A linear array detector (LAD) for scanning an object is provided. The detector includes a scintillator layer configured for generating a number of optical signals representative of a fraction of an incident X-ray beam passing through the object. The plane of the scintillator is parallel to the X-ray beam. The LAD further includes a two dimensional array of photo-conversion elements configured to receive several X-rays of the X-ray beams and configured to generate corresponding electrical signals. An arrangement of the photo-conversion elements is independent of the X-ray paths.