X-Ray Projection Imaging

Abstract

X-ray imaging is the oldest medical imaging modality, which found its way into medical practice shortly after the discovery of the X-rays in 1895. X-ray imaging is a projection technique, and image formation takes place traditionally on photosensitive film, although direct digital X-ray imaging is becoming more and more common. In its most common form, X-ray imaging is a qualitative modality. X-rays are high-energy photons, and atomic interaction with inner shell electrons is fundamental to both X-ray production and generation of X-ray contrast. Soft-tissue contrast is comparatively low, but bone and air provide excellent contrast. In some cases, contrast can be enhanced with contrast agents. An undesirable (but unavoidable) side-effect of the photon-atom interaction is the ionization of tissue along the beam path, which can lead to radiation damage. X-ray images can reveal very subtle features, and its popularity is further enhanced by the relatively inexpensive equipment and the straightforward imaging procedure.