Skull Radiography- Lateral and PA views

SKULL-LAT VIEW

Patient position

-         Patient lies supine to the x ray table.

-         Median sagittal plane is parallel to the table.

-         The interorbital line is perpendicular to the cassette.

Central ray:

Horizontal ray Centre midway between the glabella and the external occipital

protuberance to a point approximately 5 cm superior to the external auditory meatus.

Essential image characteristics

-         The image should contain all of the cranial bones and the first cervical vertebra.

-         Both the inner and outer skull tables should be included.

-          A true lateral will result in perfect superimposition of the lateral portions of the floors of the anterior cranial fossa and those of the posterior cranial fossa.

-         The clinoid processes of the sella turcica should also be superimposed.

1. Coronal Suture

2. Orbital Plates of the Frontal Bone

3. Posterior Clinoid Process

4. Auricle or Pinna (Ear)

5. Lambdoidal Suture

6. External Occipital Protuberance

7. Posterior Arch of C1

8. Sphenoid Sinus

Note: Skull lateral can also be done while the patient is in erect position using vertical ray in the uncooperative patient.

Skull PA (Occipito frontal)

Patient position:

-         The patient sits facing the erect Bucky.

-         Median sagittal plane is perpendicular to the cassette.

-         Neck flex so that the orbito-meatal base line is perpendicular to the Bucky.

Direction of central ray

Centre in the midline of the occiput so that the exit ray emerges in the midline at the level of the glabella.

Essential image characteristics

-          All the cranial bones should be included within the image, including the skin margins.

-         It is important to ensure that the skull is not rotated which can be assessed by measuring the distance from a point in the midline of the skull to the lateral margin. If this is the same on both sides of the skull, then it is not rotated.

1. Lambdoidal Suture

2. Ethmoid Sinus

3. Petrous Ridge

4. Maxillary Sinus

5. Body of the Mandible

6. Condyle of the Mandible

7. Mastoid Air Cells

With the degree of beam angulation, the position of the petrous ridges within the orbit can be evaluated:

– Occipito-frontal: the petrous ridges should be completely superimposed within the orbit, with their upper borders coincident with the upper third of the orbit.

– OF10° caudally: the petrous ridges appear in the middle third of the orbit.

– OF15° caudally: the petrous ridges appear in the lower third of the orbit.

– OF20° caudally: the petrous ridges appear just below the inferior orbital margin.

Note: Never use skull PA when there is a possibility that the facial bones may be fractured or when the patient is unconscious. When the patient cannot be X-rayed in a prone position, then Skull AP- Supine (frontal-occipital) is used.

Reference:

1. Clark's Positioning Radiography, 12th Edition