Beta spectroscopy with liquid scintillation systems: applications in dosimetry of 90Sr and 90Y

We have demonstrated that commercially available liquid scintillation counters are adequate for obtaining useful information about the variation of beta spectral shapes as a function of attenuation. A gel scintillation system that permitted the approximation of point source geometry worked well. The spectral shapes predicted by the Fermi equations were reasonably matched with experimental spectra of sources with geometry close to a point source. For energies in the range of 50-2300 keV, we found sufficient linearity of the energy scale and uniformity of detection limits for the direct output of the instrument to be experimentally useful. The gel scintillation system has been used to directly measure the energy distribution of the beta flux coming out of bone samples and incident on the soft tissue of dogs fed 90Sr-90Y from in utero to 540 days of age.