PURPOSE: We assessed the value of N-ammonia PET-computed tomography (PET/CT) in recurrent glioma and compared the results with those of contrast-enhanced MRI (CE MRI).
MATERIALS AND METHODS: Fifty-two (mean age, 39.8±11.6 years; male, 33; female, 19) histopathologically proven and previously treated glioma patients with clinical suspicion of recurrence were evaluated with 13N-ammonia PET/CT and CE MRI. PET/CT images were evaluated qualitatively and quantitatively (maximum standardized uptake value). Tumour to white matter (T/W), tumour to grey matter (T/G) and tumour to pituitary (T/P) ratios were calculated and cutoff levels were derived with receiver operating characteristic curve analysis. Sensitivity, specificity and predictive values were compared. A combination of clinical follow-up, repeat imaging and biopsy (when available) was taken as the reference standard.
RESULTS: On the basis of the reference standard, 23 out of 52 patients were seen to have recurrence. Overall sensitivity, specificity, positive predictive value, negative predictive value and accuracy of 13N-ammonia PET/CT were 82.6, 86.2, 82.6, 86.2 and 84.6%, respectively, whereas those of CE MRI were 96.7, 48.3, 59.5, 93.3 and 69.2%, respectively. Overall, 13N-ammonia PET/CT was statistically superior to CE MRI (P=0.001). In low-grade tumours, 13N-ammonia PET/CT performed better than MRI with an accuracy of 86.8 versus 68.4% (P=0.003). In high-grade tumours, both the modalities had comparable performances with accuracies of 78.6% for N-ammonia PET/CT and 71.4% for CE MRI (P=0.250). Among the ratios, T/P was the most useful, with the largest area under the curve (0.825; P=0.0001).
CONCLUSION: N-Ammonia PET/CT shows higher accuracy compared with contrast-enhanced MRI for detecting recurrent gliomas, particularly in low-grade tumours.
Nucl Med Commun. 2013 Nov;34(11):1046-54