Combination of ¹³N-ammonia PET/CT and ¹⁸F-FDG PET/CT in differentiation of primary central nervous system lymphoma from glioma

Objective: To investigate whether ¹³N-ammonia PET/CT combined with ¹⁸F-FDG PET/CT may differentiate primary central nervous system lymphoma (PCNSL) from gliomas effectively. Methods: Ten patients (7 males, 3 females, age range: 43-74 (59.10 ± 12.47) years) with PCNSL and fifteen patients (8 males, 7 females, age range: 14-72 (46.73 ± 19.62) years) with glioma lesions from January 2010 to July 2012 were included in this study. ¹⁸F-FDG and ¹³N-ammonia PET/CT scans were performed in all subjects. Tumor-to-gray matter (T/G) ratios were calculated. Two-sample t test and discriminant analysis were applied to assess the differential efficacy of the two tracers. Results: The T/G ratios of ¹⁸F-FDG in PCNSL lesions were higher than those in gliomas (3.27 ± 1.21 vs 1.57 ± 0.39, t = 5.630, P < 0.001), while the T/G ratios of ¹³N-ammonia in PCNSL lesions were lower than those in gliomas significantly (1.43 ± 0.26 vs 2.12 ± 0.69, t = -3.551, P < 0.01). All PCNSL lesions (n = 14) showed higher T/G ratios of ¹⁸F-FDG than those of ¹³N-ammonia, whereas 77.8% (14/18) of glioma lesions showed contrary results. Canonical discriminant analysis yielded an overall accuracy of 96.9% (31/32) for tumor classification and only one glioma lesion was misclassified as PCNSL. Conclusion: The combination of ¹³N-ammonia PET/CT and ¹⁸F-FDG PET/CT is helpful for differentiating PCNSL from glioma. (authors)