Chemistry:Technetium (99mTc) albumin aggregated

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Technetium Tc 99m albumin aggregated
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Technetium 99mTc albumin aggregated (99mTc-MAA) is an injectable radiopharmaceutical used in nuclear medicine. It consists of a sterile aqueous suspension of Technetium-99m (99mTc) labeled to human albumin aggregate particles. It is commonly used for lung perfusion scanning. It is also less commonly used to visualise a peritoneovenous shunt and for isotope venography.[2][3]

Preparation

DraxImage MAA kits for preparing 99mTc-MAA are available in the United States[1] from only a single manufacturer; Jubilant DraxImage Inc. The kits are delivered to nuclear pharmacies as lyophilized powders of non-radioactive ingredients sealed under nitrogen. A nuclear pharmacist adds anywhere from 50 - 100 mCi of Na[99mTcO4] to 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.[4]

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 blockade.[4][5] 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.[6]

Dosage and imaging

The typical adult dose for a lung imaging study is 40-150 Megabecquerels (1-4 mCi) (containing between 100,000 - 200,000 albumin particles).[7][8] The particle burden should be lowered for most pediatric patients and lowered to 50,000 for infants.[9] 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.[10][11] 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:

[math]\displaystyle{ \%\ \text{Right-to-left shunt} = \left(\frac{(\text{Total body counts}) - (\text{Total lung counts})}{(\text{Total body counts})}\right)\times 100\% }[/math].

History

The technetium tc 99m aggregated albumin kit was approved for use in the United States in December 1987.[12]

References

  1. ↑ 1.0 1.1 1.2 "DraxImage MAA- kit for the preparation of technetium tc 99m albumin aggregated injection, powder, for solution". DailyMed. U.S. National Library of Medicine. 31 October 2017. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=bbefaa05-1dc0-3ae7-7264-ce1eddf0da2b. 
  2. ↑ "Infrequently performed studies in nuclear medicine: Part 1". Journal of Nuclear Medicine Technology 36 (3): 132–43; quiz 145. September 2008. doi:10.2967/jnmt.108.051383. PMID 18703616. 
  3. ↑ "Tc-99m macro aggregated albumin scintigraphy - indications other than pulmonary embolism: A pictorial essay". Indian Journal of Nuclear Medicine 28 (3): 152–162. July 2013. doi:10.4103/0972-3919.119546. PMID 24250023. 
  4. ↑ 4.0 4.1 Saha, Gopal B. (1992). "Quality Control of Radiopharmaceuticals". Fundamentals of Nuclear Pharmacy (3rd ed.). New York: Springer-Verlag. pp. 143–167. doi:10.1007/978-1-4757-4027-1_8. ISBN 978-1-4757-4027-1. 
  5. ↑ "Studies of quality control of 99mTc-labelled macroaggregated albumin--Part 1. Aggregation of non-mercaptalbumin and its conformation". Nuclear Medicine and Biology 20 (5): 643–648. July 1993. doi:10.1016/0969-8051(93)90034-R. PMID 8358350. 
  6. ↑ British Pharmacopoeia Commission (2016). "Technetium (99mTc) Albumin Injection". British Pharmacopoeia (Ph. Eur. 9.0 ed.). ISBN 9780113230204. https://www.pharmacopoeia.com/bp-2017/radiopharmaceutical/technetium--99mtc--albumin-injection.html?date=2017-01-01. 
  7. ↑ "EANM guidelines for ventilation/perfusion scintigraphy : Part 1. Pulmonary imaging with ventilation/perfusion single photon emission tomography". European Journal of Nuclear Medicine and Molecular Imaging 36 (8): 1356–1370. August 2009. doi:10.1007/s00259-009-1170-5. PMID 19562336. 
  8. ↑ "SNM practice guideline for lung scintigraphy 4.0". Journal of Nuclear Medicine Technology 40 (1): 57–65. March 2012. doi:10.2967/jnmt.111.101386. PMID 22282651. 
  9. ↑ Zolle, Ilse (2007). "Monographs of 99mTc Pharmaceuticals". Technetium-99m pharmaceuticals (1st ed.). Berlin: Springer. p. 187. ISBN 978-3-540-33989-2. https://archive.org/details/technetiummpharm00zoll. 
  10. ↑ "Effect of particle number on lung perfusion images: concise communication". Journal of Nuclear Medicine 18 (3): 260–262. March 1977. PMID 839273. http://jnm.snmjournals.org/content/18/3/260.long. 
  11. ↑ "Pulmonary uptake of technetium 99m macroaggregated albumin: a predictor of gastrointestinal toxicity during hepatic artery perfusion". Journal of Clinical Oncology 2 (11): 1266–1269. November 1984. doi:10.1200/JCO.1984.2.11.1266. PMID 6491704. 
  12. ↑ "Technetium tc 99m aggregated albumin kit: FDA-Approved Drugs". 23 March 2020. https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=017881. 

Further reading

  • Radiopharmaceuticals in Nuclear Pharmacy and Nuclear Medicine (2nd ed.). American Pharmacist Association. 2004. 

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