Macroaggregated human serum albumin (MAA)

Macroaggregated human serum albumin (MAA) is a diagnostic radiopharmaceutical agent composed of heat-denatured human serum albumin particles, typically ranging from 10 to 90 micrometers in diameter (StatPearls, 2023). It is primarily utilized in nuclear medicine, specifically for lung perfusion scintigraphy, where it is labeled with Technetium-99m (Tc-99m) to visualize pulmonary blood flow (FDA, 2017). The mechanism of action involves capillary blockade, where the particles are mechanically and temporarily entrapped in the pulmonary precapillary arterioles (PubChem, 2024). MAA is not a therapeutic target; rather, it serves as a carrier for radioactive isotopes to diagnose conditions like pulmonary embolism or to evaluate right-to-left cardiac shunts (NIH, 2022). The phrase non-specific surface binding in this context refers to the physical adsorption of substances onto the particle surface, which is a technical phenomenon often monitored in assays to distinguish specific biological interactions from background noise or artifacts (Journal of Nuclear Medicine, 2021).

Other names

Technetium Tc 99m Albumin AggregatedAggregated albuminHuman serum albumin macroaggregates99mTc-MAAMacroaggregated albumin

Mechanical entrapment in pulmonary precapillary arterioles (capillary blockade) based on particle size (10-90 micrometers), allowing for visualization of regional pulmonary blood flow.