Question: What is particle therapy?
About the article "Radiation therapy", section "Types".

Candidate passages:
Particle therapy is a form of external beam radiotherapy using beams of energetic protons, neutrons, or positive ions for cancer treatment.
The most common type of particle therapy as of 2012 is proton therapy.
Although a photon, used in x-ray or gamma ray therapy, can also be considered a particle, photon therapy is not considered here.
Additionally, electron therapy is generally put into its own category.
Because of this, particle therapy is sometimes referred to, more correctly, as hadron therapy (that is, therapy with particles that are made of quarks).
Neutron capture therapy might be considered a type of particle therapy, but it is not discussed here, as the damage it does to tumors is mostly from energetic ions produced by the secondary nuclear reaction after the neutrons in the external beam are absorbed into boron-10 (or occasionally some other nuclide), and not due primarily to the neutrons themselves.
It is therefore a type of secondary particle therapy.
Muon therapy, a rare type of particle therapy not within the categories above, has occasionally been attempted. 
Energetic particle beams consisting of protons, neutrons, or positive ions (also called particle microbeams) may also be used for cancer treatment in particle therapy. 
In particle therapy (proton therapy being one example), energetic ionizing particles (protons or carbon ions) are directed at the target tumor.
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 this energy deposition profile is that less energy is deposited into the healthy tissue surrounding the target tissue. 
Proton therapy is a type of particle therapy which uses a beam of protons to irradiate diseased tissue, most often in the treatment of cancer.
The chief advantage of proton therapy is the ability to more precisely localize the radiation dosage when compared with other types of external beam radiotherapy, though it is controversial whether this provides an overall advantage compared to other, less expensive treatments. 
The Particle Therapy Co-Operative Group continuously lists treatment centers in operation and in the planning or construction stage.
Three centers using carbon ions are in operation, two in Japan: the HIMAC at Chiba and the HIBMC at Hyogo.
In Germany, treatment at the "Gesellschaft für Schwerionenforschung" (GSI) in Darmstadt, which is primarily a physics laboratory, has been discontinued in 2008, but the new HIT in Heidelberg, which is a dedicated facility, started in November 2009.
The CNAO in Pavia, Italy is going to open in 2011 and will be one of the most advanced centers for particle therapy with hadrons.
CNAO will combine precise dose delivery with highly accurate patient alignment based on stereoscopic X-ray imaging.
Sophisticated approaches in image-guided particle therapy (IGPT) augments the radiotherapy machines with imaging capabilities and the latest computer vision technology to increase accuracy of target localization and enable patient alignment accuracies of 0.5 mm and better.