Ch 2 – Anatomy of the Xray MachineCH2–解剖的X射线机.pptVIP

Ch. 2 – Anatomy of the X-ray Machine Radiology The X-ray Tube X-rays are produced in an x-ray tube. X-ray tube allows x-ray beam to be produced and controlled. Components of the x-ray tube: Cathode (negatively charged) Anode (positively charged) Elements necessary for x-ray production 1. Source of electrons 2. Method of accelerating the electrons 3. An obstacle-free path for the passage of high speed electrons 4. A target in which the electrons can interact, releasing energy in the form of x-rays. 5. An envelope (tube) to provide a vacuum environment, eliminating the air molecule obstacles from the electron stream and preventing rapid oxidation of the elements. So what you need… Electrons ??Accelerate ?? Clear path ?? Target ??Provide vacuum environment. X-ray tube components 1. Cathode (-) 2. Anode (+) 3. Glass envelope encases these components and forms a vacuum. Vacuum- an area from which all air has been removed. X-ray tube continued…. Target for collision between electrons and positive charged on anode is located on the anode. This collision produces heat (99%) and x-rays/radiation (1%). Window acts as doorway for the exit of x-rays. Entire x-ray tube is encased in a metal housing to prevent stray radiation and to protect glass envelope. Cathode Cathode provides source of electrons and directs these electrons toward anode. Components of the cathode: Filament- coiled wire similar to a light bulb- emits electrons when heated. When heat is applied to atom, electrons become excited. Excitation- when electrons are moved to a higher energy level within the atom. This excitation forms an electron cloud that is then attracted towards the anode. Filament The filament is constructed of tungsten because of high melting point and high atomic number. The higher the atomic number, the more electrons that are available for excitation. Filament is housed in focusing cup and is heated by a low energy circuit. Milliamperage (mA)-amount of electrical energy being a