View Presentation Video

Wei-Tang Chang^1,2,3
1Radiology, UNC at Chapel Hill, Chapel Hill, NC, United States, ²Biomedical Research Imaging Center, UNC at Chapel Hill, Chapel Hill, NC, United States, ³Biomedical Engineering, UNC at Chapel Hill, Chapel Hill, NC, United States

Keywords: Pulse Sequence Design, Diffusion Tensor Imaging

The ability to achieve submillimter isotropic resolution diffusion MR imaging (dMRI) is critically important to study fine-scale brain structures. While the multi-shot approaches, including SMSlab and gSlider-SMS, have been proposed to mitigate the inherently low SNR, the SMSlab sequences require additional navigators for phase estimation and both SMSlab and gSlider-SMS suffered from the slab-boundary artifacts. This study proposed two new concepts: PRISM encoding and 2) pseudo slab in order to mitigate the slab-boundary artifacts and shorten the scan time. Together, this study achieved the dMRI with 0.86 mm isotropic resolution with 16.3%-43.6% reduction of scan time compared to gSlider.

View Presentation Video

Tanya Deniz Ipek¹, Victor Han¹, and Chunlei Liu^1,2
1Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA, United States, ²Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA, United States

Keywords: RF Pulse Design & Fields, RF Pulse Design & Fields, Multiphoton, SAR

Simultaneous multislice (SMS) imaging methods reduce scan time but increase specific absorption rate (SAR) because of additional radiofrequency (RF) pulses required for exciting multiple slices. Multiphoton excitation was recently proposed to significantly reduce SAR for SMS imaging. In this work, we further developed a phase-modulated multiphoton SMS excitation method that achieves CAIPIRINHA-type controlled aliasing, which improves image reconstruction quality significantly. Images obtained with our custom multiphoton CAIPIRINHA-SMS sequence have reduced aliasing artifacts and higher SNR compared to images obtained with a multiphoton SMS sequence without CAIPIRINHA. For a three-slice design, SAR is reduced by a factor of two.

View Presentation Video

Peter J Lally^1,2, Mark Chiew³, Paul M Matthews^1,4, Karla L Miller⁵, and Neal K Bangerter^6
1Department of Brain Sciences, Imperial College London, London, United Kingdom, ²Centre for Care Research and Technology, UK Dementia Research Institute, London, United Kingdom, ³Medical Biophysics, University of Toronto, Toronto, ON, Canada, ⁴UK Dementia Research Institute at Imperial, London, United Kingdom, ⁵Wellcome Centre for Integrative Neuroimaging, University of Oxford, Oxford, United Kingdom, ⁶Department of Bioengineering, Imperial College London, London, United Kingdom

Keywords: Data Acquisition, Pulse Sequence Design, SSFP, susceptibility

The behaviour of magnetisation under RF spoiling is typically considered to be pseudorandom from TR to TR. Here we describe a model for the coherent underlying phase behaviour which we exploit in a new acquisition strategy. We propose this as an SNR-efficient and motion-robust alternative to multi-echo spoiled gradient echo acquisitions.

View Presentation Video

Kartiga Selvaganesan¹, Yonghyun Ha², Chenhao Sun², Anja Samardzija¹, Zhehong Zhang¹, Heng Sun¹, Gigi Galiana², and Todd Constable^2
1Biomedical Engineering, Yale University, New Haven, CT, United States, ²Radiology and Biomedical Imaging, Yale University, New Haven, CT, United States

Keywords: Pulse Sequence Design, Low-Field MRI

The cost and complexity of MR scanners can be significantly reduced by eliminating conventional linear gradient coils, and instead using RF coils for spatial encoding. Here we have developed a novel multi-echo RF phase encoding pulse sequence that exploits the Bloch-Siegert shift for nonlinear spatial encoding in a nonuniform, field-cycling, low-field MR system. Phantoms of varying sizes were successfully imaged using this pulse sequence, demonstrating that this technique can be used to perform gradient-free imaging in an inhomogeneous B0-field at low-field.

View Presentation Video

Amir Seginer¹ and Rita Schmidt^2
1Siemens Healthcare Ltd, Rosh Ha'ayin, Israel, ²Department of Brain Sciences, Weizmann Institute of Science, Rehovot, Israel

Keywords: Data Acquisition, Artifacts, ultra-high field

Rapid 3D steady-state sequences such as SWI are sensitive to semi-periodic physiological fluctuations (e.g., cardiac pulsation, breathing, and eye movement) resulting in repeating artifacts in the images. Randomization of the phase-encoding order reduces the above artifacts but results in apparent noise from slow global changes (like motion or eddy currents changes). We propose a new semi-randomized acquisition order that allows to set a cutoff frequency for artifact suppression; above which artifacts are suppressed, whereas artifacts from slower changes are unaffected. Simulations and SWI human brain scanning at 7T validate the method.

View Presentation Video

Cagan Alkan¹, Shreyas Vasanawala², and John Pauly^1
1Electrical Engineering, Stanford University, Stanford, CA, United States, ²Radiology, Stanford University, Stanford, CA, United States

Keywords: Machine Learning/Artificial Intelligence, Data Acquisition, Data Sampling

Variational information maximization allows joint optimization of MR data sampling and reconstruction and improves reconstruction quality upon the heuristically designed sampling patterns. Here, we analyze the learned sampling patterns with respect to changes in acceleration factor, measurement noise, anatomy, and coil sensitivities in order to provide some interpretation. We show that all of these factors contribute to the optimization result by impacting the sampling density, k-space coverage and point spread functions of the learned sampling patterns.

View Presentation Video

Sebastian Mueller^1,2, Felix Glang¹, Klaus Scheffler^1,2, and Moritz Zaiss^1,3
1High-field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, ²Department for Biomedical Magnetic Resonance, University Hospital Tuebingen, Tuebingen, Germany, ³Institute of Neuroradiology, University Hospital Erlangen, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany

Keywords: Pulse Sequence Design, Pulse Sequence Design

Recently, we proposed a framework for automatized, model-free MR sequence design for contrast generation. The concept was proven by optimizing the contrast-generating sequence using a real MRI scanner for scanning model solutions repeatedly until convergence to the target. In this work, we demonstrate for the first time that this live optimization loop can also be used directly on a real subject’s brain. As an example, GM/WM contrast for a GRE sequence was optimized fully automatically in a model-free and reference-free manner live in a healthy subject at a 3T MR scanner.

View Presentation Video

Keywords: Data Acquisition, Data Acquisition

This study describes an alternative approach to Cartesian SPACE for 1 mm³ isotropic whole brain T₂-weighted imaging on a high performance 0.55T scanner. In this technique, the Cartesian readouts were replaced by interleaved, rotated spiral-in-out trajectories, combined with a variable-flip-angle refocusing, echo-reordering, and concomitant gradient compensation. Parallel imaging (PI) and compressed sensing (CS) were utilized for further acceleration. Compared to 3D-Cartesian SPACE, this method can be leveraged to mitigate the lower SNR of 0.55T via the improved SNR efficiency of prolonged spiral trajectory sampling.

View Presentation Video

Lars Bielak^1,2, Jürgen Hennig¹, Thomas Lottner¹, and Michael Bock^1,2
1Dept.of Radiology, Medical Physics, Medical Center University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany, ²German Cancer Consortium (DKTK), Partner Site Freiburg, Freiburg, Germany

Keywords: Pulse Sequence Design, Multi-Contrast

A sequence design is presented based on spiral fast spin echo acquisition with interleaved diffusion sensitization for simultaneous ADC and T₂ mapping. With spiral readout trajectories only few echoes need to be acquired per (TE,b) pair allowing to accelerate the acquisition significantly. A phantom experiment with single echo per k-space is shown for T₂ and ADC mapping. With a model-based reconstruction both parameter maps can be rapidly reconstructed.

View Presentation Video

Naoharu Kobayashi¹ and Michael Garwood^1
1CMRR, Department of Radiology, University of Minnesota, Minneapolis, MN, United States

Keywords: Data Acquisition, Pulse Sequence Design, Inhomogeneous field

3D Fast spin echo (FSE) with frequency-modulated (FM) pulses has been introduced for MRI in highly inhomogeneous fields.  B₁ dependent phase in FM pulse excitation and refocus was adjusted in the FM-FSE pulse sequence.  Refocus flip angles in FM-FSE were determined with prospective extended phase graph (EPG). Proposed flip angle and phase in FM-FSE were validated in EPG simulation and experiments at 3T by introducing a linear inhomogeneous field.  Finally, in vivo human brain imaging with T₁- and T₂-weighting was performed using the proposed 3D FM-FSE sequence.

View Presentation Video

Gabriel Varela-Mattatall^1,2, Wei-Ching Lo³, Omer Oran⁴, Jonathan Polimeni^5,6, Azma Mareyam^5,7, Borjan Gagoski^8,9, Ravi S. Menon^1,2, and Berkin Bilgic^5,6
1Centre for Functional and Metabolic Mapping (CFMM), Robarts Research Institute, Western University, London, ON, Canada, ²Department of Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada, ³Siemens Medical Solutions USA, Boston, MA, United States, ⁴Siemens Healthcare Limited, Oakville, ON, Canada, ⁵Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital & Harvard Medical School, Boston, MA, United States, ⁶Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Boston, MA, United States, ⁷Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Boston, Boston, MA, United States, ⁸Fetal-Neonatal Neuroimaging & Developmental Science Center, Boston Children’s Hospital, Boston, MA, United States, ⁹Department of Radiology, Harvard Medical School, Boston, MA, United States

Keywords: Data Acquisition, New Trajectories & Spatial Encoding Methods

MP2RAGE is considered the workhorse sequence at ultra-high field (UHF) as it provides high-contrast and bias-free structural imaging for both anatomical and segmentation purposes. However, high-resolution MP2RAGE imaging is hampered by lengthy acquisitions, which can be partially mitigated using parallel imaging, but this comes at the cost of g-factor and √R penalties on SNR; thus, limiting the usefulness of this sequence at the submillimeter scale. In this work, we show preliminary results on how wave encoding, and blipped-controlled aliasing could allow efficient MP2RAGE acquisitions at up to 560 um isotropic resolution at 7T.

View Presentation Video

Guillaume Daval-Frérot^1,2,3, Chaithya G R^2,3, Fernanda Ponce^2,3, Aurélien Massire¹, Boris Mailhe⁴, Mariappan Nadar⁴, Alexandre Vignaud², and Philippe Ciuciu^2,3
1Siemens Healthineers, Saint-Denis, France, ²CEA, NeuroSpin, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France, ³Inria, MIND, Palaiseau, France, ⁴Digital Technology & Innovation, Siemens Healthineers, Princeton, NJ, United States

Keywords: Data Acquisition, Data Acquisition, Non-Cartesian; SPARKLING

Non-Cartesian sampling patterns allow for highly accelerated MRI exams at the cost of exacerbated and more complex artifacts, each impacting image quality in unique ways. Patient-induced B0 field inhomogeneities can notably cause distortions and blurring, but some trajectories are by design more robust to them.  We propose to retrospectively benchmark 16 different non-Cartesian sampling patterns with high acceleration factor (AF=20) and realistic off-resonance artifacts over 9 volumes acquired at 3T with 0.6 mm isotropic spatial resolution. SPARKLING and spiral-based trajectories achieve higher image quality scores, but only the former shows robustness to off-resonance effects through the MORE-SPARKLING extension.

View Presentation Video

Zijing Dong^1,2, Jonathan R. Polimeni^1,2,3, Lawrence L. Wald^1,2,3, and Fuyixue Wang^1,2
1Athinoula A. Martinos Center for Biomedical Imaging, MGH, Charlestown, MA, United States, ²Department of Radiology, Harvard Medical School, Charlestown, MA, United States, ³Harvard-MIT Health Sciences and Technology, MIT, Cambridge, MA, United States

Keywords: Data Acquisition, Brain

Pushing the spatial resolution of diffusion MRI to mesoscale is technically challenging due to the low SNR efficiency and severe image artifacts. Last year, we presented a novel ROtating-view Motion-robust supEr Resolution Echo Planar Time-resolved Imaging method (Romer-EPTI), providing significant gains (~3.5×) in SNR efficiency and high-quality images free from distortion with minimized motion artifacts. In this work, we further developed Romer-EPTI at 7T for in-vivo mesoscale dMRI. By exploiting the higher signal of 7T and the short-TE, high-SNR, distortion-free acquisition provided by Romer-EPTI, mesoscale whole-brain dMRI at an unprecedented 485-μm isotropic resolution was acquired.

View Presentation Video

Maria Engel¹, Lars Müller^1,2, André Döring¹, and Derek Jones^1
1Cardiff University Brain Research Imaging Centre (CUBRIC), Cardiff University, Cardiff, United Kingdom, ²Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, United Kingdom

Keywords: New Trajectories & Spatial Encoding Methods, New Trajectories & Spatial Encoding Methods

Diffusion weighted imaging (DWI) for advanced modelling of tissue microstructure is notoriously short in SNR and requires long scan times. In this work we boost the SNR of DWI by combining highly efficient T-Hex sampling with multiband imaging and spiral readout schemes. This allows for an unprecedented SNR efficiency and holds promise for advanced microstructural scans especially in clinical populations.

View Presentation Video

Richard Thompson¹, Christopher Keen¹, Hefin Jones², Richard Coulden², Peter Seres¹, and Justin Grenier^1
1Biomedical Engineering, University of Alberta, Edmonton, AB, Canada, ²Radiology & Diagnostic Imaging, University of Alberta, Edmonton, AB, Canada

Keywords: Pulse Sequence Design, Lung, UTE, Heart Failure, Cartesian

The Cartesian UTE (CUTE) sequence provides high quality three-dimensional imaging of the lung parenchyma (TE = 140 us) without the requirement for k-space gridding in a short breath-hold. Phantom validation and comparison to an existing UTE sequence (Spiral VIBE) is provided in 64 healthy subjects and in clinical examples.