Bragg PeakBy: Megan Whitley

Bragg Peak

Bragg Peak is the characteristic exhibited by protons that makes them SO appealing for cancer treatment.

Due to stopping power, the pristine explosion of energy at the end of the protons path, and the succinct dose fall off that occurs after the peak, the integral dose delivered by protons is half of that of photons.1

Explanation of the plan comparison on the next slide

The previous slide held a comparison of two plans, created for the same patient; the plan on the left was created using protons and the plan on the right was created using photons.

The comparison allows visualization of the dose delivered outside the tumor, from both entrance and exit dose, in the photon plan.

With the proton plan, you can see that although there is entrance dose, it is not in the dangerous or “hot” range, and that there is very little exit dose on the distal portion of the tumor.

Proton Therapy vs Photon Therapy

Explanation of Slide 6

The next slide demonstrates not only the wasted dose delivered by the photon beam before and after the tumor, but it graphically represents Spread Out Bragg Peak (SOBP).

By clicking the mouse, the graph will build on itself, portraying both the differences in photon and proton pathways, and the building of the flat SOBP.

This shows how radiation oncology uses the proton to treat cancer.

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Depth in Tissue (cm)

Rela

tive D

ose

High Energy X-Rays

200 MeV Protons

Spread Out Bragg Peak (SOBP)

Tumor

The Physics of Protons

Depth Dose Curves for Different Treatment Types

Healthy Tissue

Healthy Tissue

Thank you for you time!

I hope that these illustrations were beneficial in understanding Bragg Peak and its use in cancer treatment.

References

1. Khan FM, Gerbi B. Treatment Planning in Radiation Oncology. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2012: 394.