2934.     Wireless Local Coil Signal Transmission Using a Parametric Upconverter

Sebastian Martius¹, Oliver Heid², Markus Vester², Stephan Biber², Juergen Nistler²

¹Siemens Corporate Technology, Erlangen, Germany; ²Siemens Healthcare, Erlangen, Germany

A wireless local-coil MRI signal transmission based on a microwave parametric upconverter was successfully demonstrated for the first time.

                  2935.     Multi-Purpose, Multi-Nuclei, Multi-Channel Data Acquisition System

Pekka Sipilä^1,2, Rolf Schulte¹, Gerhard Wachutka², Florian Wiesinger¹

¹GE Global Research, Munich, Bavaria, Germany; ²Institute for Physics of Electrotechnology, Munich University of Technology, Munich, Germany

Based on off-the-self components, a multi-channel, multi-purpose data acquisition system with sampling rate up to 100 Msamples/s/channel is described. Except the possible image-reject filtering, the complete heterodyne receiving is done digitally, and the system can be applied for multi-nuclear MRI detection beyond 130 MHz.

                  2936.     Using On-Board Microprocessors to Control a Wireless MR Receiver Array

Matthew J. Riffe¹, Jeremiah A. Heilman², Natalia Gudino¹, Mark A. Griswold³

¹Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA; ²Case Western Reserve University, Physics, Cleveland, OH, USA; ³Radiology, University Hospitals of Cleveland and Case Western Reserve University, Cleveland, OH, USA

Recently, wireless receiving technology has been gaining attention as a way to alleviate many of the engineering costs and complexities associated with modern MR systems. For such systems to become commercially feasible, a method must be devised to control the new parameters associated with wireless reception, such as channel identification and spacing. We propose to use microprocessors to control any wireless MR receiving system. In this abstract we demonstrate this idea in a simple amplitude modulated wireless case. It is shown image quality is not adversely affected by this technology.

                  2937.     Modeling Low Magnetic Moment PIN Diodes for MR Scanner Applications

Robert Caverly¹, William E. Doherty², Ronald Watkins³

¹Villanova University, Villanova, PA, USA; ²Microsemi-Lowell, USA; ³Department of Radiology, Stanford University, USA

A new model for PIN diodes used in MR scanners is presented and is applicable for devices used in higher field 7T, 9.4T and 11.7T scanners as well as both transmit control in high RF power MR scanners and passive blocking and detune functions. The model has been shown to accurately predict the operation of ULM diodes in these applications and is fully compatible with industry-standard simulators such as SPICE as well as it variants.

                  2938.     Validation of Noise Figure Measurements by Means of MR Imaging

Jurek A. Nordmeyer-Massner¹, Klaas P. Pruessmann¹

¹Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

The noise figure of a preamplifier reflects the amount of noise added by this device and must be strictly minimized for MRI detection. A refined method for noise figure measurements at MR frequencies has recently been described. The aim of the present work was to cross-validate this method by means of actual MR measurements. This is achieved on the basis of an extended model of noise superposition along an MR system’s receive chain, permitting to track the preamplifier contribution. It is shown that noise factors thus calculated from image SNR agree very well with bench measurements of the noise figure.

                  2939.     A Probe for Electric Properties of Phantom Liquids

Christian Findeklee¹, Gesa Lilith Franke², Ulrich Katscher¹

¹Philips Research Europe, Hamburg, Germany; ²Life Sciences, Hamburg University of Applied Sciences, Hamburg, Germany

MRI phantoms for system tests or coil design should behave electrically similar to the patient, and thus, should be made of materials which have similar electric properties. In this study, a resonant probe was built up for the determination of electric conductivity and permittivity of phantom liquids. It is based on a measurement of resonance frequency and quality factor, which makes it more exact than standard direct methods.

                  2940.     Theory of Radiation Damping Without the FIlling Factor

James Tropp¹

¹Applied Science Laboratory, GE Healthcare, Femont, CA, USA

We write the Bloch-Kirchhoff equations for radiation damping, replacing one of the usual parameters – the filling factor – by the probe efficiency, i.e. the radiofrequency field strength divided the square root of power. Representative calculations are given to predict the linewidth due to damping of hyperpolarized[1-13C] Pyruvate, at a static field strength of 14.1 tesla.

                  2941.     Large Field-Of-View in Vivo Imaging Using Traveling Waves on a Whole Body 7 Tesla Scanner

Nadine Smith¹, Kristina Haines², Maarten Versluis¹, Andrew Webb¹

¹Radiology, Leiden University Medical Center, Leiden, Netherlands; ²Electrical Engineering, Penn State University, University Park, PA, USA

Human brain images have been obtained using excitation from a tuned patch antenna placed ~50 cm away from the subject in a whole body 7 tesla scanner. Dielectric loading of the magnet bore by the subject reduces the cutoff frequency below the Larmor frequency, allowing a traveling wave to propagate along the bore. Large field-of-view images have been obtained of the head, neck and shoulders. Although transmission is relatively low efficiency, a localized phased array can be used as the receiver coil for sensitive detection and parallel imaging.

                  2942.     Traveling Wave Imaging of the Human Head at 7 Tesla: Assessment of SNR, Homogeneity and B1+ Efficiency

Graham Wiggins¹, Bei Zhang¹, Qi Duan¹, Daniel K. Sodickson¹

¹Radiology, Center for Biomedical Imaging, NYU School of Medicine, New York, NY, USA

In contrast to standard volume coil designs, which set up a standing wave within the volume of the coil, it is possible with a patch antenna to excite a traveling wave mode down the entire bore of the scanner. We assess the utility of this approach for human head imaging at 7 Tesla. Homogeneity was improved compared to a CP head coil, though results were subject-dependent. The B1+ efficiency of the patch antenna and the SNR obtained when it is used in transmit-receive mode were assessed.

                  2943.     Reciprocity Relations in Travelling Wave MRI

David Otto Brunner¹, Klaas Paul Pruessmann¹

¹Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

NMR signal generation has been generally described by a generalized or gyrotropic reciprocity relation between sending and receiving port of the RF probe used. This reciprocity has been profoundly validated in experiments in which the spins reside within the near-field of the RF probe. In this work, verification and implications of NMR signal phases in travelling wave NMR setups are studied. It was found that the axial phase delay inside a wave guide used for excitation and detection coincides with the phase found in the NMR signal, confirming the reciprocity for long-range regimes of RF interaction.

                  2944.     Optimizing Traveling Wave RF Excitation for in Vivo Use

Cornelis A.T. van den Berg¹, Hugo Kroeze¹, Bart L. van de Bank¹, Bob van den Bergen¹, Peter R. Luijten¹, Jan J.W. Lagendijk¹, Dennis W.J. Klomp¹

¹Dept. of Radiotherapy and Radiology, University Medical Centre Utrecht, Utrecht, Netherlands

Traveling waves has recently been introduced as a fundamentally new RF excitation concept for high field MRI. A great challenge is to achieve a sufficient transmit field at distant locations in the body since the wave is dampened during its passage through the body. In this study it is demonstrated by means of simulations and in-vivo experiments that dielectric insets can be used to generate 1.7 to 3 times higher B1+ field per unit power. Furthermore, it was found that an incoming wave reflects strongly at air-tissue interfaces in the shoulders region resulting in B1+ field focusing in the neck.

                  2945.     Local Intensity Shift: A Comparison of Loop and Micro-Strip Receivers at 3.0T

Selaka Bandara Bulumulla¹, Eric Fiveland¹, Keith J. Park¹, Randy O. Giaquinto¹, Graeme C. McKinnon², Christopher J. Hardy¹

¹GE Global Research, Niskayuna, NY, USA; ²GE Healthcare, Waukesha, WI, USA

In standard loop receivers, the sensitivity is shifted from the center of the loop to the left or right, depending on the orientation of the main field. This local-intensity-shift artifact (LISA) carries over to multi-channel arrays, leading to sometimes-pronounced intensity asymmetries in MR images. In this work, we use full-wave electromagnetic simulation and MR imaging to compare the intensity shift of loop receivers to microstrip receivers and show reduced intensity shift in microstrips. The results indicate the feasibility of obtaining images with more uniform signal to noise ratio using microstrip receivers.

                  2946.     A Microstrip Volume Coil with Easy Access for Wrist Imaging at 7T

Chunsheng Wang¹, Alex Pai², Bing Wu¹, Roland Krug¹, Sharmila Majumdar^1,3, Xiaoliang Zhang^1,3

¹Dept. of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA; ²Dept. of Electrical Engineering and Computer Science, University of California Berkeley, Berkeley, CA, USA; ³2UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco & Berkeley, CA, USA

An 8-element microstrip transmission line (MTL) wrist coil was designed and tested at 7T. It consists two half-volume pieces with split ground. This open structure can easily fit human wrist very closely and gain high sensitivity.

                  2947.     Prostate Imaging at 7T Using Four Stripline Elements and One Amplifier

Alexander J. Raaijmakers¹, Bob van den Bergen¹, Bart L. van de Bank², Hugo Kroeze², Dennis W. Klomp², Cecilia Possanzini³, Paul R. Harvey³, Cornelis A. van den Berg¹

¹Department of Radiotherapy, University Medical Center Utrecht, Utrecht, Netherlands; ²Department of Radiology, University Medical Center Utrecht, Utrecht, Netherlands; ³MR systems, Philips Healthcare, Best, Netherlands

We present a new transceive RF coil and driver design that is able to visualize the prostate at 7T using one 4 kW amplifier and only two receive channels. The array contains 4 stripline elements, of which two elements were placed ventrally and two elements were positioned at the dorsal site of the patient. Decoupling circuitry was not necessary and although dark signal voids exist in the image, good images of the prostate were obtained.

                  2948.     Signal Intensity Profile Comparison of Two Different QD Surface Coils

Suk-Min Hong¹, Kyoung-Nam Kim¹, Jae-Yong Han¹, Jung-Hwan Kim¹, Zang-Hee Cho¹

¹Neuroscience Research Institute, Gachon University of Medical and Science, Incheon, Korea

Quadrature or circularly polarized surface coil can improve by a factor of root mean square compared to surface coils that used for linear polarized. The profile of B1 field generated by QD surface coils depend on geometry of coil. Nevertheless, no comparisonal analysis for B1 field uniformity among various types of coil geometry was reported. In this study, QD surface coils such as two single (TS) coil and combination of single loop Helmholtz (SH) coil were compared in terms of signal intensity profiles at 1.5T.

                  2949.     Design of a New Dual-Helix Loop Coil for Intravascular MR Imaging

Mohammad Mohammadzadeh¹, Mahmud Shahabadi²

¹Dept. of Diagnostic Radiology, Medical Physics, University of Freiburg, Freiburg, Germany; ²Tehran University, Tehran, Iran

The lack of spatial resolution is an important problem in MR imaging of the vessel wall and plaque structures. To alleviate this problem, researchers have recently developed intravascular coil technology to increase the SNR of MR images. This can then be traded to achieve higher spatial resolution. In this work we present a new dual-helix loop coil design to increase the conventional single-helix loop coil SNR. We show that the SNR distribution around this coil is enhanced over the conventional single-helix coil case.

                  2950.     Design of a Multi-Segmented Flexible Loop-Gap Resonator for High Sensitivity Imaging of the Human Wrist at 7 Tesla

Andrew Webb¹, Maarten Versluis¹

¹Radiology, Leiden University Medical Center, Leiden, Netherlands

Synopsis. A multi-segmented flexible loop gap resonator has been designed for imaging the human wrist at 7 tesla. The design has higher sensivitiy than a comparably-sized birdcage coil, has an intrinsically low SAR-to-B1 ratio, and allows comfortable patient positioning. Both high resolution 3D and conventional clinical 2D scans have been acquired in less than 10 minutes.

                  2951.     B1+ and SNR Optimization of High Field RF Coils Through Offsetting of Transmit and Receive Elements

Graham Wiggins¹, Qi Duan¹, Riccardo Lattanzi¹, Daniel K. Sodickson¹

¹Radiology, Center for Biomedical Imaging, NYU School of Medicine, New York, NY, USA

In high field MR the B1+ transmit and B1- receive patterns of a surface coil no longer coincide, but twist in opposite directions. When such a coil is used in a transmit-receive mode this leads to a loss of efficiency. Through full wave electromagnetic simulation and experiment we investigate the benefits of using separate transmit and receive elements and offsetting them so that the B1+ and B1- fields curl towards each other. SNR benefits of up to 40% are obtained, and it is found that there is an optimal angular offset for a given depth in the sample.

                  2952.     A Modular MRI Probe Design for Large Rodent Neuroimaging at 21.1 T (900 MHz)

Peter L. Gor'kov¹, Chunqi Qian¹, Barbara L. Beck², M.D. Clark¹, Ihssan S. Masad^1,3, Victor D. Schepkin¹, Samuel C. Grant^1,3, William W. Brey¹

¹National High Magnetic Field Laboratory, Tallahassee, FL, USA; ²McKnight Brain Institute, University of Florida, Gainesville, FL, USA; ³Chemical and Biomedical Engineering, Florida State University, Tallahassee, FL, USA

MRI at high magnetic fields can facilitate investigation of biomedical processes in rodent brains. At the same time, high magnetic fields can become a headache for the MRI probe designer, partly because of the wavelength effects in the large sample and RF coil, but also because the animal life support system must be adapted to the smaller bore of a higher field magnet. We report the design of a MRI probe (56 mm OD) developed for in vivo imaging of adult rat brain at 21.1 Tesla, inside the 900 MHz vertical magnet system at the National High Magnetic Field Laboratory.

                  2953.     Design and Implementation of a Quadrature RF Volume Coil for in Vivo Brain Imaging of a Monkey in a Stereotaxic Device<

Colin A. Roopnariane¹, Patti A. Miller², Bu Sik Park², Lukas Ansel², Sukhoon Oh², Christopher Lieu³, Thyagarajan Subramanian³, Mohammed Reza Tofighi¹, Christopher M. Collins²

¹Electrical Engineering, The Pennsylvania State University, Middletown, PA, USA; ²Radiology, The Pennsylvania State University, Hershey, PA, USA; ³Neurology, The Pennsylvania State University, Hershey, PA, USA

To facilitate in vivo brain imaging of a monkey placed in a stereotactic device, we designed and implemented a unique coil. The coil is a 2-coil array connected in quadrature with the first coil being a 2-turn solenoid and the second being a saddle coil. Numerical methods were used in coil design, and images acquired with the coil show excellent homogeneity and SNR throughout the monkey brain.

                  2954.     How Much Does Coil Geometry Matter in High-Field Brain Imaging?  a Numerical Study with High-Fidelity Coil Modeling

Shumin Wang¹, Jeff Duyn¹

¹NIH, Bethesda, MD, USA

Transmit coil design at high-field is challenging due to the increasing B1 in-homogeneity and SAR. Both designs with independently controlled elements and non-conventional birdcage-like coils have been proposed. The latter has the advantage of simplicity and the easiness of manufacture. However, the effects of applying different volumetric coil patterns have not been careful studied due to the lack of modeling accuracy of the popular Finite-Difference Time-Domain (FDTD) method. Here, we applied a newly developed high-fidelity full-wave simulation software package to study such effects on both B1 homogeneity and SAR.

                  2955.     Dedicated Endoluminal Coil for Anal Sphincter MR Imaging

Olivier Beuf¹, Franck Jaillon², Mircea Armenean², Hervé Saint-Jalmes³, Frank Pilleul⁴

¹Université de Lyon, CREATIS-LRMN , CNRS UMR 5220; Inserm U630; INSA-Lyon; Université Lyon 1, Villeurbanne, France; ²Université de Lyon, CREATIS-LRMN, CNRS UMR 5220; Inserm U630; INSA-Lyon; Université Lyon 1, Villeurbanne, France; ³LTSI, Inserm U642, Université Rennes 1; Département d'Imagerie, Centre Eugène Marquis, Rennes, France; ⁴Université de Lyon, CREATIS-LRMN, CNRS UMR 5220; Inserm U630; INSA-Lyon; Université Lyon 1; Hospice Civils de Lyon, Lyon, France

The imaging of the anal apparatus is important in the management of patients suffering from anorectal disease. A double loop coil prototype (10 mm outer diameter) was designed based on electromagnetic simulations. The angle between both loops was optimized to improve radial uniformity of the RF B1 field compared to a single loop. Minimum radial variation of signal intensity was found for an angle between 50° and 70°. SNR measured at the close vicinity of the coil was 30 times higher than with the phased-array body coil used for abdominal clinical exams. Moreover, the SNR was superior to phased-array body coil up to about a radius of 30 mm from the coil centre. High-resolution magnetic resonance imaging acquired in the swine provided excellent visualizations of normal anal sphincter complex anatomy. The results are promising and suggest useful applications in the management of anorectal diseases with minimally invasive procedure.

                  2956.     Experiments and Quantification of Lumped Elements Volume Coil for B1+ Excitation at 7T

Kyoung-Nam Kim¹, Suk-Min Hong¹, Jae-Yong Han¹, Hyo Woon Yoon¹, Jun-Young Chung¹, Jung-Hwan Kim¹, Zang-Hee Cho¹

¹Neuroscience Research Institute, Gachon University of Medical and Science, Incheon, Korea

In ultrahigh field MRI, B1+ inhomogeneity causes contrast difference and spatially varying image signal in region-of-interest. Recently, several designs of radiofrequency coils have been suggested to compensate this B1+ inhomogeneity. Using parallel transmission system is also meaning for compensating B1+ inhomogeneity. However, most of available 7T system does not have parallel transmission systems. Therefore, the finding of optimal circularly polarized volume coils with lumped element components is meaningful for compensating B1+ homogeneity. In this study, we applied four different types of volume coil (hybrid birdcage, dual Helmholtz, hybrid spiral birdcage, and slotted tube) for image acquisition using double-angle method.

                  2957.     Common Mode Volume Coil Design for in Vivo MR Imaging at 7T

Zhentian Xie¹, Duan Xu¹, Daniel Vigneron^1,2, Xiaoliang Zhang^1,2

¹Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA; ²UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco/Berkeley, CA, USA

An unshielded 7T volume coil using common mode technique was developed for in vivo rat MRI. With the common mode method, the B1 homogeneity was improved with less number of elements or rungs compared with conventional designs. Less number of elements results in less number of resonance modes of a volume coil, which potentially improve coil efficiency and alleviate design difficulties of high frequency volume coils.

                  2958.     Design of Actively Decoupled Implant Coil System with Improved B1 Homogeneity in Rat Spinal Cord

Andrew C.H. Yung¹, Nathan Wolfe¹, Tinny Lai¹, Lynn Tsai¹, Jenny C.H. Tso¹, Jie Liu¹, Piotr Kozlowski¹

¹University of British Columbia, Vancouver, BC, Canada

A receive-only actively-decoupled implanted coil system (in combination with birdcage coil for transmission) which requires no decoupling circuitry on the implant is described. During reception, the implant overcouples with the pickup coil and produces a split resonance that operates at the Larmor frequency. During transmission, the pickup is detuned via PIN diode, while the uncoupled implant’s frequency response reverts to a single peak away from the Larmor frequency. In vivo experiments on rat spinal cord compare performance between the proposed system and the pickup-implant system operating in TX/RX. Flip angle uniformity is improved while maintaining comparable SNR.

                  2959.     MRI with a Rapidly Rotating RF Coil

Adnan Trakic¹, Ewald Weber¹, Bing Keong Li¹, Hua Wang¹, Stuart Crozier¹

¹The School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, Queensland, Australia

In this work we rapidly rotate a single RF transceive coil about the subject to excite the nuclear spin and acquire the MR signal. RF coil rotation offers a new degree of freedom for MR imaging in that it emulates a RF coil array. A rotating RF transceive system for head imaging at 2 Tesla was implemented and the acquired images exhibit good quality. The rotating RF coil approach may obviate the need for multiple signal pathways and intricate RF decoupling of many stationary array coils.

                  2960.     Remote Detection Coil Setup for Imaging High Velocity Flow Dynamics of Gases with Hyperpolarized 3Helium

Florian Martin Meise¹, Elena Knaub¹, Julien Rivoire¹, Maxim Terekhov¹, Alexander-Wigbert K. Scholz², Ursula A. Wolf¹, Wolfgang G. Schreiber¹

¹Section of Medical Physics, Department of Diagnostical and Interventional Radiology, Johannes Gutenberg University Medical School, Mainz, RLP, Germany; ²Department of Anesthesiology, Johannes Gutenberg University Medical School, Mainz, Germany

High-frequency oscillatory ventilation (HFOV) is a ventilation technique used in patients with acute respiratory distress syndrome (ARDS). MRI can contribute to the understanding of the complex gas transport mechanisms in HFOV. One approach is the usage of phase contrast imaging. High flow speeds up to 40 m/sec and the small structures are a big challenge in this process. To achieve high spatial resolution on a trachea phantom a remote detection coil setup using an eight rung birdcage resonator for exciting the gas and two separate receive elements which can be placed on the tube was designed.

                  2961.     Micro-MR Coil Construction by Combining Metal-On-Glass Inkjetting and MEMS Techniques

Dario Mager¹, Vlad Badilita¹, Ute Loeffelman¹, Patrick James Smith¹, Jan Gerrit Korvink¹

¹Dept. of Microsystems Engineering – IMTEK, University of Freiburg, Freiburg, Germany

This paper presents the inkjet printing of coils directly onto a

                  2962.     Micro Helmholtz Coil Pair Towards Cellular Applications

Kai Kratt¹, Vlad Badilita¹, Tobias Burger¹, Jan G. Korvink¹, Ulrike Wallrabe¹

¹Department of Microsystems Engineering – IMTEK, University of Freiburg, Freiburg, Germany

We present the development of mass production compatible micro Helmholtz coils based on an automatic wire bonder. The coils are suitable for cheap on-chip MR analysis. SU-8 pillars serve as sample containers for cellular applications. By passing a current of 100 mA, a magnetic field of 0.9 mT is created. A homogeneous region of 100 µm around the center of the coil allows for analysis of several cells. With resistances of less than one ohm and inductances in the low nanohenry range, the coils can be tuned and matched for various resonant frequencies.

                  2963.     Development of Superconducting RF Probe for Low Field Orthopedic Imaging

Jack Liu¹, S. Y. Chong¹, S. M. Yeung¹, Q. Y. Ma¹

¹Time Medical Inc., Shanghai, China

An liquid nitrogen based cryostat and surface coil

                  2964.     Dual-Frequency Coil Design Using Common Mode and Differential Mode (CMDM) Technique for 1H/13C MRSI at 7T

Zhentian Xie¹, Daniel Vigneron^1,2, Xiaoliang Zhang^1,2

¹Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA; ²UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco/Berkeley, CA, USA

A new dual-tuned RF coil technique based on common-mode and differential mode (CMDM) was proposed for high field multi-nuclear MR applications. The proposed CMDM coils combined with magnetic wall decoupling, a broadband decoupling technique, may be advantageous in designing high field double-tuned coil arrays for parallel imaging applications.

                  2965.     A Practical Multi-Tuned Birdcage Resonator for MRI/MRS at 7T

Chunsheng Wang¹, Bing Wu¹, Dan Vigneron¹, Xiaoliang Zhang^1,2

¹Dept. of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA; ²2UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco & Berkeley, CA, USA

A multiple-tuned Birdcage coil was built and tested at 7T. Well-defined resonant mode for ¹³C, ²³Na MRS and ¹H MRI were easily identified at bench test. Relatively homogeneous intrinsic B1 field and high SNR at MRI and MRS experiment were also demonstrated.

                  2966.     ¹⁹F/¹H Double-Tuned RF Coil for ¹⁹F-Labeled Drug Distribution Monitoring at 7 T

Yosuke Otake¹, Yoshihisa Soutome¹, Koji Hirata¹, Yoshitaka Bito¹

¹Central Research Laboratory, Hitachi Ltd., Kokubunji-shi, Tokyo, Japan

A ¹⁹F/¹H double-tuned RF coil with increased sensitivity has been developed. The greatest characteristic of the coil is not use a conventional trap circuit. The sensitivity was increased by eliminating the signal loss caused by the trap circuit with sample coil. This coil is resonated at two frequencies using the frequency characteristics of three series resonance circuits. Monitoring of ¹⁹F-labeled drug distribution was demonstrated using the coil and a PFCE nano-emulsion administered rat.

                  2967.     A Dedicated 4-Channel RF Receiving Array for Orthodontic Examinations

Markus Düring¹, Daniel Gareis², Olga Tymofiyeva¹, Marcos Lopez¹, Peter Jakob¹

¹Department of Experimental Physics 5, Universitty of Würzburg, Würzburg, Bayern, Germany; ²NORAS MRI Products, Höchberg, Germany

For orthodontic examinations we developed a dedicated receiving coil array, which allows high resolution imaging in short measurement times. To maintain the flexibility, which is needed for fitting the array to different anatomic of jaws, the connecting network is been placed about 17 cm away from the patient and connected with rf-lines to the receiving coils. Capacitive decoupling of neighboring coils and decoupling of non-neighboring coils by connecting the coils to low input impedance preamplifiers allow the single coils to receive independently. In vivo measurements demonstrate SNR improvement and good anatomic coverage. These properties can facilitate detailed orthodontic examinations.

                  2968.     A Multi-Purpose Cardiac and Abdominal Surface Coil with Up to 36 Elements

Karsten Jahns¹, Markus Adriany¹, Stephan Biber¹, Wilhelm Horger¹, Sonia Nielles-Vallespin¹, Michaela Schmidt¹, Hubertus Fischer¹

¹Healthcare Sector, Siemens AG, Erlangen, Germany

With the advent of multi channel array coils, the limits of parallel imaging using large numbers of small loop antennas have been investigated. In research applications, head coils at 1.5T have been developed up to 32 channels, and up to 96 elements at 3T. Commercial products are available with up to 32 channels for head coils and for cardiac coils at 1.5T and 3T. One major challenge especially for anterior thorax/abdominal coils with high channel count is to integrate both the electronics and the antennas in a housing which is mechanically flexible along the x- and the z-direction. Flexibility in both directions is important for optimum adaption of the antenna to the variations in human anatomy which is largest in the abdominal region. We present the design of a mechanically flexible 36 element multi-purpose anterior coil for 3T and demonstrate its performance for both cardiac as well as abdominal imaging applications. Acceleration factors up to 4 with high image quality and decreased breathhold time could be shown.

                  2969.     A 16 Channel Phased Array Coil Optimized for Diagnostic Breast Imaging

Tobias Wichmann¹, Rainer Kurth², Christian Geppert², Alexander Weisser¹, Florian Odoj¹, Peter M. Jakob^3,4, Titus Lanz¹

¹Rapid Biomedical GmbH, Rimpar, Germany; ²Siemens Healthcare, Erlangen, Germany; ³Experimental Physics 5, University Würzburg, Würzburg, Germany; ⁴Magnetic Resonance Bavaria e.V., Würzburg, Germany

MR imaging has become an important technique for the diagnosis of breast diseases. Crucial for the image quality is the performance of the RF coil. In this study a 16 channel breast phased array coil for 1.5T and 3T each is presented. The coil size is adjustable to match a large variety of breast sizes, thus maintaining high filling factors. Additional elements for explicit axilla coverage are included in the coil. Noise correlation, parallel imaging properties as well as image quality were evaluated. The SNR-performance was compared to a standard 4 channel breast coil.

                  2970.     Eight Channel Custom Breast Coil for Parallel Imaging in Two Directions

Anderson Nnewihe^1,2, Thomas Grafendorfer^3,4, Bruce Daniel¹, Paul Calderon⁴, Marcus Alley, Brian Hargreaves¹

¹Radiology, Stanford University, Palo Alto, CA, USA; ²Bioengineering, Stanford University, Palo Alto, CA, USA; ³Electrical Engineering, Stanford University, Palo Alto, CA, USA; ⁴GE Healthcare, USA

Advances in MRI hardware and pulse sequences, specifically the phased array radiofrequency coil and parallel imaging, have improved our ability for fast, high resolution imaging of the breast, but there is still significant room for improvement. Due to their coil element placement, industrial coils only allow acceleration in the left/right (L/R) direction. The purpose of this paper is to demonstrate that a breast coil array optimized for acceleration in two directions in combination with parallel imaging pulse sequence design substantially reduce scan time without adding visible artifacts and maintaining similar SNR values.

                  2971.     A Flexible Highly Configurable 16 Channel Array Coil for Fetal Imaging

David Herlihy¹, David J. Larkman¹, Joanna Allsop¹, Mary Rutherford¹, Jo V. Hajnal¹

¹Imaging Sciences Department, Imperial College London, London, UK

Fetal imaging is a demanding MRI application requiring coverage of a large field of view to avoid repositioning the mother when the fetus moves, imaging at depth and accommodation of the needs of the mother to achieve a tolerable examination. Currently there are no dedicated receiver array coils designed for fetal imaging and so most examinations are performed with torso or cardiac coils. We report initial progress towards designing a dedicated fetal imaging coil.

                  2972.     Flexible 8 Channel Receive Only Array for Elbow Imaging

Robert Ladkani¹, Tim Farina¹

¹Product Development, Invivo Diagnostic Imaging, Gainesville, FL, USA

A receive only array to demonstrate feasibility of flexible coil design. Prototype methods and design choice explanations are detailed.

                  2973.     16 Channel, Bell Shaped Surface Coil for Knee Imaging

Modhurin Banerjee Snyder¹, Pei H. Chan¹, Madwesha Rao², Fraser Robb¹

¹GE Healthcare, Aurora, OH, USA; ²GE Healthcare, Bangalore, India

A novel coil element and array geometry is explored for a 1.5Tesla, 16 channel phased array knee application. The coil element, resembling a bell, exhibits a marked improvement in center-of-view SNR (12% relative to standard rectangle), while simultaneously giving a rapid drop off in sensitivity outside of the periphery, thus reducing artifact occurrence. We examine the optimization of array geometry, and demonstrate the performance of the proposed array through phantom experimental studies, as well as simulation design.

                  2974.     A Novel Inter-Resonant Coil Decoupling Technique for Parallel Imaging

Raghad Aal-Braij¹, Andreas Peter², Laura Del Tin², Jan G. Korvink²

¹Department  of Microsystem Engineering - IMTEK, University of Freiburg, Freiburg , Germany; ²Department  of Microsystem Engineering - IMTEK, University of Freiburg, Freiburg, Germany

One of the challenges of designing coil arrays is to obtain sufficient decoupling among closely placed resonant elements. A novel technique for decoupling phased array coils without overlapping the nearest coil pairs is presented, which is based on the addition of additional resonant elements. A prototype of the proposed design has been built. The decoupling measured between two coils was better than -35 dB, showing that the mutual inductance is well minimized. MR experiments were performed on a 9.4 T MR System (Brucker Biospec 94-21), the MR images showed that this design is suitable for realizing arrays for parallel imaging at ultrahigh fields.

                  2975.     A Closed-Form Expression for Ultimate Intrinsic Signal-To-Noise Ratio in MRI

Emre Kopanoglu¹, Vakur B. Erturk¹, Ergin Atalar¹

¹Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey

Calculating the ultimate intrinsic signal-to-noise ratio (UISNR), which gives the lowest upper bound on SNR excluding the effect of imaging parameters, requires a complicated analysis. In this study, a closed-form expression for UISNR in a cylindrical body is derived, and the dependence of UISNR on geometric and electromagnetic properties of the body of interest is shown explicitly. Using the formulation given, UISNR can easily be calculated. The derived expression is applicable to small animal imaging, MR microscopy, high-field NMR spectroscopy and human imaging up to 1.5T.

                  2976.     OCEAN: Offset Centre-Frequency Encoded Array Network

Martyn NJ Paley¹, Hoon-Sin Cheong¹

¹Academic Radiology, University of Sheffield, Sheffield, Yorkshire, UK

A design for an array of high temperature supreconducting coils which are tuned to different frequencies to prevent coupling is described and simulated. The Offset Centre-Frequency Encoded Array Network (OCEAN) method is applicable at low frequency/field (250KHz) and can allow encoding without gradients like the SEA and MAMBA 2D methods.

                  2977.     Procedure for RF Coil Array Analysis Using the Method of Moments

Rostislav Lemdiasov¹, Reinhold Ludwig², Gene Bogdanov²

¹InsightMRI, Worcester, MA, USA; ²ECE, WPI, Worcester, MA, USA

A new approach to the numerical modeling and analysis of unloaded/loaded RF coils or coil arrays using the Method of Moments has been proposed. We outline a procedure to analyze coils and coil arrays based on the signal to noise ratio (SNR).

                  2978.     Information Theory in MRI

David Otto Brunner¹, Jurek A. Nordmeyer-Massner¹, Klaas Paul Pruessmann¹

¹Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

NMR signal reception is usually considered and benchmarked on the basis of SNR yield, acquisition speed or parallel imaging performance based on a specific trajectory and reconstruction paradigm. These benchmarks are therefore inherently bound to its reconstruction methods or acquisition schemes (trajectory, orientation, reduction factor etc.). In this work, a method is presented to measure the performance of a coil array or alternatively an entire acquisition sequence using an information theoretical approach. From this, a holistic metric of MRI signal acquisition could be derived.

                  2979.     Layout Optimization of a 24-Channel Receive Array for 7.0 Tesla Brain Imaging

Shumin Wang¹, Jeff Duyn¹

¹NIH, Bethesda, MD, USA

With the advances of high-field MRI and parallel imaging techniques there is growing interest in the design of RF receive coil arrays for high-field SENSE imaging. Since the array performances depend on the geometric features, an optimized design in terms of geometry is of great importance in practice. In this work, we developed an optimization strategy by using the Genetic Algorithm and the Surface Integral Equation (SIE) method. It is applied to 24-channel array for brain imaging at 7.0 Tesla.

                  2980.     Field of View Reduction with RF Shield Mesh Sheet

Shin-ichi Urayama¹, Naozo Sugimoto, Takashi Azuma², Hidenao Fukuyama¹

¹Human Brain Research Center, Kyoto Univ., Kyoto, Japan; ²Medical Simulation Engineering, Kyoto Univ., Kyoto, Japan

Reduction of FOV is a key technique to shorten scan time or to decrease voxel size. Here, we introduced a RF shielding mesh sheet which is a net of nylon fiber covered with 99% silver and examined its usefulness (safety and shielding effectiveness) for FOV reduction on a 1.5T environment. Although no heating was occurred, only with balanced-SSFP, some volunteers felt tiny stimulation at their peripheral part because of large and rapid gradient switching. Signal intensity of arms covered with the mesh decreased to the noise level. By wrapping with insulated cloth, the mesh can reduce FOV effectively and safely.

                  2981.     Novel Method to Estimate Coil Coupling for Enhanced Tuning and Parallel Image Reconstruction

Liang Liu¹, Thomas Talavage¹, Charles Bouman¹, YunJeong Stickle², Limin Feng², Victor Taracila², Pei H Chan², Fraser Robb²

¹Purdue University, West Lafayette, IN, USA; ²GE Healthcare, Aurora, OH, USA

Model-based coupling matrix approach for MR phased array

                  2982.     A New Electronically Controllable Tuner System for Precise Noise Figure Measurement

Stephan Biber¹, Sebastian Martius², Klaus Huber²

¹Healthcare, Siemens AG, Erlangen, Germany; ²Corporate Technology, Siemens AG, Erlangen, Germany

In order to achieve the minimum possible noise figure for a low-noise amplifier (preamplifier) such as they are used in local coils of MRI systems, it is necessary to know the optimum source impedance of the preamplifier. As the optimum source impedance of transistors is usually not specified for MR frequencies, we propose an automated system based on an electronically controlled tuner with fully automated calibration and measurement evaluation. With that system we get deeper insight in both the reproducibility of the noise parameters as well as the noise added by the preamplifier when the coil does not present the optimum source impedance to the preamp (varying load situation from patient to patient).

                  2983.     Optimized Coil Design for Parallel Imaging

Walid Elias Kyriakos^1,2, Ehud Schmidt^1,3, Ferenc A. Jolesz^1,4, Robert V. Mulkern^1,5

¹Harvard Medical School, Boston, MA, USA; ²Children's Hospital, Boston, MA, USA; ³Radiology, Partners, Boston, MA, USA; ⁴Radiology, Brigham and Women's Hospital, Boston, MA, USA; ⁵Radiology, Children's Hospital, Boston, MA, USA

Parallel MRI utilizes multiple RF receiver coils as encoding engines, whereby the spatial sensitivity profiles of these coils is used in unison with phase encoding to obtain higher accelerations with reduced folding artifacts. The current state-of-the-art in electronics and manufacturing allows construction of coil arrays with a greater and greater number of similarly shaped coil elements, resulting in a considerable increase in data volume., and leading to overload of computational resources and impractical image reconstruction times. In this work, we show that it is possible to follow a simple intuitive approach, to reduce the size of the array without loss of image quality or acceleration speed by linearly combining subsets of small coils into larger coil elements, where these elements have differing sizes.

                  2984.     Short Hybrid Micro-Strip Coils

Selaka Bandara Bulumulla¹, Ken W. Rohling¹, Eric Fiveland¹, Keith J. Park¹, Maxine M. Gibeau¹, Luca Marinelli¹, Christopher J. Hardy¹

¹GE Global Research, Niskayuna, NY, USA

Microstrip receivers are designed as half-wave or quarter-wave resonators, aligned along the axis of the static magnetic field. The long wavelengths at imaging frequencies result in coils that are too long to be arrayed in the superior/inferior direction, and these receivers are typically arrayed only in the left-right and/or anterior/posterior directions. Using short microstrip receivers, we demonstrate parallel imaging with accelerations in the S/I direction. The length of microstrip resonators is reduced using two different methods at 3.0T: 1) a hybrid design incorporating lumped elements 2) a design that alternates between microstrips and coax lines of the same characteristic impedance.

                  2985.     Modular Preamplifier Design and Application to Animal Imaging at 7 and 11.7T

Stephen J. Dodd¹, George C. Nascimento¹, Meng-Chi Hsieh², Hellmut Merkle¹, Joseph Murphy-Boesch¹, Jyh-Horng Chen², Alan P. Koretsky¹, Afonso C. Silva¹

¹Laboratory of Functional and Molecular Imaging, NINDS, National Institutes of Health, Bethesda, MD, USA; ²Dept of Elec. Eng., National Taiwan University, Taipei, Taiwan

We are currently developing the building blocks for coil development for very high field 7T and 11.T animal and human MRI systems. Here we report the development of low-impedance, low noise preamplifiers for both field strengths and application of this technology to a high-field phased array for imaging of small animals at 500 MHz. Two FET’s are used in the cascode configuration instead of an FET-bipolar combination, allowing the preamplifier to operate with lower supply voltage but retaining low-noise and high dynamic range. A four-element array for animal studies at 11.7T is presented to demonstrate their performance.

                  2986.     300 MHz Receive Array Setup for High Resolution in Vitro Studies of Human Brain Tissue

Hellmut Merkle¹, Peter van Gelderen¹, Shumin Wang¹, Bing Yao¹, Jeff H. Duyn¹

¹NINDS, NIH, Bethesda, MD, USA

A novel setup within a 'clinical MRI scanner' is described which is optimized to study brain tissue in vitro with high sensitivity and high resolution (nanoliter size voxels) at 300 MHz. Size, shape and placement of coils (up to 32) within the receive array as well as a B0 correction method is simulated, implemented and experimentally verified. This setup requires little preparation time and is now routinely used to study post mortem brain.

                  2987.     Evaluation of High Temperature Superconducting (HTS) Coil Performance Gain for 3T Small Animal MR Imaging

Bobo Hu¹, Chris Randell², Colin Sunderland², Brett Haywood¹, Paul Glover¹

¹Sir Peter Mansfield Magnetic Resonance Centre, University of Nottingham, Nottingahm, UK; ²2Pulseteq Ltd., Wotton-under-Edge, Gloucestershire, UK

Estimation of the likely performance gain of the HTS coil requires accurate modelling of important coil sensitivity parameters such as loaded Q factor and SNR gain in MR imaging experiments. Firstly this work proposes an FDTD mesh based numerical mouse model which will accurately simulate a realistic loading effect on the HTS coil at 3T. Secondly, effective techniques are developed to assess the high Q factor and SNR gain of the HTS coil, and comparisons are made with that of the room temperature copper coil. Finally MR imaging experiments performed on room temperature copper coils demonstrate the accuracy of the method.

                  2988.     Implementation of a Four-Channel Phased-Array Coil for PatLoc Imaging

Elmar Fischer¹, Andreas Peter², Laura Del Tin², Jürgen Hennig¹, Jan Korvink², Maxim Zaitsev¹

¹Dept. of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany; ²Dept. of Microsystems Engineering – IMTEK, University of Freiburg, Freiburg, Germany

This work is on the implementation of an in-house-constructed four-channel phased-array coil for PatLoc imaging (=parallel imaging technique using localized gradients), developed to study the non-linear geometry of these gradient fields. Tests of the coil setup using phantoms show that coil performance and also coil decoupling on the cylindrical receive-array coil are sufficient for the goal of imaging with PatLoc gradients.

                  2989.     A Thin-Walled, Cylindrical 4-Channal Receive-Only Coil Array Suitable for PatLoc Imaging at 9.4 T

Andreas Peter¹, Laura Del Tin¹, Jan G. Korvink¹

¹Department of Microsystems Engineering – IMTEK, University of Freiburg, Freiburg, Germany

A very thin-walled, cylindrical four-channel receive-only surface coil array on flexible substrate for small-animal MRI at 9.4 T is presented. The very small overall wall thickness enables the use of this array together with a PatLoc gradient coil.

                  2990.     4-Channel Transceive Surface Coil Array for Reduction of EPI-Induced Artifacts Using SENSE and GRAPPA

Samuel O. Oduneye^1,2, Craig K. Jones², Ravi S. Menon^2,3

¹Biomedical Engineering Graduate Program, The University of Western Ontario, London, Ontario, Canada; ²Robarts Research Institute, London, Ontario, Canada; ³Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada

EPI-induced artifacts are an obvious detriment to image quality and a challenge for most fMRI studies. With a multi-channel surface coil array, parallel imaging can be used to accelerate image acquisition and decrease EPI-induced artifacts. Here we present a novel high field transmit-receive surface coil array for small animal imaging at 9.4T. The coil is designed for parallel imaging and to determine the feasibility of EPI-induced artifacts reduction at 9.4T.

                  2991.     A 1-Channel Transmit Birdcage and 8-Channel Receive Array for in Vivo Rodent Imaging on a 7 T Human Whole-Body System

Stephan Orzada^1,2, Stefan Maderwald², Sophia L. Goericke², Nina Parohl², Sabine Begall³, Angelica G. Montero³, Anika Schinköth³, Harald H. Quick², Mark E. Ladd²

¹ Erwin L. Hahn Institute for MRI, Essen, Germany; ²Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany; ³Department of General Zoology, University of Duisburg-Essen, Essen, Germany

In this work we describe a single channel transmit coil and 8-channel receive array for in vivo rodent imaging on a 7 T whole-body scanner. The coil system consists of a linearly polarized, actively detuned birdcage coil for transmit and a circumferential, 8-loop actively detuned receive array with an inner diameter of 54 mm suitable for rats and other similarly sized rodents. The birdcage and the receive array are both mounted on transparent PMMA tubes for easy visual positioning and monitoring of the subject; additionally, a halogen lamp can be used to prevent cooling of the animal.

                  2992.     Development of New Dual Tuned Coil and Array for Multi Nuclear Imaging

SeungHoon H. Ha¹, Lutfi Tugan Muftuler¹, Orhan Nalcioglu¹

¹Tu & Yuen Center for Functional Onco-Imaging, University of California Irvine, Irvine, CA, USA

Dual-tuned RF coils for multi-nuclear imaging has been considered about loss of an intrinsic quality (Q) factors at each resonant frequencies due to trap circuits which is used at the dual-tuned coil conventionally. New coil using PIN diode switching without trap circuit is presented for keeping inherent Q-factor and the possibility for clinical study is introduced by building dual tuned array coil based on new concept using PIN switching.

                  2993.     Design and Evaluation of a 32 Channel Phased Array Coil for Human Lung Imaging Using Hyperpolarized ³He

Florian Martin Meise¹, Julien Rivoire¹, Wiggins C. Graham^2,3, Boris Keil⁴, Maxim Terekhov¹, Davide Santoro¹, Zahir Salhi⁵, Sergei Karpuk⁵, Lawrence L. Wald^2,3, Wolfgang G. Schreiber¹

¹Section of Medical Physics, Department of Diagnostical and Interventional Radiology, Johannes Gutenberg University Medical School, Mainz, RLP, Germany; ²Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, MGH, Harvard Medical School, Charlestown, MA, USA; ³Harvard-MIT Division of Health Sciences and Technology; ⁴Department of Diagnostic Radiology, University Hospital, Philipps University, Marburg, Germany; ⁵Institute of Physics, Johannes Gutenberg University, Mainz, Germany

The high potential of functional lung imaging using hyperpolarized 3He is tempered by the long breath-holds necessary to acquire the needed data. In addition to patient discomfort, every RF-pulse diminishes the hyperpolarisation of the 3He. To understand and analyse the possibilities of parallel imaging for shortening scan times and increase SNR compared to commonly used volume coils, a 32-channel phased array was developed and compared with a standard single channel volume coil. SNR gain up to factor of 7 in the periphery was achieved and can now be used to improve human lung imaging significantly.

                  2994.     Design of a Coil System for Hyperpolarized 3He Human Lung Imaging

Jian-xiong Wang¹

¹Applied Science Laboratory, GE Healthcare, London, Ontario, Canada

To maximize the imaging speed and SNR and ensure patient comfort, a coil system was designed for Hyperpolarized 3He human lung imaging. This system consisted an asymmetric quadrature birdcage coil as the transmit coil, and an 8-channel coil array as the receive coil. The asymmetric transmit coil used up the nearly entire bore volume with a profile calculated with conformal mapping. The receive coil was a modification of a proton Cardiac coil array to reduce the mechanic works and maximize the patient safety. This coil system was designed for the upgrading new GE MR750 system.

                  2995.     Endorectal Combined Surface Array for Prostate Imaging at 7T

Gregory J. Metzger¹, Steen Moeller¹, Carl J. Snyder¹, Kamil Ugurbil¹, Pierre-Francois van de Moortele¹, Gregor Adriany¹

¹Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, USA

Optimal RF coils must be developed for 7T prostate imaging if the promise of increased spatial, temporal and spectral resolution are to be realized. We previously demonstrated the tradeoffs between an external 16 channel transceive stripline array coil and a transceive endorectal coil. The focus of this abstract is on the development and characterization of a new receive-only ERC (roERC) combined with the previously reported transceiver external stripline array. Along with increased SNR and consistent contrast over the prostate, the combined coil allows for better parallel imaging performance and visualization of important structures close to the endorectal coil.

                  2996.     7T Transmit Four-Channel Receive Array for High-Resolution MRI of Trabecular Bone in the Distal Tibia

Alexander C. Wright¹, Michael Wald¹, Tom Connick¹, Jeremy Magland¹, Hee Kwon Song¹, Branimir Vasilic¹, Rosti Lemdiasov², Reinhold Ludwig², Felix W. Wehrli¹

¹Laboratory for Structural NMR Imaging, Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA; ²Insight MRI, Worcester, MA, USA

We have designed and constructed a Helmholtz-pair local transmit coil with a decoupled 4-element receive phased array for imaging the distal tibia in a whole-body 7 T MRI scanner. The coils are described and initial experiences imaging the trabecular bone of volunteers is discussed. Image data were of high quality and showed a gain in SNR of about 3x for imaging the same individual at 7 T and using an identical 3 T version of the 4-element receive array.

                  2997.     7T Human Spine Arrays with Adjustable Inductive Decoupling

Bing Wu¹, Chunsheng Wang¹, Roland Krug¹, Douglas Kelley², Duan Xu¹, Suchandrima Banerjee¹, Daniel Vigneron^1,3, Sarah Nelson^1,3, Sharmila Majumder^1,3, Xiaoliang Zhang^1,3

¹Radiology&Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA; ²GE Healthcare, San Francisco, CA, USA; ³UCSF/UC Berkeley Joint Group Program in Bioengineering, SanFrancisco&Berkeley, CA, USA

One of technical challenges in implementing ultrahigh field parallel imaging is to design the required transceiver arrays, especially the large size arrays, for signal excitation and reception. In this work, we explore the feasibility of designing transceiver arrays for human spine parallel MR imaging at 7T using loop-type microstrip design with a proposed adjustable inductive decoupling. The preliminary 7T spine images acquired from healthy volunteers using the proposed transceiver arrays are presented.

                  2998.     A New Simple High Field Transmit Coil Design: Open Cavity Resonator

Ozlem Ipek¹, Bob van den Bergen¹, J. J. W. Lagendijk¹, Cornelis A T van den Berg¹

¹Department of Radiotherapy & Radiology, University Medical Center Utrecht, Utrecht, Netherlands

The concept of a body coil is not eligible for high field MRI (> 7T) due to waveguide action. We inserted a tubular dielectric inset into the RF cavity which will tune part of the cavity above the cut-off frequency creating an open cavity resonator. FDTD simulations were performed with a dielectric patient model to compare this new coil design to a traditional 7T body coil concept. Our study demonstrates that the RF shield with a dielectric inset excited by four dipole antennas can achieve comparable excitation efficiency and homogeneity with a simpler coil design as a 7T body coil.

                  2999.     A Flexible 8-Channel Transmit/receive Body Coil for 7 T Human Imaging

Stephan Orzada^1,2, Harald H. Quick², Mark E. Ladd², Achim Bahr³, Thomas Bolz³, Pedram Yazdanbakhsh⁴, Klaus Solbach⁴, Andreas K. Bitz²

¹ Erwin L. Hahn Institute for MRI, Essen, Germany; ²Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany; ³IMST GmbH, Kamp-Lintfort, Germany; ⁴HFT, University of Duisburg-Essen, Duisburg, Germany

Using intrinsically decoupled stripline elements with meanders, a flexible 8-channel transmit/receive body coil was built which tightly accommodates to various subject body sizes. The coil was successfully employed to perform body imaging in 3 volunteers of differing body habitus to demonstrate that it can be used for chest (cardiac) and abdominal imaging.

                  3000.     A Hemispherical 8 Independent Element Probe Suitable for Transmit SENSE at 7T

Daniel James Lee¹, Paul M. Glover¹

¹Sir Peter Mansfield Magnetic Resonance Centre, University of Nottingham, Nottingham, Nottinghamshire, UK

A novel eight-element head coil is proposed for imaging at 7T. This coil utilises a hemispherical geometry and a strip line short-circuited at the open end in order to minimise SAR in the shoulders while still providing good image quality. Simulations confirm that SAR in the shoulders is reduced compared to a birdcage coil. The coupling between elements is measured using a prototype and network analyzer. Decoupling of the elements is achieved using an electrical and magnetic screen as well as a decoupling circuit.

                  3001.     UHF Propagation in a Partially Filled Short Cylindrical Waveguide

Jennifer A. Black^1,2, James E. Richie²

¹GE Healthcare, Waukesha, WI, USA; ²Marquette University, Milwaukee, WI, USA

An experiment is conducted to determine expected signal attenuation when the bore is empty (air-filled) or dielectrically loaded (patient-filled). Experimental results show that the MR bore shows impressive path loss performance at UHF, specifically 433 MHz, with greatest signal strength arriving at the receiver when the bore is dielectrically loaded.

                  3002.     Variable Geometry Elliptical Transceiver Phased Array for Imaging of the Human Brain at 7 T

Nikolai I. Avdievich¹, Jullie W. Pan¹, Andrey M. Kuznetsov¹, Hoby P. Hetherington¹

¹Neurosurgery, Yale University, New Haven, CT, USA

Despite the availability of 7T systems dating from late 1990s, their widespread use in clinical applications has been slowed by technical hurdles associated with detector design. Transceiver phased arrays in combination with multi-channel transmit systems provide a platform for RF shimming. Array performance can be further improved by adjusting array’s geometry to accommodate various head sizes. In this work we describe an 8-element split elliptical 7T transceiver phased array with adjustable geometry and a method for individualized optimization of the RF phases and amplitudes. This combination provides for the efficient generation of a sufficiently homogenous B1 at 7T.

                  3003.     32 Channel Coil Array for Parallel RF Transmission

Yudong Zhu¹, Randy Giaquinto², Xu Chu³, Eric Fiveland², Xing Yang³, Tingting Song³, Keith Park², Joseph Piel²

¹New York University Langone Medical Center, New York, USA; ²GE Global Research Center, Niskayuna, NY, USA; ³GE Global Research Center, Shanghai, China

As part of a study that investigates a substantially distributed multi-channel parallel transmit approach, head-size 32-element transmit/receive arrays were developed. The specific goal of the coil development is to facilitate reduction of RF power dissipation in the imaged object / the coil structure, and to facilitate B1 shimming / accelerated parallel excitation for an arbitrarily oriented target slice or volume. This abstract describes the coil design and construction process, and presents 3T imaging results that were obtained by driving in parallel the elements of one array with current-source RF power amplifiers.

                  3004.     An Inverse Method for the Design of RF Array Coils with a Sparse Structure and Its Application for Breast Imaging

Yu LI¹, Feng Liu¹, Ewald Weber¹, Bing Keong Li¹, Stuart Crozier¹

¹The University of Queensland, Brisbane, Queensland, Australia

In this work, a novel RF phased array coil for breast imaging was designed, constructed and tested. In the inverse design, an iterative optimization approach was used to determine the coil geometry. The main focus of this study is to design an arracy coil with simple strucure and good RF field profile. Both the simulated and experimental results demostrate the performance of the proposed method in terms of sparsity of the designed coil structure and the improved B1 field.

                  3005.     A 16 Channel T/R Open-Faced Head Array for Humans at 9.4T.

Gregor Adriany¹, Dinesh Deelchand¹, Pierre-Gil Henry¹, Jinfeng Tian¹, John Thomas Vaughan¹, Kamil Ugurbil¹, Pierre-Francois van de Moortele¹

¹Center for Magnetic Resonance Research, University of Minnesota Medical School, Minneapolis, MN, USA

A 16 channel transmit/receive array based on decoupled transmission line elements for 9.4T is presented. The coils slim housing design along with shortened resonance elements in front of the eyes supports task presentation within a Head Gradient Coil. The coil consisted of eight channel upper and lower parts which can be used either in a half volume or in a whole head configuration. The circuitry layout of coil elements allows for decoupling independent of load. FDTD simulations are presented that explore the effect of the shortened transmission line elements on the achievable B1 and SAR.

                  3006.     7T Breast Imaging with a 2-Channel Bilateral Loop Design

Leighton Lloyd Warmington¹, Gregor Adriany¹, Carl Snyder¹, Edward J. Auerbach¹, Patrick J. Bolan¹

¹Center for Magnetic Resonance Research, Radiology/University of Minnesota Medical School, Minneapolis, MN, USA

The development of MR imaging and spectroscopy of the breast at 7T is limited by the lack of acceptable coil designs. Our goal for this project was to develop a simple bilateral coil design that could be used without a parallel transmit RF system, and to determine if this configuration would be suitable for use in MRI/MRS investigations of patient populations. Our results showed that this simple coil design produced images of acceptable quality and had sufficient B1+ efficiency to allow single-voxel spectroscopy.

                  3007.     An Eight-Channel Transmit/Receive RF Array for Imaging the Carotid Arteries at 7 Tesla

Oliver Kraff^1,2, Andreas K. Bitz^1,2, Stephan Orzada^1,2, Stefan Maderwald^1,2, Stefan Kruszona^1,2, Lena C. Schaefer^1,2, Janine Y S Grootfaam^1,2, Mark E. Ladd^1,2, Harald H. Quick^1,2

¹Erwin L. Hahn Institute for MRI, Essen, Germany; ²Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany

An eight-channel transmit/receive RF array was built for imaging the carotid arteries at 7T. The array was made of four overlapping loop coils per side to assess both arteries in one acquisition. We characterize this prototype in simulations and bench measurements and show first in vivo results. Numerical simulations were performed for design optimization as well as safety validation. In vivo images reveal a good excitation of the arteries on both sides of the neck. The vessel walls are well visualized. Our results indicate that this phased array coil could open a promising new application field in 7T clinical research.

                  3008.     A Concentrically Shielded Transceive Array Coil Optimized for B1+ Inhomogeneity Correction at 7T<

Vijayanand Alagappan¹, Kawin Setsompop², Ulrich Fontius³, Franz Schmitt³, Elfar Adalsteinsson^4,5, Lawrence Leroy Wald^2,5

¹Department  of Radiology, A.A Martinos Center for Biomedical Imaging, Charlestown, MA, USA; ²Department of Radiology, A.A Martinos Center for Biomedical Imaging, Charlestown, MA, USA; ³Siemens Healthcare, Erlangen, Germany; ⁴Department of Electrical Engineering and Computer Science, MIT, Cambridge, MA, USA; ⁵Health Science and Technology, MIT, Cambridge, MA, USA

We describe an 8-channel concentrically shielded loop transmit/receive coil for parallel excitation at 7T. Decoupling the neighboring elements with the concentrically shielded loops gives an extra degree of freedom on the size of the loop elements. The size of the coil could be optimized to improve the B1+ homogeneity. The constructed concentrically shielded loop coil is compared against an 8-channel stripline array coil on its performance for B1+ shimming. Initial results show that the concentric shielded loops serves as a good compromise between the conventional loop and the stripine coil elements.

                  3009.     Multi-Channel Transceive Coil for Improved Knee Imaging at 7T

Can Akgun¹, Lance DelaBarre¹, Ute Goerke¹, Carl J. Snyder¹, Jutta Ellerman¹, Kamil Ugurbil¹, John Thomas Vaughan¹

¹University of Minnesota-Center for Magnetic Resonance Research, Minneapolis, MN, USA

An application that can benefit from high SNR of high fields (7T and above) is musculoskeletal imaging (MSK). The ability to see structures as fine as cartilage can prove to be valuable when evaluating the knee for morphology. We present a robust 8 channel transceiver array coil with a Faraday cage structure to eliminate the impact of the other knee in the FOV. Imaging results obtained with this coil at 7T for the knee are presented. Initial results demonstrate high resolution in knee imaging can be achieved taking advantage of the gain in SNR at ultrahigh magnetic field.

                  3010.     8-Channel Transmit/receive Head Coil for 7 T Human Imaging Using Intrinsically Decoupled Strip Line Elements with Meanders

Stephan Orzada^1,2, Oliver Kraff², Lena C. Schäfer², Irina Brote², Achim Bahr³, Thomas Bolz³, Stefan Maderwald², Mark E. Ladd², Andreas K. Bitz²

¹ Erwin L. Hahn Institute for MRI, Essen, Germany; ²Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany; ³IMST GmbH, Kamp-Lintfort, Germany

An 8-channel transmit/receive head coil for 7 T was built and tested for B1 efficiency, B1 homogeneity, and SAR efficiency. The head coil consists of 8 intrinsically decoupled strip line elements with meanders. It was found that the new design allows 5.3 times more energy to be put into the coil before reaching the SAR limit and achieves nearly the same flip angle at the same input power when compared to a commercially available 8-channel head coil.

                  3011.     An Adaptable 8-Channel Transmit Array Head Coil for Parallel Transmit and B0 Mitigation at 3T

Vijayanand Alagappan^1,2, Weiran Deng³, Cungeng Yang³, Andrew Victor Stenger³, Lawrence Leroy Wald^4,5

¹Department  of Radiology, A.A Martinos Center for Biomedical Imaging, Charlestown, MA, USA; ²Deprtment of Biomedical Imaging, Tufts University, Medford, MA, USA; ³Department of Medicine, University of Hawaii John A. Burns School of Medicine, Honolulu, HI, USA; ⁴Department of Radiology, A.A Martinos Center for Biomedical Imaging, Charlestown, MA, USA; ⁵Health Science and Technology, MIT, Cambridge, MA, USA

Parallel excitation has a lot of application which includes B1+ inhomogeneity correction, thru plane B0 inhomogeneity correction and also localized excitation. These different techniques have different requirements in terms of the spatial sensitivity of the Tx array coil. In this work we have designed and constructed an 8 channel stripline based transmit array coil whose spatial profile is easily adaptable to the imaging needs using different Wilkinson splitter configuration and four transmit channels.

                  3012.     Parallel Transceive Array for 9.4 T Animal Studies

Christopher J. Wargo¹, Malcolm J. Avison¹, John C. Gore¹

¹Vanderbilt University Institute of Imaging Science, Nashville, TN, USA

Parallel receive coils provide benefits in obtained SNR and enable rapid imaging techniques such as SENSE to be applied. This approach has been extended to parallel transmit of RF with benefits such as accelerated excitation to improve spatial selection, and B1 inhomogeneity correction. In this abstract, we describe the modification of an existing parallel receive array to operate as a multi-channel transceive system for 9.4 T animal studies. A significant SNR improvement is observed in the rat brain when compared against a volume coil and the receive only configuration with volume coil transmission.

                  3013.     A New Decoupling Method for Coil Elements on a Cylinder Surface

xuelian Lu¹, yao Xing¹, haining Wang¹, jianmin Wang²

¹Siemens Mindit Magnetic Resonance Ltd., Shenzhen, Guangdong, China; ²Siemens Mindit Magnetic Resonance Ltd., Shenzhen , Guangdong, China

Decoupling of multi-element coil is becoming increasingly important due to the parallel transmitting application. Capacitive decoupling is easy to implement and capacitors with high Q-value are easy available. Because conventional capacitive decoupling requires direct connection between coil elements, the size of the connected coil element should be kept as small as possible compared to the wavelength. In this abstract we demonstrate a novel method to decouple up to 9 coil elements by combining capacitive and geometrical decoupling concept. The decoupling network presented here doesn¡¯t change the signal profile of each individual element which could be an advantage for the parallel transmitting applications.

                  3014.     Single-Feed Quadrature Coils as Transceiver Array Elements for Improved SNR and Transmit Efficiency

Xiaoliang Zhang^1,2, Chunsheng Wang¹

¹Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA; ²UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco/Berkeley, CA, USA

A method for generating quadrature mode by single-feed surface coil for ultrahigh field MR was presented. With the proposed single-feed quadrature surface coil, high frequency quadrature coil array for parallel imaging can be readily built. To demonstrate the concept, a single-feed quadrature coil array with two elements was designed and tested. The bench test and FDTD simulation results are presented.

                  3015.     Geometrically Decoupled Phased Array Coils for Mouse Imaging

Sahil P. Bhatia¹, Yiping Guan², Fraser Robb², Mary P. McDougall¹

¹Department of Biomedical Engineering, Texas A & M University, College Station, TX, USA; ²GE Healthcare, Aurora, OH, USA

Array coils offer several advantages in MR techniques for mouse imaging. Typical array designs use a combination of geometric and additional techniques for decoupling coil elements. A transmit/receive 4 channel volume array coil, that is purely geometrically decoupled is presented which eliminates the need for expensive isolation preamplifiers. Coil bench S parameter measurements and images of homogenous phantom are shown. Preliminary design work for a modified ‘open’ configuration to facilitate the loading of animals is also presented.

                  3016.     A Reliable Method for Calculating RF Coil Performance

Mikhail Kozlov¹, Christoph Leuze¹, Robert Turner¹

¹Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Sachsen, Germany

We present an approach for matching actual and simulated MRI coil performance, defined as the ratio of the RF field magnitude to the RF voltage applied to the coil input. The maximum mismatch is less than 3% near the coil geometrical center, for a tissue-saline solution and more complicated phantoms, such as a plastic skull filled with gel. Phantoms were simulated as voxel-based models obtained from segmented 3-D MRI scans.

                  3017.     A Fully Digital RF Pulse Generator Designed for Multiple Transmission Channels

André Kuehne¹, Werner Hoffmann¹, Frank Seifert¹

¹Physikalisch-Technische Bundesanstalt, Berlin, Germany

Parallel excitation (PEX) is a key technique to tackle RF issues in high and ultra-field MR. Since multi-channel transmit arrays are still rare and an upgrade of existing scanners using standard hardware is limited by cost and size of the equipment, a novel approach using direct digital signal generation is presented. Our set-up features four channels but the design is capable of supplying up to twenty independent RF channels for frequencies up to 300 MHz. We present measurements of phase jitter and first static phase images using a 4-channel transmit/receive coil array demonstrating the feasibility of this approach.

                  3018.     Planar Butler Matrix Technology for 7 Tesla MRI

Pedram Yazdanbakhsh¹, Andreas Bitz², Stephan Orzada², Oliver Kraff², Mark E. Ladd², Klaus Solbach¹

¹High Frequency Technique, University Duisburg-Essen, Duisburg, NRW, Germany; ²Erwin L. Hahn Institute for Magnetic Resonance Imaging, Essen, Germany

Butler Matrix is used to drive the individual rungs of the DBC (Degenerate Birdcage Coil) in linear combinations to form the uniform birdcage mode as well as higher gradient modes. The advantage of using the modes of a birdcage coil excited by a Butler Matrix is that they form naturally decoupled orthogonal modes that do not require decoupling strategies. The Butler Matrix can also provide reflection coefficients that are insensitive to the load. In this work a novel reduced-size 8×8 high-power Butler Matrix has been designed and fabricated at 300 MHz to excite a coil array in 7T MRI.

                  3019.     Development of a 64 Channel Parallel Transmit System

Neal Anthony Hollingsworth¹, Ke Feng¹, Chieh-Wei Chang², Steve M. Wright¹, Mary Preston McDougall²

¹Electrical Engineering, Texas A&M University, College Station, TX, USA; ²Biomedical Engineering, Texas A&M University, College Station, TX, USA

The use of transmit arrays for transmit SENSE, B1 shimming, and phase compensation of SEA coils has made large scale parallel transmit systems desirable. Our group has developed a system capable performing static modulation on 64 channels, or fast modulation on 8 channels with an output power of 100W per channel. The large channel count drove design to produce a modular system that is easier to test, troubleshoot, and construct. Consideration was also given to thermal and space issues that could arise from such a large system.

                  3020.     Highly Distributed RF Transmission with a 32-Channel Parallel Transmit System

Yudong Zhu¹, Xu Chu², Chengtao Cao², Eric Fiveland³, Randy Giaquinto³, Tingting Song², Xing Yang², Cheng Zhang², Joseph Piel³, Keith Park³

¹New York University Langone Medical Center, New York, USA; ²GE Global Research Center, Shanghai, China; ³GE Global Research Center, Niskayuna, NY, USA

Parallel RF transmission supports flexible spatiotemporal coil current control with multiple sources driving a distributed RF coil structure, and promises to address major challenges facing conventional transmission in high field MR. This study explores substantially distributed parallel Tx, aiming at its applications in reducing RF power dissipation in the subject / the coil structure, as well as in B1 shimming / accelerated parallel excitation of an arbitrarily oriented target slice or volume. We developed a cost effective 32-channel exciter module, RF coil arrays that support 32-channel parallel Tx and Rx, and 32 current-source amplifiers that facilitate coil current control.

                  3021.     An Inexpensive, Scalable Vector Modulator and Application to 2D RF Pulses

Ke Feng¹, Neal Anthony Hollingsworth¹, John Carl Bosshard¹, Douglas C. Noll², Steven M. Wright¹

¹Electrical and Computer Engineering, Texas A&M University, College Station, TX, USA; ²Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA

Using a vector modulator system constructed for B1 shimming, full capability of high speed modulation for more complex transmit pulses is shown. By exciting the vector modulators with a hard pulse from a host Varian Inova system, and analog modulation control signals from a D/A card, each board is able to create four completely independent RF waveforms. In order to test the system, one channel was used to create a checkerboard pattern, and the results are shown to be comparable to the Varian Inova system.

                  3022.     PC Controlled 8-Transmit Channel Circuit with Independent Phase and Amplitude Control for 7T

Yong Pang¹, Zhentian Xie², Bing Wu¹, Chunsheng Wang¹, Daniel Vigneron^1,3, Sarah Nelson¹, Xiaoliang Zhang¹

¹Radiology&Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA; ²GE Healthcare, Waukesha, WI, USA; ³UCSF/UC Berkeley Joint Group Program in Bioengineering, San Francisco & Berkeley, CA, USA

In this work, a PC controlled 8-transmit channel circuit for 7T MR scanner is designed. Both the phase and the amplitude of each channel can be adjusted independently by PC via a 16-channel Digital Analog Converter (DAC) with custom-written software. The phase adjustment range is from -30° to 380°, while the range of RF power attenuation is 26dB. RF power transistor and MOSFET are then applied to amplify the RF pulse of each channel up to 100W which can be used for driving transmit arrays. This design can be utilized to perform B1 shimming or parallel transmission.

                  3023.     Imaging Study with Ultra-Low Output Impedance RF Power Amplifiers

Xu Chu¹, Tingting Song¹, Xing Yang¹, Eric W. Fiveland², Yudong Zhu³

¹GE Global Research Center, Shanghai, China; ²GE Global Research Center, Niskayuna, NY, USA; ³Langone Medical Center, New York University, New York, NY, USA

The feasibility of inter-element decoupling in parallel excitation by ultra-low output impedance RF power amplifier in a high field MR environment was evaluated. By presenting low source impedance at the output port of an amplifier, the current induced by neighbor coils is blocked by the high impedance at the input port of the coil. The transmit coil could be driven by this amplifier through a nλ/2 cable, which enabled the placement of amplifiers in the equipment room and relaxed the compatibility requirements on power electronics and facilitated system integration. The 1st set of images acquired with 3T scanner were presented.

                  3024.     A Versatile In-Line Sensor for Power Monitoring and Calibration of Transmit Arrays

Pascal Pawel Stang¹, John Mark Pauly¹, Greig C. Scott¹

¹Electrical Engineering, Stanford University, Stanford, CA, USA

Parallel transmit pulse designs demand high-fidelity RF reproduction, even as transmit arrays add substantial complexity to MRI scanner electronics and systems. As channel counts grow, accurate transmit path measurements are needed to verify system performance, maintain patient safety, and ease equipment serviceability. We present a versatile transmit path monitor using an in-line vector RF power sensor connected to a Medusa MRI Console. Our system enables a wide range of performance and diagnostic measurements at relatively low cost. Successful results include measurement of RF forward and reverse power, coil impedance, loading, and tuning, and RF amplifier performance.

                  3025.     A Load Pull/Hot S22 Analyzer for Transmit Array Amplifiers

Greig Scott¹, Pascal Stang¹, Adam Kerr¹, John Pauly¹

¹Electrical Engineering, Stanford University, Stanford, CA, USA

Transmit arrays are dependent on well controlled output impedances from power amplifiers. In reality, nonlinearities exist, causing this behavior to be ill defined. We present a load pull and hot S22 analyzer that can quantify amplifier output impedance under power transmit conditions.

                  3026.     Design of MOSFET Matching Networks Without Inductors

Ke Feng¹, Neal Anthony Hollingsworth¹, Mary Preston McDougall², Steven M. Wright¹

¹Electrical and Computer Engineering, Texas A&M University, College Station, TX, USA; ²Biomedical Engineering, Texas A&M University, College Station, TX

Inductors used in matching networks for MOSFET amplifiers tend to be problematic because of availability and the magnetic field it creates. A design of MOSFET amplifiers’ matching networks using only capacitors and microstrip transmit lines constructed on standard FR-4 boards is given. By completely eliminating inductors from our matching network, isolation was significantly improved. Once one amplifier is successfully tuned to 50 Ω, additional amplifiers can be constructed using fixed value capacitors. This greatly simplifies constructing a large quantity of amplifiers.

                  3027.     A Four Channel Transmission Array Based on CMCD Amplifier

Jeremiah Aaron Heilman¹, Natalia Gudino², Matthew Joseph Riffe², Philipp Liu³, Mark A. Griswold²

¹Physics, Case Western Reserve University, Cleveland, OH, USA; ²Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA; ³Carnegie Mellon University, Pittsburgh, PA, USA

We present a four channel transmission array based on current mode class D (CMCD) amplifiers integrated on-coil. This development shows the decoupling capabilities of the CMCD technology in phantom imaging studies, including the ability to derive signals from a synchronized, digital source and transmit them to the array over fiber optic cables.

                  3028.     Evaluation of Spatial Distortion in the 7.0T MRI for Clinical Use Using New 3D Mesh Phantom

Young-Don Son¹, Hang-Keun Kim¹, Sung-Tae Kim¹, Nam-Beom Kim¹, Young-Bo Kim¹, Zang-Hee Cho¹

¹Gachon University of Medicine and Science, Neuroscience Research Institute, Incheon, Korea

Clinically useful images are obtained from high-field MRI over 7 Tesla, but no study has been reported its spatial accuracy yet. A new 3D mesh phantom was designed and manufactured for the measurement of the spatial distortion in 7Tesla MRI. A CT image and gradient echo T2*-weighted image of 1.5T and 7.0T MRI was taken at two different pixel bandwidths: 200 and 30 Hz/pixel. 7.0T MRI is not distorted almost same as 1.5T at minimal bandwidth although 7.0T MR image became more distorted as pixel bandwidth decreased. Finally, 7.0T MRI can be utilized for the clinical purpose at proper parameters.

                  3029.     Maximum Sound Pressure Levels at 7 Tesla – What’s All This Fuss About?

Sebastian Schmitter¹, Marco Mueller¹, Wolfhard Semmler¹, Michael Bock¹

¹Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany

In this work the acoustic resonances of a 7 T system were examined and the linear dependency of the sound pressure on the gradient amplitude were verified. The protocols of three different, fast imaging sequences were adjusted on the scanners resonances so that they generate a maximum SPL. A maximum SPL value of 112 dB was found for a sinusoidal EPI sequence, which is similar to SPL values of a 1.5 T system. Thus, regarding acoustic safety, the same safety measures can be applied for this specific 7 T MR system as to 1.5 T systems from the same manufacturer.

                  3030.     RF Heating of Pacemaker Leads: Do Open MR Systems Perform Better Than Close Bore Systems?

Roger Luechinger¹, Volkert A. Zeijlemaker², B Mengiardi³, Peter Boesiger¹

¹Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland; ²Medtronic Bakken Research Center, Maastricht, Netherlands; ³Imamed, Liestal, Switzerland

In open MR system with a main magnetic field orthogonal to the feet-head axis of the patient, it could be assumed that RF heating on extended implants like pacemaker leads may be strongly reduced compared with a conventional close bore systems. However, measurements shows that also on these systems high temperature increases could be found in some configuration. The position of the lead within body coil may have the smaller impact than the position of the lead within the phantom.

                  3031.     Efficacy of Diphenhydramine in the Prevention of Vertigo and Nausea at 7 Tesla

Markus Thormann¹, Jens Ricke¹, Astrid Wollrab¹, Daniela Adolf², Oliver Speck¹

¹Biomedical Magnetic Resonance, Otto-von-Guericke University, Magdeburg, Germany; ²Biometrics and Medical Informatics, Otto-von-Guericke University, Magdeburg, Germany

In recent years the number of Ultra-High-Field-MR-Scanners is increasing. The most frequently reported side effects at 7-Tesla are vertigo and nausea during table motion. The purpose of this study was to test whether Diphenhydramine can improve patient comfort and the subjective acceptance of high field MR-scanners by preventing vertigo and nausea. In a prospective, double blinded, placebo controlled, cross-over randomized study we quantified the sensations of 30 volunteers before and after exposure to the static magnetic field with and without drug respectively placebo administration. A reduction of the strength of vertigo and a prevention of nausea is possible.

                  3032.     TMS/fMRI: Risk Assessment at 4T

Paolo Ferrari¹, Jorge Jovicich¹, Jens Volkmar Schwarzbach¹, Marco Sandrini¹, Simon Robinson¹

¹Center for Mind/Brain Sciences, University of Trento, Mattarello, Trento, Italy

For cognitive neuroscience research Transcranial Magnetic Stimulation (TMS) is a useful method for probing brain connectivity, combined with fMRI. Standard fMRI experiments interleaved with TMS are possible as proven from several studies, but to date, there are no specific studies that thoroughly characterize and discuss all risks related to concurrent TMS-fMRI. Our goal is to identify main risks of such multimodal experiments. By means of thermal map, flip angle map, tSNR and signal stability evaluation of EPI (percent fluctuation and drift), we try to identify the influence of the TMS-coil in terms of safety and quality.

                  3033.     The Correct Method for Numerical Calculation of Induced Electric Fields for Rotational Movements in Static Magnetic Fields

Paul Glover¹, Clemente Cobos Sanchez, Henry Power, Richard Bowtell

¹School of Physics and Astronomy, University of Nottingham, Nottingham, Notts, UK

There is currently great interest in knowing the electric fields and current densities induced in the human body due to movement in and around MRI scanners. Regulations have been published which describe action thresholds in terms of parameters which are not directly accessible to measurement or routine dosimetry. Hence there is a great reliance on numerical simulations. Here we show that when body rotations are simulated it is vital that the driving electric field is calculated from the vector product of velocity and magnetic field rather than using the rate of change of vector potential.

                  3034.     Safety Evaluation of a 3T Neonate Head Coil Using Numerical Calculations

Bu Sik Park^1,2, Ravi Srinivasan³, Christopher M. Collins^2,4

¹Bioengineering , The Pennsylvania State University, Hershey, PA, USA; ²Radiology, The Pennsylvania State University, Hershey, PA, USA; ³Advanced Imaging Research, Inc., Cleveland, OH, USA; ⁴Bioengineering, The Pennsylvania State University, Hershey, PA, USA

Here we report the numerical calculation results for the B1 field and SAR evaluation in a 3T neonate head coil containing an anatomically-accurate head model using the finite difference time domain (FDTD) method. The FDTD model of the coil was created directly from CAD models of the actual coil, and features an end cap, four-port drive, asymmetric end ring, and slightly larger spacing of anterior-most elements to allow for ventilation/monitoring equipment. Maximum time-average dissipated power to avoid exceeding limits on local and average SAR are presented.

                  3035.     Measurement of Occupational Exposure to RF and Gradient Fields in an Open 1T MR System

Myles Capstick¹, Sven Kuehn¹, Michael Oberle¹, Rebecca Quest², Annie Papadaki², Marc Rea², Donald McRobbie², Niels Kuster

¹IT'IS Foundation , Zurich, ZH, Switzerland; ²Radiological Sciences Unit, Imperial College Healthcare Trust, London, UK

Interventional MR procedures in an open 1T MRI scanner have been investigated for occupational exposure of staff to electric and/or magnetic fields and/or magnetic flux density values that exceed action values (AVs) defined in the EU Directives 2004/40/EC and 2008/46/EC. A specific measurement procedure and analysis to systematically measure field strengths during pre-selected procedures with regard to movements of a radiologist has been developed and applied. Measurements have been performed with clinical as well as specific test sequences. The results have been compared with the existing AVs of Directive 2004/40/EC.

                  3036.     RF Safety and Thermal Charecterists of Porcine Heads After Euthanasia

Devashish Shrivastava¹, Timothy Hanson, Jeramy Kulesa, J. Thomas Vaughan

¹CMRR, Radiology, University of Minnesota, Minneapolis, MN, USA

Thermal decay response right after the euthanasia was within 15 % of the thermal response obtained after 12 hours of death in the head of human sized porcine models. Thermal decay over time is a function of thermal properties alone (i.e., thermal conductivity, density, and specific heat). Thus, the thermal decay response measurements suggest that the variation in the thermal properties was less than 15% after 12 hours of death. This further suggests that the RF heating related thermal responses obtained with in 12 hours of death in fresh, perfused cadavers may closely mimic thermal responses in live humans.

                  3037.     Towards Direct B1 Based Local SAR Estimation

Martijn Anton Hendrik Cloos¹, Giorgio Bonmassar¹

¹Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, M.A., USA

In contrast to numerical SAR simulations, a B1 based method for SAR estimation is presented. Closed form solutions for the dielectric properties and axial-electric field component are derived from the Maxwell’s equations. The method is applied to simulated B1-images of a human head and compared to the simulated SAR.

                  3055.     Gradient Coil Induced Eddy Current Computation Using the Boundary Elements Method

Shmaryu Shvartsman¹, John L. Patrick¹, James F. Dampsey¹, K. M. Prasad²

¹Viewray Incorporated, Oakwood Village, OH, USA; ²Integrated Engineering Software, Winnipeg, Manitoba, Canada

The Boundary Element Method “Faraday” software, developed by Integrated Engineering Software Inc., Winnipeg, Canada, was employed for analysis of 3D eddy currents induced by both transverse and axial MRI gradient coils. We applied this method to a split whole-body gradient coil designed for a MRI guided Radiation Therapy device. The device requires three multi-leaf collimators to be positioned in the gap of the split gradient coils. The presence of the collimators results in eddy current asymmetry that should be characterized and accounted for in image reconstruction to provide imaging adequate for treatment planning.

                  3056.     Design Strategy for Shielded Open MRI Magnets

Franco E. Bertora¹, Elisa Molinari², Andrea Viale¹

¹Robotics, Brain and Cognitive Sciences, Italian Institute of Technology, GENOVA, GE, Italy; ²Robotics, Brain and Cognitive Sciences, Italian Institute of Technology, GENOVA, Ge, Italy

A magnet design strategy is proposed, starting from a three-dimensional finite configuration that completely confines the field and that contains a closed cavity where the field is perfectly homogeneous. When the cavity is opened on one or more sides to allow patient access distortions are induced and a stray field arises, but the three-dimensional starting point introduces a new degree of freedom that would be otherwise absent

                  3057.     Comparison Between CCMI and CAHM for Design Shielded Gradient Coils for MRI.

Silvia Sandra Hidalgo^1,2, Carl Gadzinski², Brian Rutt²

¹CI3M, UAM Iztapalapa, Mexico, City, Mexico; ²Imaging Department, Robarts Research Institute, London, Ontario, Canada

This work is focussed on a comparison between two methods based in the target &#64257;eld method (TGM) to design Shielded Gradient coils for MRI. The main problem of the TGM is that a current of in&#64257;nite extent is designed with a set of constraints but the current is modi&#64257;ed, and in consequence the &#64257;nal coil might not have the desired characteristics. Carlson proposed a current distribution using a Fourier Series for a coil of &#64257;nite length. Another solution was proposed by Chronik that adds a set of current constraints forcing the current to lie over a certain length.

                  3058.     Evaluation of Two Shielding Strategies

Hector Sanchez¹, Michael Poole¹, Feng Liu¹, Stuart Crozier¹

¹School of Information Technology & electrical Engineering, The University of Queensland, Brisbane, QLD, Australia

This paper presents an evaluation between shielded gradient coils designed by the traditional methods (magnetic field minimization on the cryostat wall, method A) and the magnetic field control of Eddy Currents at the DSV (method B). Using the Equivalent Magnetization Current method we designed a set of gradient coils using methods A and B. We show that coils designed by method A require a larger pre-emphasis than those of method B. The interested contaminant field harmonics produced by method B dissipates faster than those harmonics produced by the coil designed with method A. Parameters such as residual gradient field and figure of merit are analysed.

                  3059.     A Novel Gradient Design: Simultaneous Generation of Fast Switchable Linear and High Order Field Gradient for MR Imaging

Stefan Wintzheimer¹, Florian Fidler², Michael Ledwig¹, Toni Drießle¹, Daniel Gensler¹, Peter Michael Jakob^1,2

¹Department of Experimental Physics 5, University of Würzburg, Würzburg, Germany; ²MRB, Research Center Magnetic-Resonance-Bavaria, Würzburg, Germany

Shimming a magnetic field usually requires an additional set of complex coils which act independently from the linear gradient system used for MRI. In this study a novel matrix gradient design is presented, which is capable of generating both linear gradient fields for imaging and at the same time high order shim fields to compensate inhomogeneities in the main magnetic field. They provide the possibility to create a large variety of field profiles. Furthermore the new design is able to switch every field order very fast due to low inductivity of the coils.

                  3060.     Theoretical Design of 3D Gradient Coils

Peter Thomas While¹, Larry K. Forbes¹, Stuart Crozier²

¹School of Maths and Physics, University of Tasmania, Hobart, Tasmania, Australia; ²School of Information Technology and Electrical Engineering, University of Queensland, Brisbane, Queensland, Australia

An analytic inverse method is presented for the theoretical design of 3D transverse gradient coils. This method solves for the precise geometry of the coil windings as part of the optimisation, rather than restricting the solution to some predetermined coil surface. An ill-conditioned integral equation is solved for a 3D current density using regularisation and a minimum power constraint. Coil windings are obtained using a priority streamline seeding technique followed by a secondary optimisation of the coil currents. Results are found to display an interesting general geometric form involving sets of closed loops plus spiral-type coils with excellent gradient homogeneity.

                  3061.     High Order Stream Function Method to Automatically Design MRI Gradient Coil

Feng Jia¹, Zhenyu Liu¹, Anna M. Welz², Maxim Zaitsev², Jan G. Korvink¹, Jürgen Hennig²

¹Dept. of Microsystems Engineering – IMTEK, University of Freiburg, Freiburg, Germany; ²Dept. of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany

In this paper, we present a high-order discretization method to design the cylindrical gradient coil. The cylindrical surface can be exactly discretized using a high-order triangular mesh when the surface is expressed using a cylindrical coordinate system. The magnetic field is calculated using the Biot-Savart law where the surface current density is expressed using a stream function and the surface integration is implemented using surface numerical integration based on the shape functions of the finite element. One numerical example demonstrates that this method can be used to design the surface gradient coil.

                  3062.     Adaptive Method for Gradient Coil Design

Shmaryu M. Shvartsman¹, Xin Chen², Tanvir N. Baig³, Minhua Zhu², John L. Patrick¹, James F. Dempsey¹, Robert W. Brown²

¹ViewRay Inc., Oakwood, OH, USA; ²Department of Physics, Case Western Reserve University, Cleveland, OH, USA; ³Department of Physics, University of Dhaka, Dhaka, Bangladesh

We present a practical method for designing the transverse and the axial gradient coils for MRI. This method is based on a modification of previous pro-cedures for discretizing the continuous current solution of a gradient coil design. It leads to improved target field quality characteristics as well as other characteristics such as minimization of the energy/inductance, minimization of the residual eddy current effect, minimization of the thrust forces on the coil and cold shields, coil resistance, etc. The new discretization method involves a set of parameters that can be varied to achieve the desired trade-offs of the coil characteristics.

                  3063.     An Inverse Design Method for 3D Toroidal Gradient Coils

Peter Thomas While¹, Larry K. Forbes¹, Stuart Crozier²

¹School of Maths and Physics, University of Tasmania, Hobart, Tasmania, Australia; ²School of Information Technology and Electrical Engineering, University of Queensland, Brisbane, Queensland, Australia

An analytic inverse method is presented for the theoretical design of toroidal transverse gradient coils. This coil structure is chosen based on previous results for a fully 3D current density solution of optimal geometry. A regularisation strategy with a minimum power constraint is used to obtain toroidal current densities, and the method is applied to the design of unshielded and shielded, whole-body and head coil gradient systems. Resultant coil winding sets are found to display high efficiency, low inductance, high gradient homogeneity and good force balancing.

                  3064.     A Novel Cradle-Shaped Gradient Coil for High-Field MRI

Kyle M. Gilbert¹, Joseph S. Gati¹, Ravi S. Menon¹

¹Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada

By replacing a head-only gradient coil in a neurology-dedicated scanner with a single-sided gradient coil, the functionality of the scanner can be extended to include localized imaging within the torso. As a prototype, a cradle-shaped gradient coil was designed, fabricated, and tested in a 9.4-T animal scanner. A dedicated three-dimensional algorithm was developed to correct for non-linear image distortion.

                  3065.     Double Region Local Bi-Planar Gradient Array Design for Breast Imaging

Sung Man Moon¹, Kenneth Craig Goodrich¹, J. Rock Hadley¹, Dennis L. Parker¹

¹UCAIR (Utah Center for Advanced Imaging Research), Radiology, University of Utah, Salt Lake City, UT, USA

Local planar Gradients can achieve higher efficiency with higher slew rates compared to conventional cylindrical gradients resulting in higher spatial and temporal resolution, Further, with reduced coil dimensions, which help minimize the extent of associated magnetic field excursions, planar gradient systems may have reduced PNS. However, for certain applications such as breast imaging, the homogeneous volume may be too small to cover the both breasts. We present a local biplanar gradient insert that has two imaging regions along the x-axis to overcome this limitation by applying the multiple-region gradient concept along the x-axis instead of along the z-axis as in the original paper.

                  3066.     MR Microscopy Using Uniplanar Magnetic Field Gradients

Lin Zhao¹, Andrey V. Demyanenko¹, Shuyi Nie¹, J. Michael Tyszka¹

¹California Institute of Technology, Pasadena, CA, USA

A three-axis uniplanar microscopy gradient set is optimized to image millimeter scale samples using sub-second echo planar imaging sequences with short echo spacing at 7T. The gradient set is also used to acquire 3D time-resolved gradient echo images of cell division in fertilized frog embryos.

                  3067.     Forces and Torques on Small Animal Insert Gradient Coils

Matthew Aloysius McAlpine¹, William Handler, Blaine Chronik

¹Physics and Astronomy, University of Western Ontario, London, Ontario, Canada

A numerical approach to determine the safety of small animal insert gradient coils in there use in MR main magnets by calculating the net force and torque at varying coil positions.

                  3068.     Simple Method for MR Gradient System Characterization

Nii Okai Addy¹, Hochong H. Wu¹, Dwight G. Nishimura¹

¹Electrical Engineering, Stanford University, Stanford, CA, USA

For fast imaging sequences such as EPI, spirals and 3D cones, the actual k-space trajectories achieved on the scanner may deviate from the ideal case resulting in image artifacts in reconstruction. The typical solution to this problem is to measure the trajectories. This however, can potentially be a time consuming process. This work provides a simple, time efficient method to both characterize the MR scanner’s gradient system and provide a means for estimating the actual trajectories achieved on the scanner.

                  3069.     A Four Mirror-Current Planes Model for the Gradient Field Enhancement in a Permanent Magnet

Shinya Handa¹, Katsumi Kose¹, Tomoyuki Haishi²

¹Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibraki, Japan; ²MRTechnology Inc., Tsukuba, Ibraki, Japan

A four mirror-current planes model for the magnetic circuits on magnetic field gradients produced by planar gradient coils was developed and compared with the two mirror-current planes model. The gradient field distribution measured for a 0.3 T permanent magnet showed a good agreement with that calculated from the four mirror-current planes model. It was concluded that the four mirror-current planes model was better suited to explain the effects of magnetic circuits on magnetic field gradients produced by planar gradient coils.

                  3070.     EPI Imaging with a Dual Gradient System

K Craig Goodrich¹, Seong-Eun Kim¹, Sung Man Moon¹, J. Rock Hadley¹, J Ulrich Fontius², Franz Schmitt², Dennis L. Parker¹

¹U.C.A.I.R., Univ of Utah, SLC, UT, USA; ²Siemens Health Care AG, Erlangen, Germany

Given the experience and issues with reduced volume and switchable gradient systems, it is logical to consider the evaluation of insertable gradients that can operate simultaneously with the system body gradients. Local and whole-body gradients can be combined in such a manner as to exhibit the best advantages of both gradient systems. We have constructed an imaging system with dual gradients and amplifiers that can be operated simultaneously. Each gradient axis (X,Y,Z) can be dynamically chosen to operate in a combined mode or separately. In this work we demonstrate improvements to EPI imaging with such a system.

                  3071.     Overcoming Coil Phase Effects in Highly Accelerated Imaging with a Dedicated Fourth Gradient Channel

John Carl Bosshard¹, Mary Preston McDougall², Steven Michael Wright^1,2

¹Electrical and Computer Engineering, Texas A&M University, College Station, TX, USA; ²Biomedical Engineering, Texas A&M University, College Station, TX, USA

Wide field of view magnetic resonance microscopy using RF coils of similar dimension to the voxel sizes requires use of a “phase compensation” gradient to compensate for the phase pattern of each RF coil. However the necessary phase shift is dependent on the position of the voxel relative to the RF coil. A fourth gradient channel and gradient coil were implemented to create a y dependent x gradient, allowing simultaneous phase compensation over a range of distances from the RF coils, thus allowing the use of 3D imaging and dual or “sandwich” arrays.

                  3075.     Prediction of Susceptibility-Induced Artefacts for Prospective Motion Correction

Rainer Boegle¹, Julian Maclaren¹, Maxim Zaitsev¹

¹Dept. of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany

In prospective motion correction, orientation and position changes of the imaged object lead to susceptibility-induced image distortions. In real time imaging, like real-time fMRI it is not possible to acquire field maps of the object for each step in the time series. We therefore apply a method for rapidly calculating field inhomogeneities for an object with a known susceptibility distribution. The resulting field maps are compared to acquired field maps for a custom-made phantom and found to match well. This is an important step towards prediction and correction of susceptibility-induced image distortions in prospective motion correction.

                  3076.     Susceptibility-Matched ²H₂O NMR Probes for Magnetic Field Monitoring<

Pekka Sipilä^1,2, Sebastian Greding¹, Gerhard Wachutka², Florian Wiesinger¹

¹GE Global Research, Munich, Bavaria, Germany; ²Institute for Physics of Electrotechnology, Munich University of Technology, Munich, Germany

Cross-talk between magnetic field monitoring NMR probes and imaging elements during MRI scan is eliminated by using deuterium for the NMR probe samples. The probes are a part of an independent magnetic field monitoring tool-kit.

                  3077.     Can a Generalized Passive Shimming Array Improve Field Homogeneity for Human Brain Imaging at 7 T?

Dennis F R Heijtel^1,2, Peter van Gelderen¹, Jeff H. Duyn¹, Jacco A. de Zwart¹

¹Advanced MRI, LFMI, NINDS, National Institutes of Health, Bethesda, MD, USA; ²Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands

Static magnetic field homogeneities negatively affect image quality, in particular at high magnetic field strength. For human brain imaging, predominant sources of such inhomogeneities are the nasal cavity and ear canals. With the current technology, active shim coils cannot adequately compensate for these spatial field perturbations. We investigated the feasibility of generalized passive shimming based on a cylindrical array of ferrous particles, placed in between transmit and receive coil array, for improved field homogeneity in human brain imaging at 7 T. Results (n=34) show consistently improved field homogeneity, albeit limited (~12%), predominantly due to volunteer-to-volunteer variability.

                  3078.     Refocusing Method for Mapping Imaging Gradients with High SNR

Jason Peter Stockmann¹, Robert Todd Constable²

¹Biomedical Engineering, Yale University, New Haven, CT, USA; ²Diagnostic Radiology, Neurosurgery, and Biomedical Engineering, Yale University, New Haven, CT, USA

Field mapping is typically used to map B0 inhomogeneities but there are cases where it is desireable to map the imaging gradients themselves. This work introduces a modification to conventional field mapping to widen the range of gradient strengths over which reliable field maps may be obtained. Rather than apply a constant test field over the duration of each TR, the field is pulsed through dephasing and then rephrasing lobes so as to thereby avoid the signal loss at the time t = TE. This allows shim and imaging gradient coil performance to be calibrated at strengths for which conventional field mapping is rendered inaccurate by dephasing.

                  3079.     Whole Brain Field Homogenization with Localized Electrical Coils

Christoph Juchem¹, Terence W. Nixon¹, Mark Abildgaard¹, Scott McIntyre¹, Douglas L. Rothman¹, Robin A. de Graaf¹

¹Diagnostic Radiology, MRRC, Yale University School of Medicine, New Haven, CT, USA

Strong field distortions created by largely varying magnetic susceptibility conditions in the human head pose a major limitation in the study of brain areas like the prefrontal cortex as they hamper whole brain imaging and spectroscopy. The distortions are usually minimized by a set of low-order spherical harmonic shim functions. Based on field simulations, we show that largely improved whole brain shimming can be achieved with a set of 100 circular electrical coils placed directly around the head of the subject. Shim fields can be generated that exhibit a strength and complexity that by far exceeds the capabilities of the not problem-oriented, spherical harmonic functions.

                  3080.     Magnetic Field Homogenization of the Human Prefrontal Cortex with a Set of Localized Electrical Coils

Christoph Juchem¹, Terence W. Nixon¹, Scott McIntyre¹, Douglas L. Rothman¹, Robin A. de Graaf¹

¹Diagnostic Radiology, MRRC, Yale University School of Medicine, New Haven, CT, USA

Large differences in magnetic susceptibility result in strong and highly localized field distortions in the human prefrontal cortex, which cannot be addressed by low-order spherical harmonic shimming. A fixed configuration of external, electrical coils has been developed to provide a localized and high amplitude shim field in the prefrontal cortex with minimum impact on the rest of the brain. The experimental realization enabled us to strongly minimize signal dropout for gradient-echo images and settings typically used in fMRI.

                  3081.     First-To-Fourth Order Spherical Harmonics Shimming with a Grid of Circular Electrical Coils

Christoph Juchem¹, Douglas L. Rothman¹, Robin A. de Graaf¹

¹Diagnostic Radiology, MRRC, Yale University School of Medicine, New Haven, CT, USA

Magnetic field inhomogeneity is typically decomposed into low-order (n≤4) spherical harmonic functions. In order to compensate the inhomogeneity MR scanners have specialized built-in electrical coils, each of which can create one spherical harmonic field term. Here we propose the use of a grid of 100 local coils to generate spherical harmonic fields instead of one dedicated coil per term. Based on field simulations we show that by placing the coils around the head of the subject, strong first-to-fourth order spherical harmonic shim fields can be generated very flexibly.

                  3082.     Design of a High Power Customized Shim Set Insert for in Vivo Spectroscopy of Deep Brain Structures in Humans at 4T

Parisa Hudson¹, L. Martyn Klassen², William Bradfield Handler¹, Blaine Alexander Chronik¹

¹Department of Physics and Astronomy, The University of Western Ontario, London, Ontario, Canada; ²Robarts Research Institute, London, Ontario, Canada

One of the major challenges in very high-field magnetic resonance spectroscopy is the detection and characterization of the hippocampi deep inside the medial temporal lobes. The demands placed on the resistive shim systems by this application are beyond the capability of existing whole-body shim coil systems. We are investigating the development of an extremely high performance, high order, short, insertable shim set specifically designed for the medial temporal lobes of the human brain. A first goal is to determine how much improvement could possibly be achieved using such a shim set

                  3083.     Shielding Requirements for a Complete 3^rd Order Shim Set for a 31cm Bore 9.4T System

Dustin Wesley Haw¹, Blaine Alexander Chronik²

¹Physics and Astronomy, University of Western Ontario, London , Ontario, Canada; ²Physics and Astronomy, University of Western Ontario, London, Ontario, Canada

Our goal is to develop and optimize high-strength, dynamic shim systems. It is clear that dynamic shim systems will need to be actively shielded. We investigate the performance of shielded shim coils as a function of shim order in a complete 3rd order shim set. The efficiency of unshielded shims is better than that of shielded shim, as expected. However, the difference decreases considerably with increasing shim order. This suggests that there is more freedom with higher order shields than lower orders.

                 3084.     An Experimental Study of the Feasibility of Simultaneous MRI and Spect Imaging

Mark J. Hamamura¹, Seung Hoon Ha¹, Werner W. Roeck¹, Orhan Nalcioglu¹, Douglass J. Wagenaar², Dirk Meier², Bradley E. Patt²

¹Center for Functional Onco-Imaging, University of California, Irvine, CA, USA; ²Gamma Medica-Ideas, Inc., Northridge, CA, USA

We experimentally demonstrate the feasibility of operating a SPECT system inside a 4T MR system for simultaneous data acquisition. In the present study we investi-gated the mutual interference of MR and SPECT during simultaneous data acquisition and shown that the system presented here is capable of acquiring spatially and temporally co-registered images by both modalities without any artifacts. It is our belief that the availability of such system will open up new opportunities in molecular imaging that can also be translated to humans by scaling up the current design appropriately.

                  3085.     Effective RF Shielding with Carbon Fiber Composites for Simultaneous PET/MRI

Bo Joseph Peng¹, Yibao Wu¹, Simon R. Cherry¹, Jeffrey Walton²

¹Department of Biomedical Engineering, University of California, Davis, Davis, CA, USA; ²NMR Facility, University of California, Davis, Davis, CA, USA

We have investigated carbon fiber composites as a RF shielding material for simultaneous PET and MR imaging. In this abstract we outline the results of initial investigations of the shielding effectiveness of this material and compare it with more traditional copper shielding.

                  3086.     Multifunctional PET/MR Imaging in Small Animal Models

Hans F. Wehrl¹, Martin S. Judenhofer¹, Petros Martirosian², Florian Maier¹, Gerald Reischl³, Fritz Schick², Bernd J. Pichler¹

¹Laboratory for Preclinical Imaging of the Werner Siemens-Foundation, Department of Radiology, University of Tuebingen, Tuebingen, BW, Germany; ²Section on Experimental Radiology, Department of Radiology, University of Tuebingen, Tuebingen, BW, Germany; ³Radiopharmacy and PET-Center, Department of Radiology, University of Tuebingen, Tuebingen, BW, Germany

Simultaneous, small animal PET/MR imaging has a great potential in preclinical research. Differences between MR contrast agent enhancement and PET uptake were observed in a brain tumor mouse model. The influence of a Choline-PET tracer on MR spectroscopy was evaluated. Simultaneous [¹⁵O]Water PET and ASL-MR perfusion measurements were performed and compared.

                  3087.     Investigation of Detector Collimator Effects for Dual Modality MR -Nuclear Imaging

Seung Hoon Ha¹, Mark J. Hamamura¹, Werner W. Roeck¹, Orhan Nalcioglu¹, Douglass J. Wagenaar², Dirk Meier², Bradley E. Patt²

¹Center for Functional Onco-Imaging, University of California, Irvine, CA, USA; ²Gamma Medica-Ideas, Inc., Northridge, CA, USA

The effect of nuclear collimators made of lead (Pb) on MR imaging was investigated using a dedicated dual modality RF coil built for small animal imaging. The intro-duction of the collimator affected both the SNR as well as MR image uniformity. The signal non-uniformity was reduced considerably by the introduction of additional lead shielding around the object at the expense of reducing the image SNR. In spite of this minor shortcoming the effect of Pb collimator on the MR image was reduced considerably that should make it useful for dual modality MR – nuclear imaging such as MR - SPECT and MR - PET. Additionally since the imaging time for nuclear images is much longer than MRI one can easily increase the number of averages in the MRI to overcome this problem.

                  3088.     A Stationary SPECT System for Simultaneous MRI/SPECT Dual-Modality Pre-Clinical Imaging

Douglas Jay Wagenaar¹, Dirk Meier¹, Orhan Nalciolgu², L. Tugan Muftuler², Yuchuan Wang³, Benjamin Ming-Wa Tsui³, Bradley Earl Patt¹

¹Research, Gamma Medica-Ideas, Inc., Northridge, CA, USA; ²Tu & Yuen Center for Functional Onco-Imaging, University of California, Irvine, Irvine, CA, USA; ³Radiology, Johns Hopkins Medical Center, Baltimore, MD, USA

A portable and stationary SPECT system has been engineered to operate simultaneously within the 12.0 cm diameter bore of high-field, pre-clinical MRI imaging systems. For decades the photomultiplier tubes used in nuclear medicine precluded such a system. The use of pixellated semiconductor CZT as the detection material allows gamma-ray imaging in the high-field setting. This mouse-only apparatus is capable of producing dynamic SPECT with 1.5 mm FWHM spatial resolution and high sensitivity. Multimodality imaging is established in pre-clinical research and we present first images of phan-toms and laboratory animals of this SPECT/MRI instrument.

                  3089.     Design of a Docking PET and Field-Cycled MRI System for Small Animal Imaging

Geron Andre Bindseil¹, Timothy J. Scholl¹, William B. Handler¹, Blaine A. Chronik¹

¹Department of Physics and Astronomy, The University of Western Ontario, London, Ontario, Canada

There is great interest in combining functional and anatomical imaging systems. Current approaches to PET/MRI typically a) change PET to make it compatible with conventional MRI, or b) change MRI to make it compatible with conventional PET. An approach of the latter kind is investigated and the design of a docking PET/Field-Cycled MRI (FCMRI) system using the Siemens Inveon small-animal PET is proposed. Advantages of PET/FCMRI over other PET/MRI approaches for small-animal preclinical imaging are explored.

                  3090.     MRI Attenuated Whole Body PET Reconstruction: An in Vivo Study Using Animal Subjects

Jeffrey Steinberg¹, Guang Jia², Steffen Sammet², Jun Zhang², Nathan Hall², Michael V. Knopp²

¹Department of Radiology, Duke University, Durham, NC, USA; ²Department of Radiology, The Ohio State University, Columbus, OH, USA

In this paper we compared MRI-based attenuation correction methods for MRI/PET hybrid scanners to CT attenuated PET images acquired in a PET/CT scanner. The MRI-based attenuation maps were acquired by segmentation of the MRI into regions of air, lung, tissue, and bone. These segmented maps were assigned the corresponding attenuation values and were used for reconstruction. The resulting PET images were nearly identical to the CT attenuated PET images, indicating that using an approximation yields acceptable results for most clinical purposes.

                  3091.     Precise Co-Registration of SPECT and MRI for Small Animal Imaging Using a Common Animal Bed with External References: A Feasibility Study

Masayuki Yamaguchi¹, Hirofumi Fujii¹, Kazumasa Inoue¹, Ryutaro Nakagami^1,2, Koutaro Tani^1,2, Izumi Ogihara Umeda¹, Yasuko Mutou¹, Akira Nabetani³, Akira Hirayama^1,3, Atsushi Nozaki³

¹Functional Imaging Division, National Cancer Center Hospital East, Kashiwa, Chiba, Japan; ²Faculty of Health Sciences, Tokyo Metropolitan University, Arakawa, Tokyo, Japan; ³GE Yokogawa Medhical Systems, Ltd., Hino, Tokyo, Japan

A software-based post-processing technique in SPECT and MRI fusion was explored for small animal imaging. The latest animal SPECT scanner equipped with multi-pinhole collimators provides unique information about neuroreceptors in the brain and phagocytotic activity in sentinel lymph nodes (SLN) of mice. We obtained ¹²³I IMZ or ^99mTc SPCET and high-resolution MRI for the mouse brain and SLN, respectively, using separate scanners with a dedicated common animal bed and external references, and successfully co-registered these images using post-processing software. This technique may aid in the simultaneous evaluation of functional and anatomical aspects of small animal organs in vivo.

                  3092.     Development and Evaluation of a Dedicated Setup for Co-Registered PET/MRI Abdominal Imaging of the Mouse

Carole Lartizien¹, Laurence Canaple², Olivier Beuf³

¹Université de Lyon, CREATIS-LRMN, CNRS UMR 5220; Inserm U630; INSA-Lyon; Université Lyon 1, Villeurbanne, France; ²Institut de Génomique Fonctionnelle de Lyon, CNRS UMR 5241, ENS-Lyon, Lyon, France; ³Université de Lyon, CREATIS-LRMN , CNRS UMR 5220; Inserm U630; INSA-Lyon; Université Lyon 1, Villeurbanne, France

One of the main challenges to fully exploit the combination of PET with MRI is to achieve good co-registration between both modalities. A dedicated setup and co-registrated PET/MRI processing for abdominal images of the mouse acquired on two independent imaging systems (Bruker Biospec 7T and Raytest ClearPET) and based on external fiduciary markers was assessed. A mouse holder for both imaging systems was equipped with three non parallel fiduciary tubes. Different co-registration methods were evaluated on phantom experiments, based on rigid and non-rigid transformations and a semi-automated method using the external fiduciary markers. The semi-automated method and the non-rigid transform allowed the best co-registration. The protocol was then used on mouse models of digestive tumors. Visual analysis of the PET images of a mouse model developing spontaneous intestinal tumors, allowed in 2 out of the 3 mice, to localize tumors that were not seen on the MR images.

                  3093.     Mobile MR: A Battery Driven Broadband MRI System for Portable Magnets Up to 3T

Michael Ledwig¹, Toni Michael Drießle², Stefan Wintzheimer¹, Daniel Gensler², Peter Michael Jakob^1,2, Florian Fidler¹

¹MRB, Research Center Magnetic-Resonance-Bavaria, Würzburg, Germany; ²Dept. of Experimental Physics 5, University of Würzburg, Würzburg, Germany

Purpose of this work was to develop a fully digital mobile MRI system with state of the art broadband high speed electronics. The system is battery driven and can run virtually any user defined pulse sequence as well as standard methods. Furthermore the same system can also be used to upgrade older stationary MR scanners to fully digital driven imaging systems.

                  3094.     System for Optimal Stress During Clinical Cardiac MRS

Hee-Won Kim¹, Karam Souibri², Gerald M. Pohost^1,3

¹Radiology, University of Southern California, Los Angeles, CA, USA; ²Medicine, University of Southern California, USA; ³Medicine, Loma Linda University, Loma Linda, CA, USA

An automatic handgrip stress control system was developed in order to obtain improved precision of the phosphate metabolic alterations during the cardiac stress MRS at 3T. The load-cell/strain-gauge provided the stress signals. By feed-forward or feedback control, the error signals have actuated audio-visual stimulation to the subject. It was clearly demonstrated that the stress level is far more stable during the entire session with the control system so that more accurate measurement of the metabolite changes during moderate stress is available. The spectral resolution was also improved by proactively sustained control during stress 31P MRS.

                  3095.     A Novel Design for a 1 Tesla Magnet for Mobile MR

Michael Ledwig¹, Florian Fidler¹, Toni Drießle², Stefan Wintzheimer¹, Daniel Gensler³, Peter Michael Jakob^1,2

¹MRB, Research Center Magnetic-Resonance-Bavaria, Würzburg, Germany; ²Dept. of Experimental Physics 5, University of Würzburg, Würzburg, Germany; ³Dept.  of Experimental Physics 5, University of Würzburg, Würzburg, Germany

Purpose of this work was to develop a lightweight magnet with a large field of view and a high field strength. The resulting new permanent magnet design has a field strength of 1T while offering a 4cm bore. The weight of the magnet is 15kg.

                  3096.     Development of a Compact MRI System for a Low Temperature (-5 Degree) Room

Satoru Adachi¹, Toshihiro Ozeki², Shinya Handa¹, Ryosuke Shigeki¹, Katsumi Kose¹, Tomoyuki Haishi³

¹Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki, Japan; ²Sapporo, Hokkaido University of Education, Sapporo, Hokkaido, Japan; ³MRTechnology, Tsukuba, Ibaraki, Japan

A compact MRI system for a low temperature (-5 degree) room was developed for several useful applications. The magnet, 2nd order shim coil set, and gradient probe were installed in the low temperature (LT) room and the MRI console was installed in a usual temperature operation room next to the LT room. The control lines for transmitter, receiver, and gradient coils were connected through a hole opened in the wall between the LT room and the operation room. Magnetic field inhomogeneity measured using a geometric phantom showed an increase of inhomogeneity with decreasing temperature. However, it was concluded that this system can be used even at -5 degree using the 2nd order shim-coil set.

                  3097.     Development of a Shield-Room Free Compact MRI System with a Highly Homogeneous RF Coil for Bone Density Measurements at the Calcaneus

Kazuya Taniguchi¹, Shinya Handa¹, Katsumi Kose¹

¹Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki, Japan

A local RF shield and an RF coil with a highly homogeneous RF magnetic field were developed to reduce the installation space and the measurement time in a compact MRI system for measurements of trabecular bone volume fraction (TBVF) in the calcaneus. To achieve a homogeneous RF magnetic field, the coil wire distribution of the oval solenoid was optimized using a genetic algorithm. The homogeneous RF magnetic field enabled a multiple spin-echo sequence, which achieved 50% measurement time reduction with a 30% CV (coefficient of variance) reduction.

                  3098.     RF and Gradient Coils for an Elliptical Surface NMR Device

manola Ciarrocchi¹, angelo Galante¹, piero Sebastiani², maria Alfonsetti¹, marcello Alecci¹, antonello Sotgiu¹

¹Dipartimento Scienze della Salute, University of L'Aquila, L'Aquila, Italy; ²ITA srl, L'Aquila, Italy

Mobile unilateral magnets have been developed in the past ten years to investigate samples that cannot be moved or do not fit within the bore of traditional MRI scanners. We have designed a novel device based on an elliptical magnet with a large free space at the centre of the magnet to host the entire coil system and, eventually, other sensor for multimodal studies. The magnet generates a magnetic field parallel to its surface and has been optimized to have a highly homogeneous B0 along the ellipse major axis to allow 1D imaging along such direction. The maximum field intensity B0=124 mT is reached at 7 mm distance from the surface magnet. We present a complete coils system, receiver rf and gradient coil.

                  3099.     Numerical Evaluation of Induced Field by Body-Motion Around High Field MRI Magnets: A Case Study with an Implanted Pacemaker

Hua Wang¹, Feng Liu¹, Bing Keong Li¹, Adnan Trakic¹, Stuart Crozier¹

¹The University of Queensland, Brisbane, QLD, Australia

In MRI, patients and occupational workers can be exposed to strong gradients of the static magnetic fields. Body motion through these static field gradients can produce substantial currents within tissue. Numerical evaluations of induced fields in a tissue-equivalent model with/without an implanted pacemaker model are presented to improve our understanding of the interactions. Lorenz forces were computed based on the induced electric current and charge. The methodology presented in this work can be extrapolated to high static field strengths to evaluate motion effect for a variety of body orientations, velocities and implanted devices.

                  3100.     Impedance Method for Calculation of Induced Voltage on Implanted Cardiac Leads Due to MRI Gradient Magnetic Fields

Jonathan Edmonson¹, Rungkiet Kamondetdacha², John Nyenhuis², Ben Herberg¹, Dave Manahan¹

¹CRDM, Medtronic, Inc., Mounds View, MN, USA; ²School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, USA

An impedance method has been implemented to simulate the induced electric field within a patient due to the MRI gradient magnetic fields. The electric field is used to calculate the induced voltage along an implantable cardiac lead path for the purpose of evaluating the risk of unintended cardiac stimulation of patients with an implantable pacemaker or defibrillator undergoing an MR scan. The impedance method results are compared to measured results collected within a phantom to validate the method.

                  3101.     Average SAR Constrained Local RF Shimming

Yigitcan Eryaman¹, Celal Alp Tunc¹, Pierre Francois van de Moortele², Kamil Ugurbil², Ergin Atalar¹

¹Electrical Engineering, Bilkent University, Ankara, Turkey; ²Medical School-Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, USA

In this study particle swarm optimization method is used to solve an average SAR constrained local RF shimming problem. Flatness ratio in a region of interest is minimized while satisfying given average SAR constraints. The results are verified by phantom simulations of a 16 channel transmit coil array at 7 T.

                  3102.     Numerical Investigation Into Effects of a Receive Array on SAR in MRI

Zhangwei Wang¹, Jason Jin¹, Christopher M. Collins², Shuren Zhao¹, Sukhoon Oh², Qing X. Yang², Fraser J. Robb¹

¹GE Healthcare Coils, Aurora, OH, USA; ²Department of Radiology, College of Medicine, The Pennsylvania State University, Hershey, PA, USA

Although it is common clinical practice to transmit with a large body coil and receive with an array, very few investigations have examined the effect of the receive array on SAR. Here we present numerical calculations showing approximately 10% different in local and whole-body SAR due to the presence of a receive array

                  3103.     MR Safety of Implants: Numerical Assessment of SAR Distribution at Design-Simplified Stents of Different Lengths Placed Inside a Virtual Phantom Model Investigated at an MR Frequency of 63.9 MHz

Mark Pawlenka¹, Gregor Schaefers²

¹MR:comp GmbH, Gelsenkirchen, Germany; ²MR.comp GmbH, Gelsenkirchen, Germany

In respect of imaging quality and patient safety, temperature rises and SAR distributions, which are caused by interaction of the applied electromagnetic fields during MR exams, are of high interest for implants in MR tomography. High local SAR values are equivalent to high local temperature increases. For developing support for radio frequency (RF) induced heating experiments, SAR values were virtually investigated at design-simplified stents with different lengths inside a virtual human torso shaped phantom model

                  3104.     Comparative Analyses of MR-Induced Distal Heating in Novel Filtered Cardiac Pacing Leads Using Two Geometric Configurations

Frank G. Shellock^1,2, Holly Moschiano², Robert S. Johnson², Robert Stevenson², Scott Brainard³, Sam Ye³, Warren Dabney²

¹Shellock R&D Services, Los Angeles, CA, USA; ²Cardiac & Neurology, Greatbatch, Inc., Clarence, NY, USA; ³Cardiac & Neurology, Greatbatch, Inc., Plymouth, MN, USA

MRI related heating may be excessive for lead systems, as in those used for cardiac rhythm management. The heating on a 46-cm control lead and a Band Stop Filter lead were evaluated in a 1.5T MR unit at different positions and geometries in the bore. As the control and Band Stop Filter leads were moved closer to the center of the MR system bore, the heating that occurred at the distal lead tip decreased significantly. The Band Stop Filter lead exhibited a notable temperature decrease in all bore and geometry configurations compared to the control lead.

                  3105.     Changes in RF Transmit Gain Before and After DBS Lead Placement in 36 Consecutive Patients

Matt A. Bernstein¹, Heidi A. Ward¹, Kiaran P. McGee¹, Joel P. Felmlee¹, Vicki L. Knudsen¹, Krzysztof R. Gorny¹, John Huston III¹, Kendall H. Lee¹

¹Mayo Clinic, Rochester, MN, USA

The RF power level, as measured by auto-prescan during 1.5T MRI scanning with a transmit/receive head coil was recorded for 36 consecutive patients before and after placement of one (n = 8) or two (n = 28) deep brain stimulator leads (DBS). The average change in power level was 0.111 +/- 4.65 counts, as measured in units of 1/10 dB. In these units, 30 counts represent a factor two in power. These data suggest that placement of DBS leads does not significantly affect the RF power calibration.

                  3106.     Safety Testing of Performing MRI Scans with Implanted Soletra Pulse Generator at 3 Tesla

Pallab K. Bhattacharyya¹, Ken Baker², Micheal Phillips¹, Mark Lowe¹

¹Imaging Institute, Cleveland Clinic, Cleveland, OH, USA; ²Neurosciences, Cleveland Clinic, Cleveland, OH, USA

We have performed safety testing of running MR scans with active Soletra 7426 implantable pulse generator (IPG) at 3 telsa. Performing anatomical and functional MRI scans using a 3 tesla whole body Siemens Total Imaging Matrix Trio system with a circularly polarized transmit/receive head coil of a gel phantom with the IPG placed in the gel with a pair of 3387-40 leads, we did not measure any significant heating at any lead contacts or the IPG case. The temperature measurement was done using fluro-optic cables, and the ON/OFF state of the IPG was constantly monitored externally by voltage measurement.

                  3107.     Comparison of Targeting Accuracy with Conventional and MR Guided Deep Brain Stimulator Implantation

Alastair Martin¹, Paul Larson², Philip Starr²

¹Radiology, University of California - San Francisco, San Francisco, CA, USA; ²Neurosurgery, University of California - San Francisco, San Francisco, CA, USA

We compare the targeting accuracy of conventional stereotactic methods to MR guided methods for implanting deep brain stimulator electrodes. MR guidance is found to produce statistically superior accuracy, as determined by the difference between the intended versus actual electrode tip location, in all directions other than depth, which was not significant. For MR guided procedures a correlation was found between higher trajectory angle in the coronal plane and greater lateral offsets. There were otherwise no statistically significant correlations between potential predictors of accuracy and measured outcomes.

                  3108.     Practical Aspects of MR Imaging in the Presence of Conductive Guide Wires

Natalie Tong¹, Andriy Shmatukha², Peter Asmah³, Jeff Stainsby²

¹McMaster University, Hamilton, Ontario, Canada; ²Applied Science Laboratory, GE Healthcare, Toronto, Ontario, Canada; ³General Electric Healthcare, Toronto, Ontario, Canada

Various aspects of RF-induced heating of guide wires during their MRI guidance have been investigated in the past. However, the previous works focused on worst-case tip heating in either fully-immersed or tip-immersed (and otherwise free) guide wires of unpractical lengths. This study simulates real clinical conditions. A product guide wire and a same-length conductive wire were partially inserted into a torso-size phantom. Significant heating occurred at the insertion point, independent of tip heating, with a strong correlation to excitation frequency dependent imaging parameters. Heat transfer through the wire was demonstrated to be a safety concern.

                  3109.     Current Challenges for Creating a Wireless MR-Compatible Intracranial Pressure Monitor

Sukhoon Oh¹, Usmah Kawoos², Mohammad-Reza Tofighi³, Arye Rosen², Christopher M. Collins¹

¹Radiology, The Pennsylvania State University, Hershey, PA, USA; ²School of Biomedical Engineering, Drexel University, Philadelphia, PA, USA; ³Electrical Engineering, The Pennsylvania State University, Middletown, PA, USA

In this study, newly developed wireless intracranial pressure (ICP) monitoring devices were evaluated under MR imaging conditions at 3.0T. Significant image distortions were observed near the devices due to magnetic susceptibility effects. Temperature changes near the ICP devices, during MR scanning (with 16.65W of RF power), were directly measured using fiber optic thermal sensors. Of three devices, a smaller ICP device with titanium casing showed the lowest temperature change. Future ICP device developments will focus on minimizing image distortions and ensuring proper function and safety with the active device.

                  3110.     The Clinical Impact of 1.5T MRI in Patients with a Permanently Implanted Pacemaker: A Necessary Procedure for Indicated Cases.

Gary Michael Miller¹, Norbert G. Campeau¹, Win-Kuang Shen², Joel P. Felmlee¹, Robert E. Watson¹

¹Diagnostic Radiology, Mayo Clinic, Rochester, MN, USA; ²Cardiovascular Diseases, Mayo Clinic, Rochester, MN, USA

We reviewed all 1.5T MRI examinations performed in non-pacemaker dependent patients with implanted pacemakers to determine the clinical impact. Requests were screened by neuroradiology and patients were evaluated by cardiology. Nineteen 1.5 Tesla MRI examinations of the head and/or spine were performed on 15 patients. Neuroradiology, cardiology and radiology physics staff were present during scanning for monitoring. A variety of pathologic conditions were identified. In over half of the patients the diagnosis could only be obtained by MRI, with a diagnosis not made on alternate modalities. Continued development of safe MRI protocols is warranted.

                  3111.     Evaluation of the Forces Acting on a Highly Ferromagnetic Orthopaedic Implant at 1.5T and 3T

Christie McComb¹, Barrie Condon¹, David Allan²

¹Department of Clinical Physics, Institute of Neurological Sciences, Southern General Hospital, Glasgow, UK; ²Queen Elizabeth National Spinal Injuries Unit, Southern General Hospital, Glasgow, UK

The purpose of this study was to assess the translational and rotational forces acting on an orthopaedic implant called the Posterior Fixator in 1.5T and 3T MRI systems. The forces were measured using existing methods, and assessed using guidelines produced by the ASTM. The results showed that the forces acting on the constituent components of the implant were substantial and, based on the ASTM guidelines, would be considered unsafe in both MR systems. However, when the rigid fixation of the implant in bone and the counterbalancing effect of the configuration of the assembled implant are taken into account, the forces are considered unlikely to result in implant migration or rotation.

                  3112.     Dedicated MR ECG Amplifier

Lingchuan Zhou¹, Mohsen Ayachi², Julien Oster^3,4, Roger Abächerli¹, Odille Fokapu⁵, Michel Kraemer⁶, Johann-Jakob Schmid¹, Jean-Philippe Blondé², Jacques Felblinger^3,4

¹Schiller AG, Baar, Switzerland; ²InESS UMR 7163, University of Strasbourg / CNRS, Strasbourg, France; ³U947, Inserm, Nancy, France; ⁴IADI, Nancy-Université, Nancy, France; ⁵UMR 6600, UTC/CNRS, Compiègne, France; ⁶Schiller Médical, Wissembourg, France

Electrocardiogram (ECG) acquisition is difficult in an MRI environment. We have developed the first MR dedicated ECG amplifier in microelectronic technology to perform safe and accurate ECG acquisition. The chip size was 3.8x2.9 mm² for 2 leads. No artefact is visible due to the ECG chip. Better sensitivity of QRS detection was observed than with standard ECG sensors. This technological step allows obtaining a non magnetic and very small ECG amplifier that could be placed in the field of view. Higher bandwidth is thus possible, which reduces the delay and allows a more precise synchronization.

                  3113.     The Effect of Longitudinal Magnetic Resonance Imaging on the Quality of Neurophysiological Recordings Using Implanted Micro-Wire Electrodes.

Kunal Paralikar¹, Thomas Neuberger², Joy Matsui¹, Alistair Barber³, Ryan Clement¹, Andrew Webb^1,4

¹Bioengineering, Penn State University, University Park, PA, USA; ²Huck Institute, Penn State University, USA; ³Opthalmology, Penn State University; ⁴Radiology, Leiden University Medical Center, Leiden, Netherlands

The purpose of this paper was to investigate: (1) the feasibility of carrying out longitudinal MRI studies in animals with implanted micro-wire electrodes adapted for MRI compatibility, (2) the effect of MRI studies on the quality of neurophysiological recordings, and (3) the use of MRI to study the extent and recovery of tissue damage due to electrode insertion. There was no evidence of short-term or chronic neural damage caused by repeated MRI, nor any statistical difference in the quality of the electrophysiological recordings between animals that had undergone MRI scans and those that had not.