Iron and Non-Iron-Related Characteristics of Multiple Sclerosis and Neuromyelitis Optica Lesions at 7T MRI

Non-iron-laden MS lesions (2 differential signal-intensity patterns). In the upper rows, schematic sketches are shown for pattern A and B lesions depicting ideal signal-intensity distribution on the GRE-T2*-weighted image, SWI, and QSM. In the lower rows, axial GRE-T2*-weighted image shows a hyperintense lesion traversed by a central intralesional venule. This lesion is located in close proximity to the posterior horn of the lateral ventricle. However, it appears isointense on SWI and QSM (pattern A) and hence inconspicuous on these images; this feature suggests a chronic inactive stage of lesion development comprising variable degrees of edema, demyelination, micronecrosis, and gliosis. Axial GRE-T2*-weighted image highlights a hyperintense lesion in the periventricular region traversed by a clearly distinguishable central venule. This lesion also appears hyperintense on corresponding SWI and QSM (pattern B), suggesting acute and extensive demyelinating (loss of diamagnetism) and inflammatory processes within the lesion.

Iron-laden MS lesions (2 geometrically distinct susceptibility patterns). In the upper rows, schematic sketches are shown for pattern C and D lesions, depicting a characteristic signal-intensity distribution on GRE-T2*-weighted images, SWI, and QSM. In the lower rows, axial GRE-T2*-weighted image presents a pair of lesions in the subcortical WM region. While one lesion is nodular hyperintense (white arrow), another lesion is nodular hypointense (black arrow). Both lesions are crisscrossed by intralesional central venules and show hypointense signal on SWI but hyperintense signal on QSM, thus indicating iron deposition (pattern C). Axial GRE-T2*-weighted image reveals a lesion (white arrow) with a hypointense peripheral rim having a central venous structure in the subcortical WM region. The lesion also shows a hypointense rim on the corresponding SWI and a hyperintense rim on the corresponding QSM, suggesting a ringlike lesion with iron deposition only at the edges (pattern D).

Large MS lesions with well-defined and ill-defined margins. Axial GRE-T2*-weighted images (A–C) demonstrate large but faint hyperintense lesions (black arrow) without any definite margins. These lesions appear hyperintense on SWI (black arrows) and isointense on QSM; this appearance indicates the absence of iron deposits (left panel). On the other hand, axial GRE-T2*-weighted images (D–F) also show large hyperintense lesions (white arrows) with well-defined margins. These lesions are visible as hypointense structures on SWI and hyperintense on QSM; this appearance is highly suggestive of intralesional iron deposits (right panel). The scale bar is for the QSM image with units of parts per billion.