BREMSSTRAHLUNG RADIATION-DOSE IN Y-90 THERAPY APPLICATIONS

The bremsstrahlung component of the decay scheme of beta emitters has been traditionally ignored in internal dosimetry calculations. Methods : We have estimated the radiation dose from the bremsstrahlung compone nt of the decay scheme of Y-90 as a function of distance from a point source in a liquid medium and to body organs from distributed sources of Y-90 in the liver and spleen. Results: These estimates agree with m easurements of bremsstrahlung dose measured in a Rando phantom, and gi ve an estimate of the importance of this contribution to the overall d osimetry. Conclusions: The bremsstrahlung radiation absorbed dose cont ribution from an organ to itself is very small compared to that from t he beta dose, but the contribution to other organs is not always negli gible, especially when large amounts of Y-90 may be involved, as in th erapy applications.