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Concept
Scintigraphie au gallium
Résumé
A gallium scan is a type of nuclear medicine test that uses either a gallium-67 (67Ga) or gallium-68 (68Ga) radiopharmaceutical to obtain images of a specific type of tissue, or disease state of tissue. Gallium salts like gallium citrate and gallium nitrate may be used. The form of salt is not important, since it is the freely dissolved gallium ion Ga3+ which is active. Both 67Ga and 68Ga salts have similar uptake mechanisms. Gallium can also be used in other forms, for example 68Ga-PSMA is used for cancer imaging. The gamma emission of gallium-67 is imaged by a gamma camera, while the positron emission of gallium-68 is imaged by positron emission tomography (PET).
Gallium salts are taken up by tumors, inflammation, and both acute and chronic infection, allowing these pathological processes to be imaged. Gallium is particularly useful in imaging osteomyelitis that involves the spine, and in imaging older and chronic infections that may be the cause of a fever of unknown origin.
Gallium-68 DOTA scans are increasingly replacing octreotide scans (a type of indium-111 scan using octreotide as a somatostatin receptor ligand). The gallium-68 is bound to an octreotide derivative chemical such as DOTATOC and the positrons it emits are imaged by PET-CT scan. Such scans are useful in locating neuroendocrine tumors and pancreatic cancer.
In the past, the gallium scan was the gold standard for lymphoma staging, until it was replaced by positron emission tomography (PET) using fludeoxyglucose (FDG). Gallium imaging is still used to image inflammation and chronic infections, and it still sometimes locates unsuspected tumors as it is taken up by many kinds of cancer cells in amounts that exceed those of normal tissues. Thus, an increased uptake of gallium-67 may indicate a new or old infection, an inflammatory focus from any cause, or a cancerous tumor.
It has been suggested that gallium imaging may become an obsolete technique, with indium leukocyte imaging and technetium antigranulocyte antibodies replacing it as a detection mechanism for infections.
Source officielle
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