Novel RF & Other Systems
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Thursday May 12th
Room 511D-F  16:00 - 18:00 Moderators: Richard Bowtell and Mike Poole

16:00 621.   Enhancement of RF field by high dielectric constant pad at 3T: Cervical Spine Imaging 
Qing X Yang1,2, Zachary George Herse1, Mathew Ketterman3, Jianli Wang1, Chris Sica1, Christopher Collins1,2, Jinhua Wang4, and Michael Lanagan3
1Radiology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States, 2Bioengineering, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States, 3Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania, United States, 4Diagnostic Radiology, Yale School of Medicine

Experimental results demonstrated that placement of a high dielectric constant (HDC) pad within a cervical spine coil improved the image SNR by 40-67% throughout the cervical spine, while RF power was reduced by 60%. Thus, HDC pads can be broadly used for improving image quality and safety of MRI in a variety of clinical applications at 3T

16:12 622.   New barium titanate based dielectric materials for high field imaging 
Wouter M Teeuwisse1, Kristina N Haines2, Nadine B Smith1, and Andrew G Webb1
1Radiology, Leiden University Medical Center, Leiden, Netherlands, 2Electrical Engineering, Penn State University, University Park, United States

New high dielectric constant pads have been formed using barium titanate. These pads can have dielectric values up to 300. Initial studies at 7T have shown that these pads increase the transmit field by up to 100-200% in regions close to the pad itself, thus allowing the RF field to be locally concentrated.

16:24 623.   B1 shimming using phase shifts for travelling wave MRI with a coaxial waveguide 
Stefan Alt1, Marco Müller1, Reiner Umathum1, and Michael Bock1
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany

Travelling wave MRI with a coaxial waveguide can be used to focus RF energy to a predefined imaging region and has no lower cut-off frequency. However, the coaxial TEM mode creates destructive interference and consequently a signal void along the longitudinal axis of the waveguide. A B1 shimming approach using four independent feed points with phase shifted excitation was successfully tested with a coaxial waveguide setup at a 7T MRI system.

16:36 624.   Improved RF control of the travelling wave MR using a multi-mode coaxial waveguide. 
Anna Andreychenko1, Hugo Kroeze1, Peter Luijten1, Jan J.W. Lagendijk1, and Cornelis A.T. van den Berg1
1University Medical Center Utrecht, Utrecht, Utrecht, Netherlands

A multi-transmit travelling wave setup with a coaxial feeding section capable of supporting several modes for optimal RF shimming performance is demonstrated. Selective mode excitation is performed in the feeding section at a distant location from the sample. The cut-off frequencies of higher order modes were decreased by placing a circular array of water tubes along the RF screen. Such a dielectrically lined waveguide can support surface modes with similar field patterns and B1+ efficiency as normal volume waveguide modes but are less susceptible to RF attenuation. This preserves B1+ control even at the distant locations from the feeding section

16:48 625.   Sideband Excitation for Concurrent RF Transmission and Reception 
David Otto Brunner1, Matteo Pavan1, Benjamin Dietrich1, Daniel Rothmund1, Alexander Heller1, and Klaas Paul Pruessmann1
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

Observation of the nuclear magnetization during RF transmission would be interesting for many applications, such us ultra-short T2-imaging, stochastic resonance approaches, relaxometry and many more. The main hindrance of acquiring NMR signals during transmission is the extremely high dynamic range between the transmitted and received signal levels. In this work, the problem of isolating the transmit signal from the receive signal was circumvented by using modulation techniques in order to allow RF transmission for excitation at a different frequency than receiving the NMR signal. The transmit signal can then be simply filtered out of the receive signal.

17:00 626.   Integrated Detection, Amplification and Wireless transmission of MRI Signals Using a Parametric Amplifier 
Chunqi Qian1, Joseph Murphy-Boesch1, Stephen Dodd1, and Alan Koretsky1
1LFMI/NINDS, National Institute of Health, Bethesda, MD, United States

Synopsis An integrated detection coil and parametric amplifier has been constructed to provide local signal amplification and wireless transmission. The sample coil is one element of a triple frequency resonator containing a zero-bias varactor that mixes the MR signal with a pump frequency to produce an output with gain at the difference frequency. The detection scheme can potentially improve the detection sensitivity of implanted or catheter coils.

17:12 627.   Development of an MRI system using a high Tc bulk superconducting magnet 
Kyohei Ogawa1, Takashi Nakamura2, Yasuhiko Terada1, Katsumi Kose1, and Tomoyuki Haishi3
1Institute of Applied Physics, University of Tsukuba, Tsukuba, 305-8573, Japan, 2RIKEN, Wako, 351-0198, Japan, 3MRTechnology, Tsukuba, 305-0047, Japan

An MRI system was developed using a high critical temperature (Tc) bulk superconducting magnet. The bulk superconducting magnet was energized using a conventional superconducting NMR magnet operated at 4.7 T. Field homogeneity of the magnet was measured using a phase method. The inhomogeneity in the central lower case Greek phi6.2 mm multiplication sign 9.1 mm cylindrical region was 3.3 (RMS) and 35 (peak to peak) ppm, respectively. 3D spin echo MR images of water phantoms have demonstrated a promise of our system.

17:24 628.   Ultrasound/MR hybrid imaging: truly simultaneous motion monitoring in the abdomen and image co-registration 
Lorena Petrusca1, Valeria De Luca2, Patrik Arnold3, Zarko Celicanin4, Thomas Goget1, Vincent Auboiroux1, Magalie Viallon1, Francesco Santini4, Sylvain Terraz1, Klaus Scheffler4, Christine Tanner2, Philippe Cattin3, and Rares Salomir1
1Radiology Department, University Hospitals of Geneva, Geneva, Switzerland, 2Computer Vision Laboratory, Zurich, Switzerland, 3Center for Medical Images Analysis, Basel, Switzerland, 4Radiological Physics, University of Basel Hospital, Switzerland

Simultaneous US and MR acquisition is a hybrid method that offers a complementary description of the investigated anatomy. The study on healthy volunteers presented here with simultaneous 4DMRI/dynamic 2D ultrasound showed that the technical set-up is appropriate for clinical use and no significant RF mutual interferences were detectable in the acquired images. Post-processing of dual modality data permitted the accurate registration of the same imaging plane in US and MR images, and to overlay the 4DMRI motion vectors on the simultaneous US images from the abdomen during free breathing.

17:36 629.   Results on Rapid 3D Magnetic Particle Imaging with a Large Field of View 
Jürgen Rahmer1, Bernhard Gleich1, Claas Bontus1, Ingo Schmale1, Joachim Schmidt1, Jürgen Kanzenbach1, Oliver Woywode2, Jürgen Weizenecker3, and Jörn Borgert1
1Philips Research Laboratories, Hamburg, Germany, 2Philips Medical Systems DMC GmbH, Hamburg, Germany, 3University of Applied Sciences, Karlsruhe, Germany

Magnetic particle imaging (MPI) is a new tomographic imaging approach that quantitatively maps concentrations of iron oxide nanoparticle distributions. It combines high sensitivity with the ability of fast volumetric imaging. Previously, in vivo 3D real-time MPI of a bolus of particles flowing through the heart and lung of mice has been demonstrated, but with an imaging approach that is limited to small fields of view (FoVs). Recently, a new scanner type with a bore diameter of 12 cm allowing rapid imaging with enlarged FoVs has been developed. This contribution describes the sequences used for imaging of large FoVs and presents initial phantom results acquired on the new system.

17:48 630.   A combined MR- fluorescence tomography system for quantitative small animal imaging: in vivo validation 
Yuting Lin1, Michael Ghijsen1, Orhan Nalcioglu1, and Gultekin Gulsen1
1University of California, Irvine, CA, United States

Multi-modality imaging is becoming a trend in developing new generation in vivo imaging techniques. We have developed a hybrid frequency domain fluorescence tomography (FT) and magnetic resonance imaging system (MRI) for small animal imaging. The main purpose of this system is to obtain quantitatively accurate fluorescence concentration and lifetime images from a time-resolved FT system using a multi-modality approach. In this study, we show that the concentration and lifetime of a fluorescent inclusion located 15 mm deep inside a rat can only be recovered within 5% when anatomical a priori information from MRI are available.