
Neutron Radiation is produced from a large and expensive particle accelerator called a cyclotron. This high-LET (high linear-energy-transfer) radiation is also called "fast neutron therapy". Neutrons, pions and heavy ions (such as carbon, neon and argon) deposit more energy along their path than x-rays or gamma rays, thus causing more damage to the cells they hit. The cyclotron accelerator produces protons and then a series of powerful magnets bend and aim the beam to strike a beryllium target, where the interaction produces neutrons.

High-LET radiation has increased energy deposition in tissue per-unit-tract-length.  Neutrons interact with the atomic nuclei of cells and produce densely ionizing protons. These proton particles transfer high amounts of energy to the tumor and inflict a significant percentage of single-hit double-stranded DNA damage. This type of damage is generally considered lethal to a cell. By contrast, low-LET radiation is more sparsely ionizing and causes a higher percentage of single-stranded DNA events, which have a greater capacity for repair. 

Photon radiation [Xrays or Gamma rays] causes most of its cellular damage through the generation of free radicals.  Neutrons have a greater tendency to cause death to the cell through direct interaction. 

Because the biological effectiveness of neutrons is so high, the required tumor dose is about one-third the dose required with photons, electrons or protons. A full course of neutron therapy is delivered in only 10 to 12 treatments. Side effect severity depends on the total dose delivered and the general health of the patient. The treatment field is shaped by computer so that the radiation beam conforms to specific volume with reduced exposure to adjacent normal tissue.

High Energy Neutrons can be very effective in killing tumor, but they can be equally lethal to normal tissue.  Evaluate the site and the probable side effects from the radiation on the structures which might be in the beam, ask what they could be and discuss these carefully with the radiation oncologist.  For large inoperable tumors that photon radiation would not be able to treat, high energy neutrons could be a lifesaver.   

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