Important Notes on X-Ray Imaging System
The function of the X-ray Imaging System is to provide a controlled flow of electrons intense enough to produce an X-ray beam appropriate for imaging.
Three Main Components of an X-ray Imaging System
- X-ray Tube
- Operating Console
- High-Voltage Generator
Operating Console – is used to control the voltage applied to the X-ray tube, the current through the X-ray tube and the exposure time.
“The many different type of X-ray Imaging Systems are usually identified according to either the energy of the X-rays they produce or the purpose for which those X-rays are intended”.
Basic Control of Operating Console
- On/off Control
- mAs Selection
- kVp Selection
- Table/wall unit activation
- Exposure Switch
Additional Components of Some Modern Control Console
- Adjustment of the Line Compensator
• Line Compensator – measures the voltage provided by X-ray unit and adjust the voltage to precisely 220V. - Separate mA and Time Exposure Control
• Automatic Exposure Control/ Phototimer – the mAs control only is present.
- kVp Meter – placed across the outwood terminal of the autotransformer
- read the Volt (V) not the kVp - Pre-reading Voltmeter – allows the voltage to be monitor before the examination.
- mAs Selection – Number of electron flowing from Cathode to Anode.
- mA Control – number of electron emitted by the filament (filament needed).
- Spinning Stop Timer – simple device that can be used to check the accuracy of X-ray timer in half-wave and full-wave rectified units and used by medical.
- Fluoroscopic X-ray Tube – located under the examining table.
- Radiographic X-ray Tube – attached to an overhead movable crane assembly that permits easy positioning of the tube and aiming of the X-ray beam.
- Examination Table – may be flat or curved but must be uniform in thickness and as transparent to X-rays as possible.
- Carbon Fiber Table Top - are strong and absorb little X-ray radiation and contributes to reduced patient dose.
- Bucky Tray – hold the cassette and grid.
- discovered by Gustave Bucky and Hollis Potter and known as Potter-Bucky Tray. - Half Wave Layer – the thickness of the material to reduce its intensity to half of its original value.
Two Types of AEC
- Photomultiplier Sensing Device
- Ionization Chamber
- Solid State Radiation Defectors – used for exposure time check and replace the spinning top.
- High-Voltage Generator - responsible for increasing the output voltage from the autotransformer to the kVp necessary for X-0ray production.
Three Primary Parts of High-Voltage Generator
- High-Voltage Transformer
- Filament Transformer
- Rectifier
- Voltage Rectification – required to ensure that electron flow from Cathode to Anode.
- Rectifier – electronic device that allows current flow in only one direct.
- all diode rectifier were vacuum tubes called Valve Tube; those have been placed by solid-state rectifier mad of silicon. - Thermionic Emission – if a large current is passed though this filament, it heats up and “boil” electron soft it surface.
therm – refers to the heat ,
ion-refer to charged particles ,
emission - to give (process of giving off electron from a heated surface.
- Simple Vacuum Tube – conducts electron in only one direction, from Cathode to Anode, sometimes called a diode.
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