Simulation of dose enhancement in radiotherapy caused by cisplatin

Abstract

This research considers potential dose increase in a target due to cisplatin (Pt) concentration and radiation type. Dose changes were calculated with cisplatin concentrations from 0.003 to 120 mM. Monte-Carlo simulation of Linear accelerator (Elekta Synergy) and X-ray tube (Xstrahl300) was carried out using Geant4 and PClab. At the first stage of this research, we performed a simulation of energy spectrum from radiotherapy units (spectrum model). The next stage was the modeling of a linear accelerator head and an X-ray tube, and the dose distribution in the water phantom (PDD model). At the second stage, dose changes were investigated in the presence of cisplatin in the target (CIS model). The simulation results showed that the dose escalation can be caused by photon-capture therapy (PCT). There is a dose enhancement in the volume where cisplatin is accumulated. However, the photon energy increase from 60 to 250 kV and the increase of the target depth reduces the effect of PCT due to the decrease of the photoelectric effect cross-section. It should be noticed, that the orthovoltage X-rays energy, listed in the table with results, shows higher dose enhancement, than the megavoltage photon beam generated from linear acceleration sources. In addition, the dose enhancement factors (DEF) are higher in a linac without a flattening filter, than in a linac with a flattening filter.