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Renzo Huber¹, Rüdiger Stirnberg², David A Feinberg^1,3,4, Samantha J Ma⁵, Philipp Ehses², Omer Faruk Gulban^1,6, Jonathan R Polimeni⁷, Kenshu Koiso^1,8, Emily Ma¹, Alexander JS Beckett^3,4, Tony Stöcker², Peter Bandettini⁹, and Benedikt A Poser^1
1Maastricht University, Maastricht, Netherlands, ²German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany, ³Helen Wills Neuroscience Institute, University of California, Berkeley, CA, United States, ⁴Advanced MRI Technologies, Sebastopol, CA, United States, ⁵Siemens Medical Solutions USA, Inc., Berkeley, CA, United States, ⁶Brain Innovation, Maastricht, Netherlands, ⁷Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, ⁸Graduate School of Informatics and Engineering, The University of Electro-Communications, Tokyo, Japan, ⁹National institutes of HEalth, Bethesda, MD, United States

Keywords: Artifacts, fMRI, layer-fMRI, UHF, EPI

High-resolution layer-fMRI has great potential to inform network-neuroscience. However, it is limited by EPI artifacts. Here, we discuss a class of fuzzy EPI ghosts arising from asymmetric trapezoidal gradients with ramp sampling. A meta analysis across layer-fMRI datasets finds this artifact everywhere, without exceptions. We believe that this artifact is constraining spatiotemporal resolutions more than SNR. In this abstract we aim to raise awareness for this artifact and evaluate mitigation strategies: dual-polarity EPI. We show that dual-polarity EPI allows layer-fMRI to break the barriers of current resolution limits: It allows 0.53mm imaging at 3T, and whole-brain 0.6mm fMRI at 7T. 

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Keywords: Artifacts, High-Field MRI, Motion-resolved field map, cardiac shimming

B0 inhomogeneity imposes imaging artifacts on CMR images and compromises the reliability of popular B0-sensitive sequences such as SSFP at 3T. B0 shimming is the standard way to improve the B0 field. However, motion-induced field inhomogeneity is an unknown factor in routine practice and compromises B0 shimming. Here, we adopted a motion-resolved mGRE CMR sequence to investigate the cardiac B0 field perturbation caused by cardiac and respiratory motion. We found that respiratory motion has more impact on field inhomogeneity. We recommend acquiring a field map for shimming under an end-expiration breath-hold for better shimming and imaging at 3T CMR. 

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Quentin Raynaud¹, Thomas Dardano^1,2, Christopher Roy³, Jérôme Yerly^3,4, Tobias Kober^3,5,6, Ruud B. van Heeswijk³, and Antoine Lutti^1
1Department for Clinical Neuroscience, Laboratory for Research in Neuroimaging, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland, ²Physics section, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland, ³Department of Diagnostic and Interventional Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland, ⁴Center for Biomedical Imaging (CIBM), Lausanne, Switzerland, ⁵Advanced Clinical Imaging Technology, Siemens Healthineers International AG, Lausanne, Switzerland, ⁶LTS5, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland

Keywords: Artifacts, Relaxometry

Cardiac pulsation enhances the noise level in MR images of the brain and reduces the sensitivity of the data in studies of brain disease. We propose two data acquisition strategies that mitigate cardiac-induced noise in quantitative brain maps of the MRI parameter R₂*. The first strategy sets the number of samples at each k-space location according to the local level of cardiac-induced noise. The second strategy adjusts data acquisition in real-time to acquire the data most sensitive to cardiac-induced noise during the diastolic period of the cardiac cycle. 

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Chong Chen¹, Yingmin Liu², Yu Ding³, Mathew Tong⁴, Yuchi Han⁴, and Rizwan Ahmad^5
1Biomedical Engineering, The Ohio State Univerity, Columbus, OH, United States, ²Davis Heart and Lung Research Institute, The Ohio Sate University, Columbus, OH, United States, ³Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, United States, ⁴Internal Medicine, The Ohio State University, Colubmus, OH, United States, ⁵Biomedical Engineering, The Ohio Sate University, Columbus, OH, United States

Keywords: Artifacts, Artifacts

We propose a novel method to automatically identify and discard coils that strongly contribute to image artifacts. This is achieved by projecting coil images to the space spanned by the ESPIRiT coil sensitivity maps. The proposed method is evaluated using the real-time cine data collected from twelve volunteers during exercise. The artifacts in the reconstructed real-time cine images are suppressed significantly with the proposed coil selection method.

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Min Lang¹, Azadeh CD Tabari¹, Komal Awan¹, Wei Liu², Clifford Bryan³, Wei-Ching Lo³, Daniel Nicolas Splitthoff⁴, Stephen Cauley¹, Huang Susie¹, and Conklin CD John^1
1Massachusetts General Hospital, Boston, MA, United States, ²Siemens Shenzhen Magnetic Resonance Ltd., Shenzhen, China, ³Siemens Medical Solutions USA, Boston, MA, United States, ⁴Siemens Healthcare GmbH, Erlangen, Germany

Keywords: Artifacts, Data Acquisition, MR Value, Clinical Application, Neuro, Artifacts, Flow, Data Acquisition

Flow-related artifacts have been consistently observed in highly accelerated Wave-CAIPI post-contrast 3D-T1 MPRAGE and have an atypical appearance. Such artifacts introduce a diagnostic conundrum as they can mimic enhancing lesions and may require callback for repeat imaging, posing a critical barrier to wider clinical adoption of this technique. To address this, we developed an optimized flow-mitigated Wave-CAIPI post-contrast 3D T1 MPRAGE acquisition, tested it in a novel flow phantom, and deployed it in 17 patients undergoing contrast-enhanced brain MRI. Flow-mitigation was successful at reducing flow-related artifacts in most cases without sacrificing SNR, gray-white matter contrast, or enhancing lesion conspicuity.

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Jonathan K. Stelter¹, Mingming Wu¹, Johannes Raspe¹, Philipp Braun¹, Christof Boehm¹, Kilian Weiss², and Dimitrios C. Karampinos^1
1Department of Diagnostic and Interventional Radiology, Technical University of Munich, Munich, Germany, ²Philips Healthcare, Hamburg, Germany

Keywords: Artifacts, Motion Correction

Multi-echo gradient-echo imaging is known to be affected by temporally varying B0 effects, including B0 drifts and respiratory motion-induced B0 fluctuations. The radial stack-of-stars trajectory enables the oversampling of the k-space center and has been previously employed for B0-navigation without the consideration of fat. The present work develops a methodology for Dixon-based B0-navigation to correct for B0 drift and B0 fluctuations in stack-of-stars multi-echo gradient-echo imaging for body imaging. Simulations and in vivo measurements show the advantage of the Dixon-based B0-navigation in correcting quantification errors in proton density fat fraction, T2* and field-map, when using stack-of-stars multi-echo gradient-echo acquisitions.

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Mustafa Utkur^1,2, Tess E Wallace^1,2, Tobias Kober^3,4,5, Camilo Jaimes^1,2, Simon K Warfield^1,2, Sila Kurugol^1,2, and Onur Afacan^1,2
1Radiology, Harvard Medical School, Boston, MA, United States, ²Computational Radiology Laboratory, Boston Children's Hospital, Boston, MA, United States, ³Advanced Clinical Imaging Technology Group, Siemens Healthcare International AG, Lausanne, Switzerland, ⁴Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland, ⁵LTS5, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland

Keywords: Artifacts, Susceptibility

3D EPI is a clinically promising alternative for susceptibility weighted imaging due to multi-shot acceleration. However, achieving submillimeter resolution with 3D EPI is challenging as shot-to-shot B0 variations result in artifactual images that limit detection of small veins which can be decisive for detection of the central vein sign in multiple sclerosis. FID navigators have been shown to estimate phase drifts in EPI sequences. We demonstrate that FID-navigated 3D EPI acquisitions enable correction for phase-induced distortions and achieve high-quality submillimeter-resolution susceptibility weighted images.

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Zhiqiang Li¹, Melvyn B Ooi², Rory KJ Murphy¹, John P Karis¹, and Richard D Dortch^1
1Barrow Neurological Institute, Phoenix, AZ, United States, ²Philips Healthcare, Houston, TX, United States

Keywords: Artifacts, Artifacts, metal, implant, spinal cord, diffusion, multi-spectral imaging

Diffusion-weighted (DW) spinal cord MRI based on single-shot EPI suffers from strong geometric distortion and signal loss artifacts. While strategies have been developed to reduce these artifacts in DW-EPI, their application in spinal cord DWI is challenging when metal implants are present near the spine. A multispectral DW-PROPELLER has been proposed to overcome this challenge; however, this requires long scan times. In this work, we developed a single-shot TSE technique with multispectral imaging and reduced FOV to achieve fast speed / increased SNR for spinal cord DWI near metals. Volunteer and patient results demonstrated reduced artifacts and improved speed/SNR performance.

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Wenchuan Wu^1
1Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom

Keywords: Artifacts, Data Acquisition, EPI distortion

In this work, we propose a new method for dynamic distortion correction by integrating a tailored EPI trajectory and a joint multi-echo reconstruction, which permits robust dynamic field mapping and distortion correction without compromising spatial resolution. The performance of the proposed method is demonstrated using in vivo experiments. 

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Keywords: Artifacts, Cardiovascular, bSSFP, parallel imaging, spatial harmonics, Cine, Outflow effects

In the present of through plane flow in 2D bSSFP imaging, we used the variation coil sensitivity profile along the through-slice direction to estimate the spatial harmonics needed to slice-encode for outflowing spins.  Estimating the outer partitions unfolded the outflowing spins from the target center slice with a faster acquisition time than our previous slice-encoding technique.  

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Myung-Ho In¹, Norbert G Campeau¹, Joshua D Trzasko¹, Daehun Kang¹, Kirk M Welker¹, John III Huston¹, Yunhong Shu¹, and Matt A Bernstein^1
1Department of Radiology, Mayo Clinic, Rochester, MN, United States

Keywords: Artifacts, Diffusion Tensor Imaging

A novel distortion-free multi-shot diffusion-weighted-imaging (DWI), termed DIADEM (Distortion-free Imaging: A Double Encoding Method), was compared with commercially available state-of-the-art DWI techniques for clinical brain imaging. High-resolution distortion-free DWI is feasible within clinically acceptable acquisition times using the DIADEM technique, and demonstrated better performance than current commercially available DWI techniques.

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Philip Kenneth Lee¹, Xuetong Zhou^1,2, Nan Wang¹, and Brian Andrew Hargreaves^1,2,3
1Radiology, Stanford University, Stanford, CA, United States, ²Bioengineering, Stanford University, Stanford, CA, United States, ³Electrical Engineering, Stanford University, Stanford, CA, United States

Keywords: Pulse Sequence Design, Diffusion/other diffusion imaging techniques, abdomen, free-breathing

Abdominal imaging is frequently performed with uncomfortable breath holds, or respiratory triggering to reduce the effects of respiratory motion. Diffusion weighted sequences provide a useful clinical contrast but have prolonged scan times due to low SNR. These scans cannot be reliably completed in a single breath hold, and respiratory triggering has low scan efficiency. We present a respiratory resolved, diffusion-prepared 3D sequence that obtains distortionless diffusion weighted images during free-breathing. We describe techniques to address the myriad of challenges including: 3D shot-to-shot phase correction, respiratory binning, diffusion encoding during free-breathing, and robustness to off-resonance.

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Seong Dae Yun¹, Erhan Genc², and N. Jon Shah^1,3,4,5
1Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Juelich, Juelich, Germany, ²Department of Psychology and Neurosciences, Leibniz Research Centre for Working Environment and Human Factors (IfADo), Dortmund, Germany, ³Institute of Neuroscience and Medicine 11, INM-11, JARA, Forschungszentrum Juelich, Juelich, Germany, ⁴JARA - BRAIN - Translational Medicine, Aachen, Germany, ⁵Department of Neurology, RWTH Aachen University, Aachen, Germany

Keywords: Pulse Sequence Design, fMRI, 7T, improved fMRI mapping accuracy, EPI, geometric-distortion correction, opposite phase-encoding and reduced acquisition time

In high-resolution fMRI using EPI, geometric distortions typically seen in reconstructed images significantly hinder the accurate mapping of activated voxels. One method to correct for distortions is to acquire EPI data with an opposite phase-encoding direction. However, this method is usually implemented with an additional run of the same protocol, leading to a redundant measurement of parallel imaging calibration scans. Here, we present an EPI scheme that measures the opposite-direction data in a single fMRI session, substantially reducing the total acquisition time. We demonstrate more accurate functional mapping with the distortion correction in submillimetre whole-brain visual fMRI at 7T.

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Sebastian Mueller^1,2, Jonas Bause¹, Rüdiger Stirnberg³, and Klaus Scheffler^1,2
1High-field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, ²Department for Biomedical Magnetic Resonance, University Hospital Tuebingen, Tuebingen, Germany, ³German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany

Keywords: Data Acquisition, fMRI

A segmented 3D GRE EPI was adapted and optimized specifically for BOLD fMRI at a 9.4T MR system. While EPI is widely used in fMRI, especially at UHF its application becomes challenging for instance for long echo trains used at high spatial resolution. In this work, investigations on the stability of the system, tSNR, flexible sequence design, different temporal phase correction schemes, and efficient use of the limited SAR budget were performed. Finally, a protocol for BOLD fMRI of the motor cortex at 1.0mm nominal isotropic resolution (FOV=200x215x44mm³) with a volume TR of 3 seconds was set up.

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Fatih Calakli^1,2, Tess E. Wallace^1,2, and Simon K. Warfield^1,2
1Computational Radiology Laboratory, Boston Children's Hospital, Boston, MA, United States, ²Department of Radiology, Harvard Medical School, Boston, MA, United States

Keywords: Motion Correction, Brain

High-resolution, 3D structural scans are susceptible to patient motion as they take several minutes or more to acquire. Radial MRI acquisitions are emerging as a motion-robust alternative to Cartesian trajectories. Most approaches involve co-registration of navigator images once the acquisition is complete. However, the time needed for co-registration of navigator images, coupled with the long reconstruction times required for high-resolution NUFFT, is a challenge for integration of motion-compensated non-Cartesian imaging into clinical protocols. In this work we developed a motion-compensated online gridding algorithm to perform adaptive motion compensated reconstruction overlapped with the acquisition.