Different types of radiation interact with the body in different ways. X-rays (also known as photons) are a standard type of radiation, used both to take X-ray pictures and for radiation treatment. Proton therapy is a different type of radiation which uses positively charged particles (protons) from the center (nucleus) of an atom. Proton particles release radiation energy in a different way than X-rays, concentrating more of the radiation in the target while reducing or avoiding radiation to surrounding healthy areas.
Rather than traveling all the way through the body (like an X-ray beam), proton particles only travel as far as their energy allows and then stop. Each proton beam is calibrated to deliver its peak radiation dose to match the shape and the depth of the target. The “Bragg peak” is the point at which a proton beam releases the bulk of its energy before stopping. Think of it as the main deposit zone, so precise that physicians can concentrate radiation inside a tumor while sparing healthy tissue around it. The Bragg peak is a key feature of proton therapy that sets it apart from other forms of radiation treatment, and a main reason that oncologists choose proton therapy to target tumors near sensitive tissues and organs.
How Proton Therapy’s Bragg Peak Differs from Other Radiation Treatments
Most radiation therapy uses X-rays (photons). An X-ray beam delivers radiation all along its path through the body: strong near where it enters, then gradually weaker the deeper it goes, like a flashlight beam fading over distance. This means some radiation reaches healthy tissue both before and after it treats the target. For most patients, that’s safe and effective.
But when a tumor is near sensitive organs, like the brain, spinal cord, heart, or bowels, or in children or others especially sensitive to radiation, proton therapy’s ability to avoid radiation outside the target can help protect those organs from damage.
Protons are charged particles that release a low dose of radiation as they travel through the body, before depositing almost all of their energy (the Bragg peak) at the specific location of the radiation target. Once protons hit that point, they stop, delivering essentially no radiation beyond the target. The result: the radiation dose concentrates in the target itself, with minimal dose to surrounding tissue and little to no radiation passing beyond the target.
The Spread-Out Bragg Peak
A single proton’s Bragg peak is like a laser pointer: all the energy lands on one tiny spot. But most of the time, the area that needs to be treated is bigger than that single pinpoint. To cover the entire treatment area, physicians combine many proton beams at slightly different energies, creating what’s called a “spread-out Bragg peak.” Think of it like layering overlapping brushstrokes to fully cover a surface, rather than trying to paint it with a single dot. The spread-out Bragg peak allows proton therapy to treat the entire tumor rather than just one point within it.
What the Bragg Peak in Proton Therapy Can Do for Patients
Because proton therapy targets radiation so precisely, it may allow physicians to:
- More safely treat difficult tumors near sensitive organs and tissues
- Lower the risk of short-term and long-term side effects from radiation
- Deliver a higher radiation dose, when needed, to resistant tumors
- More safely deliver a second course of radiation for patients with new or recurrent disease in a previously treated area
- Reduce radiation risks for children, young adults, and others who are especially sensitive to radiation side effects.
Take the Next Step
Developing a comprehensive treatment plan can be complex. The right treatments depend on the type of tumor or cancer that you are facing, where it’s located, and the treatment goals. At Emory Proton Therapy Center, your care is coordinated by specialists from Winship Cancer Institute of Emory University, Georgia’s only National Cancer Institute-designated Comprehensive Cancer Center. Our expert physicians review your case and discuss proton therapy alongside other treatment options. Schedule a consultation with us to learn what benefits proton therapy could offer for your care.