Gradients, Shims & Novel Systems
Tuesday 4 May 2010
Room A6 10:30-12:30 Moderators: Labros S. Petropoulos and Michael S. Poole

10:30 216

Concurrent Higher-Order Field Monitoring for Routine Head MRI: An Integrated Heteronuclear Setup - not available
Christoph Barmet1, Bertram Jakob Wilm1, Matteo Pavan1, Georgios Katsikatsos1, Jochen Keupp2, Giel Mens3, Klaas Paul Pruessmann1
Institute for Biomedical Engineering, ETH and University, Zurich, Switzerland; 2Philips Research Europe, Hamburg, Germany; 3Philips Healthcare, Best, Netherlands

A higher-order concurrent field monitoring setup is introduced for routine head MRI. It enables the tracking of dynamic field evolution up to 3rd order concurrently with data acquisition. This is particularly important for non-reproducible field contributions, e.g. due to magnet heating, breathing or external fields. The field information allows for the correction of image artifacts at the reconstruction stage.

A heteronuclear approach – monitoring is performed on the 19F nucleus – guarantees perfect separation of monitoring and imaging experiment. As a result, scan protocols and procedures can remain unchanged, which greatly simplifies translation into clinical practice.

10:42 217. 

Coherent Excitation Scheme to Operate Pulsed NMR Probes for Real-Time Magnetic Field Monitoring
Pekka Sipilä1,2, Gerhard Wachutka2, Florian Wiesinger1
GE Global Research, Munich, Bavaria, Germany; 2Institute for Physics of Electrotechnology, Munich University of Technology, Munich, Bavaria, Germany

Description of an apparatus for improving image quality during MRI-scan by measuring the magnetic fields with pulsed NMR probes. Closely interleaved excitation pulses, of which phase is in coherence with the precessing spins, offer high SNR also during short TR and high-resolution imaging. This offers more general functionality with respect to MR imaging parameters, and has not been achievable with previous magnetic field monitoring NMR probe designs. The applicability of the developed feedback based coherent excitation scheme to operate NMR probes for monitoring k-space trajectories is shown with a spiral acquisition scheme.

10:54 218

Fast MPI Demonstrator with Enlarged Field of View - not available
Bernhard Gleich1, Jürgen Weizenecker2, Holger Timminger1, Claas Bontus1, Ingo Schmale1, Jürgen Rahmer1, Joachim Schmidt1, Jürgen Kanzenbach1, Jörn Borgert1
Philips Technologie GmbH, Forschungslaboratorien, Hamburg, Germany; 2Fakultät für Elektro- und Informationstechnik, University of applied sciences, Karlsruhe, Germany

Magnetic particle imaging (MPI) is a new tomographic imaging modality that directly and quantitatively images iron oxide nanoparticle concentration without anatomical background signal. It combines high sensitivity with the ability of fast volumetric imaging. Current demonstrators either provide fast imaging or a large field of view. Here, a solution is proposed, that allows for both, fast imaging with large FOVs.

11:06 219.  

Development of a Simultaneous PET-MRI Breast Imaging System - not available
Bosky Ravindranath1, Sachin S. Junnarkar2, David Bennett3, Xiaole Hong3, Ken Cheng3, Sean Stoll2, Martin L. Purschke2, Sri Harsha Maramraju1, Dardo Tomasi2, Sudeepti Southekal1, Paul Vaska2, Craig Woody2, David J. Schlyer2
1Biomedical Engineering, Stony Brook University, Brookhaven, NY, United States; 2Brookhaven National Laboratory, Upton, NY, United States; 3Aurora Imaging Technology Inc.,, North Andover, MA, United States

At Brookhaven National Laboratory, we are developing a MRI compatible dedicated breast PET scanner that will enable simultaneous PET-MRI imaging of the breast. We have developed and tested a prototype version of the PET system that has an average resolution less than 2 mm FWHM. Good quality MRI images were obtained with the PET system operating unshielded inside the field of view of a 1.5 T dedicated breast MRI. Our next goal is to acquire simultaneous PET-MRI images using the prototype PET and dedicated breast MRI system.

11:18 220.

In Vivo Simultaneous MR/PET Images of the Rat Brain and Mouse Heart at 9.4 Tesla
Sri-Harsha Maramraju1,2, S. David Smith2, Martin Purschke2, Sean Stoll2, Bosky Ravindranath1, Sergio Rescia2, Sachin Junnarkar2, Sudeepti Southekal1, Paul Vaska2, Craig Woody2, David Schlyer2
1Biomedical Engineering, Stony Brook University, Stony Brook, NY, United States; 2Brookhaven National Laboratory, Upton, NY, United States

We have developed a MRI compatible PET tomograph for use inside a 9.4 T microMRI scanner. This synergistic integration resulted in simultaneous acquisition of MR and PET imaging of rodents with minimal mutual interference between the two systems. New MRI coils have been built that fit inside the PET detector and obtain high quality MR images. Simultaneous MR and PET images of a rat striata phantom, rat brain and gated mouse cardiac images have been acquired, providing the flexibility to perform both rat brain and mouse cardiac studies using the same PET detector inside MRI.

11:30 221

A Single-Axis Composite Shim Coil Insert for Spectroscopy in the Medial Temporal Lobe of the Human Brain
Parisa Hudson1, Chad T. Harris1, William B. Handler1, Timothy J. Scholl1, Blaine A. Chronik1
1Department of Physics and Astronomy, The University of Western Ontario, London, Ontario, Canada

High field magnetic resonance imaging (MRI) and spectroscopy (MRS) of the human brain suffer from large field inhomogeniety, caused by the presence of air inside the brain, due to the susceptibility differences between air and tissue. To correct for the large inhomogeneities that are consistent between subjects, we present a new approach that utilizes very efficient, short, single-axis composite shim coils used together with existing system shims.  These coils require less power, occupy less space, and perform better than a set of general purpose, high order shims.

11:42 222

Zero- To Third-Order Dynamic Shim Updating  of the Human Brain at 7 Tesla
Christoph Juchem1, Terrence W. Nixon1, Piotr Diduch2, Scott McIntyre1, Douglas L. Rothman1, Piotr Starewicz2, Robin A. de Graaf1
1MR Research Center, Yale University, New Haven, CT, United States; 2Resonance Research Inc., Billerica, MA, United States

The first realization of full zero- to third-order DSU with full preemphasis and B0 compensation is presented which allowed high quality shimming of the human brain at 7 Tesla. The achievable magnetic field homogeneity could be largely improved not only in comparison to global (i.e. static) zero- to third-order shimming, but also when compared to state-of-the-art zero- to second-order DSU.

11:54 223

Motor Design for an MR-Compatible Rotating Anode X-Ray Tube
Prasheel Lillaney1, Robert Bennett1, Rebecca Fahrig1

1Radiology, Stanford University, Stanford, CA, United States

This work discusses the development of an alternate motor design for rotating anode x-ray tubes to be used in hybrid x-ray/MR image guidance systems.  The novel aspect of our design is that we propose to use the MR fringe field to generate torque in our motor.  A proof of concept of our design has been assembled and can rotate at a maximum speed slightly above 450 RPM in a 45 mT external field.  With further research and optimization of parameters we are confident that we can meet the design constraints for typical x-ray tube motors.

12:06 224.

Portable MRI Magnets and Spinning Micro-Detectors - not available
Dimitrios Sakellariou1, Cédric Hugon1, Alan Wong1, Pedro Aguiar1, Guy Aubert2, Jacques-François Jacquinot3
1DSM/IRAMIS/LSDRM/SIS2M, CEA - Saclay, Gif-sur-Yvette, Essone, France; 2DSM / IRFU / Neurospin, CEA - Saclay; 3DSM / IRAMIS / SPEC, CEA - Saclay

The message of my presentation is that permanent magnet engineering together with ideas from solid-state NMR can give place to innovation in medical Magnetic Resonance. We demonstrate a new strategy to develop portable MRI magnets and show the first example of a high uniformity one-sided system. We also use spinning micro-detectors as a means to achieve high resolution microscopy by magic angle sample spinning in the stray field of a magnet. Ideas on magic angle field spinning will be the common denominator for these projects. Ideas and preliminary instrumentation will be presented.

12:18 225

Active Localized Shielding for Devices Within MRI Gradient Coils
Chad Harris1, William Handler1, Blaine Alexander Chronik1
1Physics and Astronomy, University of Western Ontario, London, Ontario, Canada

There are an increasing number of applications in which non-MRI active or passive devices are being introduced into the MRI system and required to operate normally while exposed to the static, RF, and audio-frequency (i.e. gradient) magnetic fields produced during normal scanning. In this study, we focus on gradient fields and consider the possibility of designing a very localized, active shield to cancel the time-varying magnetic fields for an arbitrary device located within the inside diameter of the gradient system.



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