Which component controls the physical size of the x-ray beam in a CT system?

The component that controls the physical size of the x-ray beam in a CT system is the pre-patient collimators. These collimators are located before the x-ray tube and are responsible for shaping and restricting the x-ray beam as it exits the tube. By controlling the size and shape of the beam, pre-patient collimators help enhance image quality by reducing scatter radiation and limiting the exposure area to only the region of interest. This is critical in CT imaging as it helps minimize radiation dose to surrounding tissues while maximizing the quality of the resulting images. This function is essential for optimizing patient safety and ensuring that the images produced are both clear and diagnostically useful.