Alignment of the x-ray tube to the receptor is important in providing proper geometry for a radiographic image. Stationary radiographic units provide tools to assist the radiographer in achieving consistant alignment. It is difficult to achieve the same level of consistency using mobile equipment because such alignment tools are generally not available.
Alignment of the x-ray tube and receptor improves image quality in several ways. A consequence of rendering three-dimensional anatomy as a two-dimensional image is geometric distortion. This effect can cause variation in the size, shape, or imaged position of objects within the body. The central beam or central ray is the center of the radiation area in the divergent beam. If there is misalignment, the center of the radiation beam may not be located in the center of the image field which can cause distortion because of variation in the orientation of objects with respect to the direction of the x-ray beam.
