Diagnostic Utility of Cone Beam Radiography

This advanced, three-dimensional imaging technology can aid diagnoses and treatment planning.

By Carol H. Naylor, DMD, RDH and Rex T. Christensen, MHA, RT(R)(MR)(CT)(ARRT) CIIP, MRSO (MRSC) On May 2, 2017

This advanced, three-dimensional imaging technology can aid diagnoses and treatment planning

Advances in three-dimensional (3D) imaging units and software can help clinicians in the diagnosis of maxillofacial pathology, thereby enhancing treatment planning that ultimately contributes to improved outcomes. Today’s diagnostic tools reduce patient risk through improved imaging capability, which also assists practitioners in the early detection of oral anomalies. Cone beam computed tomography (CBCT) uses the universal imaging format known as digital imaging and communications in medicine — perhaps best known by the acronym DICOM. This technology allows the use of software to view areas of interest in other planes, in addition to grayscale values.¹

Interactive diagnostic imaging is a software technology used in maxillofacial diagnosis. It derives from medical imaging and is primarily used in computed tomography (CT) and magnetic resonance imaging. The term “3D advanced visualization technique” describes this type of image data manipulation.

**FIGURE 1.** The use of three-dimensional advanced visualization software enables views of the coronal, sagittal and axial planes. This image of the case study patient shows a reconstructed inverted coronal view. The red arrow is pointing to a cystic lesion in the left maxilla region. *COURTESY BRETT D. NAYLOR, DDS, FICOI*

**FIGURE 2.** This view is of the case study patient’s reconstructed inverted sagittal plane. The red arrow is pointing toward the cyst in the left maxilla region. *COURTESY BRETT D. NAYLOR, DDS, FICOI*

The information stored in a CBCT scan can be used to display reformatted images of various anatomical planes to aid diagnosis. Current software offers the ability for multiplanar imaging and reformatting; other clinically useful features include magnification, annotation and window/leveling — which allow grayscale manipulation for enhanced viewing.²

**FIGURE 3.** The reconstructed inverted axial view is shown here. The case study patient’s cyst in the left maxilla region is seen near the red arrow. *COURTESY BRETT D. NAYLOR, DDS, FICOI*

Multiplanar imaging is the standard 3D mode offered by most imaging software. It can be used to view images in the coronal, sagittal and axial planes throughout the data volume set. Figure 1 through Figure 3 demonstrate the three planes with the window/leveling inverted to display the dental anatomy in extensive detail.

**FIGURE 4.** This axial inverted image with curved reformat planing (red line) demonstrates the maxillo facial region, and is similar to a panoramic view. *COURTESY BRETT D. NAYLOR, DDS, FICOI*

**FIGURE 5.** In this curved reformat inverted image of the case study patient, the red arrow is pointing to the cyst located in the left maxilla region. This view is similar to a traditional panoramic X-ray. *COURTESY BRETT D. NAYLOR, DDS, FICOI*

A curved plane reformat image can also be created along the curve of the maxilla or mandible on the axial plane to display the volume set in a panoramic view. The curve can be adjusted specifically to the patient’s maxilla or mandible, providing even more accurate detail when creating a panoramic projection (Figure 4 and Figure 5).

ADDITIONAL TOOLS

Segmentation is another feature that enables clinicians to extract or isolate specific structures in the 3D model. This tool is useful in diagnosis and treatment planning because superficial structures (e.g., soft tissue) that may inhibit the ability to visualize the area of interest can be digitally removed. In addition, color rendering can be used to highlight various brightness/grayscale values. This is similar to attenuation values, called Hounsfield units, in medical CTs (Figure 6).³

**FIGURE 6.** A three-dimensional, color-rendered image highlights different brightness/grayscale values. *COURTESY BRETT D. NAYLOR, DDS, FICOI*

Surface-shaded display and maximum intensity pixels (MIP) are also valuable software tools that can aid diagnosis and treatment planning. The former provides an overall view of anatomical structures and surface morphology that can be manipulated and viewed at various angles. This is useful for examining the alignment of the maxilla and mandible in the anterior-to-posterior position, as well as the alignment along the left and right lateral margins of the maxilla and mandible. By comparison, MIP displays the brightness voxel values within the data set. This tool can remove all superficial structures that may be superimposed over the bony anatomy (Figure 7).⁴ An inverted MIP projection that provides a reversed grayscale view of the anatomical structures is seen in Figure 8.

**FIGURE 7.** Maximum intensity pixel images display only the brightness voxel values within the data set, removing all superficial structures that may be superimposed over the bony anatomy. *COURTESY BRETT D. NAYLOR, DDS, FICOI*

**FIGURE 8.** This inverted maximum intensity pixel image shows a reversed grayscale view of the anatomical structures. *COURTESY BRETT D. NAYLOR, DDS, FICOI*

Some CBCT software (especially older programs) may not have the ability to perform these cutting-edge 3D and interactive features. Dental practices should consider using advanced visualization software in order to improve diagnostic accuracy.

CASE STUDY

A 23-year-old woman visited a dental practice complaining of “squishy gum tissue” associated with the maxillary left third molar region. The clinical team did not note facial asymmetry. The patient’s second molars had been removed for orthodontic reasons, and her third molars had been orthodontically guided into the second molar position. She was compliant with her recare schedule and was in good oral health.

The patient reported pain in the maxillary left third molar region and said she was able to drain the swollen area with digital pressure. An oral exam revealed an expansile purulent lesion approximately 14 mm in diameter superior and distal to the maxillary left third molar. A panoramic radiograph revealed a radiolucency superior and distal to #16 (Figure 9). The lesion appeared to be extending into the sinus.

**FIGURE 9.** This panoramic radiograph of the case study patient shows the presence of a radiolucent lesion (red arrow). *COURTESY BRETT D. NAYLOR, DDS, FICOI*

Determining the cause of this radiolucency was difficult to ascertain on the panoramic X-ray, so CBCT scans were taken. The scans demonstrate the three planes, with the window/leveling inverted to display the dental anatomy in greater detail (Figure 1 through Figure 3). The red arrows indicate the purulent lesion. These additional views clearly outline the cystic lesion in three planes, as well as the reconstructed panoramic view. The data provided by the scans provide enhanced clinical understanding of the lesion’s orientation to the surrounding anatomical structures.

The patient’s clinical history and images were submitted to an oral pathology laboratory that described the lesion as a 2-cm unilocular cyst posterior to #16 in the maxilla. The differential diagnosis was based on the patient’s history, radiographs and clinical examination. The histological exam conclusively indicated the lesion was a keratocystic odontogenic tumor. With additional utilization of CBCT radiology, the precise location was noted and the tumor was surgically excised with little trauma to the surrounding tissue.

CONCLUSION

This case study illustrates how 3D visualization technology is a valuable addition to clinical practice for the diagnosis of dental pathology and enhanced treatment planning. The implementation of CBCT provides clinicians with additional dynamic tools that allow manipulation of the image data and visualization of specific anatomical areas. The ability to manipulate image grayscales and anatomical planes using sophisticated software assists dental professionals in achieving optimal outcomes.

KEY TAKEAWAYS

Cone beam computed tomography (CBCT) allows clinicians to use specialized software to view areas of interest in other planes and enhance images in a manner that aids diagnosis and treatment planning.
Multiplanar imaging is the standard three-dimensional (3D) mode offered by most CBCT imaging software. It can be used to view images in the coronal, sagittal and axial planes throughout the data volume set.
A curved plane reformat image can also be created along the curve of the maxilla or mandible on the axial plane to display the volume set in a panoramic view.
Segmentation enables clinicians to extract or isolate specific structures in the 3D model to better visualize areas of interest.
Color rendering can be used to highlight various brightness/grayscale values to help improve diagnostic capability.
The ability to manipulate CBCT images and anatomical planes using sophisticated software assists dental professionals in achieving optimal outcomes.

References

Dreyer KJ, Hirschorn DS, Thrall JH, Mehta A. PACS: A Guide to the Digital Revolution. 2nd ed. New York: Springer Science+Business Media Inc; 2006:447–451.
Scarfe WC, Farman AG, Sukovic P. Clinical applications of cone-beam computed tomography in dental practice. J Can Dent Assoc. 2006;72:75‒80.
Seeram E. Computed Tomography: Physical Principles, Clinical Applications, and Quality Control. 3rd ed. St. Louis: Saunders Elsevier; 2009:94‒95.
Angelopoulos C, Aghaloo T. Imaging technology in implant diagnosis. Dent Clin North Am. 2011;55:141‒158.

The authors have no commercial conflicts of interest to disclose.

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From Decisions in Dentistry. May 2017;3(5):24—26.