Selenium-75-19-selenocholesterol-a new adrenal scanning agent with high concentration in the adrenal medulla.

A tissue distribution study with 75Se-19-selenocholesterol in rats, rabbits, and dogs showed high adrenal concentrations and good adrenal images. In the dog, higher concentrations were obtained in the adrenal medulla than in the cortex at Days 1 and 7 after dosing. Extraction and thin-layer chromatography of the adrenal lipid in dogs given this compound showed that 75Se in the adrenal is still attached to the steroid moiety. A reduction in production costs is expected from its longer shelf life. Selenium-75-19-selenocholesterol is being evaluated in humans not only for routine use as a adrenal cortex scanning agent, but also for the detection of pheochromocytomas and other sympathetic tissue tumors, especially neuroblastomas.