Features of an Optimal Panoramic Radiograph

There are two general features that distinguish this panoramic from a poor one – they are adequate exposure and correct anatomic representation.

Figure 31. Example of an excellent edentulous panoramic radiograph with adequate exposure and correct anatomic representation.

Figure 31. Example of an excellent edentulous panoramic radiograph with adequate exposure and correct anatomic representation.

Adequate exposure – An assessment of adequate exposure implies that there is adequate density (overall darkness) and contrast (differences in density) to recognize anatomic features.

• Density

   

  - The ideal density should be such that structures are not obstructed by areas of darkness i.e. areas of “burn out” or areas that are too light i.e. areas of “white out”. Visually this can be assessed by looking at the mandibular parasymphyseal area and region associated with the apices of the maxillary teeth. In the maxilla this is most evident when the tongue is not held in position during panoramic exposure.

   

  Excessive or inadequate density

   

  can lead to failure to detect features such as unerupted and impacted teeth or even pathology. A dark or high-density image is usually caused by overestimation of the patient’s overall size, stature, and bone density while a light or low-density image is usually caused by underestimation of the patient’s overall size, stature, and bone density.

Figure 32.Regions on a panoramic radiograph to look at to determine adequate density.

Figure 32.Regions on a panoramic radiograph to look at to determine adequate density.

Figure 33.Example of an overexposed panoramic radiograph.

Figure 33.Example of an overexposed panoramic radiograph.

Example of an overexposed panoramic image:

Images demonstrating how excessive exposure can lead to failure to detect pathologic features. The image on the right is a digitally enhanced version of the left overexposed panoramic radiograph and clearly demonstrates the appearance of a radiolucent region causing expansion and thinning of the inferior cortex of the right mandible – features that were not evident on the original.

Figure 34a.

Figure 34a.

Figure 34b.

Figure 34b.

Images demonstrating how excessive exposure can lead to failure to detect pathologic features. The image on the right is a digitally enhanced version of the left overexposed panoramic radiograph and clearly demonstrates the appearance of a radiolucent region causing expansion and thinning of the inferior cortex of the right mandible – features that were not evident on the original.

Example of an underexposed panoramic image:

Images demonstrating how inadequate exposure can lead to failure to detect pathologic features. This image on the right is a digitally enhanced version and clearly demonstrates the appearance of an impacted mandibular right third molar that was not readily apparent on the original (left). This enhancement also clearly demonstrates a large pericoronal lesion that involves the right second mandibular molar.

Figure 35a.

Figure 35a.

Figure 35b.

Figure 35b.

Images demonstrating how inadequate exposure can lead to failure to detect pathologic features. This image on the right is a digitally enhanced version and clearly demonstrates the appearance of an impacted mandibular right third molar that was not readily apparent on the original (left). This enhancement also clearly demonstrates a large pericoronal lesion that involves the right second mandibular molar.

• Contrast – The second element of adequate exposure assessment is contrast. This can best be assessed by determining if the interface between the enamel and the dentine can be seen, usually in the molar region. The dentinoenamel junction (DEJ) should be apparent.

Figure 36. Assessment of contrast in panoramic radiograph.

Figure 36. Assessment of contrast in panoramic radiograph.

Anatomically representative – A panoramic should be a good representation of the maxillofacial structures that it images. This means that there is adequate coverage of the osseous structures and that they are represented with some degree of accuracy. To determine correct anatomic representation, a visual assessment of the panoramic radiograph should be performed for accuracy of both anatomic structures and the dentition.

• Anatomic assessment – Several features can be used to determine anatomic accuracy including:

  • The condyles are on image – Usually in the upper outer sextant and at same level.

  • Palate and ghost images of palate should be above the apices of the maxillary teeth, running through the lower portion of the maxillary sinus.

  • Ramus width should be similar on both left and right sides.

Figure 37. Anatomic features to be compared in the assessment of panoramic anatomic accuracy.

Figure 37. Anatomic features to be compared in the assessment of panoramic anatomic accuracy.

Panoramic anatomy – A reference for anatomic structures commonly observed on panoramic diagram appears below. Many of these structures are mentioned in the prior text and in the subsequent discussion of common errors.

Figure 38.

Figure 38.

Features of the Dentition – Several visual features of the dentition can be used to assess whether the teeth, particularly the anterior teeth are positioned correctly within the focal trough:

• No or slight upward curve of teeth

• No tooth size discrepancy on left or right side

• Anterior teeth in focus (see pulp canal clearly)

• Anterior teeth shape “normal”

• Not too narrow or too wide

• Premolars will always overlap due to inherent x-ray beam projection to the arch of the teeth in this region.

Figure 39 - Features of the dentition to be compared in the assessment of panoramic anatomic accuracy.

Figure 39 - Features of the dentition to be compared in the assessment of panoramic anatomic accuracy.