Extra Oral Radiographs Techniques

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Extra Oral Radiographs Techniques by Mind Map: Extra Oral Radiographs Techniques

1. True lateral and lateral cephalometric projection

1.1. Main indications:

1.1.1. 1. Fractures of the cranium and the cranial base

1.1.2. 2. Middle third facial fractures, to show possible downward and backward

1.1.2.1. displacement of the maxillae

1.1.3. 3. Investigation of the frontal, sphenoidal and maxillary sinuses

1.1.4. 4. Conditions affecting the skull vault, particularly:

1.1.4.1. — Paget's disease

1.1.4.2. — Multiple myeloma

1.1.4.3. — Hyperparathyroidism

1.1.5. 5. Conditions affecting the sella turcica, such as:

1.1.5.1. — Tumour of the pituitary gland in acromegaly.

1.2. Technique and positioning:

1.3. Patient Placement: The patient is positioned so that the left side of the face touches the image receptor and the sagittal plane of the head is parallel to the film. Image Receptor: The image receptor is positioned parallel to the patient's midsagittal plane. Position of the Central X-Ray Beam: The central beam is horizontal (0°) centered over the external auditory meatus, perpendicular to the midsagittal plane of the patient and the image receptor.

2. Lateral oblique projections of the mandibular body / Ramus

2.1. Demonstrate: • Mandibular premolar and molar regions • Inferior border of the mandible

2.1.1. RAMUS: third molar-retromolar area • angle of the mandible • ramus • condyle head

2.2. Head position Head tipped 15° towards the side being imaged (to avoid superimposition of the contra-lateral side) The mandible is protruded and elevated slightly (to avoid superimposition of hyoid bone on the mandible) The patient holds the cassette in position with the thumb under the edge of the cassette and the palm against the outer surface of the cassette

2.3. Image Receptor • The cassette is placed flat against the patient cheek on the side of interest • centered over the molar- premolar area and positioned parallel with body of the mandible • The lower border of the cassette is parallel and at least 2 cm below the inferior border of the mandible.

2.3.1. RAMUS: Over the ramus and far enough posteriorly to include the condyle. • centered over the ramus of the mandible and positioned parallel with it

2.4. is directed toward the molar- premolar region from a point 2 cm below the angle of the opposite side of the mandible upwards (-15 to -20) perpendicular to the horizontal plane of the film.

2.4.1. RAMUS: is directed toward the center of the imaged ramus from a point 2 cm below the inferior border of the opposite side of the mandible at the area of the first molar.

3. Posteroanterior skull projection and posteroanterior cephalometric projection

3.1. Main indications

3.1.1. 1. Fractures of the skull vault

3.1.2. 4. Intracranial calcification

3.1.3. 2. Investigation of the frontal sinuses

3.1.4. 3. Conditions affecting the cranium, particularly:

3.1.4.1.  hyperparathyroidism

3.1.4.2.  multiple myeloma

3.1.4.3.  Paget's disease

3.1.5. 6. Lesions such as cysts or tumours in the

3.1.5.1.  medio-lateral expansion

3.1.5.2.  posterior third of the body or rami to note any

3.1.6. 5. Fractures of the mandible involving the following sites:

3.1.6.1.  Low condylar necks

3.1.6.2.  Rami

3.1.6.3.  Angles

3.1.6.4.  Posterior third of the body

3.1.7. 7. Mandibular hypoplasia or hyperplasia

3.1.8. 8. Maxillofacial deformities.

3.2. Technique and positioning:

3.2.1. Patient Placement: The head is tipped forward, so that the radiographic baseline (canthomeatal line) is horizontal and perpendicular to the film in the forehead-nose position.

3.2.2. Image Receptor: The image receptor is placed in front of the patient, perpendicular to the midsagittal plane and parallel to the coronal plane.

3.2.3. Position of the Central X-Ray Beam: The central beam is perpendicular to the image receptor, directed from the posterior to the anterior, parallel to patient's midsagittal plane, and is centered at the occiput.

4. WATERS PROJECTION (0 OCCIPITOMENTAL PROJECTION)

4.1. Main indications

4.1.1. 1. Investigation of the maxillary antra

4.1.2. 2. Detecting the following middle third facial fractures:

4.1.2.1. — LeFort I

4.1.2.2. — Le Fort II

4.1.2.3. — Le Fort III

4.1.2.4. — Zygomatic complex

4.1.2.5. — Naso-ethmoidal complex — Orbital blow-out

4.1.3. 3. Coronoid process fractures

4.1.4. 4. Investigation of the frontal and ethmoidal sinuses

4.1.5. 5. Investigation of the sphenoidal sinus.

4.2. Technique and positioning:

4.2.1. Patient Placement: The patient's head is tilted upward in the nose- chin position so that the canthomeatal line (radiographic baseline) forms 37 to 45° with the image receptor. If the patient's mouth is open, the sphenoid sinus will be seen superimposed over the palate.

4.2.2. Image Receptor: The image receptor is placed in front of the patient and perpendicular to the midsagittal plane.

4.2.3. Position of the Central X-Ray Beam: The X-ray tubehead is positioned with the central ray horizontal (0°) and perpendicular to the image receptor centered through the occiput.

5. REVERSE TOWNE PROJECTION

5.1. Main indications:

5.1.1. 1. High fractures of the condylar necks

5.1.2. 2. Intracapsular fractures of the TMJ

5.1.3. 3. Investigation of the quality of the articular surfaces of the condylar heads

5.1.4. in TMJ disorders

5.1.5. 4. Condylar hypoplasia or hyperplasia.

5.2. Technique and positioning:

5.3. Patient Placement: The patient's head is tilted downward so that the canthomeatal line forms a -30 degree angle with the image receptor. To improve the visualization of the condyles, the patient's mouth is opened so that the condylar heads are located inferior to the articular eminence.

5.4. Image Receptor: The image receptor is placed in front of the patient, perpendicular to the midsagittal and parallel to the coronal plane.

5.5. Position of the Central X-Ray Beam: The X-ray tubehead is positioned with the central ray horizontal (0°) and perpendicular to the image receptor centered at the level of the condyles.

6. ANTROPOSTERIOR VIEWS: Submentovertex (base) projection

6.1. Main indications

6.1.1. taken with reduced exposure factors.

6.1.2. 4. Fracture of the zygomatic arches — to show these thin bones the SMV is mandible before osteotomy

6.1.3. 3. Assessment of the thickness (medio-lateral) of the posterior part of the

6.1.4. 2. Investigation of the sphenoidal sinus

6.1.5. 1. Destructive/expansive lesions affecting the palate, pterygoid region or base of skull

6.2. Technique and positioning

6.2.1. Patient Placement: The patient's neck is extended as far backwards as possible so the vertex of the skull touches the film with the radiographic baseline (canthomeatal line) is vertical and parallel to the image receptor.

6.2.2. Image Receptor: The image receptor is positioned behind the patient’s head, parallel to the transverse plane and perpendicular to the midsagittal and coronal planes.

6.2.3. Position of the Central X-Ray Beam: The X-ray tubehead is aimed upwards from below the chin, with the central ray at 5° to the horizontal towards the vertex of the skull (hence the name submentovertex, SMV), and centered about 2 cm anterior to a line connecting the right and left condyles.