Figure 7. ²³Na-MR of a necrotic lesion in pediatric subject.

[A] shows a ring enhancing necrotic lesion (red arrowheads); This lesion was a new recurrent lesion, separate from a lesion in the frontal lobe (not shown) that has initially responded to peptide-based vaccine therapy [B] short echo and [C] longer echo ²³Na-MR showing total/extracellular sodium and increased foci in the periphery of lesion (red arrow); [D] co-registered targeted subtracted overlap image show that the periphery of the necrosis (red arrowheads) had increased intracellular sodium (ICS) (red and yellow voxels) and decreased central ICS (bluish and voxels) representing tumor related cavitation/necrosis confirmed to be a recurrent tumor by follow up.