Technetium Tc 99m albumin aggregated (MAA)

Macro-aggregated albumin (MAA) carrier particles are aggregates of denatured human serum albumin used as a diagnostic radiopharmaceutical vehicle [1]. When labeled with Technetium-99m (Tc-99m), they are primarily employed in lung perfusion scintigraphy to visualize pulmonary blood flow and identify defects associated with pulmonary embolism [1][3]. The particles, ranging in size from 10 to 90 micrometers, function through the mechanism of temporary capillary blockade, where they are physically trapped in the precapillary arterioles of the lungs [1][2]. In addition to pulmonary imaging, MAA is used in interventional radiology to assess the lung shunt fraction before selective internal radiation therapy (SIRT) for liver malignancies, ensuring that subsequent therapeutic microspheres do not cause excessive radiation pneumonitis [4]. As a physical diagnostic agent, MAA does not interact with specific biological receptors or enzymes and is therefore classified as a carrier rather than a therapeutic target [1][3].

Other names

Tc-99m MAAMacroaggregated albuminHuman albumin macroaggregatesTechnetium Tc-99m macroaggregated albumin

Mechanical entrapment in pulmonary precapillary arterioles (capillary blockade) based on particle size (10-90 micrometers).