  We used the GEANT4 Monte Carlo MC Toolkit to simulate carbon ion beams
incident on water, tissue, and bone, taking into account nuclear fragmentation
reactions. Upon increasing the energy of the primary beam, the position of the
Bragg-Peak transfers to a location deeper inside the phantom. For different
materials, the peak is located at a shallower depth along the beam direction
and becomes sharper with increasing electron density NZ. Subsequently, the
generated depth dose of the Bragg curve is then benchmarked with experimental
data from GSI in Germany. The results exhibit a reasonable correlation with GSI
experimental data with an accuracy of between 0.02 and 0.08 cm, thus
establishing the basis to adopt MC in heavy-ion treatment planning. The
Kolmogorov-Smirnov K-S test further ascertained from a statistical point of
view that the simulation data matched the experimentally measured data very
well. The two-dimensional isodose contours at the entrance were compared to
those around the peak position and in the tail region beyond the peak, showing
that bone produces more dose, in comparison to both water and tissue, due to
secondary doses. In the water, the results show that the maximum energy
deposited per fragment is mainly attributed to secondary carbon ions, followed
by secondary boron and beryllium. Furthermore, the number of protons produced
is the highest, thus making the maximum contribution to the total dose
deposition in the tail region. Finally, the associated spectra of neutrons and
photons were analyzed. The mean neutron energy value was found to be 16.29 MeV,
and 1.03 MeV for the secondary gamma. However, the neutron dose was found to be
negligible as compared to the total dose due to their longer range.
