ISMRM 24th Annual Meeting & Exhibition • 07-13 May 2016 • Singapore

Scientific Session: fMRI: Acquisition, Contrast, Artefacts

Thursday, May 12, 2016
Room 334-336
13:30 - 15:30
Moderators: Dimo Ivanov, Kawin Setsompop

Motion correction for functional MRI with hybrid radial-Cartesian 3D EPI
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. 

Ultra-fast gradient echo EPI with controlled aliasing at 3T:  simultaneous multi-slice vs. 3D-EPI
Rüdiger Stirnberg1, Willem Huijbers1, Benedikt A. Poser2, and Tony Stöcker1,3
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.

Evaluation of SLIce Dithered Enhanced Resolution Simultaneous MultiSlice (SLIDER-SMS) for human fMRI at 3T
An T. Vu1,2, Alex Beckett1, Kawin Setompop3, and David A. Feinberg1,2
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.

Physiology Recording with NMR Field Probe: Application to de-Noising of fMRI Time-Series at 7 Tesla
Laetitia Vionnet1, Simon Gross1, Lars Kasper1,2, Benjamin Emanuel Dietrich1, and Klaas Paul Pruessmann1
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. 

Blood volume fMRI with 3D-EPI-VASO: any benefits over SMS-VASO?
Laurentius Huber1, Dimo Ivanov2, Sean Marrett1, Puja Panwar1, Kamil Uludag2, Peter A Bandettini1, and Benedikt A Poser2
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.

Optimization of Asymmetric Spin Echo Pulse Sequences in Functional MRI
Eun Soo Choi1 and Gary Glover2
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. 

Simultaneous Multi-slice Inverse imaging for high temporal resolution fMRI
Ying-Hua Chu1, Yi-Cheng Hsu1, and Fa-Hsuan Lin1
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.

An interleaved spherical stack-of-spirals trajectory for fast segmented whole brain fMRI
Bruno Riemenschneider1, Jakob Assländer1, Pierre Levan1, and Jürgen Hennig1
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.

Effective Connectivity Measured with Layer-Dependent Resting-State Blood Volume fMRI in Humans
Laurentius Huber1, Daniel A Handwerker1, Javier Gonzalez-Castillo1, David C Jangraw1, Maria Guidi2, Dimo Ivanov3, Benedikt A Poser3, Jozien Goense4, and Peter A Bandettini1
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.

The BOLD-sensitivity of balanced SSFP at very high fields is similar to GE-EPI but more selective to small vessels. - Permission Withheld
Mario Gilberto Baez Yanez1,2, Phillip Ehses1,3, and Klaus Scheffler1,3
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

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