1. Bragg Peak By: Megan Whitley

2. 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

3. 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.

4. Proton Therapy vs Photon Therapy

5. 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.

6. 051010 1515 20253030 0 2020 4040 6060 8080 100 Depth in Tissue (cm) Relative Dose 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

7. Thank you for you time!  I hope that these illustrations were beneficial in understanding Bragg Peak and its use in cancer treatment.

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