Facial bone projection 1

ByDr/ Dina Metwaly

Severe trauma to the facial area usually proceeds to CT with 2D and possibly 3D reconstructions.

Facial radiographs remain a useful screening tool for lesser trauma with the advantages of lesser cost and radiation.

Human facial bones are (14): Inferior nasal concha (2) Lacrimal bones (2) Mandible Maxilla (2) Nasal bones (2) Palatine bones (2) Vomer Zygomatic bones (2)

Facial Bone Radiography

A good facial bone exam is based primarily on three projections:

1.Lateral2.True Waters (occipito-mental)3.Modified mento-occipital

In cases of injury, this projection should be taken using a horizontal beam in order to demonstrate any fluid levels in the paranasal sinuses. The patient may be positioned erect or supine.

Position of patient and cassette Erect The patient sits facing the vertical Bucky or cassette holder of the

skull unit. The head is rotated (not preferred in case of trauma), such that the

side under examination is in contact with the Bucky or cassette holder.

The arm on the same side is extended comfortably by the trunk, whilst the other arm may be used to grip the Bucky for stability.

The Bucky height is altered, such that its centre is 2.5 cm inferior to the outer canthus of the eye.

Supine The patient lies on the trolley, with the arms extended by the sides

and the median sagittal plane vertical to the trolley top. A gridded cassette is supported vertically against the side under

examination, so that the centre of the cassette is 2.5cminferior to the outer canthus of the eye.

THE LATERAL PROJECTION

Direction and centring of the X-ray beam• Centre the horizontal central ray to a point 2.5 cm inferior to the outer canthus of the eye.Essential image characteristics• The image should contain all of the facial bones sinuses, including the frontal sinus and posteriorly to the anterior border of the cervical spine.• A true lateral will have been obtained if the lateral portions of the floor of the anterior cranial fossa are superimposed.

Did you note the air-fluid levels in the maxillary sinuses? These can be due to sinusitis

but in the setting of acute trauma may be a clue to bleeding and an orbital floor fracture.

Position of patient and cassette the patient is seated facing the vertical

Bucky. The nose and chin are placed in contact

with the midline of the cassette holder. The head is then adjusted to bring the OML

to a 45-degree angle to the cassette holder. The horizontal central line of the

Bucky/cassette holder should be at the level of the lower orbital margins.

THE WATERS VIEW(OM)

45°

Direction and centring of the X-ray beam The central ray should be perpendicular to

the cassette holder, centred to the middle of the cassette holder.

If using a Bucky, the tube should be centred to the Bucky using a horizontal beam before positioning is undertaken.

Essential image characteristics The petrous ridges must appear below the

floors of the maxillary sinuses. There should be no rotation

Correctly positioned Waters. Z=zygoma, OR=orbital rim, ZA= zygomatic arch and ms=maxillary sinus. Note that the entire

maxillary sinus is displayed.

Patients who have sustained trauma will often present supine on a trolley in fixed position.

Position of patient and cassette The patient will be supine on the trolley and

should not be moved. If it is possible to place a cassette and grid under the patient’s head without moving the neck or in the cassette tray under the patient.

The top of the cassette should be at least 5 cm above the top of the head to allow for any cranial beam angulation.

A 24 30-cm cassette is recommended.

Modified mento-occipital

Direction and centring of the X-ray beam The patient should be assessed for position

(angle) of the orbito-meatal line in relation to the cassette.

If the baseline makes an angle of 45 degrees from the vertical (chin raised)----- then a perpendicular beam can be employed centred to the midline at the level of the lower orbital margins.

If the orbito-meatal baseline makes an angle of less than 45 degrees with the cassette because of the neck brace, then the difference between the measured angle and 45 degrees should be added to the beam in the form of a cranial angulation.

45°