Figure 1.

Jacobian analysis and SEL candidates: (a), (b) An axial slice of linearly co-registered reference and follow-up T1-weighted scans. (c) The reference scan with a regular grid overlaid. (di) The non-linearly deformed image in (c) is shown to match the follow-up scan, and (dii) an enlarged lesion area of the deformation field. (e) The Jacobian determinant is shown as a heat map, where blue represents local contraction and red local expansion. The Jacobian determinant represents the local percent volume change at each voxel, after application of the non-linear deformation that warps (a) to match (b). (f) An axial slice of a reference T2-weighted scan with overlaid T2 lesion segmentation. (g) The Jacobian determinant within reference T2 lesions. (h) Initial SEL candidate boundaries based on JE₁. (i) Refined SEL candidate boundaries based on JE₂.

JE: Jacobian Expansion; SEL: slowly expanding/evolving lesion.