  This research considers potential dose increase in target due to cisplatin
(Pt) concentration and radiation type. Cisplatin concentrations from 0.003 to
120 mM were used. Monte-Carlo simulation of Linear accelerator (Elekta Synergy)
and X-ray tube (Xstrahl300) was carried out using Geant4 and PClab. As the
first step of this research, we performed simulation of energy spectrum from
radiotherapy units (spectrum model). The next step was the modeling of linear
accelerator head and X-ray tube, and the distribution of dose 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. Then higher
is concentration, then higher is the effect. However, the photon energy
increase from 60 to 250 kV and increase of depth of target reduces the effect
of PCT due the decrease of the photoelectric effect cross-section. 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, that the dose enhancement factors
(DEF) are higher in linac without flattening filter, than in linac with
flattening filter.
