Which organ is typically not visualized on a Ga 67 scan acquired 72 hours after tracer administration?

In a Gallium-67 scan, which is often used to identify infections, malignancies, or inflammatory conditions, the organ that is typically not visualized 72 hours after tracer administration is the kidneys. Gallium-67 primarily accumulates in areas of inflammation, infection, and certain tumors due to its affinity for transferrin and lactoferrin, which are proteins involved in the immune response.

The kidneys do not concentrate Gallium-67 in the same way that they concentrate many other radiopharmaceuticals, such as technetium-based agents. Consequently, while the spleen, liver, and thyroid may show uptake due to their metabolic activity or inflammatory conditions, the kidneys generally do not display significant uptake of Gallium-67 after that amount of time. This distinction is crucial for interpreting scan results, as the absence of kidney visualization can provide important clinical insights regarding renal conditions or contribute to the assessment of the overall imaging study.