Skull - PA (Caldwell) 0°This is a featured page

Radiographic Positioning


Adult
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Name of projection Skull - PA (Caldwell) 0°
Area Covered Frontal bone, crista galli, internal auditory canals, frontal and anterior ethmoid sinuses, petrous ridges, greater and lesser wings of sphenoid and dorsum sellae
Pathology shown Fractures of the skull (medial and lateral displacement), neoplastic processes and Pagets disease
Radiographic AnatomySkull 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
FilterNo
Exposure 75 kVp
20 mAs
FFD / SID 100 cm
Central Ray CR is perpendicular to IR (parrallel to OML) and centred to exit glabella
Collimation Outer skin margins of the skull
Markers Inferior and Lateral
Marker orientation PA
Shielding Gonadal (check your department's policy guidelines)
RespirationSuspended
PositioningErect
  • Patient is standing or sitting facing the upright bucky
  • Forehead and nose are touching the bucky
  • The radiographic baseline (OrbitoMeatal Line) is perpendicular to the bucky
  • The midsaggital plane is also perpendicular to the bucky
  • The interpupillary line is parallel to the floor
  • Ensure no rotation of the head by checking that the EAMs are the same distance from bucky
  • CR directed to exit at the level of the nasion
  • CR is perpendicular to IR (parrallel to OML) and centred to exit glabella
Prone
  • Rest patients nose and forehead against table/bucky
  • Flex neck aligning OML perpendicular to IR
  • Align midsagittal plane perpendicular to midline of table/bucky
  • Ensure no rotation of the head by checking that the EAMs are the same distance from bucky
  • CR is perpendicular to IR (parrallel to OML) and centred to exit glabella
Critique

Positioning
  • petrous ridges fill the orbits
  • No rotation is evidenced by
    • The lateral borders of the orbits to the lateral borders of the skull are equidistant on both sides. (see note below)
  • No tilt is evidenced by
    • The petrous ridges are horizontal
Area Covered
  • Skull vault, maxilla
Collimation
  • Centre: Glabella
  • Shutter A: Open to include the lateral skin margins of the skull
  • Shutter B: Open to include the entire skull superiorly, and the maxilla inferiorly
Exposure
  • Assess for adequate penetration of the thickest part of the skull, the frontal bone
  • Bony trabecular patterns and cortical outlines are sharply defined
  • Soft tissues are visualised
Special NotesEffect of 0-5 degree caudal central ray angulation
  • Petrous ridges will be seen within the orbits
  • The central ray will parallel to the radiographic baseline (OML)
Effect of 15 degree caudal central ray angulation
  • Petrous ridges will be seen in the lower third of the orbits
  • The supraorbital rim will be seen
Effect of 20 degree caudal central ray angulation
  • Petrous ridges are completely clear of the orbits
  • Often used in facial bone series
Determining the direction of head rotation
The distance from the lateral border of the orbit to the lateral border of the skull on one side will be decreased on the side the patient is looking to. That is, in a PA position, if the patient is rotated to the left, then the distance will be smaller on this side when compared with the right side of the skull.)



AndyC
AndyC
Latest page update: made by AndyC , Jun 27 2011, 2:57 AM EDT (about this update About This Update AndyC Edited by AndyC

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