Nadine N Graedel¹, Mark Chiew¹, and Karla L Miller ^1
1FMRIB Centre for Functional MRI of the Brain, University of Oxford, Oxford, United Kingdom

We used a hybrid radial-Cartesian 3D EPI trajectory with a golden ratio based angle update to perform retrospective motion correction in severely motion corrupted fMRI data. Motion estimates were based on high temporal resolution image timeseries and and k-space based estimates. The calculated rotations and translations were corrected in k-space prior to the final reconstruction, allowing the correction of both inter- and intra-volume motion artifacts. This approach is self-navigated, requires no additional hardware and is suitable for correction in fast fMRI acquisition. 

Rüdiger Stirnberg¹, Willem Huijbers¹, Benedikt A. Poser², and Tony Stöcker^1,3
1German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany, ²Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, Netherlands, ³Department of Physics and Astronomy, University of Bonn, Bonn, Germany

We conducted a feasibility study to compare state-of-the-art simultaneous multi-slice EPI vs. segmented 3D-EPI – both utilizing equivalent undersampling techniques for controlled aliasing – optimized for ultra-fast whole-brain fMRI at 3T. We compared temporal signal-to-noise ratio, sensitivity per unit scan time and temporal whole-brain spectra of 8 minutes time-series. While both fast sequences are well-suited to separate physiological from BOLD signal, the 3D-EPI sequence achieves greater sensitivity and signal-to-noise ratio throughout the brain using whole-brain protocols matched for identical TR.

An T. Vu^1,2, Alex Beckett¹, Kawin Setompop³, and David A. Feinberg^1,2
1Helen Wills Neuroscience Institute, UC Berkeley, Berkeley, CA, United States, ²Advanced MRI Technologies, Sebastopol, CA, United States, ³Martinos Center for Biomedical Imaging, Charlestown, MA, United States

We evaluate the synergistic combination of super-resolution and SMS for high-resolution whole brain fMRI.  We find that SLIDER-SMS can acquire high resolution, high CNR fMRI data at 3T which is normally only acquired at 7T. The regularized deblurring/reconstruction of SLIDER yielded 40% more BOLD CNR than normally acquired high resolution (HR) data, while omitting the deblurring step altogether yielded 100% more BOLD contrast with similar high k-space frequency tSNR. Future use of SLIDER for fMRI may enable robust columnar level results at 3T and allow higher spatial resolution fMRI investigations at 7T than currently possible.

Laetitia Vionnet¹, Simon Gross¹, Lars Kasper^1,2, Benjamin Emanuel Dietrich¹, and Klaas Paul Pruessmann^1
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland, ²Translational Neuromodeling Unit, Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

NMR field probe were used to record subject physiology at 7T. The signals were used to de-noise fMRI dataset and showed to be equivalent to standard devices. 

Laurentius Huber¹, Dimo Ivanov², Sean Marrett¹, Puja Panwar¹, Kamil Uludag², Peter A Bandettini¹, and Benedikt A Poser^2
1Section of Functional Imaging Methods, National Institute of Mental Health, Bethesda, MD, United States, ²MBIC, Maastricht University, Maastricht, Netherlands

Cerebral blood volume (CBV) fMRI has the potential to overcome known limitations of BOLD fMRI with respect to spatial specificity and quantifiability of mapping brain activity. To overcome the coverage limitations of conventional CBV mapping with VASO, a novel VASO method with 3D-EPI readout was developed. This new approach is compared to BOLD fMRI and VASO with simultaneous multi-slice EPI readout. We provide evidence for a high sensitivity and improved specificity of 3D-EPI VASO compared to conventional BOLD fMRI. We conclude that because of its superior resolution in slice-direction, 3D-EPI VASO may play an important role in high-resolution fMRI.

Eun Soo Choi¹ and Gary Glover^2
1Electrical Engineering, Stanford University, Stanford, CA, United States, ²Radiology, Stanford University, Stanford, CA, United States

In BOLD contrasts fMRI, the most commonly used sequences, gradient-echo and spin-echo, have been challenged due to their limited spatial specificity or functional sensitivity. As an alternative, an asymmetric spin-echo sequence was introduced, yet, its characteristics in different conditions are still unclear. In this study, we performed simulations and in-vivo experiments to design the optimal ASE pulse sequence that maximizes functional sensitivity while preserving high spatial specificity. 

Ying-Hua Chu¹, Yi-Cheng Hsu¹, and Fa-Hsuan Lin^1
1Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan

We proposed the simultaneous multi-slice (SMS) inverse imaging (InI) method to achieve 10 Hz sampling rate and significantly improved spatial resolution (30-fold higher than typical inverse imaging; quantified by point-spread function). SMS-InI was demonstrated in a visual fMRI experiment showing maps of brain activity similar to EPI and hemodynamic response with 0.1 s precision.

Bruno Riemenschneider¹, Jakob Assländer¹, Pierre Levan¹, and Jürgen Hennig^1
1Medical Physics, University Medical Center Freiburg, Freiburg, Germany

We investigated a segmented version of the spherical stack-of-spirals trajectory that retains highly efficient data sampling and signal recovery, but grants more flexibility in data sampling compared to the single-shot version. Whole brain acquisition with nominal isotropic resolutions of 3mm in 195ms and 2.25mm in 260ms using 3- and 4-fold segmentation have been investigated. The faster read out along the slowest encoding direction leads to reduced off-resonance artifacts in comparison to the single- shot version, and higher sampling rates allow non-regularized reconstruction.

Laurentius Huber¹, Daniel A Handwerker¹, Javier Gonzalez-Castillo¹, David C Jangraw¹, Maria Guidi², Dimo Ivanov³, Benedikt A Poser³, Jozien Goense⁴, and Peter A Bandettini^1
1Section of Functional Imaging Methods, National Institute of Mental Health, Bethesda, MD, United States, ²Human Cognitive and Brain Sciences, Max Planck Institute, Leipzig, Germany, ³MBIC, Maastricht University, Maastricht, Netherlands, ⁴Institute of Neuroscience and Psychology, University of Glasgow, Glasgow, United Kingdom

Measurements of layer-dependent cortical activity provide insight on how feedforward/feedback functional connectivity affects a given cortical area. Here, we simultaneously measure layer-dependent changes in resting-state BOLD and CBV with VASO. We demonstrate that the superior specificity of CBV fMRI reveals layer-dependent resting-state activity better than GE-BOLD fMRI and gives indications of effective connectivity in the human sensory-motor system. In particular, superficial and deeper layers in M1 show different connectivity patterns than those associated with the middle layer, likely driven by input from S1. Our data show that the middle layer in M1 correlates with contralateral M1, while it anti-correlates with contralateral S1.

Mario Gilberto Baez Yanez^1,2, Phillip Ehses^1,3, and Klaus Scheffler^1,3
1Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, ²Graduate Training Centre of Neuroscience, Tuebingen, Germany, ³Department of Biomedical Magnetic Resonance, University of Tuebingen, Tuebingen, Germany

The excellent sensitivity and stability of BOLD-imaging with balanced SSFP (bSSFP) on humans at 9.4T has been demonstrated in a recent paper. Here, we analyze the signal change of bSSFP for different vessel (spheres) sizes and susceptibility differences for different repetition times and flip angles using Monte Carlo simulations and experiments on micro spheres, and compare it to gradient echo EPI. Simulated and measured signal changes (using values of susceptibility changes and vessel sized comparable to a typical BOLD experiment at 9.4T) of bSSFP are in the range of 10 to 15% with a peak sensitivity to the vessel (sphere) size at about 3 mm, and a decreased sensitivity for larger vessels (spheres). For GE-EPI, signal changes are similar to bSSFP, however, no selectivity to small vessels is visible