Dresden 2011 – wissenschaftliches Programm

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ST: Fachverband Strahlen- und Medizinphysik

ST 1: Radiation Therapy I Fast Ions: Production, Physical Dosimetry, Biological Effets, Medical Effects

ST 1.8: Vortrag

Montag, 14. März 2011, 16:15–16:30, POT 112

The full simulation of dose response curves using the Local Effect Model — •Uwe Scholz, Thomas Friedrich, Marco Durante, and Michael Scholz — Department of Biophysics, GSI Helmholtz Centre for Heavy Ion Research Darmstadt, Germany

The purpose of the Local Effect Model (LEM) is to calculate the dose dependent relative biological effectiveness (RBE) of charged particle radiation with respect to conventional photon radiation. The linear-quadratic parameters α and β (the initial slope and the curvature of ion dose response curves) are modelled based on their values for the photon dose response. Usually this is done within a low fluence approximation where the biological damage of a radiation field at arbitrarily high irradiation dose is deduced from the damage pattern deposited by one single charged particle.

To investigate the reliability of the approximation, the LEM has been extended to simulate the actual damage pattern of an arbitrarily high number of ion traversals and their stochastic distribution by means of a full Monte Carlo simulation.

The analysis of the resulting survival curves revealed that the β-term in the full simulation increases compared to the original formalism. Furthermore, investigation of the dose dependence of the RBE showed that the RBE approaches values > 1 even at very high doses. This is in line with experimental results and can be understood mechanistically within the LEM formalism.