103Pd loaded cartridge air kerma strength verification

Abstract

Using radioactive 125I or 103Pd seeds in large number to treat prostate cancer has become popular. This procedure’s popularity translates to increased physicist and dosimetrist workloads with regard to performing source strength assays. In addition, radiation exposure to the physicists’ and dosimetrists’ hands as a result of source handling has increased significantly. As a result of these increases, a method of source calibration using applicator cartridges was developed to allow safe handling of sources and expedited source assays. The method uses a holder which allows a cartridge loaded with five to fifteen seeds to be placed in a standard well ionization chamber. Ionization readings are converted to air kerma source strengths which are compared with the manufacturer’s stated activity. Excellent agreement between individual seed air kerma strength as well as comparison with the vendor’s air kerma strength statement proves the validity of this assay technique. Absorption/geometry correction factors were experimentally derived during the development of this method. These factors allow accurate determination of air kerma source strength from a shipment of Iodine or Palladium seeds.