A Monte Carlo study of absorbed dose distributions in both the vapor and liquid phases of water by intermediate energy electrons based on different condensed-history transport schemes

Abstract

Monte Carlo transport calculations of dose point kernels (DPKs) and depth dose profiles (DDPs) in both the vapor and liquid phases of water are presented for electrons with initial energy between 10 keV and 1 MeV. The results are obtained by the MC4 code using three different implementations of the condensed-history technique for inelastic collisions, namely the continuous slowing down approximation, the mixed-simulation with delta-ray transport and the addition of straggling distributions for soft collisions derived from accurate relativistic Born cross sections. In all schemes, elastic collisions are simulated individually based on single-scattering cross sections. Electron transport below 10 keV is performed in an event-by-event mode. Differences on inelastic interactions between the vapor and liquid phase are treated explicitly using our recently developed dielectric response function which is supplemented by relativistic corrections and the transverse contribution. On the whole, the interaction coefficients used agree to better than approximately 5% with NIST/ICRU values. It is shown that condensed phase effects in both DPKs and DDPs practically vanish above 100 keV. The effect of delta-rays, although decreases with energy, is sizeable leading to more diffused distributions, especially for DPKs. The addition of straggling for soft collisions is practically inconsequential above a few hundred keV. An extensive benchmarking with other condensed-history codes is provided.

Monte Carlo single-cell dosimetry of I-131, I-125 and I-123 for targeted radioimmunotherapy of B-cell lymphoma

“…For electron energies above 10 keV, the present condensedhistory scheme provides cellular S-values that are within 5% of those of a detailed simulation (Bousis et al 2009b). Furthermore, dose-point-kernels and depth-dose-distributions in water up to 1 MeV electron energies are in good agreement with those obtained by other general-purpose codes (Bousis et al 2008a(Bousis et al , 2008b(Bousis et al , 2009a.…”

“…Dosimetric calculations are performed using both the detailed-and condensed-history modules of our in-house MC code (Bousis et al 2008a). All electrons (primary and secondaries) are followed down to 1 Ry ( 13.6 eV).…”

“…The electron energy for switching from event-by-event to condensedhistory simulation is set at 10 keV. Since the physics models and transport approximations used in our MC code have been presented in detail elsewhere (Emfietzoglou et al 2000, Bousis et al 2008a, 2008b, 2009a, only a brief description is provided here. In the detailed-history simulation mode (  10 keV), inelastic cross sections are calculated semi-empirically from the Born and Bethe theories (Inokuti 1971) using a parameterized oscillator strength for water for soft collisions and the binary-encounter-approximation-with-exchange (BEAX) for hard collisions.…”

“…In this work, we use our in-house Monte Carlo code (MC4) (Bousis et al 2008a) to carry out dosimetric calculations at the cellular and sub-cellular level for the case of noninternalizing (surface-bound) and internalizing monoclonal antibody (MAb) labeled with either 131 I or the Auger-emitters 123 I and 125 I, which targets a typical lymphoma B-cell.…”

Estimation of microscopic dose enhancement factor around gold nanoparticles by Monte Carlo calculations

“…The NOREC code has been benchmarked well against several other common condensed history Monte Carlo codes including EGS4/EGSnrc and ETRAN on a larger scale. 30,31 Therefore, an event-by-event electron transport algorithm adopted by NOREC is considered to have been accurately implemented. Accordingly, NOREC is expected to produce reliable results on a nanometer scale as well by virtue of its event-by-event electron transport algorithm, although calculated results on such a small scale are difficult to verify experimentally.…”