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Proton Therapy in Radiotherapy

Radiotherapy has until now mainly been based on X-rays, gamma rays, and electron beams, but in recent years attention has been focused on proton therapy, which is expected to have even greater effects as it can reduce the effects on healthy tissue. Proton therapy is a type of particle beam treatment, like carbon ion therapy.

X-rays are strongest where they enter the body, and gradually weaken the further in they go, but in contrast, proton beams are characterized by reaching their maximum concentration some way into the body, and then do not penetrate any further.

This characteristic is called a Bragg peak. By aligning the Bragg peak with the tumor, it is possible to focus the strength of the radiation on the affected area, and reduce the radiation absorbed by the healthy tissue. For example, it is difficult to treat cancers near major organs using X-rays, but proton beams are expected to be very effective.

X-ray radiation is strong on the surface of the body, but has weakened by the time it reaches the site, and penetrates beyond the site as well.

Proton beams are noted for reaching their peak radiation output at a certain depth, so are strongest where the site is, and then stop after it. It is possible to reduce the effects on healthy tissue by concentrating the radiation on the site.