drugsAgentApproved

Technetium Tc-99m albumin aggregated (MAA)

aka 99mTc-MAA, Tc-99m macroaggregated albumin, MAA, Pulmotech MAA, DraxImage MAA

Tiny clumps of albumin, a normal blood protein, tagged with a radioactive marker and injected into a vein. They wedge briefly in the smallest blood vessels of the lung wherever blood is flowing, so the scan maps the lung's blood supply; the clumps then break up and clear.

Tc-99m macroaggregated albumin is the perfusion half of the V/Q scan and one of the oldest radiopharmaceuticals still in routine use. Two products are marketed in the US: Pulmotech MAA (BLA 210089, CIS bio International, distributed by Curium, initial US approval 2020) and DraxImage MAA (BLA 017881, Jubilant DraxImage, initial US approval 1987). Both carry the same two indications: lung scintigraphy as an adjunct in the evaluation of pulmonary perfusion in adults and paediatric patients, and peritoneovenous shunt scintigraphy as an aid in evaluating its patency.

Dosing is by particle count rather than activity alone. An adult dose is 200,000 to 700,000 particles, about 350,000 recommended, falling to 10,000-50,000 for neonates under four weeks, because each particle occludes a capillary and the margin of safety comes from how few of them there are relative to the pulmonary capillary bed. The labels contraindicate the agent in severe pulmonary hypertension, where deaths have been reported, and in albumin hypersensitivity.

Its second life is in interventional oncology. Before yttrium-90 radioembolisation, MAA is injected into the hepatic artery and imaged to estimate the lung shunt fraction, because hepatopulmonary shunting can deliver enough dose to the lungs to cause radiation pneumonitis. The dose constraint usually applied is a lung mean dose of 30 Gy from a single treatment or 50 Gy cumulative, and a shunt fraction above 20% has traditionally contraindicated resin-microsphere treatment. MAA is used as the surrogate because its particles are close in size to the microspheres, though the correspondence is imperfect and is itself an active research question.

Mechanism, step by step

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1.Technetium Tc-99m albumin aggregated (MAA) slips into a pocket on its target.

Modality

Intravenous SPECT particle agent

Mechanism

Human albumin is heat-aggregated into particles of which more than 90% measure 10-90 micrometres, none above 150. Injected intravenously, they are carried to the lungs and physically lodge in pulmonary arterioles and capillaries in proportion to regional blood flow: over 90% are trapped within 1 to 5 minutes, occluding a tiny fraction of the pulmonary capillary bed. The blockade is temporary because the aggregates are fragile and break up, and the resulting image is a perfusion map. Injected instead into the hepatic artery, the same particles follow the route Y-90 microspheres will take, which is what makes them a usable simulation of a radioembolisation treatment.

Dosing & schedule

Route: Intravenous injection for lung perfusion; intra-arterial (hepatic artery) for radioembolisation work-up
Schedule: Adults 200,000-700,000 particles per injection, approximately 350,000 recommended; paediatric doses reduced by age, 10,000-50,000 particles for neonates under four weeks
Dose modifications: Contraindicated in severe pulmonary hypertension and in albumin hypersensitivity; reduce particle number in right-to-left shunt

Source: www.accessdata.fda.gov/drugsatfda_docs/label/2023/210089s002lbl.pdf. Doses are for orientation; the current label governs.

Regulatory

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Approvals

Region	Year	Indication
US	1987	Lung scintigraphy as an adjunct in the evaluation of pulmonary perfusion, and peritoneovenous shunt patency · DraxImage MAA, BLA 017881, Jubilant DraxImage
US	2020	Lung scintigraphy as an adjunct in the evaluation of pulmonary perfusion, and peritoneovenous shunt patency · Pulmotech MAA, BLA 210089, CIS bio International, distributed by Curium

Trials

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ClinicalTrials.gov · phase 2/3

refreshed 2026-10-19

2 studies0 recruiting2 Phase 2

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Technetium Tc-99m albumin aggregated (MAA)

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