<prompt> Parathyroid adenoma best diagnosed byUSGCT scanI-131 scanTc99m-Th201 scan  <response>: Ans d Tc99m-Th201 scan. Ref. Grainger, Diagnostic Radiology 4th ed., 1380PARATHYROID SCINTIGRAPHY Tc-99m -thallium substraction scan has 70-92 sensitivity 43 specificity Tc-99m sestamibi has 88-100 sensitivity 91-98 specificity best scan. Radionuclide scintigraphy with 201 Technetium-thallium or m Tc- MIBI Technetium-99m sestamibi, using a subtraction technique whereby the image of thyroid gland as shown by m Tc or 123 I is removed, is thus a noninvasive other best technique for tumor other lesions localization of parathyroid gland.Educational points: Presently, Tc-99m sestambi is the best available agent for parathyroid scanning. Parathyroid adenoma is the most common cause of primary hyperparathyroidism. Subperiosteal resorption of bones including erosion of lamina dura, Pepper-pot skull, phalangeal erosions, platyspondyly, osteitis fibrosa cystica, Browns tumors are few typical X-ray findings of hyperparathyroidism. Superscan appearance on Tc99m-MDP bone scan is a prominent feature of hyperparathyroidism. A notable point - in primary hyperparathyroidism osteoporosis is common feature while in secondray hyperparathy- roidism osteosclerosis Rugger-Jersey spine is a important feature. 