MEDICAL - Radiation

Radiation:

As isotopes decay they emit radiation. 

The radiation is detected by a liquid scintillation counter

Sr-90 emits beta particles only to decay into Yttrium-90 shown in the decay equation below:

⁹⁰₃₈Sr --> ⁰ _-1e^-+ ⁹⁰₃₉Y

Yttrium will decay also by beta emission to achieve nuclear stability as Zr-90:

⁹⁰₃₉ Y --> ⁰_-1e^- + ⁹⁰₄₀ Zr