Microdosimetric characteristics of carbon track-segments.

Carbon ions were introduced to radiation therapy due to their special physical and radiobiological properties. In heavy ion therapy, specification of radiation quality is an important issue and rapid calculations are often required for treatment planning. Because radiation qualities are closely related to microdosimetric spectra and parameters, this study is intended to provide microdosimetric parameters of carbon track-segments in the energy range from 50 MeV to 5 GeV. Monte-Carlo techniques are used to simulate track-segments of carbon ions in water. Microdosimetric quantities (the dose mean lineal energies) are calculated for the two components of the track-segment: the track-core formed by energy deposition of carbon ions and the track-penumbra (an extended region around the track-core produced by energy deposition of secondary electrons).