title: Monte Carlo-based revised values of dose rate constants at discrete photon energies.
abstract: Absorbed dose rate to water at 0.2 cm and 1 cm due to a point isotropic photon source as a function of photon energy is calculated using the EDKnrc user-code of the EGSnrc Monte Carlo system. This code system utilized widely used XCOM photon cross-section dataset for the calculation of absorbed dose to water. Using the above dose rates, dose rate constants are calculated. Air-kerma strength Sk needed for deriving dose rate constant is based on the mass-energy absorption coefficient compilations of Hubbell and Seltzer published in the year 1995. A comparison of absorbed dose rates in water at the above distances to the published values reflects the differences in photon cross-section dataset in the low-energy region (difference is up to 2% in dose rate values at 1 cm in the energy range 30-50 keV and up to 4% at 0.2 cm at 30 keV). A maximum difference of about 8% is observed in the dose rate value at 0.2 cm at 1.75 MeV when compared to the published value. Sk calculations based on the compilation of Hubbell and Seltzer show a difference of up to 2.5% in the low-energy region (20-50 keV) when compared to the published values. The deviations observed in the values of dose rate and Sk affect the values of dose rate constants up to 3%.
authors.affiliation: Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, Health Safety and Environmental Group, Anushakti Nagar, Mumbai, Maharashtra, India.
authors.forename: T Palani
authors.initials: TP
authors.lastname: Selvam
authors.affiliation: Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, Health Safety and Environmental Group, Anushakti Nagar, Mumbai, Maharashtra, India.
authors.forename: Vandana
authors.initials: V
authors.lastname: Shrivastava
authors.affiliation: Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, Health Safety and Environmental Group, Anushakti Nagar, Mumbai, Maharashtra, India.
authors.forename: Ghanashyam
authors.initials: G
authors.lastname: Chourasiya
authors.affiliation: Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, Health Safety and Environmental Group, Anushakti Nagar, Mumbai, Maharashtra, India.
authors.forename: D Appala Raju
authors.initials: DA
authors.lastname: Babu
keywords: Absorbed dose rate; TG-43; air-kerma strength; brachytherapy; dose rate constant