Radiotracers and Half Lives

Link to commonly used radiotracer half lives

Rb-82

  • Localizes to myocytes for myocardial perfusion imaging via Na/K/ATPase

Ga 68-Dotatae

  • Normal to have some uptake in pituitary fossa

Yittrium-90

  • T1/2 - 64 hours (2.6 days)

  • Decay via beta particle emission

  • After y-90 delivery for liver mass, the beta decay will result in Bremsstrahlung radiation which can be imaged as a shit picture via a gamma camera to basically say it is in the liver (pic below)

Tc-99

  • T1/2 - 6 hours

I-123 MIBG

  • Used to evaluate neuroendocrine tumors

  • Normal uptake in

    • Liver

    • Spleen

    • Adrenal

    • Heart

    • Salivary glands

Y-90 Ibritumomab tiuxetan (Zevalin)

  • Used to treat NHL

  • Contraindications

    • Allergy to rituximab

    • Plt < 100k

    • Neutrophil < 1500

    • Bone marrow involvement >25%

    • Pregnant

Xenon-133

  • T1/2 - 5.3 days

I-131

  • Basically same distribution as I-123 but

    • Not as strong of uptake in liver

    • No uptake in heart

TI-201 Thallous Chloride

  • Physical T1/2 - 73 hours

  • Biological T1/2 -

    • 3 min at rest

    • 30 seconds with exercise

  • Energy = 60-80 keV

  • Used some in cardiac imaging

  • High sensitivity for CNS lymphoma

    • Can differentiate CNS lymphoma from toxoplasmosis

Tc-99m Sulfur Colloid

  • T1/2 - 2-3 minutes

  • Energy - 140 keV

  • Affected by colloid shift in liver failure

  • All liver masses except FNH are cold

  • Uses

    • Gastric emptying scan

    • Aspiration in kids

    • Lymphoscintigraphy

    • Liver/spleen scan

    • GI bleed study

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