What is the impact of collimator transmission on dose delivery?

Collimator transmission refers to the amount of radiation that passes through the collimator to reach the patient during radiation therapy. When collimators have a high transmission rate, they allow more of the radiation beam to be delivered to the treatment area. This results in an increase in the surface dose, as more radiation is reaching the skin or the surface of the tumor being treated.

The reasoning behind this is that as the collimator absorbs some of the radiation, it can create a differential in how much dose is received at the surface versus deeper within the tissue. Therefore, when collimator transmission is not accounted for, there can be a significant increase in the surface dose, which is crucial for accurate dose calculations and treatment efficacy.

This effect emphasizes the importance of understanding how different collimators impact dose delivery, particularly in treatments where surface doses need to be managed carefully, such as in superficial cancers. In contrast, the other options suggest different outcomes that do not take into account the actual impact of the collimator's transmission on how much dose is delivered at the surface, which is why they do not align with the correct answer.