Technetium scanning is a method of nuclear imaging based on the physiologic principles of increased blood flow, increased capillary permeability and active recruitment of white blood cells in an inflammatory reaction. Technetium Tc99m in blood is used to demonstrate areas of increased perfusion. In WBC scans, Tc99m labeled WBC demonstrates areas of infection. Examples: Tc99m pyrophosphate scintigraphy: uptake in areas of recent myocardial infarction. Tc99m labeled red cell scan: to localize site of a gastrointestinal bleed. Tc99m using iminodiacetic acid compounds to demonstrate gallstones and obstructed cystic duct. Tc99m phosphates to demonstrate metastatic cancer.