Figure 4.

Example of variations of ¹⁸F-DOPA uptake induced by TMZ chemotherapy. The left panel (a) represents the brain PET scan of a female patient with a high-grade astrocytoma acquired during the course of TMZ treatment. SUVbckgr, SUVbg and TBR were 0.87, 1.86 and 2.91, respectively. The right panel (b) shows the same patient imaged 3 years later, after conclusion of chemotherapy. Notably, a “rebound effect” can be seen at sites of physiological uptake, whilst the opposite effect is observed for TBR. In fact, SUVbckgr and SUVbg increased to 1.78 and 3.42, respectively, whereas TBR dropped to 2.19 despite an increase of SUVmax from 3.62 to 5.47. Both images were scaled to the same maximum signal intensity. ¹⁸F-DOPA, ¹⁸F–fluoro-l–phenylalanine; PET, positron emission tomography; SUV, standardized uptake value; TBR, tumour-to-brain ratio; TMZ, temozolomide.