by Dr. aysha khatri

1. CBCT
Cone Beam Computed
Tomography

2. Principle of CBCT

3. It is recent technology developed in 1982
initially for angiography, subsequently
applied to maxillofacial imaging.
• Other names for CBCT;
• 1) Cone beam volumetric tomography
• 2) Dental volumetric tomography
• 3) Dental computed tomography
• 4) Cone beam imaging.

4. Differences
between
conventional
CT and CBCT
Radiation
beam
shape
Detector
type
Conventi
onal CT
Fane Linear
CBCT Cone Two
dimensio
nal
CBCT
Conventional

5. CBCT
unit
Imaging may
performed with
patient seated,supine
or standing; seated
are most comfortable.
Patient's head
stabilzed and
positioned between
xray generator and
detector by head
holding apperatus.
Scan time is as fast as
5 seconds.

6. IMAGE ACQUISITION
• The cone-beam technique involves rotational scan of xray
source and detector exceeding 180 degrees.
• During this constant beam of radiation cause continuos
exposure to patient, so it is preferable to PULSE the xray beam;
which is done by process known as automatic exposure control.
• Field of view or Region of interest selected according to
patients individual need by collimating primary xray beam.
• Image detected by detector and processing is done by two
computers.
• Export of image data is usually done in DICOM(Digital Imaging
and Communications in Medicine) for use in specialised
software.

7. Display of CBCT reports
• Various ways:
• 1) three orthogonal planes(axial,coronal,sagittal)
• 2) multiplanar ( various nonaxial two I dimensional)
images
• 3) three dimensional volume rendering

8. Orthogonal display
C. sagittal
coronal
D axial

9. Multiplanar reformation

10. Three dimensional display

11. Clinical implications
• 1) Implant site assessment
• 2) localization of inferior alveolar canal
• 3) Conditions of the maxillofacial complex [
Impacted teeth specially canines, fractured teeth,
supernumerary teeth, periapical lesions,
periodontal lesions]
• 4) Temporomandibular joint assesment
• 5) Orthodontics and 3D cephalometry.
• 6) Detection of fractures of maxillofacial region.

12. Implant Site
Assessment
• It is most important and popular use of CBCT.
• Cross sectional images of bone
height,width,angulations and vital structures as
maxillary sinus,inferior alveolar canal can be
accurately located by CBCT.
• The most useful series of images;
• 1)axial 2) panaromic 3) serial transplanar images at
specific location.
• The thickness of slices in transplanar usually up to
1mm.

13. a b
c
a.axial, b.panalromic, c.multipalnar.
Missing mandibular left first molar

14. Bone height between alveolar crest and lower
border of mandible should be mostly 12mm so
2mm space remain between imlplant tip and
mandibular canal.
CBCT also useful during placement of implant
by analyzing annulation and positioning of drills
and fixture to avoid perforation to lingual plate.
After implant placement average marginal bone
loss and periimplant radiolucency can be
verified on follow ups
Other aspects related to implants and
CBCT

15. Missing maxillary left central incisor,verifying
angulation of implant placement

16. Impacted canine assessment
Other uses of CBCT

17. Periapical lesions
Periodontal lesions

18. Tooth fracture detection

19. Temporomandibular joint
assessment

21. Jaw fracture site detection; mandible body fracture.

22. Pathological evaluation
Central Giant Cell Granuloma
Sialolith in
submandibular gland

23. Strength and Limitations
• Advantages over conventional CT.
• Size and cost reduced to1/4 to 1/5 .
• Scanning time reduced.
• Resolution can be achieved up to sub millimeter level
ranging from 0.4mm to 0.125 mm.
• Patient radiation dose reduced up to 52 to 1025
microsieverts which is between 51% to 96% less than
CT.

24. Disadvantage over conventional CT.
• Image noise: Due to cone beam projection
geometry, scattered radiation is produced which
produces image noise.
• Poor Soft tissue contrast: xray scatter also reduces
contrast between different tissues.