Use of computers for the calculation of dose from iridium 192 implants

Iridium 192 sources utilized in substitution for radium sources in interstitial implantations result in similar radiation distributions. For equivalent sources the dose rates within the treated area or volume are 1% to 4% higher for ¹⁹²Ir than for radium implants. Provided calibration of the ¹⁹²Ir sources is in terms of exposure rate or radium equivalents, the specific gamma ray constant of ¹⁹²Ir does not enter into the calculations and the discrepancies for this constant appearing in the literature are not of concern. Paterson Parker tables which were prepared for radium sources may be used for calculation with ¹⁹²Ir sources. It is recommended that a single factor of 0.92 rad/R be applied to that calculation to obtain the absorbed dose in muscle.