A gallium scan is a nuclear medicine imaging test that uses a small amount of radioactive gallium-67 to detect areas of infection, inflammation, or cancer in the body. After the radioactive tracer is injected into a vein, it circulates through your bloodstream and gradually collects in areas where your immune system is active or where abnormal cells are growing. A special camera then captures images showing exactly where the gallium has accumulated, helping doctors pinpoint problems that other imaging tests might miss.
How Gallium-67 Works in the Body
Gallium-67 behaves similarly to iron in the bloodstream. Once injected, it binds to transferrin, a protein your blood normally uses to carry iron. This gallium-transferrin complex then travels throughout the body, and cells with high numbers of transferrin receptors pull it inside. Tumor cells and areas of active infection or inflammation tend to have far more of these receptors than healthy tissue, which is why the tracer concentrates there.
The exact mechanisms aren’t completely understood, but the end result is reliable: gallium lights up in places where something abnormal is happening, creating a visual map your doctor can use to locate and assess disease.
What Conditions It Helps Diagnose
Gallium scans have historically been used across a wide range of conditions. The two most common reasons doctors still order them are lymphoma (both Hodgkin’s and non-Hodgkin’s) and fever of unknown origin, where a patient has a persistent fever with no clear cause. In lymphoma, the scan helps determine whether the cancer is active and how it’s responding to treatment.
Beyond those primary uses, gallium scans can detect:
- Sarcoidosis, an inflammatory disease that often affects the lungs and lymph nodes
- Bone infections (osteomyelitis), including spinal disc infections
- Lung conditions like pulmonary tuberculosis, interstitial pneumonitis, and pulmonary fibrosis
- Abdominal abscesses, or pockets of infection inside the abdomen
- Various cancers, including lung cancer, melanoma, hepatocellular carcinoma, and head and neck tumors
For sarcoidosis specifically, gallium scans are remarkably sensitive. Studies have found 94 percent sensitivity for detecting active sarcoidosis, making it the most sensitive single test for that condition, outperforming blood tests and chest X-rays. Radiologists look for two characteristic patterns on the scan: the “lambda sign,” where gallium collects in chest lymph nodes in a shape resembling the Greek letter lambda, and the “panda sign,” where it accumulates symmetrically in the tear glands and salivary glands, creating a pattern that looks like a panda’s face. When both signs appear together, they are specific to sarcoidosis and aren’t seen in other conditions.
What the Procedure Looks Like
A gallium scan happens in two separate visits. During the first, you receive an injection of gallium-67 citrate into a vein, typically in your arm. The injection itself takes just a few minutes, and you can go home afterward. The tracer needs time to circulate and collect in abnormal tissue, so the actual imaging happens one to three days later, depending on what your doctor is looking for.
When you return for imaging, you’ll lie on your back on a scanner table. The machine looks like a firm bed with a large camera positioned above you. The camera detects the gamma rays emitted by the gallium-67 in your body and translates them into images. You’ll need to stay very still during the scan, which typically lasts about an hour. The camera doesn’t touch you, and the process itself is painless.
Preparing for the Scan
Your doctor may ask you to take a laxative or use an enema before the imaging session. Gallium-67 is naturally excreted through the liver into the bowel, and accumulated tracer in the intestines can obscure the images of your abdomen and pelvis. Bowel cleansing reduces this background interference and gives radiologists a clearer picture.
Pregnancy is a contraindication for gallium scans because of radiation exposure to the fetus. If you are breastfeeding, international guidelines recommend stopping for three to four weeks after the injection, or ceasing breastfeeding entirely. Milk pumped during this interruption period can be stored frozen and safely given to the infant after about 33 days, by which point the radioactivity has decayed to negligible levels. If you’ve stored breast milk before the procedure, you can use that supply during the interruption. Some hospitals can also test your milk directly to confirm when it’s safe to resume nursing.
Radiation Exposure
A standard gallium-67 scan delivers a radiation dose of roughly 7 to 12 millisieverts (mSv), depending on how quickly your body clears the tracer. For context, a standard CT scan of the chest delivers about 7 mSv, and Americans receive roughly 3 mSv per year from natural background radiation. The dose is meaningful but considered acceptable when the scan provides diagnostic information that changes your care.
How It Compares to PET Scans
In many clinical scenarios, PET/CT scans using a glucose-based tracer have largely replaced gallium-67 scans. PET scans offer higher resolution images, faster results (imaging the same day as injection), and lower radiation doses. For lymphoma staging and most cancer evaluations, PET/CT is now the standard.
Gallium scans still have a role in specific situations. They remain useful when PET/CT is unavailable, when evaluating certain infections and inflammatory conditions, or when a doctor needs a whole-body survey for a fever of unknown origin. Newer gallium-68 based tracers, which work with PET/CT scanners rather than the older gamma cameras, are also expanding the usefulness of gallium in nuclear medicine. These newer tracers target different biological processes and show promise for detecting bone infections, inflammatory diseases like Crohn’s disease and rheumatoid arthritis, and certain cancers with higher precision than the traditional gallium-67 approach.
Understanding Your Results
Gallium scan results are typically described as showing “normal” or “abnormal” uptake. Normal uptake means the tracer distributed evenly without concentrating in unexpected areas. Some gallium naturally collects in the liver, spleen, bones, and bowel, so mild activity in these locations is expected.
Abnormal uptake means the tracer concentrated in one or more specific areas, suggesting infection, inflammation, or tumor activity. The location, intensity, and pattern of uptake all help your doctor narrow down the cause. A focal hot spot in a bone might suggest infection, while diffuse uptake across the lungs could point to an inflammatory condition like sarcoidosis. Results are often interpreted alongside other imaging, blood tests, and your clinical symptoms to reach a diagnosis. In some cases, a positive gallium scan leads to a biopsy or additional testing to confirm what’s causing the abnormal uptake.