SPECT imaging of secreting pituitary adenomas using 99Tcm isonitriles (CPI and SESTAMIBI)

A method for the functional imaging of pituitary adenomas was evaluated. Twenty-one patients were studied: 14 females and 7 males, ranging in age from 11 to 74 years (x = 37 years). The inclusion criterion was the finding of a sellar or juxtasellar mass with computed tomography (CT) and/or magnetic resonance imaging (MRI). Patients with clinical suspicion of a pituitary tumour with negative CT were also included. Pathological diagnosis was made by surgery or fine needle aspiration. Serum hormonal levels were also determined by routine radioimmunoassay (RIA) procedures. The radiotracer employed was 99Tcm-CPI (6-carboxyisopropyl isonitrile) in 9 cases and 99Tcm-SESTAMIBI (6-methoxyisobutyl isonitrile) in 12 cases. A dose of 740 MBq was injected intravenously and the patients were studied 60 min post-injection. Brain SPECT (single photon emission computed tomography) studied were performed with a rotating gamma camera in a 360 deg. C orbit, acquiring 64 images in a 64 x 64 matrix. Reconstruction was made by filtered back projection and an attenuation correction algorithm was applied. Each study was visually evaluated and a semiquantitative method was used when significant uptake in the sellar region was observed. Pathology examinations revealed pituitary adenomas in 15 cases, 2 cases of craniopharyngioma and 1 of dysgerminoma. One patient had a resected pituitary adenoma with no evidence of recurrence and two patients with clinical suspicion of pituitary adenoma had both CT and RIA tests negative. SPECT studies were positive in 14 pituitary adenomas and in 1 craniopharyngioma, yielding a sensitivity of 0.93 and a specificity of 0.83. Prolactinomas exhibited the highest uptake. Recently, isonitriles have been proposed for evaluation of SESTAMIBI in neoplastic lesions. Intracellular retention related to mitochondrial membrane potentials, which depend on the metabolic activity of the tissue. SPECT imaging with this class of compounds provides a simple method for the metabolic assessment of pituitary adenomas. (author). 8 refs, 3 figs, 1 tab