Finals

• The first x-ray device was discovered by German scientist Wilhelm Conrad Roentgen on November 8, 1895
• Wilhelm Conrad Roentgen examined the first bone structure of the human (left) hand of his wife, Anna Bertha Ludwig
• Main uses for X-ray Energy

  • Diagnostic - methods used to determine the source or cause of disease, disorder, or a traumatic injury
  • Therapeutic - methods used to treat and rehabilitate a disease, disorder, or traumatic injury
• Components of X-ray Imaging System

  • X-ray Tube (diode)
  • Operating Console
  • High-Voltage Generator
• Basic Controls of Operating Console

  • On/off control
  • mAs selection
  • kVp selection
  • Table/wall unit activation
  • Exposure switch
• Components of Modern Control Console

  • Adjustment of Line Compensator
  • Separate mA & Time Exposure Control
• Autotransformer


  Has a single winding and is designed to supply a precise voltage to the filament circuit and to the high voltage circuit
• kVp Adjustment


  Determines the quality of the x-ray beam
• Control of MilliAmper (mA)


  Measures the tube current and the number of electrons crossing from the cathode to the anode per second
• Exposure Timers


  Consists of any mechanical or electronic device to break the high voltage across the tube
• Number of x-rays reaching the image receptor

  Directly related to the tube current and the time that the tube is energized
• Manipulating exposure time


  Used to adjust the number of x-rays reaching the image receptor based on the fixed mA setting
• Types of Exposure Timers

  • Mechanical timers
  • Synchronous Timers
  • Electronic Timers
  • mAs Timers
• Digital timer


  • Most sophisticated, most complicated, most accurate
• Most exposure timers are electronic and controlled by a microprocessor
• mAs Timers


  1. Located inside the bucky slot; monitors the product of mA and exposure time and terminates the exposure when desired mAs value is attained

  2. Usually designed to provide the highest safe tube current for the shortest exposure for any mAs selected

  3. APR or Anatomically Programmed Radiography timers have computers that store the technical factor in the machine
• The product of mA and time (mAs) determines the number of x-ray photons emitted and the density on the film
• Phototimer


  1. Detects radiation dose or quantity of radiation reaching the receptor and terminates the exposure when sufficient radiation is needed to produce the correct density on film

  2. Offered in addition to manual timer
• Two Types of Phototimer

  Photomultiplier Tube converts radiation to light and then light to electrical current; Ionization/Ion Chamber uses gas (Xenon gas) and is commonly referred to as Automatic Exposure Control (AEC)
• Spinning Top Timer


  Device used to check the accuracy of x-ray timer in half wave and full wave rectified units
• Solid State Radiation Detector


  Detects radiation exposure; used for exposure time check and replaces the spinning top timer
• High-Voltage Generator


  Supplies voltage and current to the x-ray tube; responsible for increasing the output voltage from the transformer to the kVp necessary for x-ray production
• Three Primary Parts of High-Voltage Generator

  High-Voltage Transformer (step up), Filament Transformer (step down), Rectifier (diode)
• Rectifier


  Device with two electrodes that allows current only in one direction; converts AC to DC in the process called rectification
• Diodes are used to absorb negative cycle and only swing the positive cycle to be sent to the anode for use in the x-ray tube
• General Types of Rectifiers

  • Vacuum Tube Rectifier, Solid-State Rectifier
• Unrectified Voltage is the voltage waveform supplied to the primary side of the high voltage transformer
• Types of Rectification


  • Half-Wave Rectification, Full-Wave Rectification
• High voltage transformer


  Device that transforms electrical energy from one circuit to another through electromagnetic induction at a higher voltage
• Types of Rectification


  • Half-Wave Rectification
  • Full-Wave Rectification
  • Self-Rectified
• Half-Wave Rectification


  1. The voltage is not allowed to swing negatively during the negative half of its cycle; uses two diodes

  2. Photons are only produced and emitted during the positive cycle; 60 pulses per second
• Full-Wave Rectification


  Contains 4 diodes to reverse the negative cycle to positive for supply back to the x-ray tube; from 60Hz to 120Hz or pulses per second
• Self-Rectified


  Example is x-ray tube that can convert AC to DC but only produce small x-ray and radiation
• Power for X-ray Generation

  • Single-Phase Power
  • Three-Phase Power
• Single-Phase Power


  Supply of electricity; 60-120 pulses per second; symbol for single phase is 1 omega
• Three-Phase Power


  3 line supply in structural institutions; results in higher quantity and quality photons; 6 pulses in half wave, 12 pulses in full wave; symbol for three-phase is 3 omega
• Ripple


  Fluctuation of power
• High Frequency Generator


  • Produces a nearly constant potential voltage waveform, improves image quality at lower patient dose; automatically adjusts to the highest mA at shortest exposure time; works with single or three-phase power
• Capacitor Discharge Generator


  Collects energy before discharging it; stores energy temporarily in electrons; uses a high voltage generator charged by a nickel-cadmium battery; Falling Load Generator is a drop in power at the end of exposure; works in conventional 110 volt power but batteries must be replaced
• Frequency and Energy


  Are directly proportional; use a high-frequency generator to increase energy