Technetium ^99mTc albumin aggregated (^99mTc-MAA) is an injectable

radiopharmaceutical Radiopharmaceuticals, or medicinal radiocompounds, are a group of pharmaceutical drugs containing radioactive isotopes. Radiopharmaceuticals can be used as diagnostic and therapeutic agents. Radiopharmaceuticals emit radiation themselves, which ...

used in

nuclear medicine Nuclear medicine or nucleology is a medical specialty involving the application of radioactive substances in the diagnosis and treatment of disease. Nuclear imaging, in a sense, is " radiology done inside out" because it records radiation emi ...

. It consists of a sterile aqueous suspension of

Technetium-99m Technetium-99m (99mTc) is a metastable nuclear isomer of technetium-99 (itself an isotope of technetium), symbolized as 99mTc, that is used in tens of millions of medical diagnostic procedures annually, making it the most commonly used medical ra ...

(^99mTc) labeled to human

albumin Albumin is a family of globular proteins, the most common of which are the serum albumins. All the proteins of the albumin family are water-soluble, moderately soluble in concentrated salt solutions, and experience heat denaturation. Albumins ...

aggregate particles. It is commonly used for lung perfusion scanning. It is also less commonly used to visualise a

peritoneovenous shunt A peritoneovenous shunt (also called LeVeen Shunt) is a shunt which drains peritoneal fluid from the peritoneum into veins, usually the internal jugular vein or the superior vena cava. It is sometimes used in patients with refractory ascites. It ...

and for isotope

venography Venography (also called phlebography or ascending phlebography) is a procedure in which an x-ray of the veins, a venogram, is taken after a special dye is injected into the bone marrow or veins. The dye has to be injected constantly via a catheter ...

Preparation

DraxImage MAA kits for preparing ^99mTc-MAA are available in the United States from only a single manufacturer; Jubilant DraxImage Inc. The kits are delivered to nuclear pharmacies as

lyophilized Freeze drying, also known as lyophilization or cryodesiccation, is a low temperature dehydration process that involves freezing the product and lowering pressure, removing the ice by sublimation. This is in contrast to dehydration by most conve ...

powders of non-radioactive ingredients sealed under

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

. A nuclear pharmacist adds anywhere from 50 - 100 mCi of Na sup>99mTcO₄to the reaction vial to make the final product, in the pH range of 3.8 to 8.0. After being allowed to react at room temperature for 15 minutes to ensure maximum labeling of the human albumin with ^99mTc, the kit can then be diluted with sterile normal saline as needed. Once prepared the product will have a turbid white appearance.

Quality control

No less than 90% of MAA particles can be between 10 - 90 micrometres in size and no particles may exceed 150 micrometres due to the risk of

pulmonary artery A pulmonary artery is an artery in the pulmonary circulation that carries deoxygenated blood from the right side of the heart to the lungs. The largest pulmonary artery is the ''main pulmonary artery'' or ''pulmonary trunk'' from the heart, and ...

blockade. No less than 90% of the radioactivity present in the product must be tagged to albumin particles. Thus, no more than 10% soluble impurities may be present.

Dosage and imaging

The typical adult dose for a lung imaging study is 40-150

Megabecquerel The becquerel (; symbol: Bq) is the unit of radioactivity in the International System of Units (SI). One becquerel is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. For applications rela ...

s (1-4 mCi) (containing between 100,000 - 200,000 albumin particles). The particle burden should be lowered for most

pediatric Pediatrics ( also spelled ''paediatrics'' or ''pædiatrics'') is the branch of medicine that involves the medical care of infants, children, adolescents, and young adults. In the United Kingdom, paediatrics covers many of their youth until the ...

patients and lowered to 50,000 for infants. The use of more than 250,000 particles in a dose is controversial as little extra data is acquired from such scans while there is an increased risk of toxicity. Patients with pulmonary hypertension should be administered a minimum number of particles to achieve a lung scan (i.e. 60,000). In any patient by administering a greater quantity of particles than necessary for the diagnostic procedure increases the risks of toxicity. Because of gravity effects, people administered ^99mTc MAA should be in the supine position to ensure as even a distribution of particles throughout the lungs as possible. The total percentage of particles trapped in the lungs can be determined through a whole body scan after the administration of ^99mTc MAA through the equation: :

\%\ \text = \left(\frac\right)\times 100\%

History

The technetium tc 99m aggregated albumin kit was approved for use in the United States in December 1987.

References

External links