Early static super(18)F-FET-PET scans have a higher accuracy for glioma grading than the standard 20-40 min scans

Current guidelines for glioma imaging by positron emission tomography (PET) using the amino acid analogue O-(2-[ super(18)F]fluoroethyl)- L-tyrosine ( super(18)F-FET) recommend image acquisition from 20-40 min post injection (p.i.). The maximal tumour-to-background evaluation (TBR sub(max)) obtained in these summation images does not enable reliable differentiation between low and high grade glioma (LGG and HGG), which, however, can be achieved by dynamic super(18)F-FET-PET. We investigated the accuracy of tumour grading using TBR sub(max) values at different earlier time points after tracer injection. Three hundred and fourteen patients with histologically proven primary diagnosis of glioma (131 LGG, 183 HGG) who had undergone 40-min dynamic super(18)F-FET-PET scans were retrospectively evaluated. TBR sub(max) was assessed in the standard 20-40 min summation images, as well as in summation images from 0-10 min, 5-15 min, 5-20 min, and 15-30 min p.i., and kinetic analysis was performed. TBR sub(max) values and kinetic analysis were correlated with histological classification. ROC analyses were performed for each time frame and sensitivity, specificity, and accuracy were assessed. TBR sub(max) values in the earlier summation images were significantly better for tumour grading (P