Gallium citrate scan

Gallium acts as an iron analog, and when administered intravenously it is transported in the blood bound to transf2242in.

It concentrates in areas of inflammation, infection, and malignancy.

Highly sensitive for diagnosing PCP.

A gallium scan is a type of nuclear medicine study that uses a radioactive tracer to obtain images of a specific type of tissue, or disease state of tissue.

Gallium salts like gallium citrate and gallium nitrate are used, and the radioactive isotope gallium-67 (67Ga), which has a decay half-life of 3.26 days, is used.

Gallium-67 is imaged with a gamma camera, with a SPECT camera, or with SPECT/CT hybrid machines.

Gallium is taken up by tumors, inflammation, allowing these pathological processes to be imaged by nuclear scan techniques.

Gallium is taken up by both acute and chronic infections, and especially useful in imaging osteomyelitis of the spine, and infections that may be the cause of a fever of unknown origin.

The free gallium isotope ion is bound and concentrates in areas of inflammation, and also areas of rapid cell division.

Ga+3 isotope binds to transf2242in, leukocyte lactof2242in, bacterial siderophores, inflammatory proteins, and cell-membranes in neutrophils, both living and dead.

Has been replaced by PET scan using fludeoxyglucose for cancer diagnosis and staging.

Presently primarily used to image inflammation and chronic infections.

An increased uptake of gallium-67 may indicate a new or old infection, an inflammatory focus from any cause, or a malignant process.

Ga-67 acts as an iron analogue, initially binding to transf2242in, and binds to any proteins that bind iron.

The Ga-67-iron complex diffuses through loose endothelial junctions of capillaries at sites of inflammation and enters the extracellular fluid.

As leukocytes migrate to sites of inflammation and degranulate, they release large quantities of iron-binding lactof2242in.

Ga-67 has higher affinity for leukocyte lactof2242in than it does for serum transf2242in, and indicates the presence of leukocytes.

Useful in detecting abscesses that provoke a leukocyte response.

Can attach to the siderophore molecules of bacteria, and can be used in leukopenic patients with bacterial infection.

Indium leukocyte imaging and technetium antigranulocyte antibodies have replaced it as a detector technique for infections.

For detection of tumors, especially lymphomas, it has been replaced by fludeoxyglucose PET imaging.

In infections, the gallium scan has an advantage over indium leukocyte imaging in imaging osteomyelitis of the spine, lung infections and inflammation, and for chronic infections because gallium binds to neutrophil membranes, even after neutrophil death.

Indium leukocyte imaging is better for acute infections as neutrophils are still rapidly and actively localizing to the infection, and also for osteomyelitis that does not involve the spine, and for abdominal and pelvic infections.

Both the gallium scan and indium leukocyte imaging may be used to image fever of unknown origin.

The indium scan will image only the 25% of FUO caused by acute infections.

Gallium will also localize to other sources of fever, such as chronic infections and tumors.

Indications for use of gallium-67: to localize source of fever in patients with FUO.

Detection of pulmonary and mediastinal inflammation/infection.

Evaluation and follow-up of active lymphocytic or granulomatous inflammatory processes.

Diagnosing vertebral osteomyelitis and/or disk space infection.

Diagnosis and follow-up of medical treatment of retroperitoneal fibrosis.

Evaluation and follow-up of drug-induced pulmonary toxicity

Evaluation of patients who are not candidates for WBC scans.

Following the injection of the isotope tracer images are taken by a gamma camera at 24, 48, and in some cases, 72, and 96 hours.

Areas that collect large amounts of tracer is a result of inflammation or rapid cell division being present.

Single photon emission computed tomography (SPECT) images may also be acquired and may be combined with computed tomography scan.

10% to 25% of the dose of gallium-67 is excreted, mostly by the kidneys, within 24 hours after injection.

After 24 hours the main excretory pathway is via the colon.

Ga-67 normally localizes at the sites which include: liver, bone marrow, spleen, salivary glands, nasopharynx, lacrimal glands, breast, kidneys, bladder and lungs in the first 24 hours.

Tissue distributions in children which differ from those in adults.

In children growth plates, spleen, and thymus manifest uptake.

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