Electron Interactions and Stopping Power

􀀁 Electrons traversing an absorber lose their kinetic energy
through ionization collisions and radiation collisions.
􀀁 The rate of energy loss per gram and per cm2 is called the
mass stopping power and it is a sum of two components:
• Mass collision stopping power
• Mass radiation stopping power
􀀁 The rate of energy loss for a therapy electron beam in
water and water-like tissues, averaged over the electron’s
range, is about 2 MeV/cm.