Cone Beam CT in Practice

• Factors that may influence the justification of a CBCT:

  • Pathology - what pathology you want to see (CBCT can sometimes not show this, so we have to be careful with it)
  • Competence - need to have been trained to use the equipment and how to interpret the images
  • Consent - patient consent is important
  • Risk/benefit - risk/benefit to the patient is important to consider
  • Dose - what radiation doses can we justify using?

  
• Cone Beam CT scanner = an x-ray cone beam produced by an x-ray tube that is spun around the patient. The data is collected on a flat panel detector.

  
• CBCT scans are low-dose examinations and give an x-ray dose to the pt that is normally considerably less than a medical CT scan. A normal CT scan of the jaws gives a radiation dose equivalent to approximately 63-15 days of background radiation (the x-radiation constantly present in the environment). A CBCT scan of the jaws would be comparable to approximately 6-30 days of normal background radiation. So a CBCT scan of the jaws will give approximately 1/5 to 1/10 of the dose of a conventional CT scan of the same area.
• Justification and authorisation need to occur before the x-ray is carried out:

  • Where is this recorded?
  • Is this a standardised approach?
  • Have you considered emergency situations when it may not be possible for this to happen prior to the exposure?
• Dose limitation:

  • Restrict the FOV (Field of View)
  • Use the shortest time
  • Use the largest voxel size where possible (S/N ratio)
  • Assess advice re-justification... OMF radiologist