Joint Annual Meeting ISMRM-ESMRMB 2014 10-16 May 2014 Milan, Italy

Unique Acquisition Strategies 1

Monday 12 May 2014
Space 3  10:45 - 12:45 Moderators: Mariya Doneva, Ph.D., Christopher P. Hess, M.D., Ph.D.

10:45 0026.   
Using Gradient Waveforms Derived from Music in MR Fingerprinting (MRF) to Increase Patient Comfort in MRI
Dan Ma1, Vikas Gulani1,2, and Mark Griswold1,2
1Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States, 2Radiology, Case Western Reserve University, Cleveland, OH, United States

The purpose of this study is to use MRF method to potentially mitigate the acoustic noise problem in normal MR scans while simultaneously quantifying multiple tissue parameters. Instead of producing quiet sequences, we instead take advantage of the extra degrees of freedom in MRF to design acquisitions to replicate music in the magnet. In this study, mp3 music files, which are converted to arbitrary readout encoding gradients, are used with varying flip angles and TRs in the MRF exam to quantify T1, T2, off-resonance and proton density maps simultaneously while providing pleasing sounds to the patient.

10:57 0027.   Magnetic Resonance Fingerprinting Trajectory Optimization
Ouri Cohen1, Mathieu Sarracanie1,2, Brandon D. Armstrong1,2, Jerome L. Ackerman1, and Matthew S. Rosen1,2
1Department of Radiology, MGH/Athinoula A. Martinos Center for Biomedical Imaging, Massachussets General Hospital, Charlestown, MA, United States,2Department of Physics, Harvard University, Cambridge, MA, United States

Current implementations of MR fingerprinting typically require over 1000 measurements to obtain the desired tissue maps. The large number entails an increased specific absorption rate and, to avoid excessive scan times, a subsampling of k-space that may incur undersampling artifacts. Here we propose an optimization method which allows reduction of the needed measurements ~100 fold without affecting image quality.

11:09 0028.   
Simultaneous T1, T2, Diffusion and Proton Density Quantification with MR Fingerprinting
Yun Jiang1, Dan Ma1, Katie Wright1, Nicole Seiberlich1, Vikas Gulani2, and Mark A. Griswold1,2
1Department of Biomedical Enginneering, Case Western Reserve University, Cleveland, OH, United States, 2Department of Radiology, Case Western Reserve University, Cleveland, OH, United States

MR Fingerprinting (MRF) is a novel platform for generating multiple parametric maps simultaneously by matching spatially and temporally incoherent signals to a pre-calculated dictionary. Here we explore MRF using a double-echo sequence with a spiral trajectory to simultaneously generate T1, T2, M0and ADC maps. The result shows quantitative diffusion and relaxation estimates can be simultaneously generated within the MRF framework, extending the concept beyond relaxometry.

11:21 0029.   
Small-tip Fast Recovery (STFR) imaging Using Spectrally Tailored Pulse
Hao Sun1, Jeffrey A. Fessler1, Douglas C. Noll2, and Jon-Fredrik Nielsen2
1Electrical Engineering and Computer Science, the University of Michigan, Ann Arbor, MI, United States, 2Biomedical Engineering, the University of Michigan, Ann Arbor, MI, United States

Small tip fast recovery (STFR) imaging has been proposed recently as a potential alternative to balanced steady state free precession (bSSFP). STFR relies on a tailored “tip-up” RF pulse to achieve comparable signal level and image contrast as bSSFP, but with reduced banding artifacts. Previous STFR implementations used 2D or 3D pulses spatially tailored to the accumulated phase calculated from a B0 field map. Here we propose to replace the spatially tailored pulse with a spectrally tailored pulse, which can be precomputed to a target frequency range. We show that this “spectral-STFR” sequence has reduced banding artifacts compared to bSSFP.

11:33 0030.   
Spin Echoes in the Weak Dephasing Regime
Jakob Assländer1, Simone Köcher2, Steffen Glaser2, and Jürgen Hennig1
1Dept. of Radiology - Medical Physics, University Medical Center, Freiburg, Germany, 2Dept. of Chemistry, Technische Universität München, Germany

It is shown that, for small flip angles, it is possible to form spin echoes after a single excitation pulse, where the time between the end of the pulse and the echo is longer than the length of the pulse itself. This is in contrast to standard Hahn-echo pulse sequences, where the length of the pulse sequence is in approximation equal to the time between the end of the composite pulse and the echo. The sequence is implemented into a FLASH sequence. At the example of lung pulmonary imaging signal enhancement is demonstrated in comparison to a standard FLASH sequence.

11:45 0031.   
Prephased O-space Imaging for Reduction of Asymmetrical Local K-space Coverage
Leo K. Tam1, Gigi Galiana1, Haifeng Wang1, Emre Kopanoglu1, Andrew Dewdney2, Dana C. Peters1, and R. Todd Constable1
1Diagnostic Radiology, Yale University, New Haven, CT, United States, 2Siemens Healthcare AG, Erlangen, Bavaria, Germany

Local k-space, the spatial derivative of the encoded phase has been used to visualize and design strategies to mitigate the spatially-varying encoding of nonlinear gradient encoding. To reduce the local k-space asymmetry of O-space imaging, the phase prior to readout is adjusted for each readout in a technique called prephasing, first proposed by Gallichan et. al. Prephased O-space imaging shows reduced MSE, though artifacts from previous simulations of asymmetrical k-space were not corroborated. Parallel receiver information may sufficiently localize signal conditional on appropriate imaging parameters.

11:57 0032.   Optimal trajectory design for higher-dimensional encoding
Kelvin J. Layton1, Feng Jia2, and Maxim Zaitsev2
1Department of Electrical and Electronic Engineering, The University of Melbourne, Melbourne, Victoria, Australia, 2Dept. of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany

Spatial encoding magnetic fields (SEMs) that vary nonlinearly over the field-of-view have the potential to accelerate imaging and overcome current safety limitations. Encoding with combinations of linear and nonlinear SEMs offer great flexibility but also make trajectory design difficult, since traditional k-space is insufficient to represent the higher-dimensional encoding space. This work presents a new method for automated trajectory design based on the predicted variance of the reconstructed pixels. In this way, the condition of the reconstruction problem is explicitly considered during trajectory design. Images reconstructed from simulated data exhibit reduced artifacts and noise using the proposed trajectory.

12:09 0033.   
Spatial resolution in rotating Spatial Encoding Magnetic field MRI (rSEM-MRI)
Clarissa Zimmerman Cooley1,2, Jason P. Stockmann1,3, Brandon D. Armstrong1,3, Mathieu Sarracanie1,3, Matthew S. Rosen1,3, and Lawrence L. Wald1,4
1A. A. Martinos Center for Biomedical Imaging, Dept. of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, 2Dept. of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States, 3Dept. of Physics, Harvard University, Cambridge, MA, United States, 4Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA, United States

MRI could find wider applicability if lightweight, portable systems were available for siting in unconventional locations. We have proposed a lightweight magnet whose inhomogeneous field pattern is physically rotated to form a rotating Spatial Encoding Magnetic field (rSEM). This is a way to lower the magnet weight and eliminate gradient coils. The resulting image resolution varies spatially in the FOV with minimal encoding in center, a common problem in non-linear gradient encoding schemes. With the goal of improving encoding throughout the FOV, we assess resolution in different rSEMs through simulations, and compare to experimentally acquired images.

12:21 0034.   Time-efficient interleaved 23Na and 1H acquisition at 7T
Paul W. de Bruin1, Maarten J. Versluis1, Peter Koken2, Sebastian A. Aussenhofer1, Ingrid Meulenbelt3, Peter Börnert1,2, and Andrew G. Webb1
1Radiology Department, Leiden University Medical Center, Leiden, Netherlands, 2Innovative Technologies Research Laboratories, Philips Technologie GmbH, Hamburg, Germany, 3Molecular Epidemiology, Leiden University Medical Center, Leiden, Netherlands

A flexible sequence interleaving method for different nuclei is used to virtually simultaneously acquire 23Na and 1H scans. This results in a high time-efficiency that is essential for patient studies involving 23Na scans.

12:33 0035.   in vivo Ultrafast Diffusion Imaging of Stroke at 21.1 T by Spatiotemporal Encoding
Jens T Rosenberg1,2, Avigdor Leftin3, Eddy Solomon3, Fabian Calixto Bejarano1, Lucio Frydman1,3, and Samuel Colles Grant1,2
1National High Magnetic Field Laboratory, The Florida State University, Tallahassee, FL, United States, 2Chemical & Biomedical Engineering, The Florida State University, Tallahassee, FL, United States, 3Chemical Physics, Weizmann Institute of Science, Rehovot, Israel

Fast imaging techniques such as echo planar imaging (EPI) are popular techniques for imaging of neuronal injuries. However, there is an inherent problem with these techniques with respect to susceptibility and geometric artifacts that distort not only anatomical information but also the quantification of relevant quantities, such as water diffusion. To provide robust and fast acquisitions at high field, this study utilizes an ultrafast single-shot spatiotemporally encoded (SPEN) imaging sequence with diffusion encoding to measure apparent diffusion coefficient (ADC) in stroke. Results show that SPEN images provide a more accurate way of measuring ADC at high field compared to EPI.