Journal Article Preprint Epublish 1 citation
PubMed: 39314458 DOI: 10.1101/2024.09.04.611294
Fuzzy ripple artifact in high resolution fMRI: identification, cause, and mitigation.
bioRxiv
Authors: Renzo Huber, Rüdiger Stirnberg, A Tyler Morgan, David A Feinberg, Philipp Ehses, Lasse Knudsen, Omer Faruk Gulban, Kenshu Koiso, Stephanie Swegle, Isabel Gephart, Susan G Wardle, Andrew Persichetti, Alexander Js Beckett, Tony Stöcker, Nicolas Boulant, Benedikt A Poser, Peter Bandettini
Affiliations
- NIMH, NIH, Bethesda, United States.
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany.
- Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA, United States.
- Advanced MRI Technologies, Sebastopol, CA, United States.
- CN, FPN, University of Maastricht, The Netherlands.
- Center of Functionally Integrative Neuroscience (CFIN), Department of Clinical Medicine, Aarhus University, Universitetsbyen 3, 8000 Aarhus C, Denmark.
- Sino-Danish Center for Education and Research (SDC), University of Chinese Academy of Sciences, 380 Huaibeizhuang, Huairou District, Beijing 101400, PR China.
- Brain Innovation, Maastricht, The Netherlands.
- University Paris Saclay, CEA, CNRS, NeuroSpin, BAOBAB, France.
Abstract
Purpose
High resolution fMRI is a rapidly growing research field focused on capturing functional signal changes across cortical layers. However, the data acquisition is limited by low spatial frequency EPI artifacts; termed here as Fuzzy Ripples. These artifacts limit the practical applicability of acquisition protocols with higher spatial resolution, faster acquisition speed, and they challenge imaging in lower brain areas.
Methods
We characterize Fuzzy Ripple artifacts across commonly used sequences and distinguish them from conventional EPI Nyquist ghosts, off-resonance effects, and GRAPPA artifacts. To investigate their origin, we employ dual polarity readouts.
Results
Our findings indicate that Fuzzy Ripples are primarily caused by readout-specific imperfections in k-space trajectories, which can be exacerbated by inductive coupling between third-order shims and readout gradients. We also find that these artifacts can be mitigated through complex-valued averaging of dual polarity EPI or by disconnecting the third-order shim coils.
Conclusion
The proposed mitigation strategies allow overcoming current limitations in layer-fMRI protocols: (1)Achieving resolutions beyond 0.8mm is feasible, and even at 3T, we achieved 0.53mm voxel functional connectivity mapping.(2)Sub-millimeter sampling acceleration can be increased to allow sub-second TRs and laminar whole brain protocols with up to GRAPPA 8.(3)Sub-millimeter fMRI is achievable in lower brain areas, including the cerebellum.
MeSH
Brain