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Alix Plumley¹, Francesco Padormo², Mara Cercignani¹, Rafael O'Halloran², Rui Teixeira², Álvaro Planchuelo-Gómez^1,3, Antoine Legouhy⁴, Tianrui Luo², and Derek K Jones^1
1Cardiff University, Cardiff, United Kingdom, ²Hyperfine Inc., Guilford, CT, United States, ³University of Valladolid, Valladolid, Spain, ⁴University College London, London, United Kingdom

Keywords: Data Analysis, Low-Field MRI, Diffusion Tensor Imaging

We present the first ever demonstration of Diffusion Tensor Magnetic Resonance Imaging (DT-MRI) including quantitative measures of mean diffusivity, fractional anisotropy, and successful tractographic reconstruction of projection and commissural pathways on a portable system operating at 64 mT.

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Courtney Joy Comrie¹, Samantha Schatz¹, Kevin Johnson¹, Scott Squire¹, Nan-kuei Chen¹, and Elizabeth Hutchinson^1
1Biomedical Engineering, University of Arizona, Tucson, AZ, United States

Keywords: Data Acquisition, Alzheimer's Disease

Diffusion MRI has been identified as a promising tool for identifying novel and early makers of AD and comorbid pathology. This study worked towards translating advanced microstructural techniques to clinical acquisitions for the purpose of potential AD diagnosis. High resolution diffusion human data was acquired using a 4-way phase-encoding and specialized hippocampal FOV in healthy subjects for method development. High quality maps were achieved that revealed more hippocampal microstructural information than what is acquired in database protocols according to preliminary results. 

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Hyunkyung Maeng¹ and Jaeseok Park^1,2
1Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Korea, Republic of, ²Department of Intelligent Precision Healthcare Convergence, Sungkyunkwan University, Suwon, Korea, Republic of

Keywords: Data Acquisition, Diffusion Tensor Imaging, High resolution 3D DTI

To propose an accelerated high resolution whole brain DTI and investigate its feasibility (1.0$$$mm^3$$$ isotropic spatial resolution, imaging time ~ 15 min)

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Assaf Tal¹, Inbal Beracha¹, and Amir Seginer^2
1Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel, ²Siemens Healthcare Ltd., Rosh Haayeen, Israel

Keywords: Hybrid & Novel Systems Technology, Pulse Sequence Design, Accelerating data acquisition

We present a completely general framework for adaptively changing the radiofrequency pulses and delays in real time in response to incoming data from the subject within the scanner. This "personalized-radiology" framework is shown to increase the precision of T2 estimation for n-acetyl-aspartate in-vivo by a factor of 1.7, and accelerate its acquisition 2.5-fold. 

 

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Keywords: Data Acquisition, Cardiovascular, aorta

Bright- and black-blood MRI sequences are clinically acquired sequentially, for aortic lumen and vessel wall imaging respectively, in patients with thoracic aortic disease. A novel, free-breathing, 3D sequence (iT2prep-BOOST) is proposed for contrast-free simultaneous depiction of lumen and vessel wall. We clinically validated the iT2prep-BOOST in a cohort of 25 patients with thoracic aortic disease against the conventional bright-blood T2-prep bSSFP sequence and black-blood 2D HASTE. Quantitative and qualitative image quality assessment demonstrated that iT2Prep-BOOST enabled time-efficient, bright- and black-blood aortic imaging, with improved image quality compared to conventional approaches, and comparable measurements for aortic wall and lumen dimensions.

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Zhiqiang Li¹, Poonam Choudhary¹, Dinghui Wang², Sudarshan Ragunathan¹, Melvyn B Ooi³, John P Karis¹, James G Pipe², Ashley M Stokes¹, and C Chad Quarles^1,4
1Barrow Neurological Institute, Phoenix, AZ, United States, ²Mayo Clinic, Rochester, MN, United States, ³Philips Healthcare, Houston, TX, United States, ⁴The University of Texas MD Anderson Cancer Center, Houston, TX, United States

Keywords: Pulse Sequence Design, DSC & DCE Perfusion, spiral, perfusion, quantitative imaging

Dynamic susceptibility contrast (DSC)-MRI is an important tool to assess brain tumor status for diagnosis, surgical planning, and surveillance. Dual-echo EPI based DSC-MRI enables accurate perfusion measurements using a single-dose of contrast agent, simultaneous DSC- and dynamic contrast enhanced (DCE)-MRI measures and greater parameter flexibility. However, EPI-related distortion artifacts impair its clinical utility. In this work, we proposed a 3D dual-echo spiral acquisition to mitigate EPI-related artifacts, and improve the fidelity of DCE-MRI derived parameters and arterial input function estimation. Preliminary data from volunteers and a glioma tumor patient showed reduced geometric distortion, increased temporal SNR, and accurate perfusion measurements.

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Silu Han¹, Sudhir Ramanna¹, and Nan-kuei Chen^1,2
1Department of Biomedical Engineering, The University of Arizona, Tucson, AZ, United States, ²BIO5 Institute, The University of Arizona, Tucson, AZ, United States

Keywords: Pulse Sequence Design, Brain

Multi-contrast imaging, commonly acquired with spoiled gradient recalled echo (SPGR) in clinical routine examinations, has less-than-optimal scan efficiency¹. Dual-pathway sequences, such as double-echo steady-state (DESS) and inverse double-echo steady-state (iDESS), have been developed to improve signal-to-noise ratio (SNR) and scan efficiency as compared with SPGR². Here we propose to further combine DESS/iDESS sequences and echo-planar imaging (EPI) to enhance scan efficiency, with significant implications to temperature mapping and parametric mapping (e.g., T1-, T2-, T2*-mapping and B0-field mapping, quantitative susceptibility mapping (QSM)^{3, 4}).

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Xi Peng¹, Dinghui Wang¹, Guruprasad Krishnamoorthy^1,2, Daniel D. Borup^1,2, and James G. Pipe^1
1Mayo Clinic, Rochester, MN, United States, ²Philips Healthcare, Rochester, MN, United States

Keywords: New Trajectories & Spatial Encoding Methods, Blood vessels

A spiral multiband localized quadratic encoding (LQE) method is proposed to achieve simultaneous brain and neck time of flight MRA within a single 2.5-minute scan. LQE acquisition is efficient for both SNR and in-flow enhancement. Multi-band LQE enables increased coverage with no increase in scan time, but can introduce venous signal contamination. We propose a multi-band LQE approach with TONE and partial-Fourier slice selection to reduce the venous signal and achieve simultaneous time-of-flight MRA of intracranial and carotid arteries.

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Michael JB McGrory¹, Edwin Versteeg¹, Alessando Sbrizzi¹, Cornelis AT van den Berg¹, Dennis WJ Klomp¹, and Jeroen CW Siero^1,2
1Radiology, University Medical Center Utrecht, Utrecht, Netherlands, ²Spinoza Center for Neuroimaging, Amsterdam, Netherlands

Keywords: Gradients, Gradients

Acoustic noise in MRI scans can be reduced by utilising gradient switching frequencies at 20kHz. High slew rates required to achieve such high-frequency switching can lead to peripheral nerve stimulation (PNS), adding difficulty for application to whole-body gradients. Instead, nonlinear encoding gradients have been shown to limit PNS while achieving desired slew rates. In this work, we show the feasibility of using a nonlinear silent gradient for spatial encoding by employing a PSF-based reconstruction and investigate image fidelity on a 4-fold accelerated in-vivo scan. This method could potentially be utilised for a whole-body gradient design for silent and fast MRI.

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Michael Schär¹, Robert G Weiss², and Allison G Hays^2
1Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States, ²Department of Cardiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States

Keywords: Pulse Sequence Design, RF Pulse Design & Fields, calibration, localized calibration, spectral-spatial, fat suppression

Spiral MRI requires fat suppression because fat and other off-resonant spins are blurred. For fast cardiac spiral MRI at 3T, spectral-spatial water-only excitation is often used. Standard spectral-spatial pulses apply a fly-back gradient, limiting how thin the slices can be (>4mm). Without fly-back gradients slices can be as thin as ~1.7mm, but require a phase calibration for the radiofrequency sub-pulses with inverted gradients due to system imperfections. Here we propose and test a fast (<1s), localized pre scan enabling thin-slice water only excitation. As a potential application we show spiral multi-slice coronary angiography images acquired in a single breath-hold.

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Jana Felz^1,2, Fabian J. Kratzer¹, Armin M. Nagel^1,3, Peter Bachert^1,2, Mark E. Ladd^1,2,4, and Tanja Platt^1
1Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany, ²Faculty of Physics and Astronomy, Heidelberg University, Heidelberg, Germany, ³Institute of Radiology, University Hospital Erlangen, Erlangen, Germany, ⁴Faculty of Medicine, Heidelberg University, Heidelberg, Germany

Keywords: Pulse Sequence Design, Non-Proton, High-Field MRI, Body, 23Na MRI, Field Mapping

²³Na MRI is a promising imaging method, but suffers from lower SNR, hence from longer acquisition times and lower image resolution than ¹H MRI. Especially in the torso, motion and magnetic field inhomogeneities impede quantitative analysis of ²³Na concentrations. To tackle this, a new pulse sequence is presented that yields self-gated respiratory-sorted B₁⁺ and B₀ maps from a single measurement. B₁⁺ mapping with the new sequence is less prone to motion artefacts, since k-space projections of two flip angles are acquired in an interleaved manner. This reduces the influence of varying respiration, which can lead to artefacts in conventional mapping.

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Cindy Ayala¹, Huiwen Luo², Kevin Godines¹, William Grissom², and Moriel Vandsburger^1
1University of California, Berkeley, Berkeley, CA, United States, ²Vanderbilt University, Nashville, TN, United States

Keywords: Pulse Sequence Design, CEST & MT

Chemical Exchange Saturation Transfer (CEST) MRI has been used to probe metabolism via total creatine contrast using conventional contrast generation with Gaussian saturation. We developed a spatial-spectral (SPSP) saturation pulsed CEST protocol to separate the contrast generated by metabolic subcomponents creatine and phosphocreatine (PCr) in phantoms and the human heart (n=10). Phantom studies revealed uniform CEST contrast for creatine and PCr following saturation with Gaussian pulses, and selective PCr contrast following saturation with SPSP pulses. Human studies revealed both enhanced B1-uniformity and selective PCr contrast with SPSP saturation, enabling quantitation of the PCr/total creatine ratio in the myocardium.

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Bradley P. Sutton^1,2,3, Georgia A. Malandraki⁴, Riwei Jin^1,3, Charles Marchini^1,3, Aaron Anderson³, Paul Arnold^2,3,5, and Zhi-Pei Liang^2,6
1Bioengineering, University of Illinois Urbana Champaign, Urbana, IL, United States, ²Carle Illinois College of Medicine, Urbana, IL, United States, ³Beckman Institute, University of Illinois Urbana Champaign, Urbana, IL, United States, ⁴Speech, Language, and Hearing Sciences, Purdue University, West Lafayette, IN, United States, ⁵Neuroscience Institute, Carle Foundation Hospital, Urbana, IL, United States, ⁶Electrical and Computer Engineering, University of Illinois Urbana Champaign, Urbana, IL, United States

Keywords: Data Acquisition, fMRI (task based)

Leveraging low rank and Partial Separability models, the SimulScan sequence and reconstruction was updated to drastically improve the quality and speed of dynamic imaging. This enables simultaneous functional MRI and dynamic imaging of oropharyngeal motions to be examined despite the many air/tissue interfaces. We demonstrate the improvement on a healthy adult performing a self-paced tongue tapping during the scan. The improved imaging will enable the examination of neural control of fine scale articulatory and oral movements critical for speech, feeding, and swallowing events.  

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François E Maingault¹, William Lefrançois¹, Nadège Corbin¹, Aurélien J Trotier¹, Laurence Dallet¹, Eric Thiaudière¹, Sylvain Miraux¹, and Emeline EJ Ribot^1
1Centre de Résonance Magnétique des Systèmes Biologiques, UMR5536, CNRS/Université de Bordeaux, Bordeaux, France

Keywords: Pulse Sequence Design, Fat, Water, pdff, Abdomen

A 3D radial-encoding MP2RAGE sequence was developed with binomial pulses within the GRE trains. These give the possibility to obtain water-specific, fat- specific or composite 3D T₁-maps of the abdominal cavity during free-breathing in less than 10 minutes. A 3D Proton Density Fat Fraction (PDFF) map can also be determined with the same scan. The T₁ values are similar with the standard MP2RAGE and the PDFF correspond to the ones obtained with MR spectroscopy. A test-retest on healthy volunteers shows the good reproducibility of the method.

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Marcelo V. W. Zibetti¹, Rajiv Menon¹, Hector L. De Moura¹, Mahesh B. Keerthivasan², and Ravinder R. Regatte^1
1Radiology, NYU Grossman School of Medicine, New York, NY, United States, ²Siemens Medical Solutions, Malvern, PA, United States

Keywords: Data Acquisition, Pulse Sequence Design, optimization

This study shows 3D-T1rho mapping of the human brain using optimized variable flip-angles (OVFAs) and weighted spin-lock pulses (WSLP). Our preliminary results suggest that the proposed sequence based on OVFAs and WSLP can improve SNR by almost 3X in brain T1rho mapping, reduces data acquisition time by half, and improve the mean of normalized absolute deviation (MNAD) compared to MAPSS sequence for the same application.

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Nan Wang¹, Yannick WE Brackenier¹, Congyu Liao¹, Siddharth Srinivasan Iyer^1,2, Xiaozhi Cao¹, Justin Haldar³, and Kawin Setsompop^1,4
1Department of Radiology, Stanford University, Stanford, CA, United States, ²Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States, ³Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, United States, ⁴Department of Electrical Engineering, Stanford University, Stanford, CA, United States

Keywords: Data Acquisition, Data Acquisition, Echo-planar imaging, time-resolved imaging

EPTI is a rapid time-resolved quantitative imaging method. In this work, we developed a spherical EPTI sampling trajectory (sEPTI) to improve its speed. To achieve fast imaging, sEPTI traverses a tight 3D spherical k-space using full ramp-sampling and variable echo-spacing, which also desirably increases its spatiotemporal incoherency. sEPTI was demonstrated in vivo to provide improved imaging performance over conventional block 3D-EPTI that requires 1.4x longer scan; achieving high-quality 1mm isotropic whole-brain proton-density and T2* maps in 48s. As part of this work, a novel and effective reconstruction approach to mitigate high-spatial-order ghosts in echo-planar acquisitions was also developed.

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Humberto Monsivais¹, Gianna Nossa¹, Seokkyoon Hong², Taewoong Park², Fethi Sila Erdil¹, Xin Shen³, Antonia Susnjar², Ali Özen⁴, Serhat Ilbey⁴, Mark Chiew⁵, Jessica Huber⁶, Ulrike Dydak^1,7, and Uzay Emir^1,2
1School of Health Sciences, Purdue University, West Lafayette, IN, United States, ²Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, United States, ³Radiology, University of California San Francisco, San Francisco, CA, United States, ⁴Department of Radiology, Medical Physics, University of Freiburg, Freiburg, Germany, ⁵Welcome Centre for Integrative Neuroimaging, University of Oxford, England, United Kingdom, ⁶Department of Audiology and Speech Sciences, Purdue University, West Lafayette, IN, United States, ⁷Department of Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, IN, United States

Keywords: Contrast Mechanisms, Brain

We have established a novel 3D dual-echo UTE-MT imaging method to assess hyperintense T1w signal in iron-rich brain areas by eliminating the ultra-short T2 constituents of the myelin signal via the magnetization transfer (MT) technique. Our preliminary results show improved positive image contrast in deep brain areas such as the substantia nigra (SN) and the LC. Other iron-rich areas in the basal ganglia (globus pallidus and putamen) also show improved contrast. 

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Nathan Newbury¹, Sam Sedaghat¹, Jiyo Athertya¹, Michael Carl², Jiang Du¹, and Hyungseok Jang^1
1Department of Radiology, University of California San Diego, La Jolla, CA, United States, ²GE Healthcare, La Jolla, CA, United States

Keywords: Fat, MSK

Fat signals can obscure morphological structures and influence quantitative parameter mapping in ultrashort echo time (UTE) musculoskeletal MRI. However, conventional fat suppression methods have challenges in UTE imaging of short T₂ species. For example, the chemical-shift based fat saturation can significantly attenuate short T₂ signals with broad spectra, and water excitation with long composite pulses may yield a long minimum echo time (TE). Alternatively, the feasibility of single-point Dixon (1p-Dixon) has been demonstrated for UTE imaging. In this study, we investigate the feasibility of 1p-Dixon based on the 3D phase modeling approach, which achieves fat suppression without additional data acquisition.

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Anh T. Van¹, Kilian Weiss², Georg C. Feuerriegel¹, Philipp Braun¹, Guruprasad Krishnamoorthy^3,4, Alexandra S. Gersing¹, James G. Pipe⁴, and Dimitrios C. Karampinos^1
1Department of Diagnostic and Interventional Radiology, School of Medicine, Technical University of Munich, Munich, Germany, ²Philips GmbH Market DACH, Hamburg, Germany, ³Philips Healthcare, Rochester, MN, United States, ⁴Department of Radiology, Mayo Clinic College of Medicine and Science, Rochester, MN, United States

Keywords: Bone, Skeletal

Ultra-short echo time (UTE) imaging enables the depiction of short-T2* tissues and is being increasingly used for the generation of CT-like bone images. UTE imaging has been recently combined with single-echo Dixon processing to enable the separation of water and fat signals from a single echo UTE image, but was primarily previously employed in radial stack-of-stars UTE acquisitions with prolonged scan durations. The present work combines single UTE-Dixon processing with a Fermat looped, orthogonally encoded trajectory (FLORET) to enable accelerated simultaneous short T2* water- and fat-separated imaging at sub-millimeter isotropic resolution. The technique is applied in the ankle.

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Mario Gilberto Báez-Yáñez¹, Vanja Curcic¹, Jeroen Siero¹, Matthias J.P. van Osch², and Natalia Petridou^1
1Department of Radiology, Center for Image Sciences, UMC Utrecht, Utrecht, Netherlands, ²C.J. Gorter MRI Center, LUMC, Leiden, Netherlands

Keywords: Signal Modeling, fMRI

GE-BOLD fMRI is the most used technique to measure functional hyperemia across cortical depth. GE-BOLD is sensitive towards all vascular contributions, while SE-BOLD increases the specificity towards small vessels– being more specific to neuronal activity. However, SE-BOLD fMRI measurements may not completely remove the macrovascular contribution. Using realistic vascular models, we simulated specific oxygenation states in different vascular compartments to characterize the GE-and SE-BOLD specificity across cortical depth quantified through the R2*/R2-ratio. Simulations show 1)similar ratio values at deeper layers indicating comparable specificity to microvessels for both sequences, 2)layer-fMRI SE-BOLD cannot completely eliminate the macrovascular contribution towards the pial surface.