A portable medical imaging system includes a movable station, a detector panel, an X-ray beam transmitter, and a controller. The movable station includes a c-arm having a first end and a second end that are movable along an arc relative to the movable station. The detector panel is attached to the first end of the movable c-arm. The X-ray beam transmitter faces the detector panel and is attached to the second end of the c-arm. The X-ray beam transmitter contains a collimator that forms a window through which an X-ray beam is transmitted toward the detector panel. The collimator is configured to move the widow in a lateral direction across a direction of the arc. The controller is configured to control movement of the window by the collimator to steer the X-ray beam laterally across the detector panel.