Major qMRI findings in MS—WM compartment
| Site | Pathologic Processes and qMRI Correlates |
|---|---|
| WM lesions | |
| Early active | Decreased R1, R2, and R2* values, along with increased PD, reflecting initial myelin degradation and edema43,45 |
| Late active | Decreased R1 and R2 values, coupled with increased PD, with myelin debris removal that determines further R2* decrease and QSM increase43,45,51 |
| Chronic active | Further R1 and R2 decrease, with PD increase, due to demyelination progression;43 increased R2* and QSM at the periphery of the lesions due to iron-laden microglia and macrophages45,46 |
| Chronic inactive | Compared with chronic active, R2* decreases with high QSM values; across time, susceptibility values gradually become similar to those in NAWM46 |
| NAWM | Decreased R1 and R2 values, with increased PD, compared with the WM of healthy controls,50,51 reflecting edema and myelin loss secondary to inflammatory infiltration. |
| During active phases of the disease, iron is released from oligodendrocytes and begins to accumulate in newly forming lesions, causing an R2* decrease50 and no relevant modification of QSM signal52 |