Figure 6. Influence of Undersampling on In-vivo $\text{a}{\mathrm{T}}_2\mathrm{*}$ Mapping.

Panels (a-d) display axial lung slices (TE = 0.080 ms) sampled at 100%, 70%, 50%, and 10%. At 70% and 50% sampling rates, images closely resemble the fully sampled image, while significantly degraded resolution is observed in the 10% sampled image, particularly near lung parenchyma edges and pulmonary vasculature. Representative parenchymal $\text{a}{\mathrm{T}}_2\mathrm{*}$ maps in panels (e-h) demonstrate regions affected by increasing undersampling. Panels (e-h) exhibit consistent $\text{a}{\mathrm{T}}_2\mathrm{*}$ mean values, while panel (h) displays areas with both increased and reduced $\text{a}{\mathrm{T}}_2\mathrm{*}$ regions, indicated by red arrows and a red-dashed arrow, respectively. (i-l) Histograms of parenchymal $\text{a}{\mathrm{T}}_2\mathrm{*}$ across 10 iterations of undersampling depict distributions at sampling levels of 100%, 70%, 50%, and 10%. Scatter plots (panels m-o) show voxel-level correlations between $\text{a}{\mathrm{T}}_2\mathrm{*}$ values calculated from full sampled data with values calculated at various sampling levels. As sampling level decreases, the correlation slope diminishes, indicating a shift towards higher $\text{a}{\mathrm{T}}_2\mathrm{*}$ values compared to fully sampled data.