Study on microdosimetric characteristics of 120 to 430 MeV/u carbon ion

Microdosimetric single event spectrum is a significant parameter in radiotherapy, which can be used to evaluate the radiation biological effect. In this paper, microscopic patterns of energy deposition are simulated with Monte Carlo code FLUKA at mixed radiation fields during carbon ions therapy. The results are compared with experimental measured results at 300 MeV/u carbon ion and good agreement has been found. Meanwhile, dose-weighted lineal energy spectra, frequency averaged lineal energy values and dose averaged lineal energy values of carbon ion with energy from 120 to 430 MeV/u were calculated, too. The frequency averaged lineal energy values are from 185 to 28.3 keV/μm while the dose averaged lineal energy values are from 272 to 64.1 keV/μm. These studies are useful for treatment plan in carbon ion radiotherapy. (authors)