A portable medical imaging system comprising: - a movable station comprising a c-arm (72, 74) having a first end and a second end that are movable along an arc relative to the movable station; - a detector panel attached to the first end of the movable c-arm; - an X-ray beam transmitter facing the detector panel and attached to the second end of the c-arm, the X-ray beam transmitter containing a collimator positioned between an X-ray source and the detector panel that forms a window through which an X-ray beam is transmitted toward the detector panel, wherein the collimator is configured to move the window in a lateral direction across a direction of the arc; and wherein the collimator comprises a first pair of shutters (1902,1904) that are on opposite sides of the window and which each have an edge surface that forms an opposing edge of the window in the lateral direction; and a first pair of motor assemblies (2020a,2020b) connected to move respective ones of the first pair of opposing shutters; - a controller configured to control movement of the window by the collimator by controlling the first pair of motor assemblies to position the first pair of shutters to steer the X-ray beam laterally across the detector panel, wherein between each of a plurality of imaging scans through which the X-ray beam transmitter and the detector panel are repetitively moved between spaced apart locations along the arc, the controller controls the first pair of motor assemblies to incrementally move the first pair of shutters a same distance in the lateral direction, and the controller controls the incremental distance based on a distance between the opposing edges of the window; characterized in that - the controller determines a level of scatter of the X-ray beam in a target area that is to be imaged in a next imaging scan that is to be performed, the X-ray scatter being determined from an image scan of the target area, and controls the first pair of motor assemblies (2020a, 202b) to set the distance between the opposing edges of the window and to control the incremental distance that the first pair of shutters (1902, 1904) are moved based on the level of scatter that is determined. - a movable station comprising a c-arm (72, 74) having a first end and a second end that are movable along an arc relative to the movable station; - a detector panel attached to the first end of the movable c-arm; - an X-ray beam transmitter facing the detector panel and attached to the second end of the c-arm, the X-ray beam transmitter containing a collimator positioned between an X-ray source and the detector panel that forms a window through which an X-ray beam is transmitted toward the detector panel, wherein the collimator is configured to move the window in a lateral direction across a direction of the arc; and wherein the collimator comprises a first pair of shutters (1902,1904) that are on opposite sides of the window and which each have an edge surface that forms an opposing edge of the window in the lateral direction; and a first pair of motor assemblies (2020a,2020b) connected to move respective ones of the first pair of opposing shutters; - a controller configured to control movement of the window by the collimator by controlling the first pair of motor assemblies to position the first pair of shutters to steer the X-ray beam laterally across the detector panel, wherein between each of a plurality of imaging scans through which the X-ray beam transmitter and the detector panel are repetitively moved between spaced apart locations along the arc, the controller controls the first pair of motor assemblies to incrementally move the first pair of shutters a same distance in the lateral direction, and the controller controls the incremental distance based on a distance between the opposing edges of the window; - the controller determines a level of scatter of the X-ray beam in a target area that is to be imaged in a next imaging scan that is to be performed, the X-ray scatter being determined from an image scan of the target area, and controls the first pair of motor assemblies (2020a, 202b) to set the distance between the opposing edges of the window and to control the incremental distance that the first pair of shutters (1902, 1904) are moved based on the level of scatter that is determined.