What commonly happens to the exit dose of a patient when compared to standard depth dose data?

The exit dose of a patient is typically higher than what standard depth dose data would suggest. This occurs because standard depth dose data are based on data obtained in homogeneous, water-equivalent media, typically used for calibration and treatment planning. However, when the radiation beam exits the patient's body, it interacts with various tissues and structures, which can enhance the dose delivered at the exit point.

Different tissues have varying densities and atomic compositions, which can lead to scattering and secondary dose production as the radiation passes through. This is particularly evident when the beam exits at an angle or encounters high-density materials such as bones or metal implants, which can further increase the exit dose due to additional interactions that are not accounted for in standard depth dose measurements.

Overall, the dose measured at exit points will often exceed the expectations set by theoretical calculations based purely on depth dose tables, hence the characterization that it is more than what is usually expected from standard models. Understanding this concept is essential for accurate dose calculation and ensures patients receive the intended treatment while minimizing potential overdose in surrounding tissues.