6533b7dafe1ef96bd126e0ac

RESEARCH PRODUCT

Influence of photon energy spectra from brachytherapy sources on Monte Carlo simulations of kerma and dose rates in water and air

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Purpose: For a given radionuclide, there are several photonspectrum choices available to dosimetry investigators for simulating the radiation emissions from brachytherapy sources. This study examines the dosimetric influence of selecting the spectra for I 192 r , I 125 , and P 103 d on the final estimations of kerma and dose. Methods: For I 192 r , I 125 , and P 103 d , the authors considered from two to five published spectra. Spherical sources approximating common brachytherapy sources were assessed. Kerma and dose results from GEANT4, MCNP5, and PENELOPE-2008 were compared for water and air. The dosimetric influence of I 192 r , I 125 , and P 103 d spectral choice was determined. Results: For the spectra considered, there were no statistically significant differences between kerma or dose results based on Monte Carlo code choice when using the same spectrum. Water-kerma differences of about 2%, 2%, and 0.7% were observed due to spectrum choice for I 192 r , I 125 , and P 103 d , respectively (independent of radial distance), when accounting for photon yield per Bq. Similar differences were observed for air-kerma rate. However, their ratio (as used in the dose-rate constant) did not significantly change when the various photonspectra were selected because the differences compensated each other when dividing dose rate by air-kerma strength. Conclusions: Given the standardization of radionuclide data available from the National Nuclear Data Center (NNDC) and the rigorous infrastructure for performing and maintaining the data set evaluations, NNDC spectra are suggested for brachytherapy simulations in medical physics applications.