Proton Beam Therapy vs. X- ray Beams（2）

    Proton beams don't emit energy in a constant stream. They typically release it in increasing amounts as they start to slow down, because the slower they move the more atoms they have time to hit. And when they stop moving, they release most of their energy in one giant burst of radiation. After that burst, there's very little energy left, and they just stop. There's no "exit dose" of radiation like there is in X-ray therapy(Through a mobile x ray machine or a c arm x ray machine).
      By altering the proton beam's energy level, which determines its velocity, doctors can send it to a very particular tissue depth. At that exact depth -- at the precise location of the tumor -- the protons release their energy. There's very little radiation damage to the tissue surrounding the tumor. By arranging various proton beams of different energies on a three-dimensional plane, doctors can create a burst of radiation that exactly matches the shape and location of the tumor. Proton therapy is ideal for tumors that are oddly shaped and/or situated in areas that can't handle much radiation exposure. With protons as the energy source, doctors can bombard the tumor with much more energy than they can using X-rays, because they don't have to adhere to the lowest common denominator approach in which the amount of radiation directed at the tumor has to be low enough for the surrounding tissue to survive the treatment. This means proton therapy can destroy a tumor in fewer sessions than are required in X-ray therapy.----Perlong Medical.