Abstract
Objectives: Intra-individual spatial overlap analysis of tumor volumes assessed by MRI, the amino acid PET tracer [F-18]-FET and the nucleoside PET tracer [F-18]-FLT in high-grade gliomas (HGG). Methods: MRI, [F-18]-FET and [F-18]-FLT PET data sets were retrospectively analyzed in 23 HGG patients. Morphologic tumor volumes on MRI (post-contrast T1 (cT1) and T2 images) were calculated using a ...
Abstract
Objectives: Intra-individual spatial overlap analysis of tumor volumes assessed by MRI, the amino acid PET tracer [F-18]-FET and the nucleoside PET tracer [F-18]-FLT in high-grade gliomas (HGG). Methods: MRI, [F-18]-FET and [F-18]-FLT PET data sets were retrospectively analyzed in 23 HGG patients. Morphologic tumor volumes on MRI (post-contrast T1 (cT1) and T2 images) were calculated using a semi-automatic image segmentation method. Metabolic tumor volumes for [F-18]-FET and [F-18]-FLT PETs were determined by image segmentation using a threshold-based volume of interest analysis. After co-registration with MRI the morphologic and metabolic tumor volumes were compared on an intra-individual basis in order to estimate spatial overlaps using the Spearman's rank correlation coefficient and the Mann-Whitney U test. Results: [F-18]-FLT uptake was negative in tumors with no or only moderate contrast enhancement on MRI, detecting only 21 of 23 (91%) HGG. In addition, [F-18]-FLT uptake was mainly restricted to cT1 tumor areas on MRI and [F-18]-FLT volumes strongly correlated with cT1 volumes (r = 0.841, p < 0.001). In contrast, [F-18]-FET PET detected 22 of 23 (96%) HGG. [F-18]-FET uptake beyond areas of cT1 was found in 61% of cases and [F-18]-FET volumes showed only a moderate correlation with cT1 volumes (r = 0.573, p <0.001). Metabolic tumor volumes beyond cT1 tumor areas were significantly larger for [F-18]-FET compared to [F-18]-FLT tracer uptake (8.3 vs. 2.7 cm(3), p <0.001). Conclusion: In HGG [F-18]-FET but not [F-18]-FLT PET was able to detect metabolic active tumor tissue beyond contrast enhancing tumor on MRI. In contrast to [F-18]-FET, blood-brain barrier breakdown seems to be a prerequisite for [F-18]-FLT tracer uptake.
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