Mediastinal parathyroid adenoma: a new method of localization

201Tl-thallous chloride/99mTc sodium pertechnetate subtraction scanning is a simple and accurate means to demonstrate enlarged parathyroid glands. We report a case in which the intra-operative location of a mediastinal adenoma was greatly facilitated by using a probe radiation detector following intravenous injection of 201Tl-thallous chloride. We believe this is the first reported use of this technique in parathyroid surgery.