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In medicine, proton therapy, or proton radiotherapy, is a type of particle therapy that uses a beam of protons to irradiate diseased tissue, most often to treat cancer.The chief advantage of proton therapy over other types of external beam radiotherapy is that the dose of protons is deposited over a narrow range of depth; hence in minimal entry, exit, or scattered radiation dose to healthy ...
When charged particles move in electric and magnetic fields the following two laws apply: Lorentz force law: = (+),; Newton's second law of motion: = =; where F is the force applied to the ion, m is the mass of the particle, a is the acceleration, Q is the electric charge, E is the electric field, and v × B is the cross product of the ion's velocity and the magnetic flux density.
The most common type of particle therapy as of August 2021 is proton therapy. [ 1 ] In contrast to X-rays ( photon beams) used in older radiotherapy, particle beams exhibit a Bragg peak in energy loss through the body, delivering their maximum radiation dose at or near the tumor and minimizing damage to surrounding normal tissues.
The relative biological effectiveness for radiation of type R on a tissue is defined as the ratio R B E = D X D R {\displaystyle RBE={\frac {D_{X}}{D_{R}}}} where D X is a reference absorbed dose of radiation of a standard type X , and D R is the absorbed dose of radiation of type R that causes the same amount of biological damage.
The dose produced by a native and by a modified proton beam in passing through tissue, compared to the absorption of a photon or x-ray beam. This characteristic of proton beams was first recommended for use in cancer therapy by Robert R. Wilson in his 1946 article, Radiological Use of Fast Protons. [5]
In particle therapy (proton therapy being one example), energetic ionizing particles (protons or carbon ions) are directed at the target tumor. [96] The dose increases while the particle penetrates the tissue, up to a maximum (the Bragg peak) that occurs near the end of the particle's range, and it then drops to (almost) zero. The advantage of ...
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All quantities are in Gaussian units except energy and temperature which are in electronvolts.For the sake of simplicity, a single ionic species is assumed. The ion mass is expressed in units of the proton mass, = / and the ion charge in units of the elementary charge, = / (in the case of a fully ionized atom, equals to the respective atomic number).