The combination of 13N-ammonia and 18F-FDG PET/CT in the identification of metabolic phenotype of primary human brain tumors.

AIM

This pilot study made a preliminary attempt to distinguish different metabolic phenotypes of primary human brain tumors with dual tracer N-ammonia and F-FDG.

METHODS

74 patients were included in this study including 12 benign meningiomas (B-MEN), 4 malignant meningiomas (M-MEN), 15 low-grade gliomas (LGG), 32 high-grade gliomas (HGG) and 11 primary central nervous system lymphomas (PCNSL). All patients underwent N-ammonia and F-FDG PET imaging. Semi-quantification analysis by tumor-to-gray matter (T/G) ratios was used for the evaluation of tracer uptakes. After the calculation of canonical discriminant functions, cross validation was done for all cases to evaluate the differential efficacy of dual tracers.

RESULTS

According to the visual analysis, B-MEN were characterized by lower uptake of F-FDG and higher uptake of N-ammonia, while PCNSLs displayed contrary results. Both M-MEN and HGG had higher uptake of F-FDG and N-ammonia, while LGG displayed negative results for both tracers. According to the T/G ratios analysis, the accuracy of predicted tumor classification by means of canonical discriminant analysis for B-MEN, LGG, HGG and PCNSL was 91.7 %, 100 %, 84.4 % and 93.3 % respectively; the overall accuracy was 90.5 %.

CONCLUSION

The combination of dual tracer N-ammonia and F-FDG has a certain potential in distinguishing different types of brain tumors (meningiomas, gliomas and PCNSL). However, an advantage of the additional use of N-ammonia PET compared to a combined diagnosis with MRI and F-FDG PET could not be demonstrated and requires further studies.