Calculations of the cell survival rate after irradiating with minibeams of protons and ${}^{12}$C

The propagation of minibeams of protons and ${}^{12}$C in a water phantom was modelled with Geant4 v10.3, and the survival probabilities of human salivary gland cells representing healthy and tumour tissues of normal radiosensitivity were calculated with the modified microdosimetric kinetic model. The advantage of minibeams over homogeneous irradiation in sparing healthy tissues proximal to the tumour was demonstrated. Survival-volume histograms were proposed to quantify the difference in the survival probability of cells inside and outside the minibeam spots.