The Combination of 13N-ammonia and 11C-methionine in Differentiation of Residual/Recurrent Pituitary Adenoma From the Pituitary Gland Remnant After Trans-sphenoidal Adenomectomy

Abstract ObjectiveTo assess the usefulness of 13N-ammonia and 11C- Methionine (MET) PET/CT in the differentiation of residual/recurrent pituitary adenoma (RPA) from the pituitary gland remnant (PGR) after trans-sphenoidal adenomectomy.Patients and MethodsBetween June 2012 to December 2019, 19 patients [clinical/MRI suggestion of RPA (14 female and 5 male, mean age: 44.86 ± 15.58 years, range: 18–79 years)] with a history of trans-sphenoidal adenomectomy before PET/CT scans in our department were enrolled in this study. The maximum standard uptake value (SUVmax) of the target and gray matter was measured, and then the T/G ratio was calculated. First, the T/G ratios of RPA and PGR for each tracer were compared by Student t-test. Second, the T/G ratios of the two tracers were adopted as multiple variables for canonical discrimination analysis. According to the canonical discriminant function, every patient was classified into one group. A P value less than 0.05 was considered statistically significant. ResultsThe T/G ratios of 13N-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 11C-MET were significantly lower in PGR than RPA (0.78±0.35 vs 2.17±0.54, P < 0.001). By the canonical discriminant analysis, we calculated the predicted accuracy of RPA (100%), PGR (92.9%), and the overall predicted accuracy (96.43%). ConclusionsThe combination of 13N-ammonia and 11C-MET PET/CT is valuable in the differentiation of RPA from PGR after trans-sphenoidal adenomectomy.