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 with the technetium is then injected back into your bloodstream.
Red blood cells with the technetium attached to them accumulate at the location of active bleeding. A machine scans the body to find where the technetium accumulates. This method of finding bleeding is sometimes more effective than angiography. The technetium-labeled red blood cell bleeding scan may find slow bleeding that can't be seen using angiography.