[Clinical application of 11C-NMSP to the patients with pituitary adenoma other than prolactinoma].

The existence of dopamine D2 receptors in the pituitary adenoma is an important factor for bromocriptine therapy. In order to evaluate the D2 receptors in the pituitary adenoma, 11C-N-methylspiperone (NMSP) and positron emission tomography was performed in a variety of pituitary adenomas other than prolactinoma. Eight patients with pituitary adenoma including four non-functioning adenomas, two growth hormone (GH) secreting adenomas, one ACTH secreting adenoma and one TSH secreting adenoma and ten normal healthy volunteers were examined. 740 MBq of 11C-NMSP was injected and dynamic scan was performed from the time of injection to 80 min postinjection. The time dependent regional radioactivity in the striatum (st) and in the tumor tissue (tm) was measured and the binding rate, alpha, was calculated according to the following equation: Cst, tm/Ccbl = alpha x integral of t0 Ccbl dt/Ccbl + 1. The ratio of total radioactivity in the striatum or tumor over total activity in the cerebellum was plotted versus "normalized time", which was obtained by dividing integrated cerebellar radioactivity by actual cerebellar radioactivity for each timepoint. In three patients with pituitary adenoma, two scans were performed before and three hours after oral intake of 2.5 mg of bromocriptine. The alpha values for pituitary adenoma and normal striatum were 0.031 +/- 0.023 (0.017-0.088) and 0.042 +/- 0.006 (0.034-0.049), respectively. Bromocriptine reduced alpha value to various degree in pituitary adenoma (13-56%) but not in striatum (-3.7-3.3%). Our data suggests that in some of pituitary adenoma other than prolactinoma, dopamine D2 receptors existed but that nonspecific binding also contributed to the radioactivity in the tumor tissue.(ABSTRACT TRUNCATED AT 250 WORDS)