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The X-Ray Machine

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The X-Ray Machine The x-ray machine Dr. Ahmed Alsharef Farah Dr. Ahmed Alsharef Farah 1 X-ray room • Floor mounted x- ray tube stand. • Wall grid cabinet or Bucky. • Mobile Table with grid cabinet (optional). • Non-Bucky Film Holder (optional). Dr. Ahmed Alsharef Farah 2 • Control Booth should contain the operator console and technique charts and space to store cassettes. • The wall between the booth and x- ray unit is shielded. Dr. Ahmed Alsharef Farah 3 • High Voltage Section or Generator used to change incoming power to levels needed to produce x-rays. Dr. Ahmed Alsharef Farah 4 Types of x-ray machines Dr. Ahmed Alsharef Farah 5 Dr. Ahmed Alsharef Farah 6 The x-ray machine is divided into four major components: • The x-ray tube. • The Operating Console. • The High Voltage Section. • The Film Holder, Grid Cabinet or Table. Dr. Ahmed Alsharef Farah 7 The x-ray tube Functions of x-ray tube: • An x-ray tube converts its input of electrical energy into an output of x-ray energy. • In the case of low power equipment, an x- ray tube also acts as a rectifier. Dr. Ahmed Alsharef Farah 8 X-ray tube components: X-ray tube comprise of 3 components: 1. Cathode structure. 2. Anode structure. 3. Glass envelope. Dr. Ahmed Alsharef Farah 9 Production of x-rays: Requires 3 main components: 1. Electron source. 2. Method of accelerating electron. 3. Method of stopping (braking) electron. Dr. Ahmed Alsharef Farah 10 Tube Housing • Shields against leakage radiation (lead lined). Dr. Ahmed Alsharef Farah 11 Glass envelope: • Glass envelope is used to enclose the vacuum within the x-ray tube. • The envelope is joined to the copper anode at one end and the nickel cathode support at the other re-entrant seal. • The glass must be a good electrical insulator, or a substantial current will flow through it when a potential difference is applied between the anode and cathode. Dr. Ahmed Alsharef Farah 12 Cathode: Cathode consists of the following components: 1. Filament. 2. Focusing cup. 3. Supporting wires. 4. Cathode support. Dr. Ahmed Alsharef Farah 13 Filament: • The source of electron is a filament, heated by an electric current. The current increases the vibration of atoms within the filament so much that it emits heat and light. • So much heat energy is acquired by the atoms that some of their electrons (outer) can break free and temporarily leave the filament’s surface. This phenomenon is known as thermionic emission. Dr. Ahmed Alsharef Farah 14 • The rate at which electrons are emitted rises with the filament’s temperature. • Thermionic emission: Emission of electrons from the surface of a metal after heated. Dr. Ahmed Alsharef Farah 15 The filament is made of thin coiled tungsten wire for the following reasons: 1. Tungsten is a good thermionic emitter. 2. Tungsten has a low vapour pressure, i.e. it does not vaporise easily. It therefore lasts a long time. 3. Tungsten is rugged and able to be drawn into the thin wire required. 4. Easy to be shaped. Dr. Ahmed Alsharef Farah 16 Focusing cup: • Focusing cups are usually made of nickel, molybdenum or stainless steel. • Cup shape metal used to focus electrons towards target material. • These materials possess high melting point and is a relatively poor thermionic emitter. Dr. Ahmed Alsharef Farah 17 Anode: • Anode is constructed of the two materials copper and tungsten, known as a compound anode. Dr. Ahmed Alsharef Farah 18 • Anode consists of: 1. The block and stem is made of copper. 2. The target or an inset of a thin (~ 2-3 mm) tungsten plate on the inclined face of the copper block. Electrons from the filament are focused on the target. Dr. Ahmed Alsharef Farah 19 • 1% of energy is converted to x-rays, plus heat. • The anode rotates to increase heat load capacity. • Electrons accelerated to positively charged anode. • Requires high potential difference to produce x-rays. • Diagnostic energy range usually 30 kV – 150 kV. Dr. Ahmed Alsharef Farah 20 Types of x-ray tube • Stationary anode x-ray tube. • Rotating anode x-ray tube. Dr. Ahmed Alsharef Farah 21 Stationary anode x-ray tube: • Low electric power. • Relative simplicity of design and construction and therefore low cost. • Suitable for the production of X-rays at low or medium intensities. • Used for applications such as dental radiography and mobile work where no sophisticated procedures such as rapid sequential imaging are required. Dr. Ahmed Alsharef Farah 22 Dr. Ahmed Alsharef Farah 23 Rotating anode x-ray tube: • Higher X-ray intensities and electrical power are providing by the anode tube since it has more efficient anode cooling. Dr. Ahmed Alsharef Farah 24 The Control Console • The control console is device that allows the technologist to set technical factors (mAs & kVp) and to make an exposure. • Only a legally licensed individual is authorized to energize the console. Dr. Ahmed Alsharef Farah 25 Main components of the control panel: • The main on/off switch and warning lights. • The timer. • An exposure time selectors. • Warning lights and audible signals. Dr. Ahmed Alsharef Farah 26 The radiographic table • Regardless of the type of x-ray imaging system used, a patient-supporting examination couch is required. Dr. Ahmed Alsharef Farah 27 • This examination couch must be uniform in thickness and as transparent to x-rays as possible. • Carbon fiber couches are strong and absorb little x-radiation. This contributes to reduced patient radiation dose. Dr. Ahmed Alsharef Farah 28 • Most patient couches are floating; easily unlocked and moved by the radiologic technologist or motor driven. • Just under the couch is an opening to hold a thin tray for a cassette and grid. Dr. Ahmed Alsharef Farah 29 • Fluoroscopic couches tilt and are identified by their degrees of tilt. For example, a table would tilt 90 degrees to the foot side and 30 degrees to the head side. Dr. Ahmed Alsharef Farah 30 The End Dr. Ahmed Alsharef Farah 31.
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