Cone beam CT

Dr Henry Knipe et al.

Cone beam CT (CBCT) is a variant type of computed tomography (CT), and is used particularly in dental and extremity imaging. It differs from conventional CT in that it uses cone-shaped x-ray beam and two dimensional detectors instead of fan-shaped x-ray beam and one dimensional detectors. 

Physics

In CBCT, a divergent cone-shaped source of radiation is directed through the target. The attenuated x-rays are detected on the opposite side by an x-ray detector, which has multiple dexels in the x and y-axis 2. Volume acquisition can thus be acquired with fewer rotations of the x-ray tube gantry. This differs from fan-beam CT, which uses a 2D fan-shaped x-ray beam in helical progression to acquire image data. Furthermore, fan-beam CT detector only has dexels in the x-axis.

The advent of CBCT has brought about several advantages over its fan-beam counterpart, but it also has its inherent disadvantages. 

Advantages
  • decreased examination time
  • decreased patient movement artifact
  • increased x-ray tube efficiency 3
Disadvantages
  • increased scattered radiation
  • potential for cone beam artifact if an inappropriate reconstruction algorithm is used

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Article Information

rID: 46277
Section: Physics
Synonyms or Alternate Spellings:
  • Cone beam CT scan
  • CBCT

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Cases and Figures

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    Figure 1: comparison of fan beam and cone beam CT
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    Case 1
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    Case 2
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    Case 3: mesially impacted wisdom teeth
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    Case 4: maxillary cyst
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