**11.6 Advantages of CBCT**

*Periodontal Disease - Diagnostic and Adjunctive Non-surgical Considerations*

ing [40]. These include:

**11.1 Rapid scan time**

20 minutes [41, 43].

**11.2 Beam limitation**

**11.3 Image accuracy**

and orthodontic analysis [42].

**11.5 Limitations of CBCT imaging**

cone-beam-related artifacts:

of high contrasting structures and is therefore particularly well-suited towards the imaging of osseous structures of the craniofacial area. The use of CBCT technology in clinical dental practice provides a number of advantages for maxillofacial imag-

Because CBCT acquires all projection images in a single rotation, scan time is comparable to panoramic radiography. This is desirable because artifact due to subject movement is reduced. Computer time for dataset reconstruction however is substantially longer and varies depending on FOV, the number of basis images acquired, resolution and reconstruction algorithm and may range from ~1 to

Collimation of the CBCT primary X-ray beam enables limitation of the X-radiation to the area of interest. Therefore an optimum FOV can be selected for each patient based on suspected disease presentation and region of interest. While not available on all CBCT systems, this functionality is highly desirable as it pro-

CBCT imaging produces images with sub-millimeter isotropic voxel resolution ranging from 0.4 mm to as low as 0.09 mm. Because of this characteristic, subsequent secondary (axial, coronal and sagittal) and MPR images achieve a level of spatial resolution that is accurate enough for measurement in maxillofacial applications where precision in all dimensions is important such as implant site assessment

Published reports indicate that the effective dose (E) varies for various full field of view CBCT devices from 29 to 477 μSv depending on the type and model of CBCT equipment and FOV selected patient positioning modifications (tilting the chin) and use of additional personal protection (thyroid collar) can substantially reduce dose by up to 40%. These doses can be compared more meaningfully to dose from a single digital panoramic exposure, equivalent CT dose, or the average natural background radiation exposure for Australia (1500 μSv) in terms of background equivalent radiation time (BERT). CBCT provides an equivalent patient radiation dose of 5–80 times that of a single film-based panoramic radiograph, 1.3–22.7% of a comparable conven-

While there has been enormous interest, current CBCT technology has some limitations related to the "cone beam" projection geometry, detector sensitivity and resolution which is contrast. These parameters create an inherent image "noise" that reduces image clarity such that current systems are unable to record soft tissue

Another factor that impairs CBCT image quality is image artifact three types of

contrast at the relatively low dosages applied for maxillofacial imaging.

vides dose savings by limiting the irradiated field to fit the FOV.

**11.4 Reduced patient radiation dose compared to conventional CT**

tional CT exposure or 7–116 days of background radiation.

**58**


#### **11.7 Disadvantages**

The only disadvantage is its cost. But considering the enormous benefits, this cost effect can be overlooked.

Indications of cone-beam computed tomography:

1.Assessment of the jaw which includes:

• Pathological lesions which are bone and soft tissue;

