Lecture 4 Equipment + specification

• Intra-oral equipment must be small, light and manoeuvrable.
• The mains voltage is converted from the available mains to the required voltage by transformers. Mains is converted to low voltage by passing it through a ‘step down transformer’. It is converted to kV through a ‘step up transformer’. A transformer consists of two sets of coils (windings)
• Collimator: internal collimater to restrict beam, external collimator to limit beam to required area. The rectangular collimator reduces dose to the patient by 50%, improving contract and sharpness.
• The purpose of an opg machine is to produce an image of the whole of the mandible and maxilla with a single exposure in one image.
• Pros of an OPG:

  • easy assessment of the relationship between all the teeth and other anatomy.
  • less time consuming for operators
  • less invasice that full mouth PAs
• Cons of OPGs:

  • exposure is 15s so long time for patient to stay still
  • low level fine detail, compared to PAs due to simultaneous movement of the tube and imaging plate.
  • if more detailed required PAs required
• Most modern OPG machines will have three positioning lights to aid successful imaging:

  }  Median sagittal plane indicator

  }  Frankforts plane

  }  Focal trough (this may be set at 2/3 or directly through 3)
• How may the focal trough be set when taking an OPG?

  Moving patient in and out of machine by moving the chin rest, changing the position of central pivot/fulcrum point,
• what is the purpose of the focal trough?

  To endure that 321123 all appear sharp and not blurred
• What is the kV of an OPG?

  60, 70, 80, or set to a predetermines level when button for child or small adult are selected