Preoperative localization of parathyroid tumors by 201Tl/99mTc subtraction scanning

29 patients with biochemically proven hyperparathyroidism underwent a 201Tl/99mTc subtraction scanning before neck exploration was done. The scanning technique seems not to be reliable for hyperplastic glands in secondary hyperparathyroidism, but in 19 of 21 patients with primary hyperparathyroidism a solitary adenoma was correctly located. This accuracy of 90.5% justifies to investigate all patients with primary hyperparathyroidism with this noninvasive double tracer technique prior to any surgery.