CLINICAL EXPERIENCE WITH 75Se SELENOMETHYLCHOLESTEROL ADRENAL IMAGING

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Abstract
The results of quantitative adrenal imaging using 75Se selenomethylcholesterol in 62 subjects are analyzed. The adrenal area was localized by a renal scan, lateral views of which enabled adrenal depth to be estimated. The first 19 cases were scanned with a rectilinear scanner and the remaining 43 cases imaged with a .gamma.-camera. Quantitation of adrenal uptake was performed on computer-stored static images obtained 7 and 14 days postinjection of 75Se selenomethylcholesterol (3 and 6 days in the 1st 10 cases studied). Normal uptake was 0.07-0.30% of the administered dose. Overall predictive accuracy of the type of adrenal disorder of 32 patients with Cushing''s syndrome was 90.6%, this included 12 cases of Cushing''s disease (mean uptake 0.58%), 7 ectopic ACTH syndromes (mean uptake 0.69%), 5 unilateral adenomata (mean uptake 0.93%), 3 post-adrenalectomy regrowths (mean uptake 1.37%), 3 adrenal carcinomas (mean uptake 0.01%), 1 congenital hyperplasia (mean uptake 3.4%) and 1 unilateral nodular hyperplasia. Overall predictive accuracy of the cause of Conn''s syndrome in 22 cases was 86.4%; this included 13 cases of bilateral hyperplasia (mean uptake 0.34%), 8 unilateral adenomata (mean uptake 0.47%) and 1 patient with mineralocorticoid excess in whom the cause was not confirmed. The mean uptake in the normal adrenal in cases of unilateral adenoma was 0.19% (range 0.07-0.30%). Causes of unsatisfactory adrenal imaging are examined. The procedure is recommended as the localizing and lateralizing technique of choice in Cushing''s syndrome except where due to adrenal carcinoma, and as an important noninvasive technique in Conn''s syndrome for the lateralization of adenoma.