X-ray imaging: Fundamentals and planar imaging

X-ray imaging is the most widespread and well-known medical imaging technique. It dates back to the discovery by Wilhelm Conrad Röntgen in 1895 of a new kind of penetrating radiation coming from an evacuated glass bulb with positive and negative electrodes. Today, this radiation is known as short wavelength electromagnetic waves being called X-rays in the English speaking countries, but “Roengten” rays in many other countries. The X-rays are generated in a special vacuum tube: the Xray tube, which will be the subject of the first subsection. The emanating X-rays can be used to cast shadows on photographic films or radiation sensitive plates for direct evaluation (the technique of planar X-ray imaging) or the rays can be used to form a series of electronically collected projections, which are later reconstructed to yield a 2D map (thus, a tomographic image). This is the so-called CAT or CT technique (see the chapter on CT imaging).