The Stopping Powers of Water and Lung for Protons in Radiotherapy

Aims: This study aims to calculate the energy losses in unit length of protons during their movement within water and lung by using two analytical equations.
Study Design: One of the equations used in this study is the mass stopping power equation suggested by Bethe-Bloch (1930-1933) and modified by Tsoulfanidis (1995) and a new approach has been suggested in the other one.
Methodology: The suggested new approach was obtained by substituting effective z*, Z* and I* values into the equation reported by Tsoulfanidis. Although the energy range of protons used in the radiotherapy is 75-250 MeV, in this study 0.001-250 MeV energy ranges were performed to identify the stopping power. In addition, a new empirical relation was given to simplify the expressions for stopping power. The results were compared with the other researcher’s results.
Results: The suggested approach for the mass stopping power (Equation 2) can be used for both high- and low energy protons. Stopping power values of protons should be especially useful in such medical fields as radiobiology, biomedical applications, radiotherapy and so on.