Traditional Posters : Engineering
Click on to view the abstract pdf and click on to view the pdf of the poster viewable in the poster hall.
RF Circuits & Systems

Wednesday May 11th
Exhibition Hall  13:30 - 15:30

1849.   Improving UHF Transmit Efficiency with Voltage Baluns  
Debra Strick Rivera1, Carsten Koegler1, and Robert Turner1
1Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany

Cable radiation reduces effective transmit power. Radiated power increases with the fourth power of frequency, and can therefore be detrimental to UHF transmit arrays. Baluns can improve voltage balance across transmit coils, and thereby reduce cable radiation. Amplitude balance, phase balance, and common-mode rejection ratio were introduced as simple quantitative methods. Wide-band and narrow-band 180° baluns were analyzed. Performance of narrow-band baluns was dramatically improved through amplitude and phase matching measurements. Transmit efficiency was characterized in the scanner from flip-angle maps. The addition of 180° baluns improved transmit power efficiency between 10% (on average) and over 50% at 7T.

1850.   High-Efficiency RF Power-Amplifier Module for Magnetic-Resonance Imaging 
Frederick H. Raab1, Martin C. Poppe2, and Daniel P. Myer3
1Green Mountain Radio Research Company, Colchester, VT, United States, 2Poppe Associates, 3Communication Power Corporation

This amplifier system is based upon the Kahn EER (envelope-elimination-and-restoration) technique. The amplifier system incorporates class-E RF-power amplifiers, class-S modulators, and a digital signal processor. The DSP includes capability for generating stored signals as well as digitizing and amplifying low-level analog RF inputs. The module incorporates four RF-power amplifiers and can produce up to 750 W with an overall efficiency of 70 percent. It has a bandwidth of 250 kHz and an envelope rise time of 1 s, and can be configured for operation between 10 and 128 MHz.

1851.   RF Coil Element Mounted Power Amplifiers 
John T Vaughan1, and Daniel Myer2
1University of Minnesota, Minneapolis, MN, United States, 2CPC

RF power amplifiers can be mounted on the coil, in the magnet for improved efficiency and lower cost.

1852.   Silicon Carbide MRI Transmitters 
Oliver Heid1, and Timothy Hughes1
1Corporate Research, Siemens AG, Erlangen, Bavaria, Germany

Silicon Carbide JFETs promise to revolutionize RF power generation up to UHF frequencies. The main advantages are extremely high efficiency, power density and the absence of RF load matching requirements. We report on the design and testing of a 11kW prototype RF transmitter module.

1853.   High Q Reactive Network for Automatic Impedance Matching 
Barbara L Beck1,2, Sien Wu3, Walker J Turner3, Rizwan Bashirullah3, and Thomas H Mareci2,4
1McKnight Brain Institute, University of Florida, Gainesville, FL, United States, 2National High Magnetic Field Laboratory, Tallahassee, FL, United States, 3Electrical and Computer Engineering, University of Florida, 4Biochemistry and Molecular Biology, University of Florida

MR coil-impedance matching for in vivo animal studies in high field, small diameter, horizontal bore magnets is a time consuming and challenging procedure due to limited space and large frequency shifts from sample loading. We developed a High-Q input circuit attached to an automatic impedance matching system that optimizes, within seconds, the tuning and matching of a single-frequency coil. The procedure can be performed with the animal in the magnet, negating the need for laborious manual tuning, while at the same time, reducing the stress on the animal. Comparison to a coil with discrete components demonstrates equivalent SNR.

1854.   Time Domain Modeling of MR Linear Balanced Duplexers Switched with Low Magnetic Moment PIN Diodes 
Robert H Caverly1, William E Doherty2, and Ronald Watkins3
1ECE, Villanova University, Villanova, PA, United States, 2Microsemi-Lowell, 3Radiology, Stanford University

The time domain simulation techniques outlined in the abstract will help MR engineers to optimize the parameters of TR switching and to help improve minimum echo time. The work will help MR engineers pick the appropriate PIN diode for their TR switching applicaiton.

1855.   Tunable Adjustable Inductive Decoupling (TAID) Board 
Victor Taracila1, Aleksey Zemskov1, Miguel A Navarro1, Vijayanand Alagappan1, and Fraser Robb1
1GE Healthcare, Aurora, Ohio, United States

One of the subsets of inductive decoupling is the so-called transformer decoupling, which in fact represents a remote inductive decoupling. It is used when overlapping between elements is not desired due to possible sensitivity overlap that affects the g-factor in accelerated imaging. The traditional transformer used in MRI coils is built out of inter-woven or adjacent inductors sharing a common axis. One of the disadvantages of this type of transformer is the difficulty of adjustment of the coupling, dimensions and possible inductive coupling to other inductors in the MRI system. In this work we propose a transformer based on “RF Invisible” inductors shape with adjustable inductive coupling strength and no self-inductance, which is very handy for MRI coil design and applications.

1856.   Noise Power Reduction Strategy by Matching Receiver Bandwidth to the Coil Sensitivity Profile of the Phased Array Coil 
Sergei Obruchkov1, William O'Reilly2, and Arsen Hajian3
1University of Waterloo, Waterloo, ON, Canada, 2Tornado Medical Systems, Toronto, ON, Canada, 3Systems Design Engineering, University of Waterloo, Waterloo, ON, Canada

Digital receiver technology is relatively a new comer to the field of MRI and it offers great opportunity for customization and research. The purpose of our work was to show how developments in digital communication technology may be used to used as MR receiver chains such that each receive channel is optimized to acquire data from an individual coil in the phased array. The findings showed that by decreasing receiver bandwidth and digital filtering it is possible to reduce noise power, thus by matching receiver channel to individual coil signal from phased array coils could be optimized.

1857.   Radio Frequency Front-End Circuitry for an Implantable Multiple Frequency Coil 
Walker J. Turner1, Barbara L. Beck2, Sien Wu1, Thomas H. Mareci3, and Rizwan Bashirullah1
1Electrical and Computer Engineering, University of Florida, Gainesville, FL, United States, 2McKnight Brain Institute, University of Florida, 3Biochemistry and Molecular Biology, University of Florida

This RF front-end circuitry is designed for clock and data extraction from wirelessly transmitted RF pulses for use in controlling the resonance of an implantable receiver coil with a digitally controlled capacitor array intended for monitoring an implanted artificial pancreas. The fabricated chip measures 650um by 450um and demonstrates the capability of data/clock recovery. The design is compatible with current NMR console technology and can be further integrated for in vivo operation.

1858.   Common-mode differential-mode (CMDM) method for quadrature transmit/receive surface coil for ultrahigh field MRI 
Ye Li1, Yong Pang1, and Xiaoliang Zhang1,2
1Department of Radiology and Biomedical Imaging, Univerisity of California San Francisco, San Francisco, California, United States, 2UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco, California, United States

We propose a CMDM design of quadrature transmit/receive surface coil at 7T. A prototype coil was fabricated. Bench test and MR phantom experiments were carried out to evaluate the coil performance. Our results show that the common-mode and differential-mode are decoupled sufficiently at 300MHz range due to the intrinsic decoupling of the two modes. SNR improvement is achieved in the whole region of interest. The CMDM coil is feasible for parellel imaging. The proposed method is an efficient, robust and simple approach to increase the SNR of surface coils as well as surface coil elements in array coils.

1859.   Vertical Loop Decoupling Method for Gapped Phased-Array Coils 
Yoshihisa Soutome1, Yosuke Otake1, and Yoshitaka Bito1
1Central Research Laboratory, Hitachi Ltd., Kokubunji, Tokyo, Japan

We have developed a new decoupling method using a vertical loop for gapped phased-array coils. The vertical loop is placed between nearest-neighbor coils, and by changing the value of the capacitor in the vertical loop, decoupling can be easily achieved. We also fabricated a 3.0T 2-ch loop array with vertical loop and demonstrated its decoupling performance. The coupling S12 measured between the two coils was −28 dB. Phantom images showed no significant coupling between the coils. These results indicate that the proposed method can effectively decouple between the nearest-neighbor coils in gapped phased-array coils.

1860.   Capacitor/Inductor Decoupling and Its New Application to Microstrip Array 
Bing Wu1, and Xiaoliang Zhang2,3
1Coil Engineering, GE Healthcare, Wauehsha, WI, United States, 2Radiology and Biomedical Imaging, UCSF, 3UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco, CA, United States

Transformer or capacitor is often required to electromagnetically decouple the gapped loops, non-adjacent loops, or microstrip resonators in RF coil arrays when conventional coil overlapping is not applicable. In this abstract, we analyze the general L/C decoupling circuits and suggest the use of inductor for decoupling at high fields. Based on the circuit analysis, a new inductive decoupling method is proposed for designing microstrip arrays at high magnetic fields.

1861.   Optimised LNAs for 3 T, 7 T and 9.4 T 
Andreas Peter1, and Jan G. Korvink1,2
1Department of Microsystems Engineering - IMTEK, University of Freiburg, Freiburg, Germany, 2Freiburg Institute of Advanced Studies (FRIAS), University of Freiburg, Freiburg, Germany

We present the design and optimisation of a novel single and dual-stage low-Z LNAs for 3 T, 7 T and 9.4 T. Cascaded two-port networks represent the small-signal behaviour of the LNA. Matlab is used to optimise the component values to fulfil the desired matching conditions at the input and the output of the LNA together with a minimal noise figure, a maximum gain and unconditional stability. A gain of 38 dB together with a noise-figure of 0.3 dB was achieved at 7 T.

1862.   Miniaturized two-stage preamplifiers for receive-array coils at 400 MHz 
Elmar Fischer1, Andreas Peter2, Daniel Sonner3, Hermann Massler3, Jan G Korvink2,4, Jürgen Hennig1, and Maxim Zaitsev1
1Radiology, University Medical Center Freiburg, Freiburg, Germany, 2Microsystems Engineering – IMTEK, University of Freiburg, Freiburg, Germany, 3Hochfrequenz-Bauelemente und -Schaltungen, Fraunhofer IAF, Freiburg, Germany, 4Freiburg Institute of Advanced Studies (FRIAS), University of Freiburg, Freiburg, Germany

This work is on the implementation of miniaturized two-stage preamplifiers for 9.4 T (400 MHz), intended to be used for each coil, respectively, in multi-parallel receive array coils. Amplifier performance has been tested successfully with signals of up to eight coils of a receive array with eight preamplifiers in parallel. Amplifier performance could be verified for magnetic fields up to 9.4 T.

1863.   Scalability and channel independency of the digital broadband dStream architecture 
Cecilia Possanzini1, Phil van Liere1, Hans Roeven1, Jan den Boef1, Charlie Saylor2, Jan van Eggermond1, Paul Harvey1, and Elisabeth Moore1
1Philips Healthcare, Best, Netherlands, 2Invivo Corp., Gainsville, Florida, United States

This work describes a scalable digital broadband receive system architecture which no longer limits the number of receive channels that can be connected and provides a consistent signal fidelity independent of the number of channels. In this study, we show that in this architecture increasing the ‘channel count’ of the system is simply achieved by placing additional coils on the patient support, without modifying anything on installed receive chain of the system as for traditional analog architecture.

1864.   Comparison of Three Preamplifier Technologies: Variation of Input Impedance and Noise Figure With B0 Field Strength 
Russell Lagore1, Brodi Roberts1, B. Gino Fallone1,2, and Nicola De Zanche1,2
1Dept. of Oncology, University of Alberta, Edmonton, Alberta, Canada, 2Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada

Three preamplifier technologies are compared at various B0 field strengths, highlighting sensitivity to changes in noise figure and input impedance.

1865.   Optical Transmission System for High Field Systems 
Taner Demir1, Lance DeLaBarre2, Burak Akin1, Gregor Adriany2, Kamil Ugurbil2, and Ergin Atalar1
1National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Ankara, Turkey, 2Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, United States

In this work, we introduce an optical transmission system for a 3T and a 7T system. The transmission system reduces the interconnection problems between large number of coil elements and the scanner and possibly enhances RF safety. The system transmits the analog MRI and detuning signals optically. In order to demonstrate the performance of the system, phantom and human experiments are performed.

1866.   Reducing Element Coupling in Array Coils Using Off-Tuned Elements 
Boris Keil1, Veneta Tountcheva1, Christina Triantafyllou1,2, and Lawrence L Wald1,3
1A. A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States, 2McGovern Institute for Brain Research, MIT, Cambridge, MA, United States, 3Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA, United States

An intentionally mistuned approach was tested as a simple additional decoupling method for array coils. To address this issue, we exploit a phenomena associated with preamplifier decoupling, which allows array coil element to be tuned off-resonance from the Larmor frequency without significant degradation of SNR. This approach can potentially facilitate decoupling in arrays with high element coupling, especially in flexible arrays where geometric decoupling from overlap or shared impedances is not feasible for all positions of the flexing former.

1867.   A 32-Channel Parallel Exciter/Amplifier Transmit System for 7T Imaging 
Lou Poulo1, Robert Haefner1, Bernd Stoeckel2, Cem Murat Deniz3, Leeor Alon3, Daniel K Sodickson3, and Yudong Zhu3
1Analogic Corporation, Peabody, MA, United States, 2Siemens Medical Solutions USA Inc, New York, NY, United States, 3Center for Biomedical Imaging, Department of Radiology, NYU School of Medicine, New York, NY, United States

The development and initial testing of a complete 7T, 32-channel RF transmit system is described. This RF subsystem, consisting of a new RF sequencer/controller, independent waveform generation, and power amplifiers, is designed to be an add-on expansion to an existing 7T imager. The new RF capability will enable research into the tradeoffs in the various questions/tradeoffs relating to the number of available channels. The system is modular in 8-channel increments, and the architecture allows relatively straightforward integration into most scanners

1868.   8-Channel Parallel Transmit and Receive System for 3 Tesla 
Wolfgang Loew1, Randy Giaquinto1, Laura Sacolick2, William Allyn Grissom2, and Mika Vogel2
1Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States, 2GE Global Research Europe, Germany

To increase homogeneity of the transmit field at 3 Tesla an 8-channel transceiver system implementation is presented. Shorter distance to the imaging object reduces the amount of power needed for a desired B1 field in the object. The system consists of an 8-channel head T/R-coil, 8 modified GE T/R-switches, and 8 high power bias tees. Imaging experiments were performed in-vivo with this setup and B1 magnitude and phase maps were acquired.

Traditional Posters : Engineering
Click on to view the abstract pdf and click on to view the pdf of the poster viewable in the poster hall.
Novel Coils & Arrays

Thursday May 12th
Exhibition Hall  13:30 - 15:30

1869.   A 7 T receive array for in vitro studies of human brain tissue 
Andreas Peter1, Matthias Kladeck2, Oliver Speck2, and Jan G. Korvink1,3
1Department of Microsystems Engineering - IMTEK, University of Freiburg, Freiburg, Germany, 2Biomedical Magnetic Resonance, Otto-von-Guericke University, Magdeburg, Germany, 3Freiburg Institute of Advanced Studies (FRIAS), University of Freiburg, Freiburg, Germany

We present a 19-channel, 2D coil array for large in vitro studies of human brain tissue, such as whole brain slices at 7 T. The sample is to be placed in a separate container horizontally between two of these arrays. The channels are amplified and decoupled from their neighbours by home-made low impedance low noise amplifiers. All adjacent elements show an isolation of > 26 dB, the circuit Q of an uloaded single element is on average 100.

1870.   A New Intravascular Loopless Monopole Antenna (ILMA) for MR Imaging 
Hong Yang Yuan1, Xing Lv1, Rui Zhang1, Xue Dong Yang2, Xiao Ying Wang2,3, Xiao Hai Ma4, Zhao Qi Zhang4, Jue Zhang1,3, and Jing Fang1,3
1College of Engineering, Peking University, Beijing, China, People's Republic of, 2Dept. of Radiology, Peking University First Hospital, Beijing, China, People's Republic of, 3Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China, People's Republic of, 4Dept. of Radiology, Beijing Anzhen Hospital, Beijing, China, People's Republic of

Although intravascular MR probe has been proposed for many years, the rigid and bulky guide-wire presents major challenges when the intravascular detectors are applied into small vessels. In this study, to overcome these inherent limitations and improve the longitudinal coverage, a novel long intravascular loopless monopole antenna (ILMA) design with a thin non-shielded flexible guide-wire is presented. In vitro and in vivo test were carried out to assess the feasibility of the ILMA. Results show that the proposed design has the advantage of providing high SNR, high spatial resolution, and greater longitudinal coverage in this preliminary study.

1871.   HTS volume coil enhanced SNR in Wideband mice whole body screening 
In-Tsang Lin1,2, Edzer L. Wu2,3, Hong -Chang Yang4, and Jyh-Horng Chen1,2
1Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, 106, Taiwan, 2Interdisciplinary MRI/MRS Lab, Department of Electrical Engineering, National Taiwan Univeristy, Taipei, 106, Taiwan, 3Department of Biomedical Engineering, National Taiwan University, Taipei, 106, Taiwan, 4Department of Physics, National Taiwan University, Taipei 106, Taiwan

With a nearly 2-fold SNR increase using the world¡¯s first high temperature superconducting (HTS) animal volume coil, the W=3 accelerated Wideband high-resolution mice whole body scan serves as an example of good balance between image quality and temporal/spatial resolution. The experiment was conducted with copper and Bi2Sr2Ca2Cu3Ox (Bi-2223) volume coils to show the difference.

1872.   High-Temperature Superconducting RF surface coil Platform for In-vivo brain structural differences 
In-Tsang Lin1,2, Bing-Hsuan Lei2,3, Hong -Chang Yang4, and Jyh-Horng Chen1,2
1Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, 106, Taiwan, 2Interdisciplinary MRI/MRS Lab, Department of Electrical Engineering, National Taiwan University, Taipei, 106, Taiwan, 3Department of Electrical Engineering, National Taiwan University, Taipei, 106, Taiwan, Taipei, 106, Taiwan, 4Department of Physics, National Taiwan University, Taipei 106, Taiwan

MRI provides useful method for revealing brain structure. Neuroanatomical differences between strains have been studied at the histologic level. However, the scanning time in 3 T MRI needs more than one hour to obtain the enough resolution to reveal neuroanatomical differences between strains. High-temperature superconducting (HTS) radio-frequency (RF) coil has been proposed as a promising tool in the investigation of the tissue microscopy with high resolution due to its low-resistance characteristic for the MR probe design. Our method to reduce the scanning time is using a 40 mm in diameter Bi2Sr2Ca2Cu3Ox (Bi-2223) HTS RF surface coil. In the present study, we succeed to apply HTS RF surface coil to evaluate the brain structural differences between C57BL/6J and 129S1/SvImJ mouse.

1873.   A 13 channel 3 Tesla Shoulder Coil on a Domed Conformable Former 
Graham Charles Wiggins1, Bei Zhang1, Christian Glaser1, Bernd Stoeckel2, Michael P Recht1, and Daniel Sodickson1
1Radiology, NYU Medical Center, New York, NY, United States, 2Siemens Medical Solutions, New York, NY, United States

Musculoskeletal imaging depends on anatomically-specific RF coils, which provide better performance than general purpose body arrays. The shoulder is poorly served by commonly available commercial coil designs, which typically consist of a rigid concave former that does not wrap substantially around the shoulder joint. We present a 13 element shoulder array on a flexible domed former which wraps around the shoulder and conforms to a variety of body types. We demonstrate SNR gains 2-fold or better in deep tissue such as the labrum and capsular-ligamentous structures. This has the potential to impact the clinical MRI-based assessment of shoulder instability.

Oliver Georg Gruschke1, Lars Clad1, Vlad Badilita1, Kai Kratt1, Mohammad Mohammadzadeh2, Nicoleta Baxan2, Dominik von Elverfeld2, Andreas Peter1, Jürgen Hennig2, Ulrike Wallrabe1, and Jan G. Korvink1,3
1Microsystems Engineering – IMTEK, University of Freiburg, Freiburg, Germany, 2Dept. of Radiology Medical Physics, University Medical Center, Freiburg, Germany, 3Freiburg Institute of Advanced Studies (FRIAS), University of Freiburg, Freiburg, Germany

Receive-only micro phased coil array for cell and thin film materials research.

1875.   A Printed Loop Element with Integrated Capacitors and Co-Planar Shield for 7 Tesla 
Mary Preston McDougall1,2, Steven M Wright1,2, Joseph Rispoli1, Mario Carillo2, Ivan Dimitrov3, Sergey Cheshkov3, and Craig Malloy3
1Biomedical Engineering, Texas A&M University, College Station, TX, United States, 2Electrical Engineering, Texas A&M University, College Station, TX, United States, 3University of Texas Southwestern Medical Center, Dallas, TX, United States

Shields for RF surface coils have been investigated since the earliest days of MRI. Some authors have stated that RF shields are essential for 7T surface coils over 10 cm in diameter, and others have successfully built smaller loops as array elements without using shields, consistent with this guideline. This abstract examines the effectiveness of a co-planar shield at 7T. The co-planar configuration, combined with coils using the capacitance of dual-sided PC boards to replace segmenting capacitors, enables simple, printed coils. This may be useful in constructing array coils, particularly when compared to coils with full ground-plane shields.

1876.   High Performance Nanomaterial Coil for Carotid Imaging 
Raju Viswanathan1, Bradley Goldstein2, Gabor Mizsei3, and Sushmitha Rajakutty2
1Tursiop Technologies, LLC, Cleveland, OH, United States, 2Tursiop Technologies, LLC, 3Tursiopp Technologies, LLC

A high performance RF coil based on a structured nanomaterial is described for high field imaging in a carotid application.

1877.   Design and Characterization of A Set Of MRI Histology RF Coils Dedicated to Standardized Slide Sections 
Dung Minh Hoang1, Chao Zhang1, Mesha Shamsie1, Latifa Fakri-Bouchet2, and Youssef Zaim Wadghiri1
1Radiology, NYU School of Medicine, New York, NY, United States, 2CREATIS, Lyon 1 University - Claude Bernard, Lyon, France

A set of three histological coils were designed and tested to accommodate standard off-the-shelf cover-slips commonly used for tissue examination under a microscope with sizes enabling the imaging of any mouse organ. The gain in sensitivity was achieved through the optimization of the filling factor by tightly fitting the cover-slip while maintaining a homogeneous rf B1 field coverage within the FOV of the tissue section of interest. Several mouse organs were examined spanning from the olfactory bulb to the liver, one of the largest organ while testing the sensitivity limits achievable at 7-Tesla. Our results show that sensitivy achieved can enable MRI section as low as 10-um thickness when immersed in 5mM doped buffer acquired during eight hours.

1878.   Counter Rotating Currents Cryogenic Surface Coils 
Jarek Wosik1,2, Andrzej Jesmanowicz3, Lian Xue4, Leiming Xie1, and Flora Suk-Yin Ip1
1Electrical and Computer Engineering, University of Houston, Houston, Texas, United States, 2Texas Center for Superconductivity, Houston, TX, United States, 3Biophysics, Medical College of Wisconsin, Milwaukee, WI, United States, 4Time Medical, Metuchen, NJ, United States

In this work we have developed a simple method of estimation of a potential SNR gain, which can be obtained for a given coil and body configuration. Four and six laboratory bench Qs measurements had to be carried out to allow for SNR gain calculations of 77 K Cu and Cu/HTS coils, respectively. It was tested on a 3 T whole-body GE scanner using planar counter-rotating-currents (CRC) and twin-horseshoe (HS) coils (receive only) integrated with a G-10 liquid nitrogen cryostat. Cryogenic performance comparison of the CRC and HS coils were carried out using a 3.0 T GE whole-body scanner.

1879.   Remote detection by MRI at 3T using a waveguide 
Fabian Vazquez1, Rodrigo Martin1, Sergio E Solis2, and Alfredo O Rodriguez1
1UAM Iztapalapa, DF, Mexico, Mexico, 2Laboratorio de Neurofisiologia Integrativa, Instituto Nacional de Psiquiatria Ramon de la Fuente, DF, Mexico, Mexico

The generation of magnetic resonance images with waveguides has been successfully demonstrated at 7 Tesla for whole-body systems. We have previously shown that the waveguide approach can also be used with magnetic field intensities lower than 7T and whole-body systems using a parallel-plate waveguide. The aim of this paper is to investigate the variation of the image intensity as a function of the separation between a coil and a phantom using a parallel-plate waveguide for MRI at 3T. In this work, a waveguide composed of only tow parallel plates was used and phantom images were acquired at different separations.

1880.   Simple quadrature volume antenna transformed from loop 
Hideta Habara1, Yoshitaka Bito1, Hisaaki Ochi1, Yoshihisa Soutome1, Yukio Kaneko1, Masayoshi Dohata1,2, Hiroyuki Takeuchi2, and Tetsuhiko Takahashi2
1Central Research Lab., Hitachi Ltd., Kokubunji, Tokyo, Japan, 2Hitachi Medical Corporation, Kashiwa, Chiba, Japan

Quadrature-driven cylindrical volume antennas, such as birdcage or TEM antennas, are indispensable hardware for commercial MRI scanners. However, they consist of many parts, making them complex to build. We introduce a simple quadrature volume antenna having only five parts by transforming a one-loop antenna. If a loop on a cylindrical surface is folded 2N times and the number of current nodes in the loop is 2(N-1), a uniform B1+ field is created in the center of the cylinder. A prototype of a 3T head antenna was made, and a phantom image was obtained.

1881.   A method for increasing electrical length of microstrip waveguides 
Rock Hadley1, Dennis Parker1, and Glen Morrell1
1Radiology - UCAIR, University of Utah, Salt Lake City, Utah, United States

A method for increasing the electrical length of non-resonant microstrip waveguides is presented. This method uses lumped element distributed capacitance evenly distributed along the length of a microstrip transmission line to effectively increase the phase shift down the length of the line. This work presents an analysis of the field properties of a single microstrip line that uses this technique to increase the electrical length of the line. This work is a step towards the development of linear phase volume coils that could be used at 3T frequencies.

Traditional Posters : Engineering
Click on to view the abstract pdf and click on to view the pdf of the poster viewable in the poster hall.
Array Coil Applications

Monday May 9th
Exhibition Hall  14:00 - 16:00

1882.   Study on a 3T Head Coil: Channel Reduction from 32 to 24 
Bing Wu1, Haidong Peng1, Dan Xu1, and Liang Xuan1
1GE Healthcare, Waukesha, WI, United States

Through the study on a commercial 32ch coil, we find that the channel number can be reduced from 32 to 24 without degrading its SNR and parallel imaging performance. Reduced losses from coil components, reduced cost and increased stability are then expected.

1883.   Simulating Array SNR and effective Noise Figure in dependance of Noise Coupling 
Christian Findeklee1, Randy Duensing2, and Arne Reykowski2
1Philips Research Laboratories, Hamburg, Hamburg, Germany, 2Invivo, United States

The effect of element coupling in receive arrays has been investigated for a long time. With new insights into noise coupling and array noise matching, we now can quantify this SNR reduction. Optimized matching is able to avoid SNR reduction for a target location; however, it may still yield significant SNR-loss in other areas. In our experiments, we demonstrate how inductive decoupling can increase the area of high SNR.

1884.   4D flow-sensitive MRI of the thoracic aorta using 12- and 32-channel coils 
Aurelien F Stalder1, Zhi Yuan Dong1, Yang Qi1, Jelena Bock2, Jürgen Hennig2, Michael Markl2, and Kun Cheng Li1
1Dept. of Radiology, Xuanwu Hospital of Capital Medical University, Beijing, China, People's Republic of, 2Dept. of Radiology - Medical Physics, University Hospital Freiburg, Germany

4D flow-sensitive MRI was performed in the thoracic aorta of 11 healthy volunteers at 3T using 12- and 32-channel coils and parallel imaging (GRAPPA) with accelerations R=2 and R=3. SNR, velocity divergence and streamlines length quantification as well as semi-quantitative image grading was performed to assess data quality. R=3 allowed to save 19.5±5% measurement time compared to R=2 (14.2±2.4 min). 12 channels with R=2 and 32 channels with R=3 produced data with significantly higher quality compared to 12 channels and R=3. There was no significant difference between 12 channels with R=2 and 32 channels with R=3 but for the depiction of supra-aortic branches where the 32-channel coil was superior.

1885.   Development of a Receiver Coil Array for 2D Accelerated Imaging of the Complete Neurovascular System 
Petrice Marie Mostardi1, Eric G Stinson1, Thomas C Hulshizer1, Phillip J Rossman1, and Stephen J Riederer1
1MR Research Laboratory, Mayo Clinic, Rochester, MN, United States

Currently there is no coil that allows for 2D acceleration over the entire head and neck. The purpose of this work was to develop a multi-element receiver coil array that has high SNR and the capability for high (R =4-8) 2D SENSE acceleration from the head through the upper torso. The coil design consists of a newly developed neck/torso array which is used in combination with the clinical 8HRBRAIN coil. The neck/torso array was designed as an eight element linear array wrapped around the neck with three circular elements on each side of the neck and two longer rectangular elements on the anterior neck and chester. In phantom and in vivo studies this coil shows higher SNR and lower g factors than clinically available coils throughout the desired FOV.

1886.   The potentialities of implantable micro-coil for detection of brain’s proton metabolites by NMR micro-spectroscopy 
Aziz Kadjo1, Ludovic Martin-Durupty1, Raymond Cespuglio2, Danielle Graveron-Demilly1, and Latifa Fakri-Bouchet1
1University of Lyon, Lyon1,Laboratoire CREATIS-LRMN, UMR CNRS 5220, INSERM U 630, INSA de Lyon, Villerbanne, France, 2University of Lyon, Lyon1, Laboratoire «Radicaux libres/substrats énergie et physiopatho cérébrale, Lyon cedex 08, France

Considering the need to explore a limited sample volume (microlitre), the feasibility to use a new micro-coil concept is proposed. Simulations of B1 field distribution correlated to MR imaging, demonstrates the potential of micro-coil in terms of sensitivity, (Vactive~2 µl), SNR and limits of detection (LOD). Estimated LOD from MR-observable brain metabolite spectra are compared to those obtained using a commercial surface-coil. A gain factor about 2 is obtained. The micro-coil advantage, in spite of its small sensitive volume, to detect a small concentration is demonstrated. This result opens the way to new spatially resolved explorations on animal model.

1887.   Experimental Verification of SNR and Parallel Imaging Improvements Using Complete Coil Arrays 
Adam Maunder1, Tyler Charlton1, B. Gino Fallone1,2, and Nicola De Zanche1,2
1Dept. of Oncology, University of Alberta, Edmonton, Alberta, Canada, 2Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada

Complete arrays capture all three components of the RF magnetic field using additional loops placed orthogonally to the standard surface coils. This experimental study at 3T confirms improvements in SNR and parallel imaging performance predicted by theory, and demonstrates an effective method to increase channel density three-fold without decreasing coil size.

1888.   Comprehensive Neurovascular Evaluation Using an Automatic Optimal SNR-based Channel Combination from a 62 Element Coil Array at 3T 
Amol Pednekar1, Claudio Arena2, Greg Wilson3, Cecilia Possanzini4, Charles Saylor2, and Raja Muthupillai2
1Philips Healthcare, Houston, Texas, United States, 2Diagnostic and Interventional Radiology, St. Luke's Episcopal Hospital, Houston, Texas, United States, 3Philips Healthcare, Cleveland, United States, 4Philips Healthcare, Best, Netherlands

The study summarises the experience with a 62 element neurovascular array. (a) It is feasible to obtain a high resolution 3D-ToF images of the entire neuro-vascular tree from the aortic arch to the intra-cranial vessels ( < 8 min), as well as targeted high-resolution carotid vessel wall imaging ( < 7 min) using a 62 element coil array without operator intervention; (b) Automated selection of coil elements using SNR contribution to the region of interest performed just as well as manual selection of dedicated coil elements.


Traditional Posters : Engineering
Click on to view the abstract pdf and click on to view the pdf of the poster viewable in the poster hall.
Non-Proton Coils & Hardware
Tuesday May 10th
Exhibition Hall  13:30 - 15:30

1889.   Proton traps for multi-nuclear RF coils: design analysis and practical implementation for 13C MRS in humans at 7T 
Martin Meyerspeer1,2, Rolf Gruetter1,3, and Arthur W Magill1,4
1LIFMET, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, 2MR Centre of Excellence and ZMPBMT, Medical University of Vienna, Vienna, Austria, 3Radiology, University of Geneva and Lausanne, Switzerland, Switzerland, 4Radiology, University of Lausanne, Lausanne, Switzerland

Trapped coil designs allow the operation of lower-frequency coils in the presence of a proton coil. Adding a second capacitor to a trap in the non-proton RF coil allows control over the trap reactance at the low and high frequency (here 13C and 1H) and the frequency of the trap mode. We demonstrate the interdependence of the parameters controlled and show analytical and numerical solutions to fulfill the design constraints. Our experiments show that, using the simulations, it possible to construct an effective second order trap for 13C at 7T.

1890.   RF Field Optimization of 4T Double-Tuned Surface TEM Resonators for 1H/23Na MRI 
Assunta Vitacolonna1, Sandro Romanzetti2, Joerg Felder2, Nadim Jon Shah2,3, Antonello Sotgiu4, and Marcello Alecci1
1Scienze della Salute, University of L'Aquila, L'Aquila, Italy, 2Inst. of Neuroscience and Medicine, Research Centre, Jülich, Germany, 3Faculty of Medicine, Department of Neurology, RWTH Aachen University, Aachen, Germany, 4ITA srl, L'Aquila, Italy

Sodium MRI/MRS benefits of improved SNR obtainable at high fields (3-12 T). Surface TEM resonators are especially designed for high-field applications. In recent works a novel double-tuned (DT) surface TEM resonator, made by three microstrip elements and suitable for sodium and proton MRI at 4T was described. Here, we report workbench and 4T MRI data showing the optimization of the RF field distribution of the 23Na channel by a proper selection of the relative distance between the external microstrips, while maintaining the 1H field distribution.

1891.   In Vivo Quantification of Renal Sodium Concentration with a Dual RF Resonator System 
Raffi Kalayciyan1, Friedrich Wetterling1, Sabine Neudecker2, and Lothar R. Schad1
1Computer Assisted Clinical Medicine, Heidelberg University, Mannheim, Germany, 2Medical Research Center, Heidelberg University, Mannheim, Germany

The quantification of local Tissue Sodium Concentration (TSC) can serve as a diagnostic measure for renal diseases, because TSC is strongly linked to the corticomedullary function regulating the vascular ion concentrations. In this work, for the TSC quantification the required homogeneous B1 is achieved by a dual RF resonator system composed of a newly-developed low noise preamplifier receive-only coil without the need to tune and match, that was used in conjunction with a commercial transmit birdcage volume resonator. The TSC quantification in the rat kidney was illustrated through TSC maps using 3D-UTE sequence.

1892.   Double tunable TxRx 1H/ 19F Helmholtz pair for MR imaging and spectroscopy at 11.7T 
Mark Jacobus van Uden1, Yi Sun1, and Arend Heerschap1
1Department of Radiology (667), Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands

Within tissue engineering the restore, replacement or regeneration of defective tissues and their function by biological substitutes is monitored. To monitor this process contrast agents that contain fluorine atoms are used. Defects that are inflicted on a rat hind leg are imaged on 1H and 19F. An overlay of these image provides a good insight in the healing process. We present a Helmholtz pair that has a good coverage and good SNR to image rat hind leg. The Helmholtz pair is combined using a Wilkinson lumped element divider/ splitter.

1893.   Zig-zag 13C surface coil at 7T for high-sensitivity subcutaneous lipid MRS 
Ivan Emilov Dimitrov1,2, Craig R Malloy3,4, and Andrew G Webb5
1Philips Medical Systems, Cleveland, OH, United States, 2Advanced Imaging Reseach Center (AIRC), UT Southwestern, Dallas, TX, United States, 3Advanced Imaging Research Center (AIRC), UT Southwestern, Dallas, TX, United States, 4VA North Texas Health Care System, Dallas, TX, United States, 5Radiology, Leiden University Medical Center, Leiden, Netherlands

The metabolic implications of lipid accumulation may depend on the composition of the fat itself. Analytical high-resolution studies of 13C have shown the ability of MRS to distinguish a variety of fat components. Here we report on a high-sensitivity 13C surface coil with tailored penetration designed to specifically obtain high-resolution human in vivo carbon spectra of subcutaneous fat at 7T. The coil uses a zig-zag pattern with 5 mm distance between the opposing-current segments and shows the desired penetration depth of a few millimeters. In vivo coupled spectra show high sensitivity, and good decoupling is observed in phantoms.

1894.   Dual-Tuned 1H/13C Orthogonal Double Solenoid Volume Coil for Simultaneous Acquisition in Small Animals in Vivo 
Laura Claire Bell1, Eric T Peterson1, Jeremy W Gordon1, Sean B Fain1, and Krishna N Kurpad1
1Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, United States

Development of radio frequency dual-tuned coils is important for spectral shimming and correct functional/anatomical registration. We present a dual-tuned 1H/13C Orthogonal Double Solenoid (ODS) volume coil for pre-clinical applications. This design can be placed coaxially within the bore of horizontal small animal scanner, upholds the 1H SNR at high fields and the sensitivity of 13C, and its versatile design has the potential to image other nuclides of choice. Preliminary results from simultaneous acquisition of a rat in vivo demonstrate feasibility of the coil design.

1895.   A 1H-31P Array Coil for Human Brain Spectroscopy at 3 T 
Wolfgang Driesel1, Andre Pampel1, Christian Labadie2, Toralf Mildner3, and Harald E. Möller4
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Saxony, Germany, 2Max Planck Institute for Human Cognitive and Brain Sciences, 3Max Planck Institute for Human Cognitive and Brain Sciences, Germany, 4Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany

In this work, the concept of a stacked combination of loop coils and microstrip transmission-line (MTL) elements was adopted to build a helmet-shaped, dual-tuned array coil for human brain 31P spectroscopy and 1H decoupling and imaging at 3 T. The 1H channel is based on a pure MTL design with four spokes. On each spoke, a loop coil was added to permit 31P transmission/reception (Tx/Rx). Initial results from investigations of the performance for 31P MRSI including phantom studies are presented.

1896.   A 7T Halo Loop Resonator for Registration of 31P MRSI 
Thomas Michael Barbara1, Manoj Sammi1, John Grinstead2, and William D Rooney1
1AIRC, Oregon Health and Sciences University, Portland, Oregon, United States, 2Siemens Healthcare, Portland, Oregon

An axially oriented loop resonator is used to obtain 1H co-registration images for 31P spectroscopic imaging at 7T using a 12 leg 31P birdcage coil. The 8 cm diameter loop provides extended coverage from crown to brain stem with low coupling to the 31P volume coil. This approach provides a useful alternative to the careful subject positioning required with two coils or the construction of a double tuned resonator.

1897.   One coil to light them all: Broadband body coil for multi-frequency imaging using a coaxial waveguide 
Stefan Alt1, Marco Müller1, Armin Michael Nagel1, Florian Meise1, Reiner Umathum1, and Michael Bock1
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany

The native wave propagation mode of a coaxial waveguide (TEM) has no cut-off frequency, which offers the opportunity of broadband operation for mulit-nuclei studies. We acquired proton (1H) and sodium (23Na) images at four different Larmor frequencies from 63 to 297MHz using the same coaxial waveguide setup for both spin excitation and signal reception.

1898.   Developement of multi-tranceiver dual-tuned knee coil at 3T 
Junghwan Kim1, Chanhong Moon1, Bumwoo Park1, Alessandro Furlan1, Anthony Defranco2, Tiejun Zhao3, and Kyongtae Ty Bae1
1Department of Radiology, University of Pittsburgh, Pittsburgh, PA, United States, 2MR research center, University of Pittsburgh, Pittsburgh, PA, United States, 3MR Research Support, Siemens Healthcare, Pittsburgh, PA, United States

We have developed a multi-transceiver dual-tuned knee coil at 3T which provides high SNR and imaging depth for sodium and co-register of both proton and sodium imaging in a single session. The coil allowed us to acquire in vivo knee cartilage with high SNR in a clinically acceptable time (~30 minutes total session). Further studies on B1-phase shimming are essential to produce a homogenous B1 field and to test the accuracy and reliability of sodium concentration measurement in knee cartilage.

1899.   A 1H-31P Array Coil for Human Brain Spectroscopy at 3T 
Wolfgang Driesel1, André Pampel1, Christian Labadie1, Toralf Mildner1, Harald E Moeller1, and Harald E Moeller1
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany

Previously, a modular approach has been suggested for designing large arrays. It is based on a stacked combination of loop coils and microstrip transmission-line (MTL) elements, which are intrinsically orthogonal. In this work, this concept was adopted to build a helmet-shaped, dual-tuned array coil for human brain 31P spectroscopy and 1H decoupling and imaging at 3 T. The 1H channel is based on a pure MTL design with four spokes. On each spoke, a loop coil was added to permit 31P transmission/reception (Tx/Rx). Initial results from investigations of the performance for 31P MRSI including phantom studies are presented.

1900.   A 7-Tesla Transmit with 15-Channel Receive-Only Array Knee Coil for Sodium Imaging 
Matthew Finnerty1, Xiaoyu Yang1, Tsinghua Zheng1, Jeremiah Heilman1, Nicholas Castrilla1, Joseph Herczak1, Hiroyuki Fujita1,2, Graham C Wiggins3, Ryan Brown3, Guillaume Madelin3, Gregory Chang3, Ravinder R Regatte3, Michael Recht3, Siegfried Trattnig4, Vladimir Juras4, Wolfgang Renz5, Franz Schmitt5, Bernd Stoeckel6, Andreas Potthast5, and Karsten Wicklow5
1Quality Electrodynamics, Mayfield Village, Ohio, United States, 2Departments of Physics and Radiology, Case Western Reserve University, Cleveland, Ohio, United States, 3Department of Radiology, NYU Langone Medical Center, New York, New York, United States, 4Department of Radiology, Medical University of Vienna, Vienna, Austria, 5Siemens Healthcare, Erlangen, Germany,6Siemens Medical Solutions USA, Inc., Malvern, Pennsylvania, United States

The higher SNR found at 7T allows for more diagnostic applications for nuclei other than hydrogen. In particular, sodium imaging has been found to be useful in characterizing cartilage degeneration in the joints, with the focus primarily on the knee. In an effort to design RF coil hardware optimized for these x-nuclei applications, a 12-rung birdcage transmitter and 15-channel receive-only array coil has been developed for sodium imaging of the knee.

1901.   1H/ 19F large coverage homogeneous transmit coil with dedicated multi-element receive coils. 
Mark Jacobus van Uden1, Fernando Bonetto1,2, E.G.W. ter Voert1, Stephan Orzada3, IJM de Vries2, Hanneke van Laarhoven4, and Arend Heerschap1
1Department of Radiology (667), Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands, 2Department of Tumor Immunology, Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands, 3Erwin L. Hahn Institute for Magnetic Resonance Imaging, Essen, Germany, 4Department of Medical Oncology, Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands

Homogeneous excitation and reception provides a much better base for in vivo absolute quantification of cells and drugs levels with respect to inhomogeneous signal distribution. In this work we present a Helmholtz pair that is capable of generating a homogeneous transmit field at both 1H and 19F at 3T. To obtain signals with high SNR and optimal coverage over the liver and lymph nodes two dedicated multiple element receive coils were developed.

Traditional Posters : Engineering
Click on to view the abstract pdf and click on to view the pdf of the poster viewable in the poster hall.
Traveling Waves in MRI

Wednesday May 11th
Exhibition Hall  13:30 - 15:30

1902.   Safety evaluation of a multiple-channel travelling-wave system at 7T 
Jan Paska1, David O Brunner2, Juerg Froehlich1, and Klaas P Pruessmann2
1Laboratory for Electromagnetic Fields and Microwave Electronics, ETH Zurich, Zurich, Zurich, Switzerland, 2Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

The travelling wave concept was recently extended to multiple channels showing promising results in phantoms. For in vivo imaging a reliable SAR evaluation is necessary considering all uncertainties particular to this RF system. Methods were developed to calculate an input power limit, such that the local SAR limits are not exceeded, in any case of operation and within the uncertainties given.

1903.   Traveling Wave Mode Transformation in a Waveguide with High Dielectric Medium for Ultra High Field MRI 
Alexey Tonyushkin1,2, and Andrew J. M. Kiruluta1,2
1Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States, 2Physics Dept., Harvard University, Cambridge, MA, United States

Existing ultra-high field MR scanners allow propagation of TE and TM modes in high permittivity dielectrics, but the actual B1 field inside the dielectric can be hard to predict. Here, we present the analysis of B1-field map of traveling waves inside a cylindrical waveguide with a dielectric insert and explain features of B1 field by mode transformation to higher order ones. In practice, the modes diversity depends on the tissue efficient diameter, relative permittivity, conductivity, and the Larmor frequency. A more complicated case of heterogeneous axial symmetric dielectric can be also analyzed using effective permittivity and mode transformation approach.

1904.   MR experiment validation of parallel traveling-wave with quadrature patch antenna transceiver array 
Yong Pang1, Daniel Vigneron1,2, and Xiaoliang Zhang1,2
1Radiology & Biomedical Imaging, University of California San Francisco, San Francisco, CA, United States, 2UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco & Berkeley, CA, United States

Recently, studies on parallel accelerated imaging with traveling-wave have been reported. In this work, the method of implementing parallel traveling-wave using single-feed quadrature patch antenna transceiver array was investigated and validated using MR experiments on a 7T whole body MR scanner. A two-element patch antenna array was built, and a human head phantom was positioned 85 cm away from the patch antenna array in experiment. Excellent parallel imaging performance in both axial and sagittal planes at acceleration factor of 2 was demonstrated with both SENSE and GRAPPA accelerated imaging.

1905.   Multi-Pass Travelling Wave Volume Coil 
Reiner Umathum1, and Michael Bock1
1German Cancer Research Center, Heidelberg, B.W., Germany

Despite the existence of the TEM resonator and some travelling wave excitation methods most 7T body imaging is performed with local TX/RX arrays. A novel volume coil concept for high and ultra high field MRI body systems is presented with simulation results which does not utilize a resonating structure but excites a large volume with a multi-pass travelling wave in a very simple way.

1906.   Travelling wave coil with limited SAR 
Marco Mueller1, Stefan Alt1, Reiner Umathum1, Wolfhard Semmler1, and Michael Bock1
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany

Travelling wave MRI exposes the human body to high levels of SAR. Recently, a targeted travelling wave approach using an interrupted coaxial wave¬guide was presented. We present hardware measurements about the opportunity of SAR restriction by using a travelling wave coaxial coil with variable imagion regions. Signal and flip angle distributions were calculated and evaluated for different sizes of the variabel imaging regions. The measurements show a good RF restriction to the respective imaging region.

1907.   Experimental Verification of Numerical EM Field Simulations for Ultra-High Field Travelling Wave MRI 
Daniel Brenner1, Frank Geschewski1, Joerg Felder1, Kaveh Vahedipour1, and Nadim Jon Shah1,2
1Institute of Neurosciene and Medicine - 4, Forschungszentrum Juelich, Juelich, Germany, 2Department of Neurology, Faculty of Medicine, JARA, RWTH Aachen University, Aachen, Germany

This work provides validation of Finite-Integral-Method (FIM) electromagnetic field simulations of a patch antenna for travelling wave excitation using experimental data measured in a 9.4T human MRI scanner. Quantification of the excitation field was performed with the Actual Flip angle Imaging (AFI) sequence. Good quantitative agreement is illustrated between simulation and experimental data.

1908.   Numerical study of the waveguide magnetic field via the principal mode for MRI at 3 T 
Fabian Vazquez1, Rodrigo Martin1, David Flores1, Sergio Solis2, and Alfredo O Rodriguez1
1UAM Iztapalapa, DF, Mexico, Mexico, 2Laboratorio de Neurofisiologia Integrativa, Instituto Nacional de Psiquiatria Ramon de la Fuente, DF, Mexico, Mexico

Waveguides have been successfully used to generate magnetic resonance images at 7 Tesla for whole-body systems. We have shown that the waveguide approach can be used at 3T and whole-body systems. A parallel-plate waveguide was used to numerically simulate the fundamental mode (TM0) describing uniform magnetic fields tangent to the copper plates. The TM0 mode can propagate at any frequency and there are no variations of the fields inside the waveguide. Numerical simulations of the magnetic field generated by a parallel plate waveguide were computed at 3T via the propagation of the principal mode and results compared with experimental data.

1909.   new travelling wave coil concepts 
Marco Mueller1, Reiner Umathum1, Stefan Alt1, Wolfhard Semmler1, and Michael Bock1
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany

Travelling wave MRI can be used to attenuate the standing wave prob¬lem of volume resonators at high magnetic field strengths, We present two designs of travelling wave stripline coils, which excite the RF field in the imaging region. These travelling wave coils limit the RF field to the region of interest, create a good homogeneous B1+ field distribution and reduce the global SAR. The coils can be realized as local TX/RX coils and also as an overall body coil. B1+ and SAR field distribution are shown and evaluated with a phantom and an anatomical human model.

1910.   Improvement of Travelling Wave Excitation for Whole Body 7T MRI with an Extended Gradient Coil RF-shield of 1.58 m Length 
Tim Herrmann1, Johannes Mallow1, Kyoung Nam Kim1, Johannes Bernarding1, and Joerg Stadler2
1Department of Biometry and Medical Informatics, OvG University Magdeburg, Magdeburg, Saxony-Anhalt, Germany, 2Leibniz-Institute for Neurobiology, Magdeburg, Saxony-Anhalt, Germany

Whole body MRI at 7T is still a big challenge on the route to clinical use. This study shows how the travelling wave concept can be optimized to work as an efficient body-coil replacement. By simulating the RF-system including the complete 7T whole body scanner it was possible to consider all the important parameters of the experiment. Directional characteristics, distance to the object, and the excitation parameters of the constructed patch antenna were optimized. Tx-only as well as Tx-Rx scenarios were performed. Furthermore, a comparison shows that the travelling wave (TW) concept can keep up with conventional RF methods.