A mathematical approach to aspects of LET, micro and nanodosimetry in radiation therapy with photons and charged particles
Abstract
The radiation effects induced by Co60 serve as a reference system for the consideration of LET and RBE in normal and tumor tissue doseeffect relations are usually handled by the linearquadratic model (LQ). This approximation excellently works up to the shoulder domain. In particle therapy we have strictly differ between RBE in the initial plateau and environment of the Bragg peak. Thus for protons LET and RBE of the initial plateau agree with Co60, whereas in the Bragg peak domain both properties are increased,, but RBE of SOBP only varies between 1.1 and 1.17. The RBE of carbon ions is increased once again Their doseeffect curves are much steeper with a rather small shoulder domain due to dense ionizing radiation effect. Thus protons are also dense ionizing in the Bragg peak region, but with rather smaller magnitude compared to carbon ions. A generalization of the LQmodel based on the nonlinear reactiondiffusion model is proposed to describe LET and RBE of dense ionizing particles, which accounts for properties of micro and nanodosimetry. A linear term of a reaction diffusion formula describes the destroy of cells, the nonlinear term is related to repair and the diffusion term accounts for the density of the radiation damages. Based on doseeffect properties of Co60 the parameters of dense ionizing particles can be determined and compared with measurement data. The local dense of radiation effects and their consequences in RBE and dose effect curves provide a key of understanding modern therapy planning with different modalities and properties of nanodosimetry are interpreted by mathematical descriptions. The irradiation of spheroids is a feature of microdosimetry, whereas intracellular exposure refers to nanodosimetry.
 Publication:

arXiv eprints
 Pub Date:
 November 2017
 arXiv:
 arXiv:1712.00072
 Bibcode:
 2017arXiv171200072U
 Keywords:

 Physics  Medical Physics
 EPrint:
 17 pages  preprint