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Sept 25, 1967

Selenomethionine Se 75 Scanning

Author Affiliations

Ann Arbor, Mich

JAMA. 1967;201(13):1053. doi:10.1001/jama.1967.03130130079030

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To the Editor:—  Toole and Witcofski (198:1219, 1966) reported visualizing a thymoma by photoscanning 24 and 48 hours following injection of selenomethionine Se 75. During the past three years we have performed such photoscans in more than 30 patients with proved primary hyperparathyroidism, and noted uptake in the mediastinum ( Figure). None of these patients had a thymoma, yet the scan was often indistinguishable from the authors' scan of a patient with thymoma.We have reported the high uptake of 75Se over the mediastinum and suggested that it may be caused by selenomethionine Se 75 localized in bone marrow (J Nucl Med5:417, 1964 ). Since there is a relatively large pool of blood containing 75Se labeled plasma proteins under this area, the scanner probably detects the blood pool as well.We urge that caution be exercised in interpreting selenomethionine Se 75 scans of the upper chest area.