Cesium-137
Background
Cesium-137 (137Cs) is a radioisotope that has been used in both interstitial and intracavitary brachytherapy. Although Cs-137 decays via beta – decay, it is the daughter nuclide’s subsequent gamma emissions that are responsible for most dose when used as an enclosed source in cancer treatment. Elemental Cesium has a low melting point (28.5°C, 83.3°F) and so is most commonly supplied in the form of insoluble powders or ceramic microspheres doubly encapsulated in stainless steel tubes or needles.
Quick Facts
- Half life: 30.07 years
- Activity loss per year: ~2%
- Clinical Source Life: ~7 years
- Decay Mode: β–
- γ Energy: 0.662MeV
- Exposure Rate Constant: Γδ = 3.26\(\frac{R \ cm^2}{mCi \ hr}\)
- Lead HVL: 5.5mm
