PRINCIPLES OF RADIOGRAPHIC EXAMINATION

In the Land of 10,000 lakes,…

…we see the fish!

Liar, Liar!! Do Our Eyes Lie?

Radiographic interpretation as you do all other aspects of evaluation – systematic and repetitive

NORMAL VS. ABNORMAL•Anatomy (hard tissue, soft tissue)•Variants (torus, root shape)•Pathology ( decay, bone loss, disease

VIEWING CONDITIONS:Ambient light in the viewing room should be reduced Intraoral radiographs should be mounted in a film

holder Light from the view box should be of equal intensity

across the viewing surfaceThe size of the view box should accommodate the size

of the filmAn intense light source is essential for evaluating dark

regions of the filmA magnifying glass allows a detailed examination of

small regions of the film

2 basic approaches can be used:

1) Picture matching or ”Aunt Minnie” method

This involves trying to match the radiographic image with a mental picture or with a image in a favorite textbook.

2) systematic and repetitive

Step by step analysis of all the radiographic characteristics of the abnormality and production of a radiographic interpretation on the basis of these findings.

Helps to ensure recognition and collection of all the information contained in the image and in turn improves the accuracy.

• STEP;1 Localize The Abnormality

Localize The AbnormalityLocalized or Generalized• The anatomic location and limits of the abnormality should be

described. This information aids in starting to select various disease categories.• If an abnormal appearance affects all the osseous structures of the

maxillofacial region, Generalized disease mechanisms, • Metabolic or• Endocrine abnormalities of bone, are considered.

Localized unilateral or bilateral.

• Variations of normal anatomy are more commonly bilateral. • For instance, a bilateral mandibular radiolucency may indicate normal

anatomy, such as extensive submandibular gland fossa.

• Abnormal conditions are more commonly unilateral. • For instance, fibrous dysplasia commonly is unilateral. This is not to

say that localized pathologic lesions cannot occur bilaterally in the maxillofacial region. • A few abnormalities, such as Paget’s disease and cherubism, are

always seen bilaterally in the jaws.• when cherubism involves the mandible, the first region to be

involved is in the midramus region, and this is the mechanism behind the anterior displacement of molars.

Position in the Jaws

• Identifying the exact location of the lesion in the maxillofacial complex aids the diagnostic process in two ways:

• (1) It determines the epicenter • (2) Some lesions tend to be found in specific locations.

• Epicenter - the point of origin assists in indicating the tissue types that compose the abnormality in question.• The epicenter can be estimated on the basis of the assumption that

the abnormality grew equally in every direction. • This estimation may become less accurate with very large lesions or

lesions with ill-defined boundaries

If the epicenter is coronal to a tooth, the lesion probably is composed of odontogenic epithelium

A, Cropped panoramic image of a lesion where the epicenter is coronal to the unerupted mandibular first molar. B, Occlusal projection providing a right-angle view of the same lesion

If it is above the inferior alveolar nerve canal (IAC), the likelihood is greater that it is composed of odontogenic tissue

Panoramic image revealing a cystic ameloblastoma within the body of the left mandible. The inferior alveolar nerve canal has been displaced inferiorly to the inferior cortex (arrows), indicating that the lesion started superior to the canal

If the epicenter is below the IAC, it is unlikely to be odontogenic in origin

Cropped panoramic image displaying a lesion (developmental salivary gland defect) below the inferior alveolar canal and thus unlikely to be of odontogenic origin

If it originates within the IAC, the tissue of origin probably is neural or vascular in nature

Lateral oblique view of the mandible revealing a lesion within the inferior alveolar canal. The smooth fusiform expansion of the canal indicates a neural lesion

If the epicenter is within the maxillary antrum, the lesion is not of odontogenic tissue, as opposed to a lesion that has grown into the antrum from the alveolar process of the maxilla

The lack of a peripheral cortex (arrows) on this retention pseudocyst indicates that it originated in the sinus and not in the alveolar process. Therefore, it is unlikely to be of odontogenic origin

• The probability of cartilaginous lesions and osteochondromas occurring is greater in the condylar region.

• The other reason to establish the exact location of the lesion is that particular abnormalities tend to be found in very specific locations. Following are a few examples of this observation:

• The epicenters of central giant cell granulomas commonly are located anterior to the first molars in the mandible and anterior to the cuspid in the maxilla in young patients.• Osteomyelitis occurs in the mandible and rarely in the maxilla.• AOT• Globulomaxillary cyst• Stafne’s cyst vs ABC

• Single or Multifocal• Establishing whether an abnormality is solitary or multifocal aids in

understanding the disease mechanism of the abnormality. Additionally, the list of possible multifocal abnormalities in the jaws is relatively short. • Periapical cemental dysplasia, • Keratocystic odontogenic tumors, • Metastatic lesions,• Multiple myeloma • leukemic infiltrates.

Exceptions to all these points may occur occasionally. However, these criteria may serve as a guide to an accurate interpretation

Cropped panoramic film revealing several small, punched-out lesions of multiple myeloma (a few are indicated by arrows) involving the body and ramus of the mandible

Size

•Finally, the size of the lesion is considered. There are very few size restrictions for a particular lesion, but the size may aid in the differential diagnosis. •differentiating between a dentigerous cyst and a hyperplastic follicle

STEP 2: ASSESS THE PERIPHERY AND SHAPE

Study the periphery of the lesion2 types:

◦Well defined

◦Ill defined

WELL DEFINED BORDERS:Punched out border

Sharp boundary no bone reaction Analogous to punching a hole in a radiograph Normal surrounding bone upto the edge of the hole

Corticated margin

• Thin• Fairly uniform- Radiopaque line• Reactive bone at the periphery of the lesion

Sclerotic margin

• Wide• Non-uniform• Radiopaque- Reactive bone• Indicate- very slow rate of growth

Radiolucent borders

R.Opaque lesions may have soft tissue capsule

Seen in conjuction with corticated periphery

Ill- defined bordersBlending border◦ Is ill defined because of gradual transition between

normal appearing bone trabeculae and abnormal appearing trabeculae of the lesion .

◦Example: Sclerosing osteitis Fibrous dysplasia

Invasive border• Rapid growth / Malignant lesions• Area of radiolucency with fewer or no trabeculae • Represents marginal bone destruction• Produces radiolucent fingerlike or bay-type extension at the

periphery• Eg; Malignant lesions

Shape:- Lesion may have a particular shape or it may be

irregular.- Eg: a circular /fluid filled shape/ inflated balloon -

referred to as hydraulic is a characteristic of cyst.

Scalloped shape

•Series of contiguous arcs or semicircles- reflects the mechanism of growth•Provides a multilocular appearance•Okc,Ameloblastoma

STEP 3 –ANALYSE THE INTERNAL STRUCTURE

Internal appearance of the lesion can be classified into three basic categories:

- Totally radiolucent- cyst - Totally radiopaque –osteomas -Mixed radiolucent and radiopaque

Radiolucent Radiopaque Mixed (RL-RO)

Radiodensity

Fuzzy or irregular trabeculae.

STEP 4 – ANALYSE THE EFECTS OF THE LESION OF SURROUNDING STRUCTURES

• Evaluating the effects of the lesion on the surrounding structures allows the observer to infer its behavior which aids in identification of the disease.

• But this requires the knowledge of the mechanisms of various diseases.

Teeth, lamina dura and periodontal space

Displacement of the teeth is seen more commonly with smaller growing space occupying lesions.

Widening of the periodontal membrane space may be seen with many diff kinds of abnormalities.

Resorption of the teeth usually occurs with more chronic or slowly growing process and may result from chronic inflammation.

Surrounding bone density and trabecular pattern

The presence of reactive bone at periphery of a lesion, whether corticated or sclerotic, usually signifies slow , benign growth and possibly the ability to stimulate osteoblastic activity in the surrounding bone.

Inferior alveolar nerve canal and mental foramen

Outer cortical bone and periosteal reactions

STEP 5; FORMULATE A RADIOGRAPHIC INTERPRETATION

The preceding steps enable the observer to collect all radiographic findings in an organized fashion.

Decision 1:The practitioner should determine whether the structure

of interest is a variation of normal or represents an abnormality-crucial decision

Decision 2:If the area of interest is abnormal , the next step is to

decide whether the radiographic characteristics indicate that the region of interest represents a developmental or an aquired change.

Decision 3: If the abnormality is acquired the next step is to select the

most likely category of acquired abnormality: cysts, benign tumors, malignant tumors, inflammatory lesions, bone dysplasias, vascular abnormalities, metabolic diseases, or physical changes such as fractures.

Decision 4:After analysing the images, the clinician must

decide in what way to proceed- further imaging treatment biopsy or observation of the abnormality

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