Thallium-201 scintigraphy

Last revised by Joshua Yap on 18 Jul 2022

Thallium-201 (Tl-201) is a radiopharmaceutical used for scintigraphy, primarily of the myocardium. The element thallium is treated by the body as an analog of potassium; it is produced in a cyclotron by bombarding thallium-203 with protons.


  • thallium is a monovalent cation
    • usually employed in the form of a chloride salt
  • photon energy: 68-80 keV (a smaller amount of γ-rays at 137 and 167 keV)
  • physical half life: 73 hours
  • biological half life
    • rest: 3 minutes
    • exercise: 30 seconds
  • normal distribution: myocardium, skeletal muscle, GI tract, liver, kidneys
  • excretion: renal
  • target organ: kidneys
  • miscellaneous facts:
    • more background noise than MUGA
    • thallium-201 cerebral SPECT can be used to differentiate toxoplasmosis vs lymphoma (increased uptake in lymphoma, decreased in toxoplasmosis)

Uses, doses and timings

Cardiac scan
  • adult dose: 55.5 MBq (1.5 mCi) IV

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