Fig. 1From: Negative 18F-FET PET/CT in brain metastasis recurrence: a teaching case reportMRI and 18F-FET PET/CT findings. In our 58-year-old female patient, a follow-up brain MRI performed 16Â months after radiosurgery showed an increase in the size of a treated right frontal lesion (white arrow) that appeared hyperintense on T2 weighted images (a), with central necrosis and peripheral thick contrast enhancement on T1 weighted images (b). The periphery of the lesion was bright on diffusion-weighted imaging (c) with moderately low ADC (d). On perfusion-weighted images, the nrCBV was 2.3 (e) and nrCBF was 2.8 (not shown) while MR spectroscopy (f) showed a high peak of choline with Cho/Cr ratio of 2.9, which overall indicated tumor residue. While 18F-FET PET/CT raw images showed moderate peripheral uptake (g, arrowhead), the maximum target-to-background ratio was 2.2 (i.e. lower than 2.55) and the time-activity-curve showed increasing uptake over time (h), which was interpreted as signs of radiation necrosisBack to article page