Several studies, including our own, combined QSM or phase imaging of MS autopsy tissue with histological analysis, and confirmed that high tissue susceptibility at the rims of MS lesions correlated approximately with the distribution of iron and CD68+ microglia/macrophages (Figure 2) (24, 27, 66, 83, 104, 105), which contain predominantly ferric iron. This evidence concerns the gene CD68 and myeloid sarcoma.