A gallium scan or gallium 67 scan (also called "gallium imaging") is a type of nuclear medicine study that uses a radioactive tracer to obtain images of a specific type of tissue, or disease state of tissue. Gallium salts like gallium citrate and gallium nitrate are used. The form of salt is not important, since it is the freely dissolved gallium ion Ga⁺³ which is active. For these applications, the radioactive isotope gallium-67 (⁶⁷Ga), which has a decay half-life of 3.26 days, is used.

The body generally handles Ga³⁺ as though it were ferric iron (Fe-III), and thus the free isotope ion is bound (and concentrates) in areas of inflammation, such as an infection site, and also areas of rapid cell division. Gallium (III) (Ga⁺³) binds to transferrin, leukocyte lactoferrin, bacterial siderophores, inflammatory proteins, and cell-membranes in neutrophils both living and dead.

This binding allows sites with tumor, inflammation, and both acute and chronic infection to be imaged by nuclear scan techniques.