Figure 5.

QSM consists of the processing of complex gradient echo MRI data, i.e. its phase (a) and magnitude components (b). Here, we used a multiecho gradient echo acquisition (TE₁ = 6.5 ms, echo spacing = 6.744 ms, #echoes = 4, TR = 32.0 ms, voxel size = 0.65×0.65×1.4 mm³). A map of field inhomogeneities ΔB is estimated from the phase data (c). Subsequently contributions from background fields are removed to extract a map of field inhomogeneities generated by susceptibility sources inside the ROI only, ${\displaystyle \mathrm{\Delta }{B}_{int}}$ (d). A dipole field inversion operation is performed on $\mathrm{\Delta }{B}_{int}$ to calculate the susceptibility map $\chi$ (e). ROI, region of interest; QSM, Quantitative Susceptibility Mapping; TE, echo time; TR, repetition time.