Gallium scan
[2] Radioactive gallium(III) is rapidly bound by transferrin, wich then preferentially accumulates in tumors, inflammation, and both acute and chronic infection,[3][4] allowing these pathological processes to be imaged.
[5][6] Due to lack of disease specificity, imaging with radioactive gallium(III) salts or simple complexes thereof, such as 67Ga-citrate, has gradually become less important over time and is rarely used these days.
However, the mentioned gallium(III) radionuclides, particularly 68Ga, are frequently used as radiolabels for peptides, proteins, oligonucleotides, drugs, and drug-like substance, turning these from regular pharmaceuticals ito radiotracers.
A popular class of such radiopharmaceuticals is formed by 68Ga-labeled small-molecule inhibitors for prostate-specific membrane antigen (PSMA), which are increasingly used for prostate cancer imaging.
In the past, the gallium scan was the gold standard for lymphoma staging, until it was replaced by positron emission tomography (PET) using 18F-fluorodeoxyglucose (FDG).
[12] Gallium (III) (Ga3+) binds to transferrin, leukocyte lactoferrin, bacterial siderophores, inflammatory proteins, and cell-membranes in neutrophils, both living and dead.
The resulting image will have bright areas that collected large amounts of tracer, because inflammation is present or rapid cell division is occurring.
[21] In a normal scan, uptake of gallium is seen in wide range of locations which do not indicate a positive finding.
Other sites of localisation can be nasopharyngeal and lacrimal glands, breasts (particularly in lactation or pregnancy), normally healing wounds, kidneys, bladder and colon.
The positron emitting isotope, 68Ga, can be used to target prostate-specific membrane antigen (PSMA), a protein which is present in prostate cancer cells.
The technique has been shown to improve detection of metastatic disease compared to MRI or CT scans.
[25] In December 2020, the U.S. Food and Drug Administration (FDA) approved 68Ga PSMA-11 for medical use in the United States.
[27] Other participants were treated before, but there was suspicion that the cancer was spreading because of rising prostate specific antigen or PSA.
68Ga DOTA conjugated peptides (including 68Ga DOTA-TATE, DOTA-TOC and DOTA-NOC) are used in positron emission tomography (PET) imaging of neuroendocrine tumours (NETs).
[33] Somatostatin receptors are overexpressed in many NETs, so that the 68Ga DOTA conjugated peptide is preferentially taken up in these locations, and visualised on the scan.
[35][36] In June 2016, Netspot (kit for the preparation of gallium Ga-68 dotatate injection) was approved for medical use in the United States.
[40] Gallium (68Ga) oxodotreotide was approved for medical use in Canada as Netspot in July 2019,[42] and as Netvision in May 2022.
