Figure 5.

Coverage of ¹⁸F-FET PET isocontour volumes by T₂ FLAIR hyperintense regions. Novel guidelines suggest inclusion of regions that are hyperintense on T₂ FLAIR MRI (orange) into CTV^FLAIR (a). In grade IV glioma, this significantly increases the volume of CTV (b). The fraction of the ¹⁸F-FET PET based isocontour volumes that lies outside of the T₂ FLAIR hyperintense volume, was calculated (c). With two exceptions for isocontours of 70% in grade III tumors and three exceptions for isocontours of either 60% or 70% in grade IV tumors, more than 80% of the isocontours were covered by the T₂ FLAIR hyperintense volume (c). Representative patient with grade IV glioma where over 90% of the ¹⁸F-FET PET active area lies within CTV^FLAIR (d). Exemplary cases of two exceptional patients circled in red in the boxplots (c) with large fractions of the isocontour volumes (70% and 60%) laying outside the T₂ FLAIR hyperintense volume are shown.