1. An apparatus for x-ray imaging, said apparatus comprising: a) a platform connected to a frame; b) a sliding bar connected to said frame; c) a first detector mounted on said sliding bar; d) an x-ray source including a collimator to generate an x-ray exposure window; and e) a control system configured to slide linearly said first detector along said sliding bar and synchronously move said collimator to direct said x-ray exposure window to said first detector, wherein movements of said x-ray exposure window are registered to movements of said first detector; and wherein said x-ray source, said sliding bar, and said first detector being able to rotate laterally around a sliding direction of said first detector.