Microdosimetric Evaluation of Physical and Biological Quantities due to Linear Energy Transfer in Proton Therapy Using Monte Carlo Simulation

In proton therapy, it is imperative to take the distribution of both the physical absorbed dose and the biological dose into account. Therefore, phenomenological models and a biophysical model such as microdosimetric kinetic model (MKM) have been developed for the biological dose calculation.

In order to determine the most accurate model for Chinese hamster V79 cell line, this study carried out comparisons between the linear term of the cell survival curve (α) and the dose parameter per 10% of the cell survival fraction (D10), calculated using phenomenological models and a biophysical model as a function of linear energy transfer (LET) and kinetic energy of proton beams as well as published experimental data. This research also calculates the biological dose with several phe-nomenological models and MKM as a function of depth in the water phantom.

The results show that the α and D10 values of proton beams calculated with MKM are more con-sistent with the biological radiation data than those calculated with the phenomenological models. Of the phenomenological models, the calculation data from McNamara model are in better consistency with the experimental data than the other phenomenological models.

The ability of MKM to properly predict the biological dose distribution of proton beams with continual innovations and modifications showcases the importance of applying the correct model in treatment planning systems.