1. A computer-implemented method comprising: obtaining a plurality of projection images of a patient positioned on a treatment couch; displaying at least one of the plurality of projection images with a corresponding synthetic projection image on a display; adjusting the position of the at least one projection image on the display to approximately align with the corresponding synthetic projection image in response to a user dragging the at least one projection image on the display with a user interface device; and moving the treatment couch to position the patient based on position adjustments of the at least one projection image.