Historically, the early scanner configurations were characterized as successive generations of scanner geometry ( Fig. Furthermore, projection radiographs have very limited ability to differentiate low-contrast differences in tissues. Because of this indeterminacy, radiologists require extensive training and experience to interpret 3D structures from the 2D image data. The projection causes a superposition of internal structures, leading to indeterminacy in the exact relationships, shapes, and relative positions of objects. In radiography, x-rays illuminate an object, resulting in a two-dimensional (2D) image that is the “shadow” of three-dimensional (3D) structures present in the beam. The attenuation of beam energy on passage through physical objects provides a noninvasive means to gather information about the amount and type of material present inside the object. X-rays are a form of electromagnetic energy that propagate through space and are absorbed or scattered by interactions with atoms.
X-ray imaging was the first diagnostic imaging technology, invented immediately after the discovery of x-rays by Roentgen in 1895.
