The combination of (13)N-ammonia and (11)C-methionine in differentiation of residual/recurrent pituitary adenoma from the pituitary gland remnant after trans-sphenoidal Adenomectomy

BACKGROUND: This study aimed to assess the clinical usefulness of (13)N-ammonia and (11)C- Methionine (MET) positron emission tomography (PET)/ computed tomography (CT) in the differentiation of residual/recurrent pituitary adenoma (RPA) from the pituitary gland remnant (PGR) after trans-sphenoidal adenomectomy. METHODS: Between June 2012 and December 2019, a total of 19 patients with a history of trans-sphenoidal adenomectomy before PET/CT scans and histological confirmation of RPA after additional surgery in our hospital were enrolled in this study. Images were interpreted by visual evaluation and semi-quantitative analysis. In semi-quantitative analysis, the maximum standard uptake value (SUVmax) of the target and gray matter was measured and the target uptake/gray matter uptake (T/G) ratio was calculated. RESULTS: The T/G ratios of (13)N-ammonia were significantly higher in PGR than RPA (1.58 ± 0.69 vs 0.63 ± 1.37, P < 0.001), whereas the T/G ratios of (11)C-MET were obviously lower in PGR than RPA (0.78 ± 0.35 vs 2.17 ± 0.54, P < 0.001). Using the canonical discriminant analysis, we calculated the predicted accuracy of RPA (100%), PGR (92.9%), and the overall predicted accuracy (96.43%). CONCLUSIONS: The combination of (13)N-ammonia and (11)C-MET PET/CT is valuable in the differentiation of RPA from PGR after trans-sphenoidal adenomectomy.