How is the spectrum of the electron beam incident on the patient characterized?

The correct characterization of the spectrum of the electron beam incident on the patient is a skewed distribution. In medical dosimetry, the electron beam is produced through the acceleration of electrons, and as these electrons interact with the patient’s tissue, the resulting energy distribution is not uniform across all depths.

Due to various factors, such as the energy loss of electrons as they penetrate matter, the spectrum does not follow a normal distribution pattern, leading to a skewed appearance. This skewness reflects the fact that a large number of lower-energy electrons might be present, with fewer higher-energy electrons. This distribution affects how dose is delivered to the treatment area, as it can lead to a more pronounced buildup of dose at specific depths, influencing the planning and delivery of radiation therapy.

Understanding that the spectrum is skewed helps dosimetrists design more effective treatment plans by considering where the maximum dose occurs and how to account for any underdosing or overdosing in the targeted tissues.