“…Despite the introduction of tumor-treating fields and the vascular epithelial growth factor (VEGF) inhibitor bevacizumab [ 4 , 5 ] to the standard approach of radical resection followed by concomitant radiochemotherapy [ 6 , 7 ] and significant advancements regarding guided surgical resection including the application of 5-aminolevulinic acid and contrast-enhanced ultrasound [ 8 ], this glioma subtype still marks a therapeutical challenge [ 9 , 10 , 11 , 12 , 13 ] and has the poorest prognosis with a median survival of under two years [ 14 ]. Furthermore, its high recurrence rate [ 15 ] limiting the patient’s survival represents a radiologic problem: Innumerable studies tried to differentiate between recurrent tumors and treatment related changes [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ]—a question with the highest clinical impact [ 25 , 26 ] and a neuroradiological challenge. Whereas initial diagnosis of GBM is often reliably feasible due to its typical radiological features, e.g., peripheral irregular ring enhancement, intralesional hemorrhage, and central necrosis [ 7 , 27 , 28 ], imaging of recurrent and/or progressive residual high-grade GBM is similar to therapy associated cerebral radiation necrosis (increasing contrast enhancement and progressive peritumoral edema at least six months up to several years after radiotherapy [ 29 ], often progresses without treatment) or pseudoprogression (increasing contrast enhancement and progressive peritumoral edema within three to six months following radiotherapy, often resolves spontaneously) after surgical resection and concomitant radiochemotherapy; both show strong contrast enhancement, increasing fluid-attenuated inversion recovery (FLAIR) hyperintensities adjacent to the enhancement, and present with punctiform intralesional hemorrhage and necrosis [ 29 , 30 ].…”