Imaging Considerations

As with mIn-leukocytes, early and delayed imaging should be performed. Due to the shorter half life, however, this is usually performed one and four hours postinjection. Images can also be performed at 24 hours, although isotope decay and normal bowel activity limit image quality.

Gallium is a heavy metal that is handled by the body in a manner very similar to iron. It is injected in the form of 67Ga-gallium citrate, the gallium component of which then binds avidly to transferrin. The circulating metal-protein complex is thought to localize at sites of inflammation through the following mechanisms: increased delivery due to hyperemia, increased pooling due to vasodilation, passive diffusion into the interstitium through "leaky" capillaries, and binding of gallium to other iron-avid proteins such as granulocyte-derived lactoferrin or bacterial siderophores. Lactoferrin is also responsible for the normal visualization of lactoferrin-secreting glands such as the lacrimal glands and breasts. It is currently believed that the most important factor is diffusion across inflamed capillaries with retention within the interstitial space. There is negligible binding of gallium to viable granulocytes and localization can occur in the absence of leukocytes. Gallium has therefore proven to be an effective agent in immunosuppressed and leukopenic

Gallium normally concentrates in sites of iron storage (liver, erythropoetic bone marrow and to a lesser degree spleen), in secretory organs that produce lactoferrin

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