What is defined as the exit dose in radiation therapy?

The exit dose in radiation therapy refers specifically to the dose that is delivered to tissues as radiation leaves the patient's body after penetrating through the target area. This concept is particularly important because it helps to assess the potential dose received by underlying and surrounding tissues beyond the area being treated, which can impact both efficacy and safety.

The dose at Dmax for the exiting field captures the accurate representation of the dose received by the tissues as the beam exits the patient. This is crucial for evaluating the balance between effectively treating the tumor and minimizing damage to adjacent healthy tissues.

Additionally, understanding the exit dose contributes to treatment planning and patient safety by ensuring that adequate consideration is given to all areas potentially affected by radiation exposure. This is why the choice aligning with the dose at the maximum depth for the exiting field is the correct representation of the concept.