A gallium scan is a type of nuclear medicine imaging test that uses a small amount of radioactive gallium-67, injected into a vein, to detect areas of infection, inflammation, or certain cancers in the body. The tracer naturally collects in tissues where cells are rapidly dividing or where the immune system is actively fighting something, making those areas light up on the scan. It’s a whole-body test, meaning it can reveal problems in places your doctor might not have thought to look.
How the Tracer Works
Gallium-67 is a radioactive form of the metal gallium, mixed with citrate and delivered through a standard IV injection. Once in your bloodstream, it behaves similarly to iron, binding to proteins that carry iron throughout the body. Because areas of infection, inflammation, and tumor growth have higher concentrations of these iron-transport proteins and increased blood flow, the gallium accumulates there in greater amounts than in healthy tissue.
A special camera called a gamma camera then detects the radiation emitted by the gallium and creates images of your body. Areas where the tracer has concentrated heavily appear as bright spots, often called “hot spots.” Some normal uptake is expected in certain areas like the liver, spleen, bones, and bowel, so radiologists compare the brightness and location of any hot spots against these known patterns to identify what’s abnormal.
What a Gallium Scan Detects
Gallium scans have traditionally been used to evaluate three broad categories of problems: infections, inflammatory conditions, and cancers. For infections, the scan can help locate hidden abscesses or sources of unexplained fever, especially when other imaging hasn’t pinpointed the cause. For inflammatory diseases like sarcoidosis (a condition where clusters of immune cells form in organs), gallium scanning was long considered a standard diagnostic tool.
On the cancer side, gallium scans have been used to detect and monitor lymphomas and other tumors that are metabolically active. The tracer tends to accumulate in these rapidly growing tissues, helping doctors see whether a cancer has spread or whether treatment is working.
The Procedure Timeline
Unlike most imaging tests, a gallium scan isn’t a single appointment. The process spans multiple days because the tracer needs time to distribute through your body and settle into any problem areas.
On day one, you receive the gallium injection, which takes only a few minutes. Then you go home and return for the actual imaging, typically 24 to 72 hours later. In some cases of acute inflammation, an early scan at 3 to 4 hours after injection can be useful. On the other end, delayed scans at 96 hours or later are sometimes necessary, particularly when doctors need to examine the abdomen, where normal bowel activity can obscure results.
The imaging session itself involves lying still on a table while the gamma camera moves slowly over your body. This can take 30 minutes to an hour depending on how many views are needed. You won’t feel anything from the camera. The overall process, from injection to final images, can take anywhere from one to four days.
Preparing for the Scan
Before the injection, your medical team will review your health history. You should mention any medication allergies, all prescription and over-the-counter medicines you take (particularly anything containing bismuth, like some stomach remedies), and whether you’ve recently had any tests using barium contrast. Barium left in your system from a prior exam can interfere with the gallium images.
In the days before your scan, you may be asked to take a laxative for several nights to help clear your bowels, since gallium naturally accumulates in the intestines and can create confusing images. A couple of hours before the scan itself, you might also need an enema. Right before imaging, you’ll empty your bladder and remove any metal jewelry or objects. Pregnancy and breastfeeding are important to disclose early, as the tracer poses risks to infants.
Safety and Side Effects
Gallium scans involve a low dose of radiation, comparable to other nuclear medicine tests. The tracer leaves your body gradually through urine and stool over the following days and weeks. For most adults, the radiation exposure is considered low-risk.
Side effects from the injection itself are rare. When they do occur, they tend to be allergic-type reactions: skin rash, hives, itching, or, very uncommonly, difficulty breathing or swelling around the face and throat. Some people experience minor irritation at the injection site, including redness, soreness, or swelling. The vial stopper contains a latex derivative, so a latex allergy is worth mentioning beforehand. The preparation also contains benzyl alcohol, which can cause serious reactions in newborns or people with liver disease.
Breastfeeding is not safe during and for some time after a gallium scan, as studies have shown the tracer can pass into breast milk and harm an infant.
Gallium Scans vs. PET Scans
Gallium scanning has been increasingly replaced by PET scans (specifically FDG-PET, which uses a radioactive sugar tracer) for many of its traditional uses. The shift has happened for several practical reasons. PET scans deliver results faster, with imaging possible within an hour or two of injection rather than days. They also expose patients to less radiation and produce images with better resolution.
In lymphoma, PET scans have largely taken over because they detect significantly more disease sites, define active disease more accurately, and are better at finding cancer in abdominal lymph nodes. For sarcoidosis, PET scans show at least comparable and possibly superior sensitivity, with less variability in how different radiologists interpret the results. One acknowledged limitation of gallium scanning in sarcoidosis is significant disagreement between readers on what constitutes a positive finding.
That said, gallium scans haven’t disappeared entirely. They remain available at facilities that may not have PET scanners, and they can still play a role in evaluating certain infections or inflammation when PET isn’t an option. Gallium has also been noted as potentially more sensitive for detecting disease in superficial locations like skin and muscle, though this advantage hasn’t been consistently demonstrated in studies. In practice, if your doctor orders a gallium scan today, it’s likely because of specific circumstances where it remains a reasonable choice or where PET is unavailable.
Understanding Your Results
Normal gallium scan results show the tracer distributed evenly with expected uptake in the liver, spleen, bones, and large intestine. Abnormal results show hot spots, areas of unusually intense tracer accumulation, that may point to infection, inflammation, or tumor activity. The location, intensity, and pattern of these hot spots all matter. For example, a specific pattern of uptake in the tear glands and salivary glands alongside lymph nodes in the chest (sometimes called the “lambda-panda” pattern) has historically been considered characteristic of sarcoidosis, though it doesn’t appear in every case.
A hot spot doesn’t automatically confirm cancer or infection. Gallium can accumulate for various reasons, and your doctor will interpret the scan alongside your symptoms, blood work, and other imaging. In some cases, a biopsy or additional testing is needed to confirm what the scan suggests. Similarly, a normal scan doesn’t always rule out disease, as small or low-activity lesions can be missed.