Ralph Kimmlingen¹, Eva Eberlein¹, Peter Dietz¹, Sabrina Kreher¹, Johann Schuster¹, Jörg Riegler¹, Volker Matschl¹, Volker Schnetter¹, Andreas Schmidt¹, Helmut Lenz¹, Ernst Mustafa¹, Daniel Fischer¹, Andreas Potthast¹, Ludwig Kreischer ¹, Michael Eberler¹, Franz Hebrank¹, Herbert Thein¹, Keith Heberlein¹, Philipp Hoecht¹, Thomas Witzel², Dylan Tisdall², Junqian Xu³, Essa Yacoub³, Gregor Adriany³, Edward Auerbach³, Steen Moeller³, David Feinberg⁴, Dietmar Lehne¹, Lawrence L. Wald^2,5, Bruce Rosen^2,5, Kamil Ugurbil³, David van Essen⁶, Van Wedeen², and Franz Schmitt^1
1Siemens Healthcare, Erlangen, Germany, ²Martinos Center for Biomedical Imaging, Dept. of Radiology, Massachusetts General Hospital, Boston, United States, ³Center for Magnetic Resonance Research, University Minnesota, Minneapolis, United States, ⁴Helen Wills Inst. of Neurosc., UC Berkeley, CA, United States, ⁵Harvard-MIT Division of Health Sciences Technology, Cambridge, United States, ⁶Dept. of Anatomy and Neurobiology, Washington U, St. Louis, United States

 

Peter T. While¹, Michael Poole², Larry K. Forbes¹, and Stuart Crozier^2
1School of Mathematics and Physics, University of Tasmania, Hobart, Tasmania, Australia, ²School of Information Technology and Electrical Engineering, University of Queensland, Brisbane, Queensland, Australia

The problem of gradient heating is addressed using a method reported elsewhere for designing gradient coils with minimum maximum temperature. The behaviour of four prototype coils is analyzed through experiment and compared to a minimum power coil and another coil designed with minimum maximum current density. Each minimaxT coil is designed to perform optimally for a specific set of thermal parameters. A thermal imaging camera is used to record temperature data for all coils at thermal equilibrium. Results show that with reasonable estimates of coil parameters the minimaxT method generates coils with improved thermal performance and considerably lower maximum temperature.

Sebastian Littin¹, Daniel Gallichan¹, Anna Masako Welz¹, Andrew Dewdney², Feng Jia³, Chris Cocosco¹, Jürgen Hennig¹, and Maxim Zaitsev^1
1Dept. of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany, ²Siemens Healthcare, Erlangen, Germany, ³Freiburg Institute for Advanced Studies (FRIAS), University Freiburg, Freiburg, Germany

Here we present the design and show the process of building a high performance nonlinear monoplanar PatLoc gradient system (FlatLoc). This hand build system is dedicated for imaging the heart, abdomen and pelvis and was successfully implemented in our 3T whole-body scanner and first images were acquired.

Chad Tyler Harris¹, William B Handler¹, and Blaine A Chronik^1,2
1Physics and Astronomy, University of Western Ontario, London, Ontario, Canada, ²Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada

In this work we present a practical design of a high-powered, actively-shielded, small-animal, variable-field MR system capable to temporally pulse magnetic fields up to +/- 1.0 T, yet with sufficient homogeneity for signal detection for fields up to 0.25 T. This system could be used as a high-power insert system withing superconducting magnets for dreMR imaging, or as a stand-alone prepolarized/low-field small-animal MRI system.

Benjamin Emanuel Dietrich¹, David Otto Brunner¹, Christoph Barmet¹, Bertram Jakob Wilm¹, and Klaas Paul Pruessmann^1
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

Magnetic field monitoring with NMR probes enables the observation of the spatio-temporal field evolution during MR experiments. This work presents a method that allows a comprehensive measurement of all the externally induced magnetic fields relevant for the spin dynamics in the system.

Veneta Tountcheva¹, Boris Keil¹, Thomas Witzel¹, Dylan Tisdall¹, Philipp Hoecht², and Lawrence L. Wald^1,3
1A.A. Martinos Center for Biomedical Imaging, MGH, Harvard Medical School, Radiology, Charlsetown, MA, United States, ²Siemens Medical Solutions USA Inc., Charlsetown, MA, United States, ³Harvard-MIT, Div. of Health Science and Technology, Cambridge, MA, United States

64ch receive-only field camera has been built to study the spatial and temporal evolution of the magnetic field in the presence of eddy currents and gradient trajectories. The field camera consists of 64 small solenoids in a 4 x 4 x 4 grid, each with a small (0.9mm diameter) water sample in a capillary plugged with susceptibility matched material. The camera was validated with field maps acquired after inducing eddy currents on the x-, y-, z-gradients at different time delays. The eddy currents frequency offsets have been mapped out as a function of position and time delay for each x-, y-, z-gradients allowing determination of the eddy current gradients and gradient cross term’s time constants and amplitudes for either pre-emphasis adjustment or inclusion in image reconstruction methods.

Y. Dürst¹, B. J. Wilm¹, B. E. Dietrich¹, S. J. Vannesjö¹, and K. P. Pruessmann^1
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

Field changes stemming from various sources such as temperature drifts, physiological motion, or any other external effects can severely degrade results of MRI/MRS experiments. We implemented a real-time feedback system where NMR field probes are employed to measure magnetic field variations and actively compensate field changes using the shim coils of a whole-body. Successful field stabilization has been achieved in three experimental situations of varying effect strength, update rate, and spatial order of the field control.

Hans F Wehrl¹, Konrad Lankes^1,2, Mosaddek Hossain¹, Ilja Bezrukov^1,3, Chih-Chieh Liu¹, Petros Martirosian⁴, Gerald Reischl¹, Fritz Schick⁴, and Bernd J Pichler^1
1Department for Preclinical Imaging and Radiopharmacy, University of Tuebingen, Tuebingen, Germany, ²Bruker BioSpin MRI, Ettlingen, Germany, ³Max Planck Institute for Intelligent Systems, Tuebingen, Germany, ⁴Section on Experimental Radiology, University of Tuebingen, Tuebingen, Germany

A new small animal PET/MR system is presented with a performance comparable to stand alone commercial solutions. A detailed evaluation of the mutual interference as well as the PET and MR characteristics is given. Additional in vivo imaging data shows the huge potential of simultaneous PET/MR.

Lisa Bauer¹, Michael Twieg², Matthew Riffe³, Yong Wu¹, Robert Brown¹, and Mark Griswold^1,4
1Department of Physics, Case Western Reserve University, Cleveland, Ohio, United States, ²Department of Electrical Engineering and Computer Science, Case Western Reserve University, Cleveland, Ohio, United States, ³Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States,⁴Department of Radiology, Case Western Reserve University, Cleveland, Ohio, United States

Magnetic Particle Imaging (MPI) is a new imaging method that relies on the harmonic response of magnetic nanoparticles to external, oscillating magnetic fields. The emergence of MPI has placed an emphasis on the ability to detect, characterize and distinguish magnetic nanoparticles in different environments, but conventional bore-type spectrometers limit the physical dimensions of nanoparticle sample holders and the environment in which the samples can be measured. This compact, single-sided spectrometer provides an alternative to conventional spectrometers, allowing nanoparticle detection from arbitrary sample holders.

Jonathan C Sharp¹, Qunli Deng¹, Vyacheslav Volotovskyy², Randy Tyson¹, Donghui Yin², Richard Bernhardt², Scott King², and Boguslaw Tomanek^1
1Institute of Biodiagnostics (West), National Research Council of Canada, Calgary, Alberta, Canada, ²Institute of Biodiagnostics, National Research Council of Canada, Winnipeg, Manitoba, Canada

TRASE is an MRI acquisition method which traverses k-space using refocusing pulses applied with phase-gradient RF transmit fields. Only a single transmit channel is used, and the switched-B0 gradient system is not required. TRASE in vivo images were collected at 0.2T using a novel RF transmitter coil array, capable of producing 2-axis encoding. TRASE-encoding was used in-plane (2D), with B0-phase encoding (1D) to encode orthogonally. We collected the first in vivo TRASE images (of wrist and knee). The results are encouraging and a step towards the development of a low-cost MR imaging technology.