What are the results of multiple scattering of a pencil beam of electrons in a scattering foil?

In the context of medical dosimetry and the use of electron beams, multiple scattering refers to the interaction of electrons with matter, such as the scattering foils used in radiation therapy. When a pencil beam of electrons passes through a scattering foil, several effects occur, which include angular spread, energy degradation, and bremsstrahlung contamination.

Angular spread results from multiple scattering interactions; as electrons collide with the nuclei of the material in the foil, they deviate from their initial trajectories. This scattering effect broadens the beam, allowing for a larger treatment area, which is essential in delivering adequate dose to the tumor while sparing surrounding healthy tissues.

Energy degradation also occurs as electrons lose energy during their interactions with the foil material. Some energy is lost to ionization and excitation of the atoms within the foil, leading to lower energy electrons exiting the foil compared to the energy of the incident pencil beam. This is critical since the energy levels of electrons determine their penetration depth in tissue.

Bremsstrahlung contamination arises when high-energy electrons interact with heavy nuclei in the scattering foil, leading to the emission of X-ray photons. This phenomenon is particularly relevant in scattered beams, as it can affect dose distribution and contribute to unwanted radiation exposure to healthy tissues.

Thus,