Influence of proton scattering angles on the energy radiograph in proton radiotherapy: A simulation study

The treatment quality of cancer patients with a proton beam critically depends on accurate predictions of proton stopping powers. Uncertainties in proton range that occur from translation of an X-ray CT patient image, of typical 3-4% or more, lead to necessary enlargements of contours around the tumor, and thus delivery of unnecessary dose to healthy tissues. A 2-dimentional proton radiography imaging technique, in which proton stopping powers of various materials (tissues) are measured directly, can improve quality of proton treatment. The proton scattering angle, causing the image degradation, has to be studied with a special care.