Project: Layer Specific fMRI
FIM Authors:
Authors:
- Laurentius Huber
- Rüdiger Stirnberg
- Tyler Morgan
- David A. Feinberg
- Philipp Ehse
- 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. Posner
- Peter Bandettini
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.
Data
Code
Journal: BioRXiv
URL: https://pmc.ncbi.nlm.nih.gov/articles/PMC11418939/
DOI: https://doi.org/10.1101/2024.09.04.611294