, Forschungszentrum Jülich, Jülich, Germany, 2Department of Neurology, RWTH Aachen University, Aachen, Germany

Transmit B1+ fields need to be accurately acquired for B1+ shimming, kt-points homogenisation, spokes slice selection and parallel RF pulse design. We investigated the application of forcing relative B1+ maps to obey Maxwell's equations in order to provide properly scaled B1+ maps. The method was applied to B1+ maps acquired at 400 MHz in phantom and in vivo and compared to AFI-weighted B1+ and DREAM maps. Furthermore predicted CP mode and kt-points excitations were compared and found to be in good agreement in phantom. The in vivo maps compare qualitatively well with DREAM but conductivity is poorly predicted.

1361.   A Numerical Study Comparing Adult Body, Head and Knee Coils for Paediatric MRI
Gemma R Cook1, Martin J Graves1, Owen J Arthurs2, Fraser J Robb3, and David J Lomas1
1Radiology, University of Cambridge, Cambridge, United Kingdom, 2Great Ormond Street Hospital, London, United Kingdom, 3GE Healthcare Coils, Aurora, OH, United States

Limited availability of dedicated paediatric coils means MRI is typically performed using a transmit/receive coil (considered to be more SAR and SNR advantageous). This study uses a FEM-compatible model of a two month infant inside birdcage coils of typical body, head and knee coil sizes. Transmit and receive fields were calculated and the Specific Absorption Rate (normalised to 4W/kg) was calculated for 1cm³ cubes. SAR maps determined the heat source for further temperature change simulations and maximal SAR and temperature change positions were compared to determine the advantages of each coil.

1362.   Illustration of the Impact of Tuning Configuration on 7T RF Coil Simulations
Joseph V Rispoli1, Steven M Wright1,2, and Mary Preston McDougall1,2
1Biomedical Engineering, Texas A & M University, College Station, TX, United States, 2Electrical & Computer Engineering, Texas A & M University, College Station, TX, United States

This work illustrates the ramifications of two different approaches to tuning and exciting coils in a high-field simulation environment: 1) forcing an ideal resonant condition versus 2) specifying actual implemented lumped element component values. This abstract uses the example of a loop coil at 7T to demonstrate that results using the second approach exhibit a more uniform current distribution, more homogeneous |B1+|, and 29% lower maximum 10-g average SAR. These results illustrate that power/safety considerations of coils at 7T benefit from a simulation approach including implemented component values rather than forcing ideal resonance as typically simulated at lower field strengths.

1363.   Skin effect estimation accuracy in FDTD coil simulations
Andre Kuehne1,2, Helmar Waiczies3, Ewald Moser1,2, and Elmar Laistler1,2
1Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Vienna, Austria, 2MR Center of Excellence, Medical University of Vienna, Vienna, Vienna, Austria, 3MRI.Tools GmbH, Berlin, Germany

1364.   Influence of Deep-Region RF Hyperthermia System on B1+ Field of 1.5T MR Scanner: a Simulation Study
Tomas Drizdal1, Matthew R. Tarasek2, Ruben Pellicer1, Muhammad H. Chishti2, Wouter C. M. Numan1, Gyula Kotek1, Desmond T. B. Yeo2, and Margarethus M. Paulides1
1Erasmus MC, Rotterdam, Netherlands, 2GE Global Research, Niskayuna, NY, United States

Modeling of radio frequency hyperthermia system and 1.5T MR scanner.

1365.   Magnetic Force Estimation around MRI Magnets
Zhenyu Zhang1 and Timothy J. Havens1
1MR Science & Technology, GE Healthcare, Florence, South Carolina, United States

Magnetic forces around MRIs have long been a major concern for operator and patient safety. Due to the difficulty to calculate exact forces, the consensus of the industry is to provide a quantity which represents a good estimation of magnetic forces. This quantity has been included in IEC 60601-2-33. However, the mathematical definition of this quantity has been discussed recently where two suggestions are presented. In this paper, we make an effort to clarify the situation by demonstrating a very simple derivation for one expression and proving that the other expression does not hold in general.

1366.   Improved method and technique for monitoring SAR in transmit coils and arrays
Carl J. Snyder1, Seunghoon Ha1, Haoqin Zhu1, and Labros Petropoulos1
1IMRIS, Minnetonka, Minnesota, United States

With the advent of multi-channel transmitters, ultra-high field imaging and power-intensive techniques like Transmit SENSE, the need for real time power monitoring is becoming an important need. Recent studies have shown that current methods, (monitoring the forward and reflected power at the output of the amplifier) is insufficient as coupling and mismatched coils can change e-field and possibly SAR in transmit arrays. We are proposing a three-point method, monitoring the forward, reflected on the coax and, monitoring the field at the coil.

1367.   Variation in thermal maps during RF heating due to variation in electrical conductivity in TEM coil at 298 MHz
Muhammad Hassan Chishti1, Matthew R. Tarasek1, Margarethus M. Paulides2, and Desmond Teck Beng Yeo1
1GE Global Research Center, Niskayuna, New York, United States, 2Erasmus Medical Center, Rotterdam, Netherlands

Synopsis: The uncertainty of electrical conductivity (σ) values used in electromagnetic (EM) simulations may lead to incorrect assessment of SAR and risks for tissue ablation in patients during MR imaging at ultra-high fields and in RF thermotherapy applications. In this work, we investigate the errors in predicted temperatures due to incorrect assignment of values to σ caused by (i) variations in reported values in the literature, and (ii) temperature-induced variations of σ. Results from our full-wave EM (298 MHz) and thermal simulations show that the uncertainties in σ may induce temperature prediction errors by up to 5.3 ºC.

1368.   Assessment of miniaturized RF traps for RF heating reduction and reception coil sensitivity profile restoration
Jean-Marie Verret1,2, Frank Pilleul3,4, Cécile Rabrait2, and Olivier Beuf1
1Université de Lyon; CREATIS; CNRS UMR 5220; Inserm U1044; INSA-Lyon; Université Lyon 1, Villeurbanne, France, 2Clinical Science Development Group, General Electric Healthcare, Buc, France, 3Hospices Civils de Lyon; Département d’imagerie digestive; CHU Edouard Herriot, France, 4Centre Léon Bérard - Centre de Lutte contre le Cancer, France

To reduce RF-induced heating, standard passive RF traps are known to be efficient. Novel miniaturized RF traps are as efficient as standard ones for this purpose. Furthermore, it is demonstrated that RF traps enable a restoration of the signal intensity pattern of the coil. It is thus possible to perform a MR endoscopy of deeper regions of the bowel (after left colonic flexure for instance) since the coaxial cable incorporating miniaturized RF traps now may be inserted through the rectum with limited discomfort for the patient.

1369.   EMF exposure and temperature increase of anatomical pregnant women models within a 3T RF shimmed birdcage.
Manuel Murbach1, Esra Neufeld1, Fraser JL Robb2, and Niels Kuster1,3
1ITIS Foundation, Zurich, Switzerland, 2GE Healthcare, Aurora, OH, United States, 3Swiss Federal Institute of Technology (ETH), Zurich, Switzerland

Our study investigates the effect of RF shimming at 3T on EMF exposure and subsequent temperature increases in pregnant women of different gestational periods. The effect of relative I-Q phases and amplitudes is investigated in terms of B1+ uniformity (CV(B1+)) and local SAR enhancements. For selected worst-case scenarios, thermal simulations − including local thermoregulation − estimate the potential temperature increase in the mother, amniotic fluid, and fetus. Preliminary results indicate a relatively low thermal load for the fetus (< 38°C) when considering local thermoregulation of the mother in the normal operating mode.

1370.   A system for calibrated measurements of RF electromagnetic fields inside a clinical MR scanner
Gerd Weidemann1, Isabela Frese1, Frank Seifert1, Antonino Mario Cassara'1, Werner Hoffmann1, and Bernd Ittermann1
1Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany

For accurate and complete SAR assessment of an RF coil all E and B field components are required. A system for the calibration of fiber optic time-domain E1 and B1 field sensors using an MR compatible TEM cell and the MR scanner itself was developed. The complex field amplitudes of E1, B 1+ and B1 were reliably measured in an ASTM body phantom equipped with provisions for internal and external field sensors. Utilizing the body coil of a clinical 3 T scanner, the measurements are used to evaluate the accuracy of EMF simulations.

1371.   Transmitted Power from a Tx/Rx Birdcage Coil to Nearby Conductors in Air and in Gel
Zoltan Nagy1,2, Aaron Oliver-Taylor3, Andre Kuehne4,5, and Nikolaus Weiskopf1
1Wellcome Trust Centre for Neuroimaging, University College London, London, United Kingdom, 2Laboratory for Social and Neural Systems Research, University of Zürich, Zürich, Switzerland, 3Institute for Women's Health, University College London, United Kingdom, 4Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Austria, 5MR Center of Excellence, Medical University of Vienna, Austria

Tx/Rx birdcage head coils are often considered safe for patients with abdominal implants but whether such practice is indeed safe has not been tested systematically. We used radio frequency B/E field probes to investigate the transmitted power through air and conductive gel by a Tx/Rx coil in a 3T scanner. We could detect significant levels of both fields at distances up to 50 cm from the Tx/Rx coil. These findings were confirmed with simulations. Preliminary heating results around straight and looped wires did not result in significant temperature elevation but this may be due to the insensitivity of the “implants”.

1372.   Determination of in-vivo temperature rise and gradient induced voltage during MRI of cut sacral neuromodulation leads
John Nyenhuis1 and John Welter2
1Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana, United States, 2Neuromodulation, Medtronic, Minneapolis, Minnesota, United States

In-vitro tests and numerical simulations were made to determine the in-vivo temperature rise and during MRI of cut Neuromodulation leads (Medtronic 3889 and 3093) which were retained in-vivo after being used for treatment of urinary incontinence in women. The overall method follows the procedure described in ISO-IEC 10974. For retained lead length of 7-cm, maximum temperature rise for whole body SAR of 2 W/kg was 2.4 C at 1.5T and 3.7 C at 3T. Rises at the cut exceeded those at the electrode. These rises yield in-vivo temperature that is less than the maximum safe value for neurological tissues.

1373.   The Feasibility of Combined Magnetic Resonance Thermometry and Multiphysics Simulation to Evaluate RF Induced Heating of Metallic Devices
David C. Gross1,2, Yu Ding2, Sergei Yushanov3, Jeff Crompton3, Alan Leewood4, and Orlando P. Simonetti5,6
1Biomedical Engineering, The Ohio State University, Columbus, Ohio, United States, 2Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio, United States, 3AltaSim Technologies, LLC, Columbus, Ohio, United States, 4MED Institute, Inc., West Lafayette, Indiana, United States, 5Cardiovascular Medicine, The Ohio State University, Columbus, Ohio, United States, 6Radiology, The Ohio State University, Columbus, Ohio, United States

RF induced heating is an important safety concern as the number of patients implanted with medical devices increases and the use of 3T MRI becomes more prevalent. We hypothesize that the combination of Magnetic Resonance Thermometry (MRT) and multiphysics simulation would provide a more accurate assessment of MR safety than current in vitro test methods, and could ultimately be used to evaluate RF induced heating of devices in vivo. The purpose of this work is to evaluate the feasibility of this approach by comparing temperature probe measurements with MRT and multiphysics simulation of RF induced heating near a metallic device.

1374.   EM and thermal validation of a numerical elliptical birdcage at 3T in the presence of a long conductive wire
Mélina Bouldi1 and Jan M. Warnking1,2
1Grenoble Institut des Neurosciences - UJF, Grenoble, Rhônes Alpes, France, 2Inserm U836, Grenoble, Rhônes Alpes, France

Understanding the risk of overheating in the presence of implants requires a rigorous simulation of experimental conditions. We have built a model of the whole body transmit coil in the Philips Achieva TX® system. The validity of that model was verified by comparing electromagnetic and thermal simulations to phantom experiments for an ASTM phantom alone and in presence of a long copper wire. RF fields are in good agreement. Local temperature variations show similar dynamics and amplitudes. Realistic temperature simulations, as opposed to SAR simulations, provide a metric directly comparable to experimental results and thus facilitate validation.

1375.   OSSARTE: an Open-Source software for SAR and Temperature Estimation
Giuseppe Carluccio1, Josh Vega1, Christian Gonzalez-Capizzi2, David Greydanus1, and Christopher Michael Collins1
1Bernard and Irene Schwartz Center for Biomedical Imaging, New York University School of Medicine, New York, New York, United States, 2Oratory Prep School, Summit, New Jersey, United States

To ensure safe use of MRI it is desirable to estimate and limit the Specific energy Absorption Rate (SAR) averaged over the whole body, whole head, and the maximum SAR averaged over any 1 or 10g region in the body. Safety guidelines by the IEC recommend limits on the maximum values of both SAR and temperature. In this work, we present a useful open source software which includes tools to locally average SAR and to compute temperature increase with different methods, letting the user choose whether to prioritize accuracy or computation speed.

1376.   MR Safety of Magneto-inductive Receivers
Richard Syms1, Khoonsake Segkhoonthod1, and Ian Young1
1EEE Dept., Imperial College London, London, Middlesex, United Kingdom

Radio frequency heating may be induced when linear conductors are inserted in the body during MRI, due to electrical excitation of surface wave resonances. The effect occurs even when inserted lengths are short, due to the high RF dielectric constant of tissue. We have developed receivers for internal imaging using magneto-inductive waveguides, a form of transformer-segmented waveguide that can be realized in thin film form and mounted on a catheter. This paper presents accurate EM simulation using AWR Microwave Office designed to confirm RF safety. The results highlight the effect of heatshrink material on surface wave resonances and parasitic capacitances.

1377.   Online SAR measurement error in high resolution slice accelerated 2D EPI
An T. Vu1, Edward Auerbach1, Kamil Ugurbil1, and Essa Yacoub1
1University of Minnesota, CMRR, Minneapolis, MN, United States

Slice accelerated or multiband (MB) 2D EPI has recently enabled fast, high resolution, whole brain imaging. However, as MB factors, resolution, and brain coverage increase so do the temporal frequency modulations of the MB RF pulses. Such rapidly modulated RF pulses can result in SAR overestimation during online SAR monitoring resulting in prematurely aborted scans even when pre-calculated SAR levels are below (60-70%) the FDA limit. We show that recent methods for minimizing peak power can also reduce SAR measurement errors with little or no cost in TR or image quality – allowing MB acceleration gains to be more fully realized.

1378.   Accurate EM modelling of a not-fully accessible RF body coil at 3T for quantitative SAR investigations
Antonino Mario Cassara'1, Gerd Weidemann1, Frank Seifert1, and Bernd Ittermann1
1Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany

Accurate electromagnetic modelling of RF transmit coils for MRI, e.g. for quantitative SAR assessments, can be difficult when not all coil details are directly accessible to the modelers. This is typically the case for commercial coils and most notably for the body coil of a clinical scanner. The present work illustrates the steps for the creation of an accurate model of a commercial 3 T body coil. Information provided by the manufacturer is merged with in-situ RF measurements on accessible ports and results from numerical simulations. The accuracy of this modeling is quantified comparing simulated and measured B1+ field maps in a extensive phantom study.

1379.   Eigen matrix approach in coupled-circuit numerical simulation of eddy currents in MRI systems
Md. Shahadat Hossain Akram1, Yasuhiko Terada1, Keiichiro Ishi1, and Katsumi Kose1
1Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki, Japan

In coupled-circuit simulation of eddy currents, system of differential equations is solved to get eddy currents transient responses in different domains at different locations. It is desirable to improve computational efficiency whenever possible. Implementing Eigen matrix techniques to solve this system of equations removes singularity problems totally and reduces calculation time to a large level. We have implemented this approach to analyze eddy currents for both open and large closed-bore MRI systems. We have also conducted FID measurement of eddy fields by NMR probe to verify our approach. We have found good agreement between simulation and experiment.

1380.   Comprehensive analysis of parallel transmission local SAR errors introduced by an assumed uniform density distribution
Andre Kuehne1,2, Sigrun Goluch1,2, Ewald Moser1,2, and Elmar Laistler1,2
1Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Vienna, Austria, 2MR Center of Excellence, Medical University of Vienna, Vienna, Vienna, Austria

In this work, the validity of the commonly made assumption of an isotropic tissue density (1000 kg/m³) for SAR calculations is investigated. SAR matrix Eigenvalues- and vectors of an 8-channel head array for 7T MRI are compared and a statistical analysis performed. It is found, that the simplified SAR distribution leads to an overestimation of local SAR by 11-12% on average.

1381.   Coil Evaluation Metrics
Jinfeng Tian1, Lance Delabarre2, and J. Thomas Vaughan2
1CMRR - Dept. of Rad., U. of Minnesota, Minneapolis, Minnesota, United States, 2CMRR - Dept. of Rad., U. of Minnesota, Minnesota, United States

Several differing coil arrays at 3T and 7T were simulated and evaluated for B1+ efficiency relative to net input power, global SAR and local SAR to demonstrate the importance of normalizing efficiency in terms of both input power and SAR. Large volume efficiency metrics are better for coils that have variation in the z-axis.


Gradients, Shims, Magnets & Field Monitoring

Monday 12 May 2014
Traditional Poster Hall  16:30 - 18:30

1382.   A new magnet design for field cycling OMRI
Constantin Job1, Jean-Philippe Galons1, and Diego Martin1
1Medical Imaging, University of Arizona, Tucson, Arizona, United States

A custom-built low-inductance solenoid magnet enables the cycling of the magnetic field strength in the range from 0 to 4700 Gauss in less than 10 msec

1383.   A finite-difference model for the analysis of Acoustic Noise generated by Gradient Coil switching
Liyi Kang1, Zhifeng Chen1, Zhiqian Ye1, Feng Liu2, and Ling Xia1
1Department of Biomedical Engineering, Zhejiang University, Hangzhou, Zhejiang, China, 2School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, Queensland, Australia

In this work, a force-vibration-noise model has been developed for the analysis of gradient switching induced acoustic noise in MRI. The acoustic model is based on the finite difference method, and it can quantitatively evaluate the acoustic noise produced by typical gradient switching procedure. With the Tikhonov regularization based optimization technique, new gradient coils are designed; compared with conventional coils, the new gradient coils offer excellent magnetic field linearity and the sound pressure level is decreased by about 10%.

1384.   generalized measure to assess gradient coil performance
Feng Jia1, Gerrit Schultz1, Anna Masako Welz1, Frederik Testud1, Hans Weber1, Sebastian Littin1, Huijun Yu1, Jürgen Hennig1, and Maxim Zaitsev1
1Department of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Baden-Württemberg, Germany

We present a general performance measure to assess all the gradient coils from the perspective of different purposes. A matrix coil is used to demonstrate this general performance measure.

1385.   Multi physics modeling of eddy current vibration damping in MRI systems
Kishore Venkata Mogatadakala1, Ming Yao1, Sampath Telikicherla Kandala1, Longzhi Jiang1, and Timothy Havens1
1Magnet and Gradient engineering, GE Health care, Florence, SC, United States

Vibration induced eddy currents generate magnetic field disturbance in MRI systems and degrade image quality (IQ). In this work, a multi-physics based finite element approach is presented to simulate mechanical vibration and eddy currents. Both simulation and test results indicate that the induced eddy currents play a significant role in attenuating the vibration response and corresponding field disturbance. In order to demonstrate the applicability of the developed technique to a complicated mechanical resonance mode, simulation was performed on a locally deforming hollow cylinder and the results are presented with and without electromagnetic damping.

1386.   Measuring the Spatial Magnetic Field Gradients within a Scanner Bore
Karlene M Fraser1,2, Elizabeth Morris3, Jonathan Ashmore4, Stephen Wastling2, Ruth O'Gorman4,5, and Gareth Barker2
1Neuroimaging, Maudsley Hospital, London, United Kingdom, 2Centre for Neuroimaging Sciences, King's College London, London, United Kingdom, 3Medical Engineering and Physics, King's College Hospital, London, United Kingdom, 4Neuroradiology, King's College Hospital, London, United Kingdom, 5Centre for MR Research, University Children's Hospital, Zurich, Switzerland

Manufacturers of medical implants and devices classify some as MR conditional, and specify maximum spatial magnetic field gradient (MFG) restrictions in G/cm or T/m. Measurements of the MF within the bores of a 1.5T and 3.0T HD.x, and two 3.0T MR750 MR scanners were obtained using a THM1176 Hall probe. Maximum spatial MFG calculated for the 1.5T and each 3.0T scanner was respectively over 400 G/cm and 700 G/cm, and approximately 1.5 and 2 times less that reported by the scanner manufacturer. Had the manufacturer’s measurements been restricted to the patient accessible area, our measurements may have been more comparable.

1387.   Faster Feedback Field Control using Shim Pre-Emphasis
Yolanda Duerst1, Bertram J Wilm1, Signe J Vannesjo1, Benjamin E Dietrich1, Simon Gross1, David O Brunner1, Thomas Schmid1, and Klaas P Pruessmann1
1ETH Zurich, Zurich, ZH, Switzerland

Real-time field feedback as implemented previously assumed instantaneous and uncoupled shim responses. The violation of this assumption by the real system leads to distortions in the feedback loop. The current work shows the implementation of self-term pre-emphasis for decreasing the shim response time and cross-term pre-emphasis in order to decouple the individual channels. This allows for a faster response to changes in the target field pattern and enables faster and more stable field feedback.

1388.   Couple Electromagnetic and Neuronal Dynamics Simulation of Gradient Coil Switching Induced Nerve Stimulation
Ioannis Vogiatzis Oikonomidis1,2, Esra Neufeld1, Johanna Wolf1, Deepika Sharma1,3, Yngve Hamnerius2, and Niels Kuster1,3
1IT'IS Foundation, Zurich, Switzerland, 2Signals and Systems, Chalmers University of Technology, Gothenburg, Sweden, 3Information Technology and Electrical Engineering, Swiss Federal Institute of Technology, Zurich, Switzerland

Nerve stimulation by rapidly switching gradient coils is a safety concern in MR. An EM and thermal simulation platform has been coupled with a neuronal dynamics modeling code, to investigate such interactions in realistic anatomical models. A locally temperature dependent variant of the SENN model, commonly employed for safety threshold assessment, has been developed. Modeling of sciatic nerve stimulation by gradient coil switching, considering the impact of RF birdcage coil induced heating, showed that the model anisotropy, the field variation along the nerve and local temperature have a relevant impact that can be studied using the coupled EM-neuron simulation platform.

1389.   Improved magnetically induced torque measurement for MRI safety testing
Fred Tam1, Peter Geng2, and Simon J Graham1,3
1Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario, Canada, 2Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario, Canada, 3Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada

Torque measurements for MRI safety testing are often qualitative, despite ASTM standard F2213-06 which prescribes a quantitative measurement method and apparatus. To facilitate quantitative measurement, practical improvements were made to this apparatus, including a calibration procedure for its torsion springs. The resulting apparatus has increased capacity and simplified construction, and its accuracy has been characterized. Calibration data reveal nonlinear behaviour, warning against naive use of the simple formula in F2213-06. Example usage of the apparatus shows a prototype tablet device for fMRI passes F2213-06 criteria.

1390.   k-t-Calibration improves continuous field monitoring for image reconstruction
Benjamin E. Dietrich1, Bertram J. Wilm1, David O. Brunner1, Yolanda Duerst1, Christoph Barmet1,2, and Klaas P. Pruessmann1
1Institut for Biomedical Engineering, University and ETH Zurich, Zurich, Zurich, Switzerland, 2Skope Magnetic Resonance Technologies, Zurich, Switzerland

By means of NMR probe based magnetic field monitoring, the spatio-temporal magnetic field evolution and hence k-space trajectory can be observed and used to improve image reconstruction. Continuous field monitoring based on time interleaved acquisition of sets of fast relaxing probes enables sequence independent monitoring over arbitrary durations without limitations on k-space range, but suffered so far under accumulated errors in the calculated trajectories due to violations of the assumption that the probes behave like point sources. The presented k-space and time domain calibration method addresses these problems and enables continuous monitoring for image reconstruction.

1391.   Mapping and correcting respiration-induced field changes in the brain using fluorine field probes
Mads Andersen1,2, Kristoffer Madsen1, Lars Hanson1,2, Vincent Boer3, Tijl van der Velden3, Dennis Klomp3, Joep Wezel4, Matthias van Osch4, and Maarten Versluis4
1Danish Research Centre for Magnetic Resonance, Copenhagen University Hospital Hvidovre, Copenhagen, Denmark, 2Biomedical Engineering Group, DTU Elektro, Technical University of Denmark, Kgs. Lyngby, Denmark, 3Department of Radiology, University Medical Center Utrecht, Utrecht, Netherlands, 4C.J. Gorter center, Department of Radiology, Leiden University Medical Center, Leiden, Netherlands

Breathing induced dynamic B0 field perturbations in the head degrade image and spectral quality. It has recently been proposed to continuously stabilize the magnetic field by real-time updating of the shim fields, based on synchronous field measurements with external probes. A thorough analysis of how accurate such field measurements outside the head can reflect the spatially varying dynamic fields inside the head is currently lacking. We present such an analysis and see that 14 external field probes reflect the field in the head sufficiently well so it can be significantly stabilized.

1392.   Design Methods for Magnetic Resonance Based Field Monitoring Devices
Wieland A. Worthoff1, Stefan Schwan1, Arthur W. Magill1, Michael S. Poole1, and N. Jon Shah1,2
1INM - 4, Research Centre Jülich GmbH, Jülich, Germany, 2Department of Neurology, RWTH Aachen University, Aachen, Germany

Developing MR based field probes requires careful design, because a distorted local magnetic field within the sample droplet can lead to a significant reduction in signal fidelity. By simulating the local field variations due to the susceptibility of the field probe itself, we demonstrate a novel approach to acquiring appropriate design parameters in order to optimise the performance of new probe prototypes. We compare our numerical results with experimental data in order to verify and explore the capabilities of the simulation.

1393.   Hybrid Digital Phase-Locked Loop and Moving Average Filtering Improves SNR in Spatio-Temporal Field Monitoring
Yu-Chun Chang1,2, Martin Eschelbach1, Klaus Scheffler1, and Anke Henning1,3
1Max Planck Institute of Biological Cybernetics, Tuebingen, Baden-Wuerttemburg, Germany, 2Graduate School of Neural & Behavioural Sciences, University of Tuebingen, Tuebingen, Baden-Wuerttemburg, Germany, 3Institute for Biomedical Engineering, University and ETH Zurich, Switzerland

Recent spatio-temporal B0 field monitoring methods utilise an array of NMR probes to measure the dynamics of the B0 field. The B0 field is usually characterised by spherical harmonic coefficients which are obtained from the phase signals (or phase coefficients) of the probe FIDs. A hybrid method is presented that uses a moving average filter in conjunction with a digital phase locked-loop filter to improve the SNR of the phase signals measured by the NMR probes. This method takes advantage of the FID SNR to reduce the phase jitter in the phase signal. It is also easy to implement for real-time applications.

1394.   Noise Reduction of Impulse Response Function of the Encoding Fields Calculation
Frederik Testud1, Johanna S. Vannesjö2, Christoph Barmet2,3, Klaas P. Pruessmann2, Jürgen Hennig1, and Maxim Zaitsev1
1Medical Physics, Department of Radiology, University Medical Center, Freiburg, Germany, 2Institute for Biomedical Engineering, University and ETH Zürich, Zürich, Switzerland, 3Skope Magnetic Resonance Technologies, Zürich, Switzerland

The Impulse Response function of the scanners’ Encoding Fields (IREFs) allows improving the scanners’ preemphasis or the image reconstruction by predicting the encoding trajectory. The impulse response function was assessed by mean of magnetic field monitoring where the field evolution of triangular-shaped waveforms were used as inputs. The IREFs need to be low-pass filtered to reduce high-frequency noise. We propose to achieve this by obtaining the field probes’ phase derivative using the Savitzky-Golay filter and to use the discrete test waveform for IREF calculation. The repetition number can be potentially reduced by the proposed improvements in the impulse response calculation.

1395.   3D-printed geometric distortion correction phantom for MRI
David W Holdsworth1,2, Matthew G Teeter1,2, Jaques S Milner2, Steven I Pollmann2, and Maria Drangova2,3
1Department of Surgery, Western University, London, Ontario, Canada, 2Robarts Research Institute, London, Ontario, Canada, 3Department of Medical Biophysics, Western University, London, Ontario, Canada

Accurate correction of geometric distortion is increasingly important for MRI applications in image-guided intervention. Advances in 3D printing have made it possible to fabricate structures with three-dimensional features that facilitate automated analysis of geometric distortions. We describe the fabrication of a plastic structure comprised of 4.5 mm beads, supported by 1.5 mm struts at 13 mm nominal spacing, which is immersed in a tissue-mimicking liquid. Automated analysis produces a point cloud of fiducial locations and a vector map of distortion. MRI imaging at 3T demonstrates the ability to determine average local distortions of ±0.53 mm, over a 500 ml volume.


PET-MRI Engineering & Methods

Monday 12 May 2014
Traditional Poster Hall  16:30 - 18:30

1396.   Validation of a PET-derived Respiratory Signal by Comparison with an MRI Pencil-Beam Navigator Signal in Simultaneous PET/MR
Richard Manber1, David Atkinson1, Anna Barnes2, Brian Hutton1, Celia O'Meara2, Sebastien Ourselin1, Simon Arridge1, and Kris Thielemans1
1University College London, London, United Kingdom, 2University College London Hospital, London, United Kingdom

Respiratory gating in PET imaging is common practice to correct for motion. It has previously been shown that a respiratory signal can be extracted from PET list-mode data using Principal Component Analysis (PCA). We demonstrate the validity of this signal by showing a strong correlation with the ‘gold-standard’ MRI navigator signal, simultaneously acquired on 9 patients with a range of PET tracers, and by showing comparable PET gating results based on the PET and MRI derived respiratory signals respectively. Finally we show improvements in image sharpness of ‘motion corrected’ images, formed by warping and combining gates.

1397.   Probabilistic Atlas-Based Generation of Continuous-Valued Attenuation Correction Maps for Hybrid MR-PET Imaging
Kevin T. Chen1,2, David Izquierdo-Garcia2, Clare Poynton2, Daniel B. Chonde2,3, and Ciprian Catana2
1Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, United States, 2A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States, 3Biophysics, Harvard University, Boston, MA, United States

We have implemented a method of generating continuous-valued attenuation coefficient maps for PET data correction in hybrid MR-PET scanners. This method combines atlas coregistration along with a trained classifier to provide information about subject local anatomy.

1398.   Improvement and Evaluation in PET Performance of 16-Channel Receive Anterior Array Coils for 3T Simultaneous PET/MR Scanner
Yun-Jeong Stickle1, Jianhua Yu2, Tae-Young Yang1, Sahil Bhatia1, and Dmitriy V Londarskiy1
1GE Healthcare, Aurora, OH, United States, 2GE Healthcare, Waukesha, WI, United States

The purpose of this study was to develop and evaluate the novel coil designs with new materials adopted to reduce the coil impact on PET image quality. We developed a new plastic-free 3T 16-channel flexible anterior array (AA) RF coil with V0 flammability rating and biocompatibility (PET/MR prototype AA2) for torso and cardiac imaging and validated the PET performances for a GE conventional AA coil and two improved PET/MR prototype coils. The results show a 48% and a 79% average sensitivity loss improvement on PET/MR prototype AA1 coil and PET/MR prototype AA2 coil, respectively, from GE conventional AA coil.

1399.   Whole Body RF Coil Design for a Simultaneous PET-MR System
Saikat Saha1
1GE Healthcare, GE, Waukesha, WI, United States

In conventional whole body RF transmit coils, various RF components such as diodes, capacitors, inductors, cables etc. are placed throughout the coil for optimal MR performance. If such components are placed in the FOV of the PET detector in a simultaneous PET/MR system, they will scatter some of the PET signals (511keV annihilation photons), affecting image quality. To address this problem we have created a “zero PET attenuation” whole body transmit/receive coil with minimal use of high density RF components. We present design and performance for the resulting body coil as implemented in our 3.0T simultaneous PET/MR system.

1400.   A Low PET Attenuation Transmit-Receive Head Coil for Simultaneous PET and MR Spectroscopy
Gillian Haemer1,2, David Faul3, Thomas Koesters1,4, Kimberly Jackson1, Oded Gonen1, and Graham Wiggins1
1The Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, United States, 2The Sackler Institute for Graduate Biomedical Sciences, New York University School of Medicine, New York, NY, United States, 3Siemens Medical Solutions, New York, NY, United States,4Center for Advanced Imaging Innovation and Research, Department of Radiology, New York University School of Medicine, New York, NY, United States

In order to allow for simultaneous PET and MR Spectroscopic imaging (MRSI) on a PET/MR Hybrid system, RF coil designs must be MR efficient, transmit-receive capable, and provide low PET attenuation. We present a birdcage coil design based on these requirements, which provides sufficient efficiency for MRSI, while creating minimal attenuation. We compare the MR efficiency of this coil to an MR Instruments TEM coil, and the PET attenuation to the attenuation-minimized receive-only head coil provided with the PET/MR system, and find that this design provides comparable MR efficiency and superior attenuation minimization.

1401.   Combining MRI with PET for partial volume correction improves image-derived input functions in mice
Eleanor Evans1, David Izquierdo Garcia2, Guido Buonincontri1, Carmen Methner3, Rob C Hawkes1, Thomas Kreig3, T. Adrian Carpenter1, and Stephen J Sawiak1,4
1Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, United Kingdom, 2Athinoula A. Martinos Centre for Biomedical Imaging, Harvard University, Massachusetts, United States, 3Department of Medicine, University of Cambridge, Cambridge, United Kingdom, 4Behavioural and Clinical Neurosciences Institute, University of Cambridge, Cambridge, United Kingdom

Kinetic modelling in Positron Emission Tomography (PET) allows metabolic measures to be obtained, but requires the tracer arterial input function (AIF). Blood sampling to acquire the AIF is prohibitive in mice due to low blood volumes. Image-derived AIFs are therefore preferred, although their extraction from blood vessels is hampered by low spatial resolution (~1.5-2mm). We found that using an AIF extraction method which employed partial volume correction (PVC) in the mouse heart was crucial for deriving accurate AIFs and gave best results when ROIs were based on MRI data rather than PET data.

1402.   Evaluation of MR Compatibility of a SiPM-based PET scanner for simultaneous PET/MR studies operating at animal 7-T MR scanner
Guen Bae Ko1, Daehong Kim2, Hyun Suk Yoon1, Min Sun Lee1, In Chan Song3, and Jae Sung Lee1
1Department of Nuclear Medicine, Seoul National University, Seoul, Korea, 2Molecular Imaging and Therapy Branch, National Cancer Center, Goyang, Gyeonggi, Korea,3Department of Radiology, Seoul National University, Seoul, Korea

Here, we¡¯d like to report relevant influences of novel SiPM-based PET scanner on MR images at ultra-high magnetic field. Several MR image including FSE, SE, GRE, 3D SPGR, and EPI were evaluated with a 7-T MRI scanner and 35-mm-inner-diameter mouse body transceiver coil. The experimental results show that the PET insert unit affects only minor effect on MR images that can be ensured for preclinical evaluation. It was also proved that to perform multi-functional study of PET and functional MRI using our PET insert unit is possible.

1403.   Bayesian segmentation of dual-echo UTE images for PET/MR attenuation correction
Gaspar Delso1, Michael Carl1, Florian Wiesinger2, Martin Hüllner3, and Patrick Veit-Haibach3
1Global MR Applications & Workflow, GE Healthcare, Waukesha, WI, United States, 2GE Global Research, Munich, Germany, 3University Hospital, Zurich, Switzerland

MR-based attenuation correction is a critical component of integrated PET/MR scanners. This is generally achieved by segmenting MR images into a set of tissue classes with known attenuation properties (e.g. bone, fat, soft tissue, lung, air). Ultra-short echo time (UTE) sequences capable of imaging tissues with short T2* times (<1 ms) have been proposed in the past as a means to locate bone tissue1-4. In this study, we used tri-modality PET/CT+MR data from oncology patients to develop an improved classification algorithm for the localization of bone tissue in the head and neck area.

1404.   Integrated PET/MR: Phantom Studies Towards Radiotracer Dose Reduction
Mark Oehmigen1, Susanne Ziegler1, Björn W. Jakoby2,3, and Harald H. Quick1
1Institute of Medical Physics, University of Erlangen-Nuremberg, Erlangen, Germany, 2Siemens Healthcare Sector, Erlangen, Germany, 3University of Surrey, Guildford, Surrey, United Kingdom

In integrated PET/MR hybrid imaging data acquisition times per bed position are comparatively longer than in PET/CT imaging. Increasing PET data acquisition times may allow decreasing the injected radiotracer dose while maintaining image quality. All measurements were performed on an integrated PET/MR whole-body hybrid system using the NEMA image quality phantom. PET images were acquired with doubled time but halved activity. The images acquired at different tracer activity levels and acquisition times show no visible difference in quality and only small quantitative measurable changes. Longer PET acquisition time in PET/MR enable the reduction of the administered PET tracer activity.

1405.   Wireless MR active marker based PET motion correction in simultaneous brain MR-PET
Chuan Huang1, Jerome L Ackerman2, Yoann Petibon1, Marc D Normandin1, Georges El Fakhri1, and Jinsong Ouyang1
1Center for Advanced Medical Imaging Sciences, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States, 2Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States

Recently, wireless active markers have been used in head motion tracking/correction in brain MRI due to its improved patient safety, ease-of-use and simpler manufacturing. Head motion is even more a problem in brain PET since dynamic brain PET can last more than an hour. Furthermore, anesthesia is often used to keep animals still during brain PET acquisitions, but many studies showed that anesthesia can also perturb the neurological process under study. Simultaneous MR-PET is a novel hybrid modality generated substantial interest in recent years. Complementary information of the brain from PET and MR can be simultaneously obtained. This new modality also opens the possibility to use MR active marker derived motion information for PET motion correction. In this work, we demonstrate in phantom and non-human primate studies the use of wireless active markers to track head motion and incorporating the measure motion information in the list-mode PET reconstruction to obtain PET images without motion artifacts in simultaneous MR-PET.

1406.   Quantitative evaluation of the short-lived eddy currents in shield boxes of the novel MRI head coil integrated with PET detectors
Mikio Suga1,2, Takayuki Obata2, Kodai Shimizu1, Fumihiko Nishikido2, Atsushi Tachibana2, Hideto Kuribayashi3, Iwao Nakajima4, Yoshihiko Kawabata4, and Taiga Yamaya2
1Chiba University, Chiba, Chiba, Japan, 2National Institute of Radiological Sciences, Chiba, Chiba, Japan, 3Siemens Japan K. K., Tokyo, Japan, 4Takashima Seisakusho Co., Ltd., Tokyo, Japan

We are developing a new PET/MRI system in which PET detectors are closely located at the MR head coil. To reduce electromagnetic interaction between PET detectors and MRI coil, the PET detectors are covered with conductive shield boxes. In this study, we quantitatively evaluated the secondary magnetic field induced by short-lived eddy currents in shield boxes and the effect of slits in shield boxes. The results showed that the secondary magnetic field induced by the shield boxes without slits was not negligible for EPI. We can observe the eddy current reduction effect by making a slit in a shield box.

1407.   An MR-PET phantom for studies of the male pelvis
Philipp Mann1, Armin Runz2, Martin Schaefer3, and Peter Bachert1
1Department of Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany, 2Department of Medical Physics in Radiation Oncology, German Cancer Research Center, Heidelberg, Germany, 3Department of Radiopharmaceutical Chemistry, German Cancer Research Center, Heidelberg, Germany

An MR-PET phantom for evaluation of studies of the male pelvis was designed. Hollow components mimicking thigh bone, bladder, and prostate were built using 3D printing technique. Experimental tests were performed with 68Ga-PET, 1H-MRI, and 1H spectroscopic imaging.

1408.   Direct evaluation of MR-derived attenuation correction maps for PET/MR of the mouse myocardium
Eleanor Evans1, Guido Buonincontri1, Rob C Hawkes1, Richard E Ansorge2, T. Adrian Carpenter1, and Stephen J Sawiak1,3
1Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, United Kingdom, 2Department of Physics, University of Cambridge, Cambridge, United Kingdom,3Behavioural and Clinical Neurosciences Institute, University of Cambridge, Cambridge, United Kingdom

Attenuation correction (AC) must be applied to provide quantitative measurements of Positron Emission Tomography (PET) tracer activity concentrations. The gold standard AC method involves passing a transmission source around the subject and surrounding scanner equipment. Due to the limited space in PET/MR scanners, MR-derived AC (MRAC) must be used instead. This is problematic as MR signals are not directly related to the amount of gamma radiation absorbed. By comparing to gold standard transmission scans, we found a single tissue region MRAC segmentation approach, derived from whole body MRI, provided accurate myocardial SUV values in mice.

1409.   Influence of patient motion in bone tissue maps obtained with ultra-short echo time MR
Patrick Veit-Haibach1, Michael Carl2, Mehdi Khalighi2, Florian Wiesinger3, Konstantinos Zeimpekis1, and Gaspar Delso2
1University Hospital, Zurich, Switzerland, 2Global MR Applications & Workflow, GE Healthcare, WI, United States, 3GE Global Research, Munich, Germany

Accurate mapping of the attenuation properties of patient tissue is instrumental for quantitative positron emission tomography (PET). In hybrid PET/MR scanners, this can be achieved using dedicated MR images to identify tissue classes of known attenuation (e.g. fat, lung, air). For the particular case of bone tissue, standard sequences are not adequate due to the fast T2* relaxation time. Ultra-short echo time (UTE) sequences have been reported to provide adequate bone tissue identification for the purposes of PET attenuation correction. These sequences do, however, require acquisition times in the order of 2 to 5 minutes to cover a typical PET station. Such long acquisition times increase the probability of patient movement occurring during the acquisition. In this study, we analyze the artifacts introduced by patient motion on the bone maps obtained with UTE.


Applications of Ultra-High Fields

Monday 12 May 2014
Traditional Poster Hall  16:30 - 18:30

1410.   Accelerated multiplexed-EPI with PSF-based distortion correction at 9.4T
Seong Dae Yun1 and N. Jon Shah1,2
1INM - 4, Research Centre Jülich GmbH, Jülich, Germany, 2Department of Neurology, RWTH Aachen University, Aachen, Germany

The relatively high imaging speed of EPI has led to its widespread use in dynamic MRI studies. The performance of the EPI can be improved by combining it with in-plane acceleration techniques such as multi-shot, parallel MRI and EPI with Keyhole (EPIK). For even faster volumetric acquisition in EPI, the multiplexed-EPI (M-EPI) method has also been presented (Feinberg et al.). This study i) verifies the use of the in-plane acceleration techniques on the M-EPI at 9.4T and ii) quantitatively assesses the performance of each imaging method. Lastly, the robust removal of geometric distortions is demonstrated with the PSF-based correction method.

1411.   High-Resolution MR Angiography at 7T: Detection of Perforating Arteries of the Anterior Communicating and Distal Middle Cerebral Arteries
Taisuke Harada1, Yuiko Sato2, Takamasa Nanba2, Takahiro Kouji2, Takaaki Beppu2, Tsuyoshi Matsuda3, Hiroyuki Kabasawa3, Fumio Yamashita1, Ikuko Uwano1, Kohsuke Kudo4, Kuniaki Ogasawara2, and Makoto Sasaki1
1Ultra-High Field MRI, Iwate Medical University, Morioka, Iwate, Japan, 2Neurosurgery, Iwate Medical University, Morioka, Iwate, Japan, 3Global Applied Science Laboratory, GE Healthcare, Hino, Tokyo, Japan, 4Diagnostic and Interventional Radiology, Hokkaido University Hospital, Sapporo, Hokkaido, Japan

Minute perforating arteries such as the hypothalamic branch of the subcallosal artery and the long insular artery, which can cause severe neurological complications when injured during surgery, have not been visualized using imaging modalities including magnetic resonance angiography (MRA) at 3 Tesla or below. We revealed that high-resolution MRA at 7T, particularly with a magnetization transfer contrast pulse, can readily visualize these arteries and their relationship with surrounding structures. This technique may contribute to avoiding complications of surgery on aneurysms at the anterior communicating artery and tumors in the insulo-opercular regions.

1412.   Clinical Application of 7T MRI for Deep Brain Stimulation (DBS) Surgery and Postoperative Programming
Yuval Duchin1, Guillermo Sapiro2, Shai Chazin1, Kenneth Baker3, Jon McIver4, Jerrold Vitek3, and Noam Harel1,5
1Radiology / CMRR, University of Minnesota, Minneapolis, Minnesota, United States, 2Electrical and Computer Engineering, Duke University, Durham, North Carolina, United States, 3Neurology, University of Minnesota, Minneapolis, Minnesota, United States, 4Neurosurgery, Regions Hospital, St. Paul, Minnesota, United States, 5Neurosurgery, University of Minnesota, Minneapolis, Minnesota, United States

Deep brain stimulation (DBS) surgery has emerged as a powerful neuromodulation clinical therapy. Current standard clinical imaging protocols do not have sufficient resolution and/or SNR to delineate brain structures relevant to DBS surgery. Structural images acquired at 7T exhibit rich informational content with potential utility for clinical applications. Here we utilized 7T images to create patient-specific anatomical models to enhance pre-surgical DBS targeting as well as post-surgical visualization of the DBS lead position and orientation, including its four individual contacts. These new visualization capabilities will enhance and improve DBS outcomes.

1413.   Imaging the human brainstem at 7 Tesla using multi-modal echo-planar imaging
Florian Beissner1, Jonathan R. Polimeni1, Marta Bianciardi1, Ville Renvall1,2, Cornelius Eichner1,3, Vitaly Napadow1, and Lawrence L. Wald1,4
1Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States, 2Brain and Mind Laboratory, Aalto University, Finland, 3Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, 4Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, United States

The human brainstem is a notoriously difficult structure to study with MRI. Here, we present an entirely EPI-based approach that allows for the acquisition of T2*-weighted functional, T1-weighted structural as well as diffusion-weighted images at a resolution of 1.2 mm isotropic. Due to matched voxel size and distortion, BOLD and DTI images can be normalized to MNI space applying transformation parameters estimated from the T1-weighted EPI image, minimizing coregistration errors. Using masked independent component analysis we were able to detect brainstem nuclei at the single-subject level and to depict their functional connectivity to the rest of the brain.

1414.   GRE reference scan for robust reconstruction of high resolution slice and in-plane accelerated 2D GE EPI at 7T
An T. Vu1, Steen Moeller1, Edward Auerbach1, Kamil Ugurbil1, and Essa Yacoub1
1University of Minnesota, CMRR, Minneapolis, MN, United States

High temporal, high spatial resolution 2D EPI requires acceleration along both the in-plane phase encode (e.g. GRAPPA) and slice directions (e.g. multiband, MB). For such acquisitions, image quality is particularly sensitive to motion during segmented multi-shot reference scans, which is lengthened by a factor of MB. We propose the GRE flash for in-plane unaliasing of high resolution slice accelerated 2D EPI. With this technique, motion during reference scan related artifacts and reconstruction noise are significantly reduces especially at higher spatial resolutions (<1.25mm isotropic). For 0.9mm data, we found SNR to improve by 40% over conventional segmented EPI reference scans.

1415.   Comparison between Single-Shot Diffusion Weighted Methodologies at 3 and 7 Tesla on Brain Volunteers
Eddy Solomon1, Noam Ben-Eliezer2, Daniel K. Sodickson2, and Lucio Frydman1
1Chemical Physics, Weizmann Institute of Science, Rehovot, Israel, 2Bernard and Irene Schwartz Center for Biomedical Imaging, Radiology, New York University School of Medicine, New York, NY, United States

The potential of a recently proposed single-shot methodology, SPatio-temporal ENcoding (SPEN), was explored towards brain diffusion imaging on a 7T whole-body scanner. To better evaluate this imaging performance, studies were repeated at 3T, and done in parallel with diffusion-weighted SE-EPI scans. In both axial and coronal scans, SPEN evidenced a higher robustness to overcome the B0-inhomogeneities that arise particularly at 7T and also at 3T. The diffusion measurements of the brain showed fair agreement between both acquisitions methods, even despite the slight differences evidenced between the 3T and 7T ADC maps.

1416.   Clinical relevance of EPI distortion correction in presurgical fMRI at 7T
Barbara Dymerska1, Florian Fischmeister1,2, Alexander Geissler1,2, Eva Matt1,2, Siegfried Trattnig1, Roland Beisteiner1,2, and Simon Robinson1
1Departement of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Vienna, Austria, 2Department of Neurology, Medical University of Vienna, Vienna, Vienna, Austria

FMRI is increasingly being applied in presurgical planning. Although ultra-high field provides higher tSNR it also induces stronger geometric distortions. We investigate the clinical relevance of distortion correction using B0 field maps. Analysis of eight patients performing hand and chin tasks at 7T revealed that neglecting geometric distortions could lead to the misidentification of the central sulcus. Moreover, the distance between the pathology and activation could be wrongly estimated, which could affect decisions about resection margins. It is therefore important to correct for distortions in patient fMRI data to ensure that reliable clinical decisions are made.

1417.   Feedback field control in 3D T2* imaging at 7T
Yolanda Duerst1, Michael Wyss1, Bertram J Wilm1, Benjamin E Dietrich1, Simon Gross1, David O Brunner1, Thomas Schmid1, and Klaas P Pruessmann1
1ETH Zurich, Zurich, ZH, Switzerland

Field changes due to respiratory motion disturb T2*-weighted imaging not only in 2D acquisition but also in 3D. Due to the inherent averaging of 3D scans, artifacts were not as pronounced as in 2D in the upper parts of the brain but manifested as a general blurring of the image. However, 3D T2*-weighted scans showed strong ringing artifacts around cavities as well as intensity modulations in the cerebellum. By using real-time field feedback breathing induced spatiotemporal field changes could be corrected and the observed artifacts were strongly reduced.

1418.   Effect of embedding media on post-mortem MRI of formalin-fixed brain tissue at 7.0 T
Petr Dusek1,2, Vince Istvan Madai3, Matthias Dieringer4,5, Fabian Hezel4, Thoralf Niendorf4,5, Jan Sobesky3,5, Radoslav Matej6, and Jens Wuerfel1,7
1Institute of Neuroradiology, University Medicine Goettingen, Goettingen, Germany, 2Department of Neurology and Center of Clinical Neuroscience, Charles University in Prague, 1st Faculty of Medicine and General University Hospital in Prague, Praha, Czech Republic, 3Department of Neurology and Center for Stroke Research Berlin (CSB), Charité-Universitaetsmedizin, Berlin, Germany, 4Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrueck Center for Molecular Medicine, Berlin, Germany, 5Experimental and Clinical Research Center (ECRC), Charité-Universitaetsmedizin and Max Delbrueck Center for Molecular Medicine (MDC), Berlin, Germany, 6Department of Pathology and Molecular Medicine, Thomayer Teaching Hospital, Praha, Czech Republic, 7NeuroCure Clinical Research Center, Charité-Universitaetsmedizin, Berlin, Germany

It is well known that formalin fixation of post-mortem material affects its contrast mechanism and MR characteristics. It is however not clear how these parameters and image quality are affected by the medium in which is the post-mortem material embedded during scanning. Our goal was to compare different embedding media (deuterium oxide (D2O), formalin, low-melting temperature agarose and phosphate-buffered-saline) for post-mortem MRI and ascertain which gives the best signal-to-noise ratio and contrast results. Also, we wanted to find out whether embedding medium has influence on signal intensity of formalin fixed brain slices. We employed T2 mapping, T1 mapping, T2* mapping, MP-RAGE and TIRM sequences. The results for all embedding media are shown.

1419.   Two-voxel Hadamard encoded semi-LASER spectroscopy for in vivo MRS at ultra-high field
Adam Berrington1, Peter Jezzard1, Stuart Clare1, and Uzay Emir1
1FMRIB Centre, University of Oxford, Oxford, Oxfordshire, United Kingdom

Large chemical shift displacement errors in MRS at ultra-high field can limit SNR and lead to spurious J-evolution across the VOI. Multi-voxel approaches are particularly susceptible to poor localisation, resulting in signal bleed between voxels. By incorporating two-voxel Hadamard encoding with a semi-LASER localisation sequence at 7T, we show that both CSD and inter-voxel bleeding can be minimised. Demonstrating this method in vivo on 4 volunteers, we are able to obtain highly resolved spectra with efficient water suppression simultaneously from both voxels. Metabolites such as GABA, Glu, Lac and Ins can be reliably determined with the method.

1420.   Laminar features of cortical natural sound processing in humans
Michelle Moerel1, Federico De Martino2, An T Vu1, Valentin G Kemper2, Kamil Ugurbil1, Elia Formisano2, and Essa Yacoub1
1Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, United States, 2Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, Netherlands

We present preliminary data showing the feasibility of examining frequency preference based on natural sounds across cortical depths. The use of natural sounds will enable the exploration of laminar tuning to features beyond frequency, such as temporal and spectral modulations.

1421.   Brain Imaging with 7T vs. 9.4T: A direct Comparison of MR parameters and SNR
Rolf Pohmann1 and Klaus Scheffler1,2
1Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany, 2Department of Bioimaging, University of Tübingen, Germany

Increasing the magnetic field strength beyond 7 T is expected to result in an increase of SNR, but this may be limited by the more unfavorable relaxation times, the B1inhomogeneity and the more difficult coil design. Here, SNR and MR parameters are compared for field strengths of 3 T, 7 T and 9.4 T. After correction for flip angle variations, a strong gain in SNR of almost a factor of two is found when going from 7 T to 9.4 T, but increasing inhomogeous B1-fields and shorter T2* demand for improved imaging techniques.

1422.   Imaging oculomotor subsystems in the cerebellum at 7 Tesla
Melissa A Batson1,2, Natalia Petridou3, Dennis WJ Klomp3, Maarten A Frens2, and Sebastian FW Neggers1
1Brain Center Rudolf Magnus, UMC Utrecht, Utrecht, Netherlands, 2Neuroscience, Erasmus Medical Center, Rotterdam, Zuid Holland, Netherlands, 3Imaging Division, UMC Utrecht, Utrecht, Netherlands

Using an innovative combination of high-density multi-unit surface coils, dual transmission, ROI shimming and 3D parallel imaging at 7T it is possible to clearly image the deep and complex structures and functions of the cerebellum during various motor tasks, including oculomotor tasks requiring eye tracking. Results demonstrate superior functional localisation within both oculomotor vermis and, when a cognitive component is present, in both CrusI and CrusII. In addition, BOLD signal strengths vary with the magnitude of difficulty of the task for both motor and cognitive components in a manner consistent with the changes in firing patterns observed in animal cerebellum.

1423.   The optimization of B1 insensitive T1 weighted MP2RAGE sequence at high field.
Wanyong Shin1, Sehong Oh1, Tobias Kober2,3, and Mark J Lowe1
1Radiology, Cleveland Clinic, Cleveland, Ohio, United States, 2Advanced Clinical Imaging Technology, Siemens Healthcare IM BM PI, Lausanne, Switzerland, 3CIBM-AIT, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland

Large spatial B1 inhomogeneities are observed at ultra-high magnetic field (=7T), which creates non-uniform signal intensity across an image volume. While MP2RAGE has shown the potential to minimize B1 variation, a long TR (>8s) is necessary to generate the high signal to noise ratio and contrast to noise ratio by providing the large dynamic contrast range. In this study, we optimize fast MP2RAGE parameters to generate T1 weighted contrast at 7T with 10% of image non-uniformity in brain tissues. A healthy subject was scanned with the optimized parameters according to different TRs at 7T and brain segmentation results were compared.

1424.   Localized Spectroscopy Without J-modulation at Ultra High Field
Clark Lemke1, Uzay Emir1, Peter Jezzard1, Stuart Clare1, and Jamie Near2
1FMRIB, University of Oxford, Oxford, Oxfordshire, United Kingdom, 2Douglas Institute, McGill University, Verdun, Quebec, Canada

In vivo quantification of coupled metabolites is hampered by J-modulation. J-modulation manifests as an echo time (TE) dependent modulation on the metabolite signal leading to increased signal loss over and beyond other relaxation processes. Short TE spectroscopy avoids the effects of J-modulation but is complicated by a broad baseline extending over the relevant frequency range. This baseline can lead to decreased accuracy of metabolite quantification. Here we present a localized metabolite quantification pulse sequence designed to remove J-modulation at long TE (<40 ms) to avoid baseline contamination. The sequence (PRESS-JR) is presented with phantom measurements.

1425.   Functional ASL at 9.4 T – a comparison between balanced SSFP and GRE-EPI readout
Jonas Bause1,2, Philipp Ehses1,3, G. Shajan1, Klaus Scheffler1,3, and Rolf Pohmann1
1High-Field Magnetic Resonance, MPI for biological Cybernetics, Tuebingen, BW, Germany, 2Graduate Training Center of Neuroscience, International Max-Planck Research School, Tuebingen, BW, Germany, 3Department for Biomedical Magnetic Resonance, University of Tuebingen, Tuebingen, BW, Germany

Functional ASL has a higher specificity and reproducibility than BOLD fMRI. However, the perfusion related signal is typically in the range of a few percent and the spatial and temporal resolution of arterial spin labeling imaging rather limited. ASL at ultra-high field can benefit from higher intrinsic SNR and increased longitudinal relaxation times. We investigated bSSFP and GRE-EPI as possible readout schemes for fASL studies at 9.4 T and were able to measure the first time stimulus evoked perfusion changes in the human motor cortex at this field strength.

1426.   Tractography of the trigeminal nerve using 7T MRI
Christophe Lenglet1, Julien Sein1, Julian Tokarev2, Andrew W Grande3, Bharathi Jagadeesan4, and Pierre-Francois Van de Moortele1
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, 2University of Minnesota, Minneapolis, MN, United States, 3Department of Neurosurgery, University of Minnesota, Minneapolis, MN, United States, 4Department of Radiology, University of Minnesota, Minneapolis, MN, United States

We performed ultra high-field (7T) diffusion MRI and probabilistic tractography on the trigeminal nerve in a series of normal volunteers. We were able to reconstruct the detailed three-dimensional course of fiber pathways from individual divisions of the trigeminal nerve, as they travel within its ganglion and the nerve root to the brain stem. This information can be useful to better understand the etiology of Trigeminal Neuralgia, a poorly understood neurological disorder, which is characterized by extremely painful episodes of facial pain produced by routine stimuli like light touch.

1427.   Physiologic noise at 7T: PESTICA for 3T obtains signals for pulse and respiration at ultra-high field
Erik Beall1 and Mark Lowe1
1Imaging Institute, Cleveland Clinic, Cleveland, OH, United States

Physiologic noise in BOLD acquisitions is problematic for fMRI and connectivity analyses, and is an increasing problem at higher field strengths. There is one existing software package, PESTICA, that can obtain signals at 3T with the same periodicity as parallel monitored pulse and respiration signals and thus can be used in physiologic corrections. PESTICA uses spatial priors generated at 3T and we test PESTICA at 7T, finding promising results.

Hye-Jin Jeong1, Jong-Yeon Lee2, Jong-Hwan Lee2, Sang-Han Choi1, Young-BO Kim1, and Zang-Hee Cho1
1Neuroscience Research Institute, Gachon University, Incheon, Korea, 2Department of Ophthalmology, Gachon University Gil Hospital, Incheon, Korea

Glaucoma is characterized by progressive degeneration of retinal ganglion cells (RGC) and their axons. Recent neuroimaging studies in human glaucoma have demonstrated degenerative changes in the visual pathway of brain including lateral geniculate nucleus (LGN). However, a precise assessment of the LGN is still a technical challenge due to anatomic characteristics. Therefore, our aim was to investigate the LGN atrophy in patients with open-angle glaucoma using high-resolution 7.0 Tesla MR imaging and correlation with retinal nerve fiber layer (RNFL) thickness

1429.   High Spatial Resolution Ophthalmic MRI at 7.0 Tesla in Healthy Subjects and in Patients with Intraocular Masses
Andreas Graessl1, Jan Rieger2, Soenke Langner3, Paul Krueger3, Oliver Stachs4, Michael Schwerter1, Max Muhle1, and Thoralf Niendorf1
1Berlin Ultrahigh Field Facility (B.U.F.F.), Max Delbrück Center for Molecular Medicine (MDC), Berlin, Berlin, Germany, 2MRI.TOOLS GmbH, Berlin, Berlin, Germany, 3University of Greifswald, Institute for Diagnostic Radiology and Neuroradiology, Greifswald, Germany, 4University of Rostock, Department of Ophthalmology, Rostock, Germany


Jutta Ellermann1, Mikko Nissi2,3, Dingxing Wang4,5, Sebastian Schmitter6, Peter Kollasch4, and Pierre-Francois Van De Moortele6
1Department of Radiology, University of Minnesota, Minneapolis, MN, United States, 2Department of Orthopaedic Surgery, University of Minnesota, MN, United States, 3CMRR, MN, United States, 4Siemens Medical Solutions, MN, United States, 5University of Minnesota, MN, United States, 6CMRR, University of Minnesota, MN, United States

Recent availability of arthroscopic treatment options for young patients with femoroacetabular impingement has increased the importance of high-resolution hip MRI as a diagnostic tool. If left untreated, this condition can lead to premature osteoarthritis. Due to SNR gains, imaging the hip joints at 7 Tesla is expected to improve diagnostic precision by accurately assessing the state of the thin (1-2 mm) acetabular cartilage,. 7T data obtained with multichannel transmit RF and transmit B1 shim methods suggests that non-enhanced bilateral hip MRI at ultrahigh fields provide the necessary gains in contrast and resolution for accurate diagnostic evaluation of the acetabular cartilage.

1431.   En route to clinical ultrahigh field musculoskeletal MR using multi-purpose transceiver RF modules for spine und shoulder imaging at 7.0 T.
Andreas Graessl1, Soenke Langner2, Marko Hoehne3, Matthias A Dieringer1, and Thoralf Niendorf1,4
1Berlin Ultrahigh Field Facility (B.U.F.F.), Max Delbrück Center for Molecular Medicine (MDC), Berlin, Berlin, Germany, 2University of Greifswald, Institute for Diagnostic Radiology and Neuroradiology, Greifswald, Germany, 3Helios Kliniken, Berlin-Buch, Germany, 4Experimental and Clinical Research Center (ECRC), Charité Campus Buch, Humboldt-University, Berlin, Berlin, Germany

Given the limited availability of RF coils for MSK-MR and recognizing the versatile range of musculoskeletal MR applications this work pursues modular RF transceiver configurations which suite the geometrical needs of a broad spectrum of musculoskeletal anatomy. The applicability of the modular configurations tailored for spine and shoulder imaging is demonstrated in healthy subjects. The multi-purpose configurations afforded the acquisition of sub-millimeter spatial resolution images of the shoulder. The sensitivity of the modular spine TX/RX configuration facilitated a spatial resolution as low as (0.13x0.13x1) mm³ for 3D GRE. This resolution helped to depict small structures such as the facet joints.

1432.   In vivo {1H}-13C NMR spectroscopy of the human calf on a 7-T whole-body MR tomograph
Tanja Platt1, Andreas Korzowski1, and Peter Bachert1
1Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Baden-Württemberg, Germany

13C NMR spectroscopy is applied to observe various metabolites in vivo, e.g. triacylglycerides (TAG). High field strengths and 1H spin decoupling enhance signal and information content of 13C NMR spectra. In this study high resolution 1H–decoupled 13C NMR spectra of the human calf were obtained on an experimental 7–T whole–body MR tomograph.

1433.   T1 and T2 relaxation times of the human calf at 7 Tesla
Anja M. Marschar1, Mathies Breithaupt1, Moritz C. Berger1, and Armin M. Nagel1
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany

On 7 Tesla we measured the relaxation times T1 and T2 of the human calf with separate consideration of muscle tissue and subcutaneous fat tissue. A saturation recovery and spin echo sequence with non-equidistantly adapted TI and TE (that match to T1 and T2 respectively) was used to get a linear sampling on the magnitude axis. For comparison with lower field strength, all measurements were also carried out on a 3T scanner and are compared with literature.

1434.   Echo-planar spectroscopic 13C and 31P NMR imaging of human calf muscle in vivo on a whole–body 7-T MR tomograph
Andreas Korzowski1, Tanja Platt1, and Peter Bachert1
1Dept. of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Baden-Württemberg, Germany

In this study an echo–planar spectroscopic imaging (EPSI) technique was applied to obtain localized high–resolution in vivo 13C and 31P NMR spectra from human calf muscle on a whole–body 7–T MR tomograph. Fast spectroscopic imaging techniques such as EPSI where information from one spatial direction is simultaneously encoded with the spectral information reduce the measurement time strongly.

1435.   3D EPSI - Exploring the potential of 3D spectroscopic imaging of the prostate at 7 tesla
Arjan D. Hendriks1,2, Tijl A. van der Velden1, Mariska P. Luttje1, Vincent O. Boer1, Peter R. Luijten1, and Dennis W.J. Klomp1
1Imaging Division, University Medical Center, Utrecht, Netherlands, 2Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands

To guide prostate cancer treatment, it is important to know the aggressiveness of the prostate tumor in question. Magnetic Resonance Spectroscopic Imaging (MRSI) has great potential to determine this aggressiveness, especially considering current progress of ultra-high field MR systems in separating choline from polyamines. A 3D EPSI acquisition & reconstruction method was developed and compared with current 2D MRSI methods. Found is that high field three-dimensional spectroscopic imaging can be performed within the prostate, using an EPSI sequence, avoiding extended scan time.

1436.   En Route to Probing Human Myocardial Microstructure in vivo Using Susceptibility Based MRI at 7.0 T
Till Huelnhagen1, Fabian Hezel1, and Thoralf Niendorf1,2
1Berlin Ultrahigh Field Facility (B.U.F.F.), Max Delbrueck Center for Molecular Medicine, Berlin, Germany, 2Experimental and Clinical Research Center, a joint cooperation between the Charite Medical Faculty and the Max Delbrueck Center, Berlin, Germany

The complex microstructure of the myocardium is pivotal for cardiac function and can provide important information about the underlying (bio)physical principles and (patho)physiological mechanisms. Probing human myocardial fiber structure in vivo has been described, but remains challenging due to cardiac and respiratory motion. Susceptibility based MRI provides excellent contrast which can be used to investigate tissue microstructure and track fibers in the brain. Recognizing this opportunity the work explores the applicability of susceptibility weighted MRI for probing human myocardial microstructure in vivo at 7.0 T.

1437.   Detection of hepatic glycogen by 1D ISIS localized 13C MRS at 7T.
Martin Krssak1,2, Martin Gajdosik2, Ladislav Valkovic2, Wolfgang Bogner2, Michael Krebs1, Anton Luger1, Siegfried Trattnig2, and Marek Chmelik2
1Division of Endocrinology and Metabolism, Department of Internal Medicine III, Medical University of Vienna, 1090, Austria, 2High Field MR Centre, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Wien, Austria

The aim of this study was to introduce and test the 13C MRS localization scheme suitable for the measurement of hepatic glycogen at 7T in short acquisition time. One dimensional slice selective version of recently introduced fully adiabatic extended ISIS sequence was proposed and tested on phantom and in vivo on healthy volunteers. 1D ISIS scheme applied at 7T presented optimal localization performance and sufficient signal to noise of natural abundance 1-13C hepatic glycogen doublet in relatively short acquisition times (4´16´´).