Principles of radiographic interpretation

RADIOGRAPHIC INTERPRETATION

Interpretation:
Step by step analytical process that provides an exact idea of the clinical problem and helps to achieve the final diagnosis of any particular lesion.

I-Essential requirements for interpretation

1- Optimum viewing conditions
2- Understanding the nature and limitations of the black,
white and grey radiographic image.
3- Knowledge of what the radiographs used in dentistry
should look like, so a critical assessment of individual film
quality can be made.
4-Detailed knowledge of the range of radiographic
appearances of normal anatomical structures.
5- Detailed knowledge of the radiographic appearances of the
pathological conditions affecting the head and neck.
6- A systematic approach to viewing the entire radiograph and
to viewing and describing specific lesions.
7- Access to previous films for comparison.


1- Optimum viewing conditions

• An even, uniform, bright light viewing screen

(preferably of variable intensity to allow viewing
. of films of different densities)
.• A quiet, darkened viewing room
• The area around the radiograph should be
masked by a dark surround so that light passes
only through the film.
• Use of a magnifying glass to allow fine detail to be
seen more clearly on intraoral films.
• The radiographs should be dry.

• Steps of interpretation

• Localization.
• Observation.
• General consideration.
• Interpretation.
• Correlation.


Localization:

Localized or generalized.

Position in the jaw.
Single or multiple.
Size.

Observation:

All shadows, other than the localized shadows of the normal landmarks must be observed.

For example: shadows in crowns, cervical area, roots, restorations, size of root canals, periodontal membrane space, periapical area, alveolar crest, foreign bodies, integrity of bone.

General consideration:

A radiograph shows only 2 dimensions of a 3 dimensional object (width and height but not the depth)
Cervical burnout: usually appears as cervical Radiolucency and misinterpreted by caries; this occurs due to less density and more penetration of rays.
Pulp exposure: never to be determined from radiograph but only the proximity to the pulp.

Interpretation:

Studying the features of teeth and bone:
Teeth
Study the whole tooth,(crown, root, enamel, pulp), number of teeth and finally supporting structures, (Periodontal membrane space, lamina dura , alveolar crest).


Bone:

Changes in bone may include:

1- Changes in density.
2- Changes in the margin.
3- Changes inside the lesion.
4- Effect on surrounding tissues.
5- Changes in structure.

Correlation:

The final step is to correlate all of the radiographic features to reach a radiographic differential diagnosis.
Then to draw a final diagnosis, we have to correlate other data as case history, clinical examination, and other diagnostic aids with the radiographic differential diagnosis

Image analysis

Identify normal anatomic landmarks.
Knowledge of normal v/s abnormal.
Attention to all regions on the film systematically.
Three visual circuits.

First visual circuit: intraoral images

Periapical before bitewing images
Right maxilla to left; left mandible to right
One anatomic structure at a time:Ex: posterior maxilla-maxillary sinus,tuberosity,zygomatic process
Normal anatomy: Ex: bones, canals, foramina.
Check for symmetry.


Use a systematic process
• Go back to the first quadrant and look at the trabecular pattern. Is it:
• Normal
• Symmetrical when compared to the contralateral
• side
• Sparse
• Dense
• In the direction of anatomical stress
• Altered

Second visual circuit

Examination of bone:
Height of alveolar bone
Crest relative to teeth
Loss of height-more than 1.5 mm-periodontal disease
Lamina dura + PDL space + tooth roots
Carcinoma-erosion of alveolar crest+ ill defined borders.

Third visual circuit

Examination of dentition & associated structures
Number, Sequence, appearance, root structure
Crowns –defective enamel, caries
Intreproximal areas & restorations
Pulp chambers-size, content
Bone-radioluscent/radioopaque lesions