What is the most commonly used type of collimation?

Variable rectangular collimation is the most commonly used type because it offers a balance between flexibility and precision in radiation therapy and imaging. This collimation type adjusts to the shape and size of the area being treated or imaged, allowing practitioners to minimize the exposed area while adequately covering the target.

By using variable rectangular collimation, it is possible to better conform the radiation beam to the dimensions of the anatomical structure of interest, which enhances the dose distribution while protecting surrounding healthy tissues from unnecessary radiation exposure. This adaptability is crucial in clinical settings where different patients and conditions require tailored approaches to radiation delivery. It also plays an essential role in adhering to principles of radiation protection, which prioritize minimizing exposure as much as possible while still achieving diagnostic or therapeutic objectives.

In contrast, fixed options provide less adaptability and do not accommodate the varying sizes and shapes of different treatment or imaging sites, making variable rectangular collimation the preferred choice in practice.