The X ray collimator is a “beam direction” device used in an x-ray tube housing, as well as a mirror and light arrangement such that the light and x-ray fields match each other. They are made of lead shutters that completely absorb photons, thereby reducing patient dose and focusing the radiation to the area of interest accordingly. They allow different X-ray field projections.
In a linear columnator, the primary collimator can be made up of depleted uranium (DU) because the material has a density of about 1.6 times that of lead. A secondary electric collimator of a more defined beam shape is composed of lead or tungsten. The multi-leaf collimator (MLC), now widely used in medical linear accelerators, consists of two columator groups consisting of thin “leaves”, each consisting of 40 to 80 leaves (hence a total of 80 to 160 leaves) . This allows each columner blade to move independently under computer control. MLC allows for an even more diverse field shape that can shield organs at risk while allowing the complex shape of the tumor bed to be illuminated to allow for maximum killing of cells.