Beam output and beam uniformity must be checked with respect to what?

Checking beam output and beam uniformity in radiation therapy is closely tied to the gantry angle. The gantry angle refers to the rotational position of the treatment machine around the patient's body. As the gantry rotates, the characteristics of the beam can change due to varying distances from the radiation source to the target tissue and the potential for beam shaping by various collimation techniques.

Understanding how the beam behaves at different gantry angles is crucial for ensuring that the delivered dose is consistent and accurate across the treatment field. Variations in beam output and uniformity can significantly affect treatment efficacy and patient safety. Therefore, regular checks at different gantry angles help ensure that any discrepancies are identified and corrected, allowing for safer and more effective treatments.

In contrast, factors such as patient age have little bearing on the physical properties of the beam itself, while distance from the source and simulator settings are important considerations but not as directly linked to the variations that can occur specifically due to the gantry angle during treatment execution.