Technetium Tc-99m albumin aggregated (Tc-99m MAA) (Tc-99m MAA)

Technetium Tc-99m albumin aggregated (Tc-99m MAA) is a diagnostic radiopharmaceutical composed of human serum albumin that has been denatured and heat-aggregated into particles typically sized between 10 and 90 micrometers [1]. These particles serve as a carrier for the gamma-emitting radionuclide technetium-99m, which binds to the denatured protein structure through a reduction process involving stannous ions [2]. When administered intravenously, the particles travel through the right heart and become physically entrapped in the pulmonary capillary bed via a process of temporary microembolization [1]. This entrapment is proportional to regional pulmonary blood flow, allowing for the scintigraphic visualization of lung perfusion using a gamma camera [3]. The primary clinical application of Tc-99m MAA is the diagnosis of pulmonary embolism, where it identifies areas of reduced or absent blood flow [2]. It is also utilized to detect and quantify right-to-left cardiac shunts by observing the extrapulmonary distribution of the particles [1]. The particles are naturally degraded over several hours by mechanical friction from respiratory motion and enzymatic action, and the resulting fragments are cleared by the reticuloendothelial system [3]. Safety considerations include avoiding use in patients with severe pulmonary hypertension or known hypersensitivity to human albumin products [1]. [1] StatPearls. Technetium Tc 99m Aggregated Albumin. https://www.ncbi.nlm.nih.gov/books/NBK559013/ [2] DrugBank Online. Technetium Tc-99m albumin aggregated. https://go.drugbank.com/drugs/DB09155 [3] FDA. DraxImage MAA (Kit for the Preparation of Technetium Tc 99m Albumin Aggregated Injection). https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/017832s034lbl.pdf

Other names

Macroaggregated albuminMAATechnetium Tc 99m MAADenatured human serum albumin particlesAggregated albumin

Physical entrapment in pulmonary capillaries (capillary blockade) proportional to regional blood flow.