الفهرس 
BACKGROUND AND INTERACTIONS OF PROTONS WITH MATTEROnly 14 pages are availabe for public view
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Abstract
Proton radiotherapy is one of the hadron radiotherapies that by far are dosimetrically more efficient and effective than photon radiotherapies thanks to their definite range in material and their Bragg peak effects. The way dose is deposited and distributed in proton therapy is remarkably different from in photon therapy. This research studied dose distribution for proton pencil beams of various energies in both homogenous and heterogeneous tissue phantoms. For the homogenous phantom, only soft tissue constituted the phantom whereas in heterogeneous phantom; soft tissue and a bone constituted the heterogeneous phantom in one scenario and in another scenario skin, soft tissue, cranium, and brain constituted the heterogeneous phantom. In all the cases it was observed that dose increases with depth from the surface and decreases with lateral distance from the central axis. It was also observed that the Bragg peak depth increases with increase in beam energy but the Bragg peak dose decreases with increase in energy of the beam. It has also been observed that dose deposited in a bone is always less than the dose deposited in tissue at the same depth and that a bone has range modulating properties. Because of the facts that a bone modulates range, dose in the bone is less than in tissue at the same depth and that higher energy proton beam has less entrance dose than less energy beam it has been suggested that treatment of tumor using higher energy proton beam where the beam passes through a bone may be safer than treating the tumor with a less energetic proton beam that passes through soft tissue only; however further studies need to be done first.