Showing papers by "Ziad Francis published in 2006"
22 citations
29 Oct 2006
TL;DR: The preliminary design of a prototype of the cell survival models implemented and preliminary results in some selected cell lines are described.
Abstract: A project, named Geant4-DNA, is in progress to extend the Geant4 simulation toolkit to model the effects of radiation with biological systems at cellular and DNA level. The first component implemented in the first development cycle of the project describes the fractional survival of a population of cells irradiated with photons or charged particles. The software system developed provides the user the option to choose among a small set of alternative models for the calculation of mammalian cell survival after irradiation. The flexible design adopted makes the system open to further extension to implement other cell survival models available in literature. The preliminary design of a prototype of the cell survival models implemented and preliminary results in some selected cell lines are described.
11 citations
01 Oct 2006
TL;DR: In this paper, a set of processes specialized for the simulation of particle interactions with water has been developed in the Geant4 Low Energy Electromagnetic package, covering the interactions of electrons, protons and light ions down to the electronvolt energy scale.
Abstract: A set of processes specialized for the simulation of particle interactions with water has been developed in the Geant4 Low Energy Electromagnetic package. The models cover the interactions of electrons, protons and light ions down to the electronvolt energy scale. They address a physics domain relevant to the simulation of radiation effects in biological systems, where water represents an important component. The software design, the physics models implemented and an overview of their tests are described.
3 citations
TL;DR: The existence of a plateau observed after low-dose neutrons suggests that a repair process might be induced after a threshold dose of 5-7.5 cGy with a saturation around 32.5cGy, and may be of interest for the domain of neutrons radiobiology and radioprotection.
Abstract: Radiobiology with fast neutrons. Human melanoma cells particularly resistant to high energy X rays were irradiated with 14 MeV neutrons at low doses ranging from 5 cGy to 1.12 Gy and using two different dose rates: a very low one (0.8 mGy mn -1 ) and a moderate one (40 mGy mn -1 ). The biological effects of neutrons were studied both by cell survival assay and chromosomal aberrations analysis. Unusual features of the survival curve at low dose rate were observed as a marked degree of cell killing at 5 cGy followed by a plateau of survival from 10 to 32.5 cGy. At low dose rate, the levels of induced chromosomal aberrations tended also to reach a plateau with doses ranging from 10 to 30 cGy. Both phenomena disappear at higher dose rate. The existence of a plateau observed after low-dose neutrons suggests that a repair process might be induced after a threshold dose of 5-7.5 cGy with a saturation around 32.5 cGy. These findings may be of interest for the domain of neutrons radiobiology and radioprotection.