The normal and abnormal distribution of the adrenomedullary imaging agent m-[I-131]iodobenzylguanidine (I-131 MIBG) in man: evaluation by scintigraphy

The scintigraphic distribution of m-[131I]iodobenzylguanidine (I-131 MIBG), an adrenal medullary imaging agent, was studied to determine the patterns of uptake of this agent in man. The normal distribution of I-131 MIBG includes clear portrayal of the salivary glands, liver, spleen, and urinary bladder. The heart, middle and lower lung zones, and colon were less frequently or less clearly seen. The upper lung zones and kidneys were seldom visualized. The thyroid appeared only in cases of inadequate thyroidal blockade. The "normal" adrenal glands were seldom seen and faintly imaged in 2% at 24 hr after injection and in 16% at 48 hr, in patients shown not to have pheochromocytomas, whereas intra-adrenal, extraadrenal, and malignant pheochromocytomas usually appeared as intense focal areas of I-131 MIBG uptake at 24 through 72 hr.     

The relationship of adrenal iodomethylnorcholesterol uptake to indices of adrenal cortical function in Cushing's syndrome

The adrenal gland uptake of 131I-6-beta-iodomethyl-19-norcholesterol (NP-59) was calculated using a semioperator-independent computer algorithm in 17 patients with Cushing's syndrome (CS). Twelve had ACTH-dependent and 5 had ACTH-independent CS. The mean adrenal gland uptake (percentage of administered dose) of NP-59 was 0.74 +/- 0.18% (range, 0.21-2.02%) in CS and was significantly higher than that of normal subjects (0.33 +/- 0.02%). Patients with the ectopic ACTH syndrome and ACTH-independent CS manifested the highest uptakes (mean, 1.18 +/- 0.08%; range, 0.74-2.02%). In the patients with ACTH-dependent CS, a significant correlation was observed between 24-h urinary free cortisol excretion and NP-59 adrenal gland uptake (r = 0.97, P less than 0.001). No relationship was seen between NP-59 uptake and urinary free cortisol in ACTH-independent CS or between NP-59 uptake and urinary 17-hydroxycorticosteroids, 17-ketosteroids, cortisol secretion rate, plasma cortisol, or ACTH levels in either ACTH-dependent or ACTH-independent CS. We conclude that in addition to localizing the sites(s) of adrenocortical hypersecretion in CS, the level of NP-59 adrenal uptake is a reflection of cortisol excretion in ACTH-dependent disease and may be utilized as another parameter to quantitate adrenal disease activity in CS.     

Preparation, quality control and clinical acceptance of labeled Macrotec.

Thirty minutes after reconstitution, radiochemical purity determinations of the lung-scanning agent Macrotec (99m-Tc-MAA) indicated 95-100% technetium labeling: 76% of the particles had a mean diameter of 10-50 mu. Rat tissue distribution studies indicated lung uptake of 98% at 15 minutes. The biological half-life in the lung was 8.3 hours. In 12 patients requiring emergency lung scans, 9 scans were rated excellent. No liver, spleen or thyroid uptake or adverse reactions were noted.     

Myocardial uptake of labeled oleic and linoleic acids.

Oleic acid labeled with 14C, (14C-OA) or 131I (131I-OA) and 131I-labeled linoleic acid (131I-LOA) were administered intravenously to rats and tissue distribution studies completed at various time intervals from 5 to 60 min. Tissue distribution of 131-I-labeled oleic acid or linoleic acid was also studied in dogs at 5- and 30-min time intervals after intravenous administration of the tracer dose. There were distinct differences in the patterns of tissue distribution between 14C-OA, 131I-OA, and 131I-LOA. Radioactivity concentration in the myocardium was the highest at all time intervals in the rats given 131I-OA only. In dogs, the myocardial uptake of 131I-OA was significantly higher than the radioactivity in the blood or other tissues at 30 min after injection. The disappearance rates of 131I-OA and 131I-LOA were almost identical but myocardial concentration of 131I-LOA at 30 min after the dose in the dog was half that of 131I-OA whereas 131I-LOA liver concentration was higher than that of 131I-OA. Since the concentrations of our formulated 131I-OA in the blood and in the myocardium are both highest at the earlier intervals, it should be difficult to detect myocardial ischemia or infarction with 131I-OA scanning.