中文摘要：

质子和重离子在现代放射治疗手段中已起着不可替代的作用，这主要取决于其独特的物理性质。利用一步过程和两步过程的物理模型解释了离子能量损失的机制，同时结合Geant4软件包模拟质子和^12C在水中的运输过程，研究了离子束的物理性质，并讨论了计算的结果，说明了质子和^12C在医学中应用的优缺点。

英文摘要：

Depending on their unique physical properties, proton and heavy ions have taken an irreplaceable role in modern means of tumor treatment. One-step process and two-step process physical models were employed to explain the mechanism of ion energy loss. The transport process of proton and ^12C in water was simulated by Geant4 toolkit to study the physical properties of ion beam. The calculation results were discussed, which showed the advantages and disadvantages of proton and ^12C in the medical application.