Dose Verification of Proton and Carbon Ion Beam Treatments

Authored by: Katia Parodi

Clinical 3D Dosimetry in Modern Radiation Therapy

Print publication date:  October  2017
Online publication date:  October  2017

Print ISBN: 9781482252217
eBook ISBN: 9781315118826
Adobe ISBN:

10.1201/9781315118826-23

 Download Chapter

 

Abstract

Ion beam therapy is a rapidly emerging treatment modality that makes use of the favorable properties of ion interaction with tissue. When ions are slowed down in matter, they transfer most of their energy in Coulomb interactions with the atomic electrons, and the energy transfer rate is relatively low at the initial therapeutic beam energies of 50–230 MeV for protons and 90–430 MeV/u for 12C ions, but rapidly increases toward the end of the beam penetration depth (Schardt et al., 2010; Newhauser and Zhang, 2015). This energy loss process is responsible for the main feature of the ion depth–dose deposition, exhibiting a pronounced sharp maximum, the Bragg peak, at an energy-dependent depth (Wilson, 1946). Additional processes that influence the exact shape of the three-dimensional (3D) dose distribution of an ion beam are (1) energy loss straggling, affecting the longitudinal Bragg peak width; (2) multiple Coulomb scattering, affecting the lateral beam spread; and (3) nuclear interactions, which modify the particle energy fluence spectrum. Energy straggling and multiple Coulomb scattering are especially responsible for the broader Bragg peak and marked lateral spread of proton beams compared to carbon ions at the same penetration depth (Figure 23.1). Nuclear reactions prevent primary particles from reaching the Bragg peak and are especially responsible for the complex mixed radiation field in the case of carbon ion beams, where secondary projectile fragments of reduced charge give rise to a characteristic dose tail distal to the Bragg peak (Figure 23.2). More information about the interaction of light ions with matter can be found in Chapter 12.

 Cite
Search for more...
Back to top

Use of cookies on this website

We are using cookies to provide statistics that help us give you the best experience of our site. You can find out more in our Privacy Policy. By continuing to use the site you are agreeing to our use of cookies.