Abstract
Background and purpose
Susceptibility estimates derived from quantitative susceptibility mapping (QSM) images for the cerebral cortex and major subcortical structures are variably reported in brain magnetic resonance imaging (MRI) studies, as average of all (μall${{{{mu}}}_{{mathrm{all}}}}$), absolute (μabs${{{{mu}}}_{{mathrm{abs}}}}$), or positive- (μp${{{{mu}}}_{mathrm{p}}}$) and negative-only (μn${{{{mu}}}_{mathrm{n}}}$) susceptibility values using a region of interest (ROI) approach.
This pilot study presents a reliability analysis of currently used ROI-QSM metrics and an alternative ROI-based approach to obtain voxel-weighted ROI-QSM metrics (μwp${{{{mu}}}_{{mathrm{wp}}}}$ and μwn${{{{mu}}}_{{mathrm{wn}}}}$).
Methods
Ten healthy subjects underwent repeated (test-retest) 3-dimensional multi-echo gradient-echo (3DMEGE) 3 Tesla MRI measurements. Complex-valued 3DMEGE images were acquired and reconstructed with slice thicknesses of 1 and 2 mm (3DMEGE1, 3DMEGE2) along with 3DT1-weighted isometric (voxel 1 mm3) images for independent registration and ROI segmentation.
Agreement, consistency, and reproducibility of ROI-QSM metrics were assessed through Bland-Altman analysis, intraclass correlation coefficient, and interscan and intersubject coefficient of variation (CoV).
Results
All ROI-QSM metrics exhibited good to excellent consistency and test-retest agreement with no proportional bias. Interscan CoV was higher for μall${{{{mu}}}_{{mathrm{all}}}}$ in comparison to the other metrics where it was below 15%, in both 3DMEGE1 and 3DMEGE2 datasets. Intersubject CoV for μall${{{{mu}}}_{{mathrm{all}}}}$ and μabs${{{{mu}}}_{{mathrm{abs}}}}$ exceeded 50% in all ROIs.
Conclusions
Among the evaluated ROI-QSM metrics, μall${{{{mu}}}_{{mathrm{all}}}}$ and μabs${{{{mu}}}_{{mathrm{abs}}}}$ estimates were less reliable, whereas separating positive and negative values (using μp,μn,μwp,μwn${{{{mu}}}_{mathrm{p}}}, {{{{mu}}}_{mathrm{n}}}, {{{{mu}}}_{{mathrm{wp}}}}, {{{{mu}}}_{{mathrm{wn}}}}$) improved the reproducibility within, and the comparability between, subjects, even when reducing the slice thickness. These preliminary findings may offer valuable insights toward standardizing ROI-QSM metrics across different patient cohorts and imaging settings in future clinical MRI studies.
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This post is Copyright: Maria Agnese Pirozzi,
Antonietta Canna,
Federica Di Nardo,
Mario Sansone,
Francesca Trojsi,
Mario Cirillo,
Fabrizio Esposito | August 30, 2024
Wiley: Journal of Neuroimaging: Table of Contents