Comparison of iodine-123 epidepride and iodine-123 IBZM for dopamine D2 receptor imaging in clinically non-functioning pituitary macroadenomas and macroprolactinomas.

Abstract. We compared pituitary iodine-123 epidepride single-photon emission tomography (SPET) and [sup 123]I-IBZM SPET for the in vivo imaging of dopamine D[sub 2] receptors in 15 patients with clinically non-functioning pituitary adenomas. Four patients with dopamine agonist-sensitive macroprolactinomas were studied as positive controls. The uptake of radioactivity in the pituitary was established using a visual scoring system and an uptake index calculated by dividing the average count rates in the pituitary area by the average count rates in the cerebellum. All four macroprolactinomas showed specific binding of [sup l23]I-epidepride, but only one showed specific binding of [sup 123]I-IBZM. Specific binding of [sup 123]I-epidepride was demonstrated in 9 of the 15 clinically nonfunctioning pituitary adenomas (60%), but specific binding of [sup 123]I-IBZM was shown in only 6 of these 15 cases (40%). The uptake of [sup 123]I-epidepride in the pituitary region was consistently higher than that of [sup 123]I-IBZM. None of the patients who showed absence of uptake of [sup 123]I-epidepride in the pituitary area showed uptake of [sup 123]I-IBZM in this area. In conclusion: [sup 123]I-epidepride SPET is superior to [sup 123]I-IBZM SPET for the visualization of dopamine receptor-positive pituitary adenomas. Therefore, [sup 123]I-epidepride should replace [sup 123]I-IBZM for future D[sub 2] receptor SPET studies of pituitary adenomas. [sup 123]I-epidepride SPET potentially might serve to predict the response of clinically non-functioning pituitary ade-... [ABSTRACT FROM AUTHOR]