Cone-beam Computed tomography

Principle:
CBCT scanners utilize a 2D detector and cone-shaped source of ionizing radiation allowing for a single rotation of gantry to generate a scan of the entire region of interest.
How does it work?

X-ray generation:
3D X-ray beam with circular collimation → Cone shaped beam
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Image detection system:
Image intensifier tube/ charged coupled device combination or flat panel detector arrays
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Image reconstruction:
Acquisition of single projection images known as “basis” images and reconstruction using Feldkamp software algorithm
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Image display:
Axial, sagittal and coronal planes

Diagnostic value:
1. Dentomaxillofacial imaging
2. Orthodontic planning
3. Periodontal diseases
4. TMJ analysis
5. Cephalometric analysis
6. Jaw pathologies
7. Radiotherapy guidance
8. Implant site assessment
9. Impacted tooth evaluation

Medical applications:
1. Interventional radiography
2. Angiography
3. Mammography
4. Airway assessment

Benefits:
1. Size: reduced
2. Cost: ¼ to 1/5 of conventional CT
3. Rapid scan time: less than 30 seconds
4. Submillimeter resolution: 0.4 mm to as low as 0.125 mm
5. Patient dose reduction: 52-1025 μSv = 4-77 digital panoramic radiographs
6. Interactive analysis: for real-time dimensional assessment and measurements
7. Image artifact: reduced

Limitations:
1. Image noise
2. Poor soft tissue contrast

Conclusion:

The ability of CBCT to provide images in three dimensions with a high level of detail makes it a very attractive method for many dental applications.
There is no doubt that cone-beam technology will become an important tool in dental and maxillofacial imaging over the coming decades.
 

Literature

1. White SC, Pharoah MJ. Oral Radiology – principles and interpretation. 6th edn. India: Elsevier; 2009. p.225-243.
2. Miracle AC, Mukherji SK. Conebeam CT of the head and neck, Part 2: clinical applications. Am J Neuroradiol 2009 Aug;30:1285–92.
3. Scarfe WC, Farman AG. What is cone-beam CT and how does it work. Dent Clin North Am 2008;52:707-730.
    

Abbreviations

2D - 2 dimensional
CT - Computed tomography
CBCT - Cone-beam computed tomography