Cyclotron-produced. Gallium behaves as an iron analogue — binds transferrin in plasma and is delivered to sites of rapid cell turnover, infection, and inflammation. Concentrates in:
- Bone marrow and liver (normal)
- Sites of infection/inflammation (binds lactoferrin released by neutrophils)
- Tumors (particularly lymphoma)
Multiple energy peaks (93, 185, 300 keV) — imaging uses all three windows, which increases complexity and reduces image quality compared to single-peak agents. Two- to three-day delay between injection and imaging is required.
Historical role: was the primary agent for infection (especially osteomyelitis, spinal infection, prosthetic joint) and lymphoma staging. Now largely replaced:
- Infection → In-111 labeled WBCs or FDG-PET
- Lymphoma → FDG-PET
Remaining niche: opportunistic infections in immunocompromised patients (especially diffuse pulmonary PCP showing “reverse” pattern — increased lung gallium without CXR abnormality), and some inflammatory conditions (sarcoidosis showing “lambda” and “panda” signs).