Radiography

2 dimensional (2D) view

Shadow image

All structures superimposed

Must angulate multiple images to infer 3D information

High resolution images
2D Radiography

Foreign Objects

Buccal Object Rule

Vertical Angulation
Radiographs vs. CBCT
Advantages:

Three-dimensional view

Direct measurements possible

Can see osseous lesions better than radiographs
Disadvantages:

Poorer resolution than radiographs

Increased radiation dosage to patients

Increased cost

Learning curve

Liability of the reader o Send out to radiologist
3D Radiography

Fan Beam Computed Tomography o Medical Imaging

Cone Beam Computed Tomography o Medical and Dental Imaging

Micro-Computed Tomography o research only to date
Fan Beam vs Cone Beam
Voxel – 3 dimensional pixel (volume pixel)
Planes of View

Sagittal

Coronal

Axial

Field of View - The Volume that is Imaged

Large FOV o Medical

Medium FOV o Medical and Dental o iCAT

Small FOV o Dental o Kodak 9000 (CareStream) o Veraviewepocs 3D (J. Morita)
Endodontics = Small FOV
Small FOV
Advantages

Higher resolution image

Lower radiation dosage

Lower cost

Less liability
Disadvantages

Difficult to image the entire jaw

Unsuitable for orthodontics or extensive implant case

Cannot make panoramic view
Resolution

Smaller voxel size = Higher resolution

Limited number of voxels that can be manipulated with commonly occurring computer processing power

Smaller FOV uses the same number of voxels as larger FOV but in a smaller space

Therefore smaller FOV = smaller voxels = greater resolution
Relative Effective Dosages
•Annual background radiation
•4 BW (Digital or F-speed, Rectangular Collimation)
•FMX (Digital or F-speed, Rectangular Collimation)
•FMX (D-speed, Round Collimation)
•Panoramic (Digital 2 brands)
•Chest Radiograph
•Lower GI Tract Radiograph
•CT Chest
3100 µSv
5 µSv
35 µSv
388 µSv
14-24 µSv
100 µSv
8000 µSv
7000 µSv

•CT (Maxillofacial Large FOV* 4 brands)
•CT (Maxillofacial Medium FOV* 8 brands)
•CT (Maxillofacial Small FOV* 5 brands)
•Airplane Round Trip to Florida
•Radon Gas (in our homes)
74-569 µSv
69-860 µSv
23-488 µSv
30 µSv
2000 µSv
Liability
“…the clinician can be liable for a missed diagnosis, even if it is outside his/her area of practice.” - AAE/AAOMR Position Statement
Should I take one on Every Patient?
“CBCT should only be used when the question for which imaging is required cannot be answered adequately by lower dose conventional dental radiography or alternate imaging modalities.” - AAE/AAOMR Position Statement
Software Interface
Clinical Outcomes
Assessment Criteria

Healed (Success)

Healing (Questionable)

Disease (Failure)
Healed (Success)

No PA Radiolucency

Asymptomatic

Clinical Signs WNL
Healing (Questionable)

PA Radiolucency Reduced

Asymptomatic

Clinical Signs WNL
OR

No Pa Radiolucency

Clinical Signs WNL

Mild Symptoms
Disease (Failure)

Overt Signs of Infection o Sinus Tract o Swelling o Increased Size of Radiolucency

Symptoms
Difficulty with Outcomes Assessments
 Difficulty in setting up double blinded RCT’s


Large variation in pre-existing patient factors

Prevents randomization process

Blinding clinician difficult

Blinding patient may be unethical
Validity of Outcomes Studies in Question

Radiographic Assessment vs CBCT

Outcomes Criteria o Radiographic

Strindberg Criteria

Periapical Index (PAI) o CBCT

???
Indications

Difficult Diagnosis

Treatment Planning

Resorption o Internal or External? o Extensive or Limited? o Prognosis?