Radiotherapy planning is presently based on CT images (tomographic images made using X-rays). High-energy X-ray photons penetrate opaque objects and reveal their internal structure. Protons, in contrast to X-ray photons, are charged particles and lose energy by interacting with electrons and nuclei in the matter, leading to multiple Coulomb interactions. Both proton energy loss and scattering can be used for radiographic imaging. Proton imaging has less spatial resolution than X-ray imaging but a higher contrast between different soft tissues. The main rationale for proton imaging (in combination with X-ray imaging) in proton therapy planning is essentially that a more accurate treatment plan can be made, because the proton image directly corresponds to the stopping power, which is not the case in X-ray imaging.
|Last modified:||25 September 2014 4.23 p.m.|