Fig 10.

Characteristic findings of progressive disease and pseudoprogression on MR spectroscopy. A, A 54-year-old man presented with a ring-enhancing lesion in the left insula (not shown) distant from the radiation field after treatment of a right frontal lobe GBM. MR imaging spectroscopy shows marked elevation of the choline/NAA ratio (2.5), indicating high cellular turnover and diminished neuronal viability, typical for a malignant tumor and indicating progressive disease. B, A previously presented case of a 56-year-old man with pseudoprogression after treatment of a GBM in the left parietal lobe (Fig 5). MR imaging spectroscopy also shows elevation of choline/NAA ratio, but only slightly lower than that in the previous case (2.2 versus 2.5), which exemplifies the findings overlap between pseudoprogression and progressive disease on spectroscopy. The lipid/lactate peak is markedly elevated in patients with pseudoprogression but is also commonly present in GBM recurrence.