Influence of photon energy spectra from brachytherapy sources on Monte Carlo simulations of kerma and dose rates in water and air.
OBJECTIVE
For a given radionuclide, there are several photon spectrum choices available to dosimetry investigators for simulating the radiation emissions from brachytherapy sources. This study examines the dosimetric influence of selecting the spectra for 192Ir, 125I, and 103Pd on the final estimations of kerma and dose.


METHODS
For 192Ir, 125I, and 103Pd, 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 192Ir, 125I, and 103Pd 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 192Ir, 125, and 103Pd, 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 photon spectra 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.
Department of Radiation Oncology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA. mrivard@tuftsmedicalcenter.org
Mark J
MJ
Rivard
Domingo
D
Granero
Jose
J
Perez-Calatayud
Facundo
F
Ballester
D000388:Air; D001918:Brachytherapy / Q000379:methods*; D003198:Computer Simulation; D004735:Energy Transfer; D006801:Humans; D008954:Models, Biological; D009010:Monte Carlo Method; D017785:Photons; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014867:Water
D014867:Water