Rapid implementation of the repair-misrepair-fixation (RMF) model facilitating online adaption of radiosensitivity parameters in ion therapy

Introduction: Treatment planning for ion therapy must account for physical properties of the beam as well as differences in the relative biological effectiveness (RBE) of ions compared to photons. In this work, we present a fast RBE calculation approach, based on the decoupling of physical properties and the ${\alpha }_x/{\beta }_x$ ratio commonly used to describe the radiosensitivity of irradiated cells or organs.

Material and methods: In the framework of the mechanistic repair-misrepair-fixation (RMF) model, the biological modeling can be decoupled from the physical dose. This was implemented into a research treatment planning system for carbon ion therapy.

Results: The presented implementation of the RMF model is very fast, allowing online changes of ${\alpha }_x/{\beta }_x$. For example, a change of ${\alpha }_x/{\beta }_x$ including a complete biological modeling and a recalculation of RBE for $2.9\cdot {10}^5$ voxel takes 4 ms on a 4 CPU, 3.2 GHz workstation.

Discussion and conclusion: The derived decoupling within the RMF model allows fast changes in ${\alpha }_x/{\beta }_x$, facilitating online adaption by the user. This provides new options for radiation oncologists, facilitating online variations of the radiobiological input parameters during the treatment plan evaluation process as well as uncertainty and sensitivity analyses. (note)