title: Directional dependence of radiation fluence from 192Ir and 198Au sources.
abstract: Radiation fluence distribution around 192Ir and 198Au seeds of the type used for brachytherapy application was measured using a NaI crystal connected to a multi-channel analyzer. The radiation fluence, determined as a function of the angle between the seed axis and the direction of detection, is anisotropic with the fluence along the seed axis amounting to 78% of that perpendicular to the seed axis for seeds of both isotopes. The region of fluence reduction is broader for 198Au seeds, extending from 0-45 degrees; for 192Ir the decrease in fluence is evident for angles of 0-20 degrees. Integration of the angular distribution over 4 pi geometry indicated the effective activity of the implants to be 4% and 1% less than the nominal activity for the 198Au and 192Ir seeds, respectively, based on calibration measurements perpendicular to the seed axis.
mesh_terms: D001918:Brachytherapy; D006050:Gold Radioisotopes / Q000627:therapeutic use*; D006801:Humans; D007495:Iridium / Q000627:therapeutic use*; D011868:Radioisotopes / Q000627:therapeutic use*; D011879:Radiotherapy Dosage
chemical_list: D006050:Gold Radioisotopes; D011868:Radioisotopes; D007495:Iridium