ISMRM 24th Annual Meeting & Exhibition • 07-13 May 2016 • Singapore

Scientific Session: UHF Applications

Wednesday, May 11, 2016
Room 324-326
16:00 - 18:00
Moderator: Lawrence Wald

Abdominal MRF at Ultra-High-Field Strengths
Martijn A Cloos1,2, Bei Zhang1,2, and Daniel K Sodickson1,2
1Bernard and Irene Schwartz Center for Biomedical Imaging, New York University School of Medicine, New York, NY, United States, 2Center for Advanced Imaging Innovation and Research (CAI2R), New York University School of Medicine, New York, NY, United States
Like other magnetic resonance (MR) techniques before it, magnetic resonance fingerprinting (MRF) was developed and applied in the traditional context of a precisely calibrated and uniform radiofrequency excitation field. Plug & Play Parallel Transmission (PnP-PTX), on the other hand, was designed to liberate MRF from these constraints. We evaluate the impact of excitation field non-uniformities on abdominal MRF experiments at different field strengths, and show that PnP-PTX has the potential to alleviate these challenges, and thereby opens opens up a new route towards robust, quantitative, whole-body MRI for ultra-high-field systems.

Spiral Acquisition for High-Speed Anatomical Imaging at 7T
Lars Kasper1,2, Christoph Barmet1,3, Maria Engel1, Maximilian Haeberlin1, Bertram J Wilm1, Benjamin E Dietrich1, Thomas Schmid1, David O Brunner1, Klaas E Stephan2,4,5, and Klaas P Pruessmann1
1Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zuerich, Switzerland, 2Translational Neuromodeling Unit, IBT, University of Zurich and ETH Zurich, Zuerich, Switzerland, 3Skope Magnetic Resonance Technologies, Zurich, Switzerland, 4Wellcome Trust Centre for Neuroimaging, University College London, London, United Kingdom, 5Max Planck Institute for Metabolism Research, Cologne, Germany
We present whole-brain, high-resolution (0.5mm) spiral imaging with proton-density and T2* contrast at 7T in less than a minute. Owing to a comprehensive characterization of the imaging process, artifact-free image reconstruction from long-readout spiral shots (20 ms) becomes feasible via an iterative SENSE algorithm. In particular, trajectory imperfections as well as dynamic off-resonance changes are captured via concurrent field monitoring, while static off-resonance as well as coil sensitivities are mapped in a multi-echo reference scan and augment image reconstruction. The resulting images exhibit the same geometric fidelity as spin-warp images at a fraction of the total acquisition duration.

First proof of more than two-fold increase in intrinsic SNR for prostate imaging at 7 tesla in comparison with 3 tesla.
Mariska P. Luttje1, Ingmar J. Voogt1, Marco van Vulpen1, Peter R. Luijten1, Dennis W.J. Klomp1, and Alexander J.E. Raaijmakers1
1Imaging Division, University Medical Center Utrecht, Utrecht, Netherlands
In this study, we demonstrate that a dipole transceive antenna array with a loop coil receive array at 7T substantially outperforms state of the art 3T MRI of the prostate. Using this setup we demonstrated for the first time the intrinsic SNR benefits of using the higher field strength of 7 tesla for prostate MR imaging compared to a clinically used prostate imaging setup at 3 tesla: an overall gain in SNR of 2.1 fold as obtained in 6 subjects.

Utilizing the improved receive sensitivity from high permittivity materials for SNR-challenged applications of ultrahigh b-factor diffusion-weighted spectroscopy at 7 Tesla
Carson Ingo1, Wyger M. Brink1, Andrew G. Webb1, and Itamar Ronen1
1C.J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, Netherlands
Diffusion-weighted 7T MR spectroscopy in white matter regions of the brain using ultrahigh b-factors have established that intracellular metabolites exhibit non-Gaussian diffusion. Such measurements using b-factors well above 10,000 s/mm2 have inherently low SNR, and so it is crucial to optimize B1 sensitivity to ensure reliable results. Here we show that a single high permittivity pad can increase the receive sensitivity by ~30%, resulting in potential reductions in data acquisition time of ~70%.

High resolution whole-brain diffusion MRI at 7 Tesla using parallel RF transmission: how fast can we go?
Xiaoping Wu1, Nicolas Boulant2, Vincent Gras2, Jinfeng Tian1, Sebastian Schmitter1, Pierre-Francois Van de Moortele1, and Kamil Ugurbil1
1CMRR, Radiology, University of Minnesota, Minneapolis, MN, United States, 2CEA/NeuroSpin, Saclay, France
The Human Connectome Project (HCP) in the WU-Minn consortium aims to acquire multiband (MB)-accelerated whole brain diffusion MRI (dMRI). Although shown advantageous over 3T dMRI in inferring connectivity, the 7T acquisition suffers from transmit B1 inhomogeneity and SAR, the latter currently limiting the slice acceleration to an MB factor of 2 (MB=2). In this study, we investigated numerically the highest possible slice acceleration for 7T HCP-type dMRI acquisition with ~1-mm isotropic resolutions. Our results suggest that parallel RF transmission can be used to enable MB=4 while improving flip angle homogeneity across the whole brain as compared to a CP mode.

Quantitative Single Breath-Hold Renal ASL Perfusion Imaging at 7T
Xiufeng Li1, Pierre-Francois Van de Moortele1, Kamil Ugurbil1, and Gregory J. Metzger1
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States
        In contrast to studies at 3T, where the whole body coil is used for RF transmission, studies at 7T use local transcieve coils, which have limited B1+ coverage producing smaller temporal bolus widths that need to be estimated in order to achieve proper renal blood flow (RBF) quantification. To estimate the temporal bolus width and to quantify RBF at 7T, single breath-hold renal perfusion studies were performed using the FAIR ss-FSE method with varied delay times. Based on the results form multi-delay perfusion study, quantitative renal perfusion imaging was further achieved by using a single-subtraction approach. 

Prospective motion correction for ultra-high resolution Time of Flight angiography at 7T under SAR constraints
Hendrik Mattern1, Alessandro Sciarra1, Frank Godenschweger1, Daniel Stucht1, Falk Lüsebrink1, and Oliver Speck1,2,3,4
1Department of Biomedical Magnetic Resonance, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany, 2Leibniz Institute for Neurobiology, Magdeburg, Germany, 3Center for Behavioral Brain Sciences, Magdeburg, Germany, 4German Center for Neurodegenerative Disease, Magdeburg, Germany
At 7T, venous saturation and magnetization transfer for Time of Flight (ToF) angiography cannot be applied directly due to the increased specific absorption rate. Additionally, motion artifacts can degrade the image quality. A sequence with prospective motion correction (PMC) and sparse saturation was implemented to overcome these challenges. In vivo ultra-high resolution ToF angiograms were acquired, providing dramatically improved level of detail and image quality if PMC and sparse saturation is used. Thus, the proposed sequence unleashes the full potential of ToF angiography at 7T.

On-resonant balanced Steady-State Free Precession imaging at 9.4T
Damien Nguyen1,2, Tom Hilbert3,4,5, Philipp Ehses6,7, Klaus Scheffler6,7, Jean-Philippe Thiran4,5, Oliver Bieri1,2, and Tobias Kober3,4,5
1Radiological Physics, Dep. of Radiology, University of Basel Hospital, Basel, Switzerland, 2Department of Biomedical Engineering, University of Basel, Basel, Switzerland, 3Advanced Clinical Imaging Technology (HC CMEA SUI DI BM PI), Siemens Healthcare AG, Lausanne, Switzerland, 4Department of Radiology, University Hospital Lausanne (CHUV), Lausanne, Switzerland, 5LTS5, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, 6High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany, 7Department for Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany
In this work, we explore the possibility of using the recently proposed highly undersampled 3D phase-cycled balanced Steady-State Free Precession (bSSFP) sequence trueCISS to generate on-resonant band-free bSSFP images at 9.4T. By applying the forward signal model, it is also possible to synthetically generate bSSFP images at higher flip angles, which would otherwise be impossible to acquire due to SAR limitations. Lastly, we show a maximum bSSFP signal intensity image of the brain using the trueCISS estimated parameter maps.

Magnetic resonance imaging of low-grade and high-grade gliomas at 7 Tesla - Permission Withheld
Bixia Chen1,2, Philipp Dammann1,2, Stefan Maderwald1, Soeren Johst1, Tobias Schoemberg1,2, Lale Umutlu1,3, Harald H. Quick1,4, Mark Edward Ladd1,5, Ulrich Sure2, and Karsten Henning Wrede1,2
1Erwin L. Hahn Institute for MRI, University of Duisburg-Essen, Essen, Germany, 2Department of Neurosurgery, University Hospital Essen, University of Duisburg-Essen, Essen, Germany, 3Institute of Diagnostic and Interventional Radiology and Neuroradiology, University of Duisburg-Essen, Essen, Germany, 4High Field and Hybrid MR Imaging, University Hospital Essen, University of Duisburg-Essen, Essen, Germany,5Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany
Magnetic resonance imaging (MRI) plays a major role in diagnosis, multimodal treatment planning, and follow-up of low-grade and high-grade gliomas. In this prospective study, 24 patients were intra-individually examined at 3 Tesla (T) and 7T utilizing MPRAGE, T2 TSE, T2 FLAIR, and SWI sequences. Image evaluation had special focus on intra-tumoral structures, vascularization, intra-lesional hemorrhages, and contrast uptake. At 7T, intra-tumoral structures were depicted in excellent image quality. Especially SWI was superior at 7T compared to 3T and revealed microhemorrhages and vascularization patterns correlating with histopathology, possibly providing an additional imaging predictor for future grading of malignant gliomas.

High-resolution placental MR angiography using a nanoparticle contrast agent
Ketan Ghaghada1, Zbigniew Starosolski1, Igor Stupin1, Saakshi Bhayana1, Haijun Gao2, Rohan Bhavane1, Chandresh Patel1, Robia Pautler3, Chandrasekhar Yallampalli2, and Ananth Annapragada1
1Pediatric Radiology, Texas Children's Hospital, Houston, TX, United States, 2Obstetrics and Gynecology, Baylor College of Medicine, Houston, TX, United States, 3Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX, United States
Non-invasive imaging of maternal and placental vasculature in rodent species is of interest to the pre-clinical study of clinically-relevant placental pathologies.  In this work, we evaluated the utility of high-resolution contrast-enhanced MR angiography using a placental non-permeable, long circulating liposomal-Gd nanoparticle contrast agent in a pregnant rat model.

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