A Gallium scan, also known as Gallium Scintigraphy, is a specialized nuclear medicine imaging test used to visualize areas of inflammation, infection, or certain tumors within the body. The procedure involves administering a small, safe dose of the radioactive isotope Gallium-67, which travels through the bloodstream. This radiotracer accumulates in tissues exhibiting pathological changes, allowing a specialized camera to detect the tracer and create images of the affected areas. The test is valuable for locating hidden sources of disease when standard imaging methods like X-rays or computed tomography (CT) scans are inconclusive. It provides functional information about the body’s processes rather than just anatomical structure.
How Gallium-67 Works in the Body
The diagnostic ability of Gallium-67 relies on its chemical similarity to ferric iron (Fe³⁺), a metal naturally transported throughout the body. When injected, the Gallium-67 ion rapidly binds to transferrin, a protein in the blood responsible for iron transport. This Gallium-transferrin complex is then delivered to tissues that have a high demand for iron, which typically include sites of high metabolic activity, rapid cell division, inflammation, and infection.
In areas of disease, cells often overexpress transferrin receptors on their surfaces to pull in more iron for growth, a mechanism Gallium-67 exploits. At sites of infection or acute inflammation, the tracer is also attracted to specific proteins like lactoferrin, which is released by activated white blood cells (leukocytes) that rush to the area. Gallium-67 is also thought to be taken up directly by certain bacteria, further enhancing its concentration in infected areas.
The radioactive isotope accumulates in these pathological regions, creating a “hot spot” that is visible on the final images. This localization process takes time. The concentration of the tracer highlights the biological activity of the disease, offering a unique diagnostic perspective not available with purely anatomical scans.
Medical Conditions Diagnosed
The scan’s primary modern utility is the detection of difficult-to-locate infections and inflammatory disorders. One of its most frequent applications is investigating a Fever of Unknown Origin (FUO), where a patient has a prolonged, unexplained fever. The scan can pinpoint the source of the hidden infection or inflammation.
It is particularly effective in diagnosing osteomyelitis, which is an infection of the bone, especially when it affects the spine, where other imaging can be challenging. Gallium-67 localization helps differentiate between a simple bone abnormality and active infection. It also plays a role in finding abscesses, or collections of pus, that may be deep within the abdomen or soft tissues.
For non-infectious inflammatory conditions, the scan is valuable for assessing diseases like sarcoidosis. It can also be used to evaluate pulmonary fibrosis and other inflammatory lung diseases. The ability of Gallium-67 to accumulate in active inflammatory sites helps physicians gauge the extent and severity of these chronic conditions.
Historically, the Gallium scan was significant, especially for staging and monitoring lymphomas, such as Hodgkin’s lymphoma. While newer imaging techniques like Fluorodeoxyglucose (FDG) Positron Emission Tomography (PET) scans have become the standard for most cancers, Gallium scans are still sometimes used for specific cancer types or in conjunction with other tests. It allows physicians to track the spread of certain tumors and monitor their response to treatment.
Preparation and the Imaging Process
The injection of the Gallium-67 tracer is the first step. The patient receives a small dose of the radioactive material intravenously. This injection has no known side effects and is generally quick, lasting only a few minutes.
There is a necessary delay between the injection and the imaging session. The first imaging session is usually scheduled 24, 48, or even 72 hours after the injection, depending on the reason for the scan. Scans for tumor localization may require imaging up to 72 or 96 hours post-injection to ensure maximum contrast.
To ensure clear images, particularly of the abdomen, patients are often instructed to undergo a bowel preparation before the scan. This preparation helps clear the digestive tract, preventing excreted Gallium-67 from obscuring potential sites of disease in the abdominal area. The patient should also stay well-hydrated during the waiting period.
During the actual imaging session, the patient lies still on a table while a specialized camera, known as a gamma camera or SPECT (Single-Photon Emission Computed Tomography) scanner, moves across the body. This camera detects the gamma rays emitted by the Gallium-67 tracer and translates the data into images that show where the material has concentrated. The scan itself usually takes between 30 minutes to an hour, and patients are asked to remove any metal objects beforehand. The radiation exposure from the tracer is minimal, often comparable to that of a few standard X-rays.