Computer Simulation and Comparison of Proton and Carbon Ion Treatment of Tumor Cells Using Particle and Heavy Ion Transport Code System

Charged particle beams are an increasingly common method of cancer treatment. Because of their Bragg peak dose distribution, protons are an effective way to deliver a dose to the tumor, while minimizing the dose to surrounding tissue. Charged particles with greater mass and higher charge than protons have an even sharper Bragg peak and a higher Relative Biological Effectiveness (RBE), allowing a greater dose to be delivered to the tumor and sparing healthy tissue. Since carbon ions are being implemented for treatment in Europe and Japan, this study will focus on carbon as the heavier ion of choice. Comparisons are drawn between moderated and unmoderated protons and carbon ions, all of which have a penetration depth of 10 cm in tissue. Scattering off the beam line, dose delivered in front of and behind the tumor, and overall dose mapping are examined, along with fragmentation of the carbon ions. It was found that fragmentation of the carbon ion beam introduced serious problems in terms of controlling the dose distribution. The dose to areas behind the tumor was significantly higher for carbon ions versus proton beams. For both protons and carbon ions, the use of a moderator increased the scattering off of the beam line, and slightly increased the dose behind the tumor. For carbon ions, the use of a moderator increased the degree of fragmentation throughout the beam path.