ABSTRACT
Visual monitoring of electron production in the glow discharge of early ion tubes by radiographers became obsolete with the advent of Coolidge tubes in 1913. e bright yellow glow of the large anode of a modern computed tomography (CT) tube might be a frightening sight for patients. us, tightly enclosed protective means against leakage radiation and the risk of implosion
along with sophisticated mechanical and electrical interfaces have been introduced for medical X-ray sources. e concept of X-ray Tube Assembly (according to IEC standards) or Tube Housing Assembly ( according to FDA regulations), as shown in Figure 7.1, has emerged and has been formalized as standardized terms. e assembly comprises a vacuum device that generates X-rays, often called “tube insert,” and a protective recyclable casing, the “ housing.” e housing comprises high-voltage receptacles, other terminals for electric supply, and safety switches, and is the mechanical interface that holds the focal spot in place with respect to the X-ray system. Means for geometrical ne adjustment are provided. Figure 7.1 shows a preadjusted interface to the beam-limiting device and trunnion rings for tangential positioning. Basic dimensions such as the distance of the focal spot to the mounting plane of the X-ray window are vendor specic. e accuracy of denition
Figure 7.1 Exemplary air convection cooled tube housing assembly, shown without beam-limiting device. (Courtesy of Philips.)
of the focal spot position has improved since the introduction of metal center section tubes. However, ne-tuning is necessary in most cases during systems assembly.
