François Emmanuel Jean Guy MAINGAULT¹, Nadège CORBIN¹, William LEFRANÇOIS¹, Aurélien J TROTIER¹, Sylvain MIRAUX¹, and Emeline J RIBOT^1
1Centre de Résonance Magnétique des Systèmes Biologiques, UMR5536, CNRS, Bordeaux, France, Metropolitan

The Magnetization Prepared Two RApid Gradient Echo (MP2RAGE) sequence with a cartesian sampling is performed to obtain 3D-T₁ weighted images of the brain. A radial encoding giving a better robustness to respiratory motion has been implemented in order to use the MP2RAGE sequence for abdominal imaging.

Sangcheon Choi^1,2, Rahel Heule^1,3, Edyta Leks^1,2,3, Felix Glang¹, Xin Yu⁴, and Klaus Scheffler^1,3
1Department of High-field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, ²Graduate Training Centre of Neuroscience, University of Tuebingen, Tuebingen, Germany, ³Department of Biomedical Magnetic Resonance, University of Tuebingen, Tuebingen, Germany, ⁴Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Harvard Medical School, Massachusetts General Hospital, Charlestown, MA, United States

We developed new calibration kernels with an alternative undersampling scheme (CASS) for parallel imaging to reduce coherent aliasing artifacts and noises. By sampling k-space lines with irregular and blockwise patterns, incoherent aliasing patterns and noise signals were spread in reconstructed CASS images. Noteworthily, the CASS method outperformed the conventional GRAPPA method at higher acceleration factors.

Maria Engel¹, Lars Kasper^1,2, and Klaas Paul Pruessmann^1
1Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland, ²Translational Neuromodeling Unit, Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland

The timing of BOLD-fMRI is typically chosen such that TE matches T₂*. This assumes contrast being exclusively elicited by signal differences at TE. While sensible for short or TE-symmetric readouts, such as EPIs, it oversimplifies contrast generation for longer or TE-asymmetric trajectories, such as spirals.

We propose the concept of a BOLD PSF for a more comprehensive perspective on the imaging characteristics of a functional experiment. Our findings indicate that TE can be reduced for spiral-out without sacrificing BOLD-sensitivity when compared to EPI. Furthermore, we characterize the intrinsic trade-off between specificity and resolution of the BOLD response under varying TE.

Lucia Navarro de Lara^1,2, Isil Uluc^1,3, Qinglei Meng^1,3, Jason Stockmann^1,3, Larry Wald^1,3, and Aapo Nummenmaa^1,3
1Martinos Center - MGH, Charlestown, MA, United States, ²Harvard Medical School, Boton, MA, United States, ³Harvard Medical School, Boston, MA, United States

For TMS/fMRI experiments, to acquire functional images without artifacts, general recommendations have been proposed. In order to apply TMS pulses in a multichannel Transcranial Magnetic Stimulation system integrated with the new constructed TMSMR 28- channel RF coil, we have explored the different options and artifacts that can be generated depending on when the TMS pulses are applied with respect to the sequence timing. As conclusion, we propose a method using an RF pick up loop to assure that the delivery of the TMS pulses are not close to the EPI navigators or the imaging gradients. 

Vahid Malekian¹, Nadine N. Graedel¹, Oliver Josephs¹, and Martina F. Callaghan^1
1Wellcome Centre for Human Neuroimaging, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom

3DEPI is widely used for cortical depth-dependent fMRI studies at 7T. However, it suffers from poor image contrast that can be problematic for fMRI post-processing steps. One solution to bolster contrast is to implement a magnetization transfer (MT) module. Here, we experimentally investigated the different MT pre-pulse characteristics to optimize image contrast, while considering power limitations at 7T. Contrast gains eased co-registration to an MP2RAGE reference, and improved cortical segmentation. Our analyses confirmed that the MT contrast is spatially variable and dependent on transmit field inhomogeneity. 

 

Stefan Posse¹, Sudhir Ramanna², Steen Moeller², Bruno Sa De La Rocque Guimaraes¹, Michael Mullen², and Essa Yacoub^2
1Neurology, U New Mexico, Albuquerque, NM, United States, ²Center for Magnetic Resonance Research, Minneapolis, MN, United States

In this study we develop highly undersampled multi-band slab-segmented echo-volumar imaging (MB_EVI), which combines the sampling efficiency of single-shot 3D encoding with the sensitivity advantage of multi-echo acquisition, and explore the feasibility of shortening the readout duration using segmented within-slab slice encoding. Kz-segmented Segmented MB-EVI enabled a nominal 1x1x1 mm isotropic voxel size with 64 slices and a temporal resolution of 618 ms with sub-second acquisition time.

Mark Bydder¹, Fadil Ali¹, Andres Saucedo¹, Chencai Wang¹, Akifumi Hagiwara¹, Alex D Pham¹, Jingwen Yao², and Ben Ellingson^1
1UCLA, Los Angeles, CA, United States, ²UCSF, San Francisco, CA, United States

The present article develops an understanding of how to choose optimal (or at least reasonable) parameter values for 3D radial density adapted sampling. This has a practical role in designing clinical protocols for short TE non-Cartesian imaging.

Zaineb Amor¹, Chaithya G.R.^1,2, Guillaume Daval-Frérot^1,2,3, Bertrand Thirion^1,2, Franck Mauconduit¹, Philippe Ciuciu^1,2, and Alexandre Vignaud^1
1Université Paris-Saclay, CEA, Neurospin, CNRS, Gif-sur-Yvette, France, ²Université Paris-Saclay, Inria, Parietal, Palaiseau, France, ³Siemens Healthcare SAS, Saint-Denis, France

For the first time, non-Cartesian 3D-SPARKLING (Spreading Projection Algorithm for Rapid K-space sampLING) encoding scheme was used for task-based fMRI (retinotopic mapping) at 7T. Additionally, this new acquisition technique was compared with 3D-EPI, considered as one of the reference acquisition schemes in high-resolution fMRI. The experiment was performed on a single participant at 1mm isotropic and for a temporal resolution of 2.4s. We found that both techniques yield similar statistically significant activation patterns in the visual cortex.

Jacob Hatef¹, Abhishek Vijaykumar¹, Chong Chen¹, Yingmin Liu¹, and Rizwan Ahmad^1
1The Ohio State University, Columbus, OH, United States

In this work, we develop and apply a method to prune channels from multi-coil Pilot Tone (PT) data. The method suppresses contributions from noisy or corrupt channels and thus improves the quality of the PT-driven cardiac signal. The method, called Spectrum Optimized Channel pruning (SOC), is based on maximizing the ratio of the signal energy in the frequencies that correspond to physiological motions to the signal energy in the frequencies that are outside the physiological motions. Using data from 15 subjects, we highlight that the proposed channel pruning method improves the quality of the extracted cardiac signal.

Edith Franziska Baader¹, Fabian Theißen¹, Nicola Pezzotti^2,3, and Volkmar Schulz^1,4,5,6
1Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen, Germany, ²Philips Research, Eindhoven, Netherlands, ³Department of Mathematics and Computer Science, Eindhoven University of Technology, Eindhoven, Netherlands, ⁴Physics Institute III B, RWTH Aachen University, Aachen, Germany, ⁵Fraunhofer Institute for Digital Medicine MEVIS, Bremen, Germany, ⁶Hyperion Hybrid Imaging Systems GmbH, Aachen, Germany

One approach to accelerate MRI scans is to acquire fewer k-space samples. Commonly, the sampling pattern is selected before the scan, ignoring the sequential nature of the sampling process. A field of machine learning addressing sequential decision processes is reinforcement learning (RL). We present an approach for creating adaptive two-dimensional (2D) k-space trajectories using RL and the so-called action space shaping. The trained RL algorithm adapts to a variety of basic 2D shapes outperforming simple baseline trajectories. By shaping the action space of the RL agent we achieve better generalization and interpretability of the agent.

Changjun Ma¹, Shifeng Tian², Lihua Chen², Nan Wang², Qingwei Song², Liangjie Lin³, and Ailian Liu^2
1Department of Radiology, the First Affiliated Hospital of Dalian Medical University, Dalian,China, China, ²Department of Radiology, the First Affiliated Hospital of Dalian Medical University, Dalian, China, ³Philips Healthcare, Beijing, China, Beijing, China

3D-ISO-T2WI can obtain ISO volume images compared with traditional 2D-T2WI imaging, reducing partial volume effects, and volume data post-processing can be omni-directional, Three-dimensional, multi-angle display of the overall picture of the uterine structure and the scope of the lesion, but its scanning time is longer [1], the peristalsis of the subject's uterus, bladder and intestine during the scanning time may affect the image quality, and the scanning time The long-term reduction of the patient’s coordination and examination circulation.In this study, different AF will be selected to optimize the best AF based on the CS-based 3D-ISO-T2WI sequence of the uterus.

Jianfeng Bao¹, Xiaoyue Ma², Qinqin Yang³, Xiao Wang², Yong Zhang², Liangjie Lin⁴, Jingliang Cheng², and Congbo Cai^3
1The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China, ²Department of Magnetic Resonance Imaging, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China, ³Department of Electronic Science, Xiamen University, Xiamen, China, ⁴Philips Healthcare, Beijing, China

Quantitative MRI (qMRI) are expected largely to provide more accuracy clinical diagnostic information. However, bound by the relative long duration for the routine MRI exam and much longer qMRI acquisition time, the qMRI is not widely used for diagnostic purpose. The change of MR signal caused by contrast agent extravasation is affected by many factors, which will increase difficulty in diagnosis. Quantitative MRI (qMRI) are expected to overcome this issue. Recently, an ultra-fast multi-parameters qMRI technique was developed by our group, and herein we aim to apply the proposed strategy on brain tumor imaging and to preliminary access the potential performance.