What is Proton Therapy

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The Bragg Peak - Something to Brag About

The Bragg Peak - Something to Brag About

Proton beam therapy is a type of external beam radiation that radiation oncologists use to protect healthy tissues from unnecessary radiation while effectively killing tumors. Protons are spun in a machine called a “cyclotron” until they reach about 223 million miles per hour. The protons then travel through the patient at high speeds, depositing only low amounts of radiation, and then release the largest dose of radiation at the very end of their journey: at the tumor site. This is thanks to a particle radiation phenomenon called the “Bragg Peak.” The Bragg Peak is named after William Henry Bragg, a British mathematician, physicist, and Nobel laureate who discovered this phenomenon in 1903.

Conventional radiation releases the most energy where it enters the body, and loses energy as it travels. It continues past the tumor, delivering radiation to any tissues it encounters on exit. Protons release most of their energy at the site of the tumor, and then stop. This Bragg Peak phenomenon means there is little to no excess radiation that travels past the tumor. Radiation oncologists can determine precisely where the proton beam will release its energy, making it a very targeted cancer treatment. Because healthy tissue is spared, proton therapy patients have a decreased risk of developing radiation-related cancers in years to come.