TY - JOUR
T1 - Intrinsic functional brain mapping in reconstructed 4D magnetic susceptibility (χ) data space
AU - Chen, Zikuan
AU - Calhoun, Vince
N1 - Funding Information:
This work was in part supported by NSF grants # 0715022 & 0840895 .
Publisher Copyright:
© 2014 .
Copyright:
Copyright 2015 Elsevier B.V., All rights reserved.
PY - 2015/2/5
Y1 - 2015/2/5
N2 - Background: By solving an inverse problem of T2*-weighted magnetic resonance imaging for a dynamic fMRI study, we reconstruct a 4D magnetic susceptibility source (χ) data space for intrinsic functional mapping. New methods: A 4D phase dataset is calculated from a 4D complex fMRI dataset. The background field and phase wrapping effect are removed by a Laplacian technique. A 3D χ source map is reconstructed from a 3D phase image by a computed inverse MRI (CIMRI) scheme. A 4D χ data space is reconstructed by repeating the 3D χ source reconstruction for each time point. A functional map is calculated by a temporal correlation between voxel signals in the 4D χ space and the timecourse of the task paradigm. Results: With a finger-tapping experiment, we obtain two 3D functional mappings in the 4D magnitude data space and in the reconstructed 4D χ data space. We find that the χ-based functional mapping reveals co-occurrence of bidirectional responses in a 3D activation map that is different from the conventional magnitude-based mapping. Comparison with existing methods: The χ-based functional mapping can also be achieved by a 3D deconvolution of a phase activation map. Based on a subject experimental comparison, we show that the 4D χ tomography method could produce a similar χ activation map as obtained by the 3D deconvolution method. Conclusion: By removing the dipole effect and other fMRI technological contaminations, 4D χ tomography provides a 4D χ data space that allows a more direct and truthful functional mapping of a brain activity.
AB - Background: By solving an inverse problem of T2*-weighted magnetic resonance imaging for a dynamic fMRI study, we reconstruct a 4D magnetic susceptibility source (χ) data space for intrinsic functional mapping. New methods: A 4D phase dataset is calculated from a 4D complex fMRI dataset. The background field and phase wrapping effect are removed by a Laplacian technique. A 3D χ source map is reconstructed from a 3D phase image by a computed inverse MRI (CIMRI) scheme. A 4D χ data space is reconstructed by repeating the 3D χ source reconstruction for each time point. A functional map is calculated by a temporal correlation between voxel signals in the 4D χ space and the timecourse of the task paradigm. Results: With a finger-tapping experiment, we obtain two 3D functional mappings in the 4D magnitude data space and in the reconstructed 4D χ data space. We find that the χ-based functional mapping reveals co-occurrence of bidirectional responses in a 3D activation map that is different from the conventional magnitude-based mapping. Comparison with existing methods: The χ-based functional mapping can also be achieved by a 3D deconvolution of a phase activation map. Based on a subject experimental comparison, we show that the 4D χ tomography method could produce a similar χ activation map as obtained by the 3D deconvolution method. Conclusion: By removing the dipole effect and other fMRI technological contaminations, 4D χ tomography provides a 4D χ data space that allows a more direct and truthful functional mapping of a brain activity.
KW - 4D magnetic susceptibility (χ) tomography
KW - Blood oxygenation level-dependent functional magnetic resonance imaging (BOLD fMRI)
KW - Dipole inversion
KW - Intrinsic functional brain mapping
KW - T2
KW - T2
KW - imaging
KW - magnitude and phase images
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U2 - 10.1016/j.jneumeth.2014.12.014
DO - 10.1016/j.jneumeth.2014.12.014
M3 - Article
C2 - 25546484
AN - SCOPUS:84920747532
VL - 241
SP - 85
EP - 93
JO - Journal of Neuroscience Methods
JF - Journal of Neuroscience Methods
SN - 0165-0270
ER -