Guodong Weng^1,2, Piotr Radojewski^1,2, and Johannes Slotboom^1,2
1Institute for Diagnostic and Interventional Neuroradiology, Support Center for Advanced Neuroimaging (SCAN), University of Bern, Bern, Switzerland, ²Translational Imaging Center, sitem-insel AG, Bern, Switzerland

Purpose: whole brain in vivo detection of GABA/GABA+ using SLOW-editing at 7T.

Methods: An EPSI-based B0/B1+ robust SLOW-editing was applied in four healthy subjects. Pure GABA was measured by two different macromolecular-nulling inversion recovery pulses, namely a broadband- and a narrowband-inversion pulse.

Results: the editing GABA/GABA+ signal at 3.01 ppm are presented. The signal intensity of GABA/GABA+ ratio is 40 – 60%.

Conclusions: whole-brain in vivo GABA/GABA+-editing can be performed using SLOW-EPSI in around 10 minutes measurement time and is therefore clinically applicable. 

Peter Truong¹ and Jamie Near^1,2
1Physical Sciences Research Platform, Hurvitz Brain Sciences Program, Sunnybrook Research Institute, Toronto, ON, Canada, ²Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada

J-difference editing techniques, such as MEGA-PRESS, are often used to detect gamma-aminobutryic acid (GABA) and glutathione (GSH). However, two separate scans are needed to acquire both metabolites. The HERMES editing scheme does address this issue, allowing simultaneous acquisition of GABA and GSH. Even then, there are limitations as the optimal echo time (TE) can only be set for one metabolite at the expense of lower editing efficiency for the other. We propose the Extended TE (ExTE) HERMES editing scheme, which allows us to acquire edited spectra at TE=120ms, ensuring maximum GSH signal while still providing efficient GABA editing.
 

Salem Alkhateeb¹, Tae Kim², Howard J Aizenstein², and tamer S. Ibrahim^3
1University of Pittsburgh, PITTSBURGH, PA, United States, ²University of Pittsburgh, Pittsburgh, PA, United States, ³University of Pittsburgh, pittsburgh, PA, United States

The feasibility of implementing pCASL technique at 7T MRI as a routine protocol uncovers the difficulties and challenges that need to be overcome and taking into consideration the many variables that need to be addressed before running the sequence. We were able to successfully implement pCASL sequence with satisfactory results. CBF quantification for the 4 volunteers was within clinical normal ranges and CBF mapping agrees with published data. Future work will include the inclusion of neck coil module for improving labeling efficiency.[GU1]  Where is figure 4 referenced [GU1]   Please add the references

Kevin Moulin^1,2, Tyler E Cork^3,4, Thomas Troalen⁵, Daniel Ennis^3,4, Pierre Croisille^1,2, and Magalie Viallon^1,2
1CREATIS, Lyon, France, ²Department of Radiology, University Hospital Saint-Etienne, Saint Etienne, France, ³Department of Radiology, Stanford University, Stanford, CA, United States, ⁴Division of Radiology, Veterans Administration Health Care System, Palo Alto, CA, United States, ⁵Siemens Healthcare SAS, Saint-Denis, France

Multi-shot (MS) reduces image distortion in EPI caused by B₀ field inhomogeneity and enables higher resolution diffusion imaging. However, interaction between physiologic motion and diffusion encoding gradients leads to strong image aliasing artifacts in MS-EPI due to phase discrepancies. We propose prospective strategies to reduce shot-to-shot phase variation for interleaved phase-segmented diffusion MS-EPI. First and second order motion compensated diffusion gradient waveforms and dual-speed EPI with oversampled k-space center were evaluated as a shot-to-shot phase mitigation strategy. Validations were performed in silico, in vitro, and in vivo in the brain, liver, and heart.

Manoj Shrestha¹, Pavel Hok^1,2, Ulrike Nöth¹, and Ralf Deichmann^1
1Brain Imaging Center (BIC), Goethe University Frankfurt, Frankfurt am Main, Germany, ²Department of Neurology, Palacky University Olomouc and University Hospital Olomouc, Olomouc, Czech Republic

Frequently, diffusion-weighting modules such as schemes based on the Stejskal-Tanner concept or the STEAM are combined with EPI readout for fast k-space sampling. In contrast to standard sequences, highly asymmetric spin-echo and highly asymmetric STEAM sequences (HASE, HASTEAM) offer shorter TE, maintaining constant diffusion preparation duration, independent of the matrix-size. In this study, HASE and HASTEAM sequences were implemented for neuronal fibre tracking, and results were compared with standard sequences. Both asymmetric sequences HASE and HASTEAM allow for more accurate estimations of the subsidiary fibre orientations, which may considerably improve the quality and quantity of the detected fibre tracts.  

Ruoyun Emily Ma¹, Dimo Ivanov¹, Renzo Huber¹, Denizhan Kurban¹, and Benedikt A Poser^1
1Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, Netherlands

We developed several ASL sequences at 7T with a FAIR-QUIPSS II labeling scheme and various spiral readout strategies using Pulseq. Iterative algebraic image reconstruction was performed with CG-SENSE, using the field evolution data measured with external NMR probes. Robust performance in detecting brain’s perfusion signal was observed in 2D single- and multi-band spiral acquisitions especially at relatively high spatial resolution, without the requirement for a longer scan time. 3D spiral acquisition showed reduced contrast level in perfusion maps and requires further investigation and optimization.

Tyler Blazey¹ and Cornelius von Morze^1
1Washington University in St. Louis, St. Louis, MO, United States

Imaging of hyperpolarized (HP) ¹³C magnetization is typically done using direct detection of the ¹³C signal. However, indirect ¹H-based detection via J-coupled protons has the advantage of reducing gradient requirements and enhancing sensitivity, as well as practical advantages. We have developed an INEPT-based EPI sequence, which we tested by acquiring 3D images of a ¹³C formate phantom after transfer of thermal polarization from ¹H to ¹³C. We also tested a novel deconvolution method to correct ghosting artifacts introduced in EPI images by J-coupling. These methods will be translated into in vivo HP imaging experiments in the next phase of research.

Aidin Arbabi¹, Vitaliy Khlebnikov¹, David. G. Norris¹, and Jose P. Marques^1
1Donders Institute, Radboud University, Nijmegen, Netherlands

Half-Fourier acquisition single-shot turbo spin-echo diffusion-weighted (DW-HASTE) is a clinically established magnetic resonance imaging tool for the detection of small lesions, particularly cholesteatoma. However, in the standard approach, half of the available signal is sacrificed through displacing one echo parity out of the acquisition window to fulfil the Carr-Purcell-Meiboom-Gill condition. We present a selective parity approach to tackle this problem. The proposed method features a near full sensitivity, a low specific absorption rate for long echo trains, and about two-fold increase in signal-to-noise ratio, compared to the manufacturer's method under the same conditions.

Nathan Ooms¹, Xin Shen², Ali Caglar Ozen³, Serhat Ilbey³, Mark Chiew⁴, and Uzay Emir^1
1School of Health Sciences, Purdue University, West Lafayette, IN, United States, ²Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, United States, ³Radiology, Medical Center- University of Freiburg, Freiburg, Germany, ⁴Welcome Centre for Integrative Neuroimaging, University of Oxford, Oxford, United Kingdom

Pulmonary imaging traditionally uses techniques utilizing ionizing radiation such as x-rays and CT. Pediatrics, pregnant patients, and patients who will be exposed multiple times over long periods of time would benefit from a non-ionizing modality. MRI does not use ionizing radiation but suffers from low signal from the lungs and breathing motion artifact. We are proposing a novel MRI technique to combat these issues: a 3-dimensional Dual-Echo FID Ultra-short Echo Time (3D DE UTE) sequence utilizing Rosette k-space acquisition. Preliminary results demonstrated better pulmonary artery segmental branches and pleural wall definition compared to other commercially available MRI sequences.

Kang Yan^1,2, Huajun She², and Yiping Du^2
1Biomedical Engineering, University of Virginia, Charlottesville, VA, United States, ²Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China

In diffusion-weighted imaging (DWI) using echo-planar acquisition, fat signals are commonly suppressed by using chemical saturation or by spectral-spatial RF excitation. In this study, we present a technique using a rosette trajectory for simultaneous mapping of apparent diffusion coefficient (ADC) and water-fat separation with inherent B0 correction. The feasibility of using this technique is demonstrated in phantom, brain, and head-neck scans.

Guodong Weng^1,2, Piotr Radojewski^1,2, Philippe Schucht³, Roland Wiest^1,2, and Johannes Slotboom^1,2
1Institute for Diagnostic and Interventional Neuroradiology, Support Center for Advanced Neuroimaging (SCAN), INSEL Gruppe AG, University of Bern, Bern, Switzerland, ²Translational Imaging Center, sitem-insel AG, Bern, Switzerland, ³Department of Neurosurgery, Inselspital Bern and University Hospital, Bern, Switzerland

Purpose: to detect phosphoethanolamine (PEtn or PE) in vivo for whole-brain MRSI, overcoming challenges of B₁⁺-inhomogeneities and CSDE at 7T.

Methods: An EPSI-based B₁⁺ robust SLOW-editing was applied to three healthy subjects. TE = 90 ms, TR = 1500 ms, and TA = 9:04 mins.

Results: the editing PE signal at 3.22 ppm was clearly present, and the B₁⁺-homogenous result/map was obtained.

Conclusions: whole-brain in vivo PE-editing can be performed in around 9 minutes measurement time and is therefore clinically applicable. 

Jabrane Karkouri¹, Christopher Wickens¹, Daniel Atkinson¹, and Christopher T. Rodgers^1
1University of Cambridge, Cambridge, United Kingdom

In this work, we present a software “sequence building block” that enables interleaving MRS acquisitions (X-nuclear or 1H) inside a base imaging sequence (typically 1H) on the Siemens 7T Terra platform. We envisage using this approach for dynamic B0 shim and frequency offset correction to mitigate breathing artefacts in 31P-MRSI of heart and liver.

Ilana R Leppert¹, Christopher D Rowley^1,2, Jennifer SW Campbell¹, Mark Nelson^1,3, Bruce G Pike⁴, and Christine L Tardif^1,2,3
1McConnell Brain Imaging Centre, Montreal Neurological Institute and Hospital, Montreal, QC, Canada, ²Department of Biomedical Engineering, McGill University, Montreal, QC, Canada, ³Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada, ⁴Hotchkiss Brain Institute and Departments of Radiology and Clinical Neuroscience, University of Calgary, Calgary, Canada, Calgary, AB, Canada

Most white matter voxels are comprised of a combination of microstructurally different tracts that kiss and cross. Conventional MRI contrasts that provide a single measurement per voxel fail to disentangle the microstructural properties of these tracts. Co-encoding diffusion with a complementary contrast offers additional insight into each tract’s individual contribution. Here we present a novel MT-prepared diffusion sequence, optimized for contrast in both MTR and orientation, acquired within a clinically acceptable scan time of under 7 min. The goal is to provide a data acquisition framework for the computation of tract-specific myelin indices and potentially more structurally specific connectomes.

Sidsel Winther^1,2, Henrik Lundell², and Tim B. Dyrby^1,2
1Department of Applied Mathematics and Computer Science, Technical University of Denmark, Kongens Lyngby, Denmark, ²Danish Research Centre for Magnetic Resonance (DRCMR), Copenhagen University Hospital Hvidovre, Hvidovre, Denmark

Magnetic susceptibility induces morphology- and orientation-dependent perturbations of the $$$B_0$$$-field and hence the DWI signal. At the micro-structural scale of brain white matter, the main contribution to these perturbations comes from myelin. To understand how the perturbations are shaped by the intrinsically undulating morphology of axons, observed in 3D reconstructions of synchrotron imaging and electron microscopy, we have implemented a framework that enables us to systematically study how undulation affects the orientation-dependency of susceptibility-induced B-field inhomogeneity, and how this affects the DWI signal - both in the intra- and extra-axonal compartments.

Jack Highton¹, Maria Yanez Lopez¹, Anthony Price¹, Vanessa Kyriakopoulou¹, Lisa Story¹, Mary A. Rutherford¹, Jo Hajnal¹, and Enrico De Vita^1
1Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom

Magnetic resonance spectroscopy (MRS) can measure the concentration of a range of metabolites to understand pathophysiological and normal development in the fetus, as well as provide diagnostic and prognostic markers [1]. However, MRS applications in the fetus are technically very challenging due to the inherently low SNR (fetal size, distance from the coil, the use of 1.5T scans) and signal disruption caused by unrestricted fetal motion during data collection.  Given the limited available SNR, outlier rejection to remove motion corrupted averages and improve spectral quality is particularly important. Spectral phase shifts are associated with motion, both during signal acquisition and between MRS repeats [2]. We propose a threshold-free method for optimal outlier rejection of fetal MRS, “Ranked residual-water Phase Shift”: the phase shift in the residual water after water suppression is used as a metric linked to potential motion in individual transients/repeats.

Ana E Rodríguez-Soto¹, Summer J Batasin¹, Lauren K Fang¹, Michael Carl², Haydee Ojeda-Fournier¹, Kathryn E Keenan³, and Rebecca A Rakow-Penner^1,4
1Radiology, University of California, San Diego, La Jolla, CA, United States, ²GE Healthcare, University of California, San Diego, La Jolla, CA, United States, ³National Institute of Standards and Technology, Boulder, CO, United States, ⁴Bioengineering, University of California, San Diego, La Jolla, CA, United States

Diffusion-weighted imaging (DWI) acquired with echo-planar imaging (EPI) is utilized in breast MRI protocols to evaluate cancer lesions. While clinical implementation is limited by the distortion artifacts which affect EPI, methods such as reverse polarity gradient (RPG) and data collection with reduced field-of-view (FOV) have been used to reduce distortion. Evaluating these methods in minimizing distortion for images acquired with parallel imaging (PI) is a promising approach to improve EPI-DWI breast imaging. Here, we evaluated the distortion magnitude of EPI-DWI data collected with and without PI on a breast phantom and tested the feasibility of this protocol in vivo.

Virendra R Mishra¹, Ofer Pasternak², Karthik R Sreenivasan¹, and Dietmar Cordes^1
1Imaging, Cleveland Clinic Lou Ruvo Center for Brain Health, Las Vegas, NV, United States, ²Harvard Medical School, Boston, MA, United States

Free-water (FW) estimation could be improved with higher spatial resolution diffusion MRI (dMRI) data acquired at multiple shells. However, the effect of multi-shell protocol features on the accuracy of estimating FW and FW-corrected fractional anisotropy (FA) across the brain structures is currently unknown. We  evaluated test-retest reproducibility of FW and FW-corrected FA across 20 major white-matter tracts across four dMRI protocols, two protocols with ADNI-3 and two protocols with HCP sequences. Our analysis suggests higher spatial resolution HCP-style dMRI data acquisition with correction of FW-estimation could be reliably performed in routine clinical investigations.

Brenden Kadota¹, Bernhard Strasser^2,3, Wendy Oakden¹, and Jamie Near^1,4
1Physical Studies Research Platform, Sunnybrook Research Institute, Toronto, ON, Canada, ²Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria, ³A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, MA, United States, ⁴Medical Biophysics, University of Toronto, Toronto, ON, Canada

Magnetic resonance spectroscopic imaging (MRSI) is a biomedical imaging tool that enables spatial mapping of metabolite signals in vivo. Dedicated software for MRSI data preprocessing, image reconstruction, visualization and simulation is vital to the development and routine application of MRSI but relatively few tools are available for this purpose. We present an open source toolbox in MATLAB for preprocessing, visualization and simulation of MRSI data. The processing toolbox includes functions for importing data, coil combination, B0 inhomogeneity correction, and non cartesian reconstruction, while the simulation toolbox can simulate MRSI acquisitions with arbitrary input k-space trajectories.