Fundamental and clinical study for 131I-metaiodobenzyl guanidine (MIBG)

Iodine-131 metaiodobenzyl guanidine (MIBG) was injected in a patient with medullary thyroid cancer (MTC) and a patient with essential hypertension (EH). The blood clearance of I-131 MIBG was rapid up to 4 hr after injection, and thereafter became slow. Fifty per cent of the dose was excreted into the urine within 24 hr. The retention of I-131 MIBG was observed in the liver and heart, along with the unaffected area of adrenal gland. The activity in these regions disappeared rapidly, as opposed to that in the tumourous area of adrenal gland that transiently increased at 4 hr postinjection and thereafter disappeared slowly. Iodine-131 MIBG scanning was performed in 3 patients with pheochromocytoma (PCC), 2 MTC patients, one patient with carcinoid (CN), and one EH patient. Hot spots were noted in the left adrenal gland and the upper region of bladder in PCC patients, and in the anterior neck, liver, spines, and right adrenal gland in MTC patients. In neither CN nor EH patient, was there accumulation of I-131 MIBG. The findings indicate that I-131 MIBG is beneficial in visualizing PCC and MTC. (Namekawa, K.)