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Quantitative susceptibility mapping of the head‐and‐neck using SMURF fat‐water imaging with chemical shift and relaxation rate corrections
Author(s) -
Bachrata Beata,
Trattnig Siegfried,
Robinson Simon Daniel
Publication year - 2022
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.29069
Subject(s) - quantitative susceptibility mapping , head and neck , masking (illustration) , voxel , relaxation (psychology) , nuclear magnetic resonance , chemistry , magnetic resonance imaging , physics , computer science , radiology , artificial intelligence , biology , medicine , surgery , neuroscience , art , visual arts
Purpose To address the challenges posed by fat‐water chemical shift artifacts and relaxation rate discrepancies to quantitative susceptibility mapping (QSM) outside the brain, and to generate accurate susceptibility maps of the head‐and‐neck at 3 and 7 Tesla. Methods Simultaneous Multiple Resonance Frequency (SMURF) imaging was extended to 7 Tesla and used to acquire head‐and‐neck gradient echo images at both 3 and 7 Tesla. Separated fat and water images were corrected for Type 1 (displacement) and Type 2 (phase discrepancy) chemical shift artefacts, and for the bias resulting from differences in T 1 and T 2 ∗ relaxation rates, recombined and used as the basis for QSM. A novel phase signal‐based masking approach was used to generate head‐and‐neck masks. Results SMURF generated well‐separated fat and water images of the head‐and‐neck. Corrections for chemical shift artefacts and relaxation rate differences removed overestimation of the susceptibility values, blurring in the susceptibility maps, and the disproportionate influence of fat in mixed voxels. The resulting susceptibility maps showed high correspondence between the paramagnetic areas and the locations of fatty tissues and the susceptibility estimates were similar to literature values. The proposed masking approach was shown to provide a simple means of generating head‐and‐neck masks. Conclusion Corrections for Type 1 and Type 2 chemical shift artefacts and for fat‐water relaxation rate differences, mainly in T 1 , were shown to be required for accurate susceptibility mapping of fatty‐body regions. SMURF made it possible to apply these corrections and generate high‐quality susceptibility maps of the entire head‐and‐neck at both 3 and 7 Tesla.