Martijn A Cloos^1,2, Bei Zhang^1,2, and Daniel K Sodickson^1,2
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.

Lars Kasper^1,2, Christoph Barmet^1,3, Maria Engel¹, Maximilian Haeberlin¹, Bertram J Wilm¹, Benjamin E Dietrich¹, Thomas Schmid¹, David O Brunner¹, Klaas E Stephan^2,4,5, and Klaas P Pruessmann^1
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.

Mariska P. Luttje¹, Ingmar J. Voogt¹, Marco van Vulpen¹, Peter R. Luijten¹, Dennis W.J. Klomp¹, and Alexander J.E. Raaijmakers^1
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.

Carson Ingo¹, Wyger M. Brink¹, Andrew G. Webb¹, and Itamar Ronen^1
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%.

Xiaoping Wu¹, Nicolas Boulant², Vincent Gras², Jinfeng Tian¹, Sebastian Schmitter¹, Pierre-Francois Van de Moortele¹, and Kamil Ugurbil^1
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.

Xiufeng Li¹, Pierre-Francois Van de Moortele¹, Kamil Ugurbil¹, and Gregory J. Metzger^1
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. 

Hendrik Mattern¹, Alessandro Sciarra¹, Frank Godenschweger¹, Daniel Stucht¹, Falk Lüsebrink¹, and Oliver Speck^1,2,3,4
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.

Damien Nguyen^1,2, Tom Hilbert^3,4,5, Philipp Ehses^6,7, Klaus Scheffler^6,7, Jean-Philippe Thiran^4,5, Oliver Bieri^1,2, and Tobias Kober^3,4,5
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.

Bixia Chen^1,2, Philipp Dammann^1,2, Stefan Maderwald¹, Soeren Johst¹, Tobias Schoemberg^1,2, Lale Umutlu^1,3, Harald H. Quick^1,4, Mark Edward Ladd^1,5, Ulrich Sure², and Karsten Henning Wrede^1,2
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.

Ketan Ghaghada¹, Zbigniew Starosolski¹, Igor Stupin¹, Saakshi Bhayana¹, Haijun Gao², Rohan Bhavane¹, Chandresh Patel¹, Robia Pautler³, Chandrasekhar Yallampalli², and Ananth Annapragada^1
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.