Gallium scan
A gallium scan is a nuclear medicine imaging procedure that assesses specific tissues by measuring their uptake of a radioactive isotope, gallium-67 citrate. The process begins with the injection of this tracer into a vein, where it circulates through the bloodstream to target areas, primarily the bones, liver, and intestines. The scan typically occurs two days after the injection, capturing images of areas where the tracer accumulates, indicating potential infection, inflammation, or tumors. While gallium scans were once the standard for diagnosing and staging cancer, they have largely been replaced by more advanced imaging techniques like positron emission tomography (PET) scans. Nevertheless, gallium scans remain useful for identifying infections and monitoring inflammatory conditions. Preparation for the scan may involve dietary adjustments to enhance image clarity, and the procedure itself is painless, typically lasting 30 to 60 minutes. Post-scan, patients can resume regular activities with minimal restrictions. Results are usually available the day after the scans are completed, contributing to the diagnosis and management of various medical conditions.
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Subject Terms
Gallium scan
ALSO KNOWN AS: Nuclear medicine scan, radioisotope scan
DEFINITION: A gallium scan is a nuclear medicine imaging study that evaluates specific tissues based on their uptake of an administered radioactive isotope.
During a gallium scan, the isotopic tracer (gallium 67 citrate) is injected into a vein. It travels through the bloodstream into the tissues, primarily the bones, liver, and intestines. It usually takes a few days for the tracer to accumulate in the tissues, so in most cases, a scan is done about two days after an injection of the tracer and repeated the following day. Areas of increased tracer uptake show up as bright, or “hot,” spots on an x-ray. Delineated problem areas may be caused by infection, inflammation, or tumor (rapid cell division). The gallium scan was the standard for cancer diagnosis and staging until it was replaced by positron emission tomography (PET) scans. Gallium 67 is often used in conjunction with a bone scan (using technetium 99m phosphate) as “a double tracer” technique to overlay areas of inflammation within organ systems. Gallium is less dependent on blood flow than technetium and may identify foci that would otherwise be missed.
Cancers diagnosed: Major cancers such as lymphomas, malignant bone tumors, and soft-tissue sarcomas; can be used to identify most neoplasms, whether or malignant
Why performed: A gallium scan is performed to detect the presence of cancerous tissue. It may be employed to determine whether a cancer has spread (metastasized) to other parts of the body, or to monitor the effectiveness of cancer treatment. It can also be used to diagnose inflammatory conditions such as pulmonary fibrosis or sarcoidosis, to monitor the response to antibiotic treatment, to detect an or certain infections, especially in the bones, and to detect an unknown source of infection that is causing a fever.
Patient preparation: Gallium accumulates in the large intestine (colon) before being eliminated in the stool. Patients may need to take a laxative the night before the scan and have an enema one to two hours prior to the scan to prevent gallium in the colon from interfering with pictures being taken of the area. The doctor and radiologist should also be informed of possible pregnancy, breast-feeding activity, and the use of a barium enema within the preceding days or medicine (such as Pepto-Bismol) that contains bismuth, as barium and bismuth can interfere with the test results.
Steps of the procedure: A gallium scan is performed by a nuclear medicine technologist. The scan pictures are interpreted by a radiologist or nuclear medicine specialist.
The arm is cleaned with soap, Betadine, or alcohol around the injection site. A small amount of the radioactive chemical is then injected through a vein. After the tracer is administered, the patient is brought back to the radiology facility, and scans are completed at eighteen to twenty-four hours and twenty-four hours after that.
The scanning protocol requires the removal of all jewelry. Most clothes are removed, and the patient is provided with a cloth gown or paper covering. The patient lies in a supine position (on the back) on a table. A large scanning (gamma) camera will be positioned closely above the patient. After the initial injection, the camera will scan for radiation released by the tracer and produce pictures of the tracer in the tissues. These images serve as a baseline to compare subsequent scan data completed in the next couple of days. The camera will move slowly above and around the body. The camera does not produce any radiation, so the patient is not exposed to any additional source of radioactive material. Different positioning may be attempted so that an area of interest can be viewed from different angles. Restricted movement is necessary during each scan to avoid blurring of the acquired images. Often, the patient will be asked to hold their breath briefly during some of the scans to minimize chest movement that occurs with respiration. Each scan can take approximately thirty to sixty minutes.
After the procedure: A gallium scan is painless. There are no activity restrictions postscan.
Risks: There is a risk of damage to cells and tissues exposed to any level of radiation, including the low level of radiation released by a radioactive tracer such as gallium. Allergic reactions to radioactive tracers are rare. Most of the tracer will be eliminated from the body (in the urine or stool) within a couple of days. Occasionally, some soreness or swelling can develop at the injection site. These symptoms can be relieved by applying moist, warm compresses to the affected area.
Results: A gallium scan utilizes a special radiographic camera to obtain pictures of certain tissues in the body after a radioisotope makes them visible. The results are available the day after the scans are completed. The entire process takes approximately four days.
Although gallium scans were still utilized in the mid-2020s, newer, more effective, and efficient techniques for identifying cancer in the body have replaced them. While PET scans have become the most common in cancer diagnoses, gallium scans are still effective in finding the sources of infection and inflammation in the body. Infrared thermography and multigated acquisition scans are other imaging techniques that have replaced gallium scans in cancer diagnoses.
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