Imaging the adrenal glands with radiolabeled inhibitors of enzymes: concise communication.

Although radioiodinated cholesterols furnished the first noninvasive imaging of the adrenal glands, it would be desirable to decrease the time for imaging and decrease the radiation dose. The relative tissue distributions of two radiolabeled enzyme inhibitors [3H] metyrapol and I-125-SKF-12185 were studied in dogs and man. Their percentage uptakes and target-to-nontarget ratios were similar. The adrenals of three dogs were imaged sharply at 2 hr after injection with 4--6 mCi of I-131-SKF-12185, confirmed by subsequent imaging with 1 mCi of I-131-6-beta-19-nor cholesterol at 5 days after injection. The use of 1 mCi of I-123-SKF will permit imaging of the adrenals in 1--2 hr and will decrease the radiation dose in the human to 0.76 rads to the adrenal, 0.18 rads to the ovaries and 1.7 rads to the liver.