Skull - Townes

Radiographic Positioning

Adult

Other related pages of interest Applied Radiography Radiographic Anatomy Radiographic Protocols

Name of projection	Skull - Townes (also called Skull - AP Axial)
Area Covered	Skull , foramen magnum
Pathology shown	Fractures and pathologies of the skull
Radiographic Anatomy	Skull Radiographic Anatomy
IR Size & Orientation	24 x 30 cm Portrait
Film / Screen Combination	Regular (CR and DR as recommended by manufacturer)
Bucky / Grid	Moving or Stationary Grid
Filter	No
Exposure	80 kVp 20 mAs
FFD / SID	100 cm
Central Ray	Directed to 6 cm superior to the glabella (this is typically the hairline) CR 30° caudal (see note below)
Collimation	Outer skin margins of the skull
Markers	Superior and Lateral Marker orientation AP
Shielding	Gonadal (check your department's policy guidelines)
Respiration	Suspended
Positioning	Patient is in an erect position, either standing or sitting Position the patient so that their back and posterior skull are touching the bucky Bring the patients chin down until the radiographic baseline orbitomeatal line (OML) is parallel to the floor, therefore perpendicular the bucky. If the patient is not able to do this, the central ray angle may have to be increased caudally so that there is a 30 degree angle between the radiographic baseline (OML) and the central ray. Ensure the midsaggital plane is perpendicular to the bucky Ensure the interpupillary line is parallel to the floor
Critique PACEMAN	Positioning No rotation is evidenced by The lateral borders of the foramen magnum are equidistant from the lateral borders of the skull. No tilt is evidenced by The petrous ridges are horizontal. The central ray is at 30 degrees to the radiographic baseline, evidenced by The dorsum sellae & posterior clinoid processes are seen in the foramen magnum. Area Covered Skull, dorsum sellae & posterior clinoid processes seen in the foramen magnum Collimation Centre: Just above the foramen magnum Shutter A: Open to include the outer skin margins of the skull laterally Shutter B: Open to include the superior aspect of the skull Exposure Assess for adequate penetration of the thickest part of the skull The dorsum sellae and posterior clinoid processes are seen in the foramen magnum Bony trabecular patterns and cortical outlines are sharply defined Soft tissues are visualised
Special Notes	Effect of the central ray angle being less than 30 degrees to the radiographic baseline (OML) The dorsum sellae will project higher. This means that it will project above the foramen magnum, rather than in it.