In a technetium-labeled red blood cell bleeding scan, blood is taken from you, and a small amount of radioactive material called technetium is added to the blood. The blood containing the technetium is then injected back into your bloodstream.
Red blood cells with the technetium attached to them will accumulate at the location of active bleeding. A machine scans the body to find where the radioactive material accumulates. This method of finding bleeding is sometimes more effective than angiography because the technetium-labeled red blood cell bleeding scan may find slow bleeding that cannot be seen using angiography.
The technetium-labeled red blood cell bleeding scan is used:
WebMD Medical Reference from Healthwise