In radiation therapy, the primary purpose of a collimator is to:

The primary purpose of a collimator in radiation therapy is to reduce scatter. Collimators are devices attached to the treatment machine that shape and limit the radiation beam being delivered to the patient. By restricting the area exposed to radiation, collimators minimize the volume of healthy tissue that receives radiation, thereby reducing the potential for scatter radiation. This not only helps in protecting normal tissues adjacent to the treatment area but also enhances the dose accuracy to the tumor.

Reducing scatter is crucial for ensuring that the radiation dose is concentrated on the target tumor while minimizing exposure to surrounding healthy tissues. Proper collimation reduces the amount of secondary radiation generated from the patient and surrounding equipment, which can contribute to unwanted radiation exposure and potential side effects.

While focusing radiation might seem like a factor in determining the effectiveness of treatment, the primary function of the collimator is aimed at controlling the scatter to enhance treatment precision. Additionally, increasing dose and enhancing imaging are not functions of the collimator; these are addressed through other means in radiation therapy practices.