An example adjustable collimator includes a housing having an aperture through which radiation is to be directed from an inlet to an outlet of the housing, a first shutter and a second shutter within the housing, a first link coupled to the first shutter, and a first yoke coupled to the housing at a pivot point and configured to pivot with respect to the housing. The first yoke may be configured to reduce an effective width of the aperture by moving the first shutter toward the second shutter via the first link when the first yoke is rotated in a first direction.