Tc-99m MAA

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[edit] Full Name

Tc-99m macroaggregated albumin

[edit] Photon energy

140 keV

[edit] Uses, dosages, and Time of imaging

  • V/Q perfusion
    • Dose: 2-5 mCi IV (1 mCi if before ventilation)
    • Time of imaging: Immediate

[edit] Physical half life

6 hours

[edit] Biological half life

2-3 hours

[edit] Normal distribution

Lungs, liver, spleen, kidneys

[edit] Pharmacokinetics

  • >90% particles trapped in lung capillaries during first pass
  • Particles < 10 um phagocytosed by liver and spleen
  • ~100,000 of 280 billion capillaries occluded during normal lung perfusion scan
  • Particles eventually enter systemic circulation and phagocytosed by RES

[edit] Excretion

Renal, RES

[edit] Target organ

[edit] Other

  • Reduced injection in pulmonary HTN, pediatric patients, pregnant patients, R-L shunt
  • Brain uptake is diagnostic of R-L shunt.
  • Blood should not be drawn back into the syringe to ensure needle is in vein before injection (in contrast, to other studies). Blood causes MAA aggregation which results in hot pulmonary microemboli.

[edit] References