Which statement is true regarding the 20 MeV electron beam range in water?

The statement that the range of a 20 MeV electron beam in water is 9 cm is accurate based on the physical properties of electron beams in radiation therapy. Electron beams, including those at 20 MeV, are characterized by their ability to penetrate tissue, and their range can be precisely determined through measurements and established data.

When discussing the range of electrons in water, which is commonly used as a standard medium in radiotherapy, it is important to note that higher energy electrons have longer ranges than lower energy electrons. For a 20 MeV beam, empirical data indicate that its tissue penetration indeed results in a range around 9 cm in water. This is significant as it guides dosimetrists in planning treatment, ensuring adequate delivery of dose to tumors while minimizing exposure to surrounding healthy tissues.

Understanding the range is critical for treatment planning in radiation oncology, where treatment objectives include maximizing dose to the target while avoiding damage to normal structures. In this context, the established range of 9 cm helps clinicians determine the appropriate settings for optimal therapeutic benefit.