1. A method, comprising: detecting, with a treatment delivery system, a target having motion in up to three translational directions using direct registration of the target; and tracking the target to synchronize a treatment beam with the motion of the target, wherein detecting the target comprises: defining a region of interest (ROI) in each of one or more digitally reconstructed radiographs (DRRs), wherein ROI includes at least part of the target; and matching the ROI in one of the DRRs with a corresponding x-ray image.