Clinical study of 131I-meta-iodobenzylguanidine on pheochromocytoma

The 131I meta-iodobenzylguanidine (131I-MIBG) was used for the scintigraphy of adrenal medulla and this was applied to examine 8 patients with pheochromocytoma and 7 patients with hypertension. The 131I-MIBG is an analogue of guanethidine, metabolized and straged in the same way as adrenaline (or cathecholamine), and this indicates 131I-MIBG is a suitable radioactive nuclide for the imaging of the adrenal medulla. Used methods were as follows; Rugol G was given orally for three days, 0.5 mCi of 131I-MIBG was injected intravenously on the fourth day, then whole body and adrenal scintigraphy were taken at 24, 48 and 72 hours after injection, respectively. Liverscintigraphy was also taken at 72 hours after injection. Six of 6 cases (100 %) in which pheochromocytomas were confirmed by operation, showed high intake of 131I-MIBG in the adrenal gland, especially in one case, metastasis to the paraaortic lymphnodes was detected clearly. Our study showed the usefulness of the subtraction scan which was obtained by using liver scintigraphy (taken at 72 h. after injection of 131I-MIBG). Computer processed images obtained by changing gains at several levels were also useful to get better understandings. No side effect was observed in this study. Control of the blood pressure is possible in this method by use of and/or blockers. For the diagnosis and localization of pheochromocytoma, the 131I-MIBG adrenal scintigraphy will be a principal method in the future by its safety, specificity and non-invasivity. (author)