title: Monte-Carlo study of energy deposition by heavy charged particles in sub-cellular volumes.
abstract: Detailed-history Monte-Carlo code is used to study the energy deposition from proton and alpha particle tracks at the sub-cellular level. Inelastic cross sections for both the vapour and liquid phases of water have been implemented into the code in order to explore the influence of non-linear density effects associated with the condensed-phase cellular environment. Results of energy deposition and its straggling for 0.5 to 5 MeV amu(-1) protons and alpha particles traversing or passing near spherical volumes of 2-200 nm in diameter relevant to DNA- and chromosome-size targets are presented. It is shown that the explicit account of delta-ray transport reduces the dose by as much as 10-60%, whereas stochastic fluctuations lead to a relative uncertainty ranging from 20% to more than 100%. Protons and alpha particles of the same velocity exhibit a similar delta-ray effect, whereas the relative uncertainty of the alphas is almost half that of protons. The effect of the phase is noticeable (10-15%) mainly through differences on the transport of delta-rays, which in liquid water have higher penetration distances. It is expected that the implementation of such results into multi-scale biophysical models of radiation effects will lead to a more realistic predictions on the efficacy of new radiotherapeutic modalities that employ either external proton beam irradiation or internal alpha-emitting radionuclides.
authors.affiliation: Medical Physics Laboratory, University of Ioannina Medical School, Ioannina 45110, Greece.
authors.forename: D
authors.initials: D
authors.lastname: Emfietzoglou
authors.forename: G
authors.initials: G
authors.lastname: Papamichael
authors.forename: A
authors.initials: A
authors.lastname: Pathak
authors.forename: A
authors.initials: A
authors.lastname: Fotopoulos
authors.forename: H
authors.initials: H
authors.lastname: Nikjoo
mesh_terms: D002468:Cell Physiological Phenomena / Q000528:radiation effects*; D003198:Computer Simulation; D004247:DNA / Q000235:genetics* / Q000528:radiation effects*; D020450:Heavy Ions; D018499:Linear Energy Transfer; D008954:Models, Biological; D009010:Monte Carlo Method; D011522:Protons; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods*
chemical_list: D011522:Protons; D004247:DNA