Physics, Techniques and Procedures

Radiolabelled red blood cell

blood cell labelled with technetium-99m either in vivo or in vitro. In-vivo labelling is accomplished by injecting pyrophosphate which binds to the erythrocytes. Then after a few minutes technetium 99m pertechnetate is injected which reacts with the pyrophosphate to label the red blood cells. Alternatively, this process is carried out in vitro with an additional centrifugation step to separate the bound from the unbound label.

Labelled erythrocytes are excellent blood-pool markers and are used in radionuclide angiocardiography and gated blood pool scanning and when looking for gastrointestinal bleeding sources (radionuclide gastrointestinal bleeding source imaging). In vitro labelled red blood cells which are heat denatured are also used to search for accessory spleens.

Red blood cells labelled with chromium or iron and reinjected into the patient serve to evaluate red blood cell survival.

GvS