What aspect is measured at Dmax in radiation therapy?

In radiation therapy, Dmax refers to the depth at which the dose delivered by the radiation beam reaches its maximum value. This is a critical concept in dosimetry and treatment planning because understanding where the dose is maximized can help in targeting the tumor effectively while minimizing exposure to surrounding healthy tissues.

The maximum dose, or Dmax, is important for several reasons. It indicates the point where the radiation energy is fully deposited within a specific tissue or organ, which is crucial for ensuring that the tumor receives an adequate dose while protecting adjacent healthy structures. Knowing the Dmax helps in optimizing treatment parameters such as beam energy, field size, and patient positioning.

In contrast to the maximum dose, surface dose pertains to the radiation dose delivered at the skin surface; this is relevant but distinct from Dmax. Peak dose may refer to the highest dose within a specific region but doesn't specifically describe the characteristics of the Dmax point. A defined margin is related to planning margins for target volumes but does not directly address the concept of maximum dose.

Thus, the focus on Dmax clearly identifies it as the location where the radiation dosage is highest for therapeutic purposes, making "maximum dose" the accurate term for what is measured at this depth.