Saturday, February 28, 2015

Skull : Lateral Projection

Lateral projection of the skull demonstrated skull fractures, neoplastic processes, and Paget's diseases. A general skull routine includes both right and left laterals.

Skull Trauma Routine: Lateral

     lateral skull
    Right Lateral Recumbent
  • A horizontal beam is required to obtain a lateral view for trauma patients. This may demonstrate air fluid levels in the sphenoid sinus- a sign of a basal skull fracture if intracranial bleeding occurs.

Right or Left Lateral Position

Technical Factors:

  • IR size - 24x30 cm (10 x 12 inches), crosswise
  • Moving or stationary grid
  • 70 to 80 kV range
  • Small focal spot
  • mAs 8

Patient Position:

  • Remove all metal, plastic, or other removable objects from patient's head. Take radiograph with patient in the erect or recumbent semiprone position.

Part Position:
  • Place the head in a true lateral position, with the side of interest closest to IR and the patient's body in a semiprone position as needed for comfort. (One method used to check for possible head rotation from a true lateral is to palpate the extenal occipital protuberance posteriorly and the nasion or glabella anteriorly and ensure that these two points are at the same distance from IR or tabletop.)
  • Align midsagittal plane parallel to IR, ensuring no rotation or tilt.
  • Align interpupillary line perpendicular to IR, ensuring no tilt of head ( see note)
  • Adjust neck flexion to align IOML perpendicular to front edge of IR. (GAL will be parallel to front edge of IR.)

Central Ray:
  • Align CR perpendicular to IR.
  • Center to a point 2 inches (5 cm) superior to EAM or halfway between the glabella and the inion for other types of skull morphologies.
  • Center IR to CR.
  • Minimum SID is 40 inches (100 cm)

  • Collimate to outer margins of skull.

  • Suspend respiration during exposure.

Note: For patients in the recumbent position, a radiolucent support placed under the chin will help in maintaining a true lateral position. A large-chested patient may require a radiolucent sponge under the entire head to prevent tilt, and a thin patient may require support under the upper thorax.

Radiographic Criteria:

Structure Shown:
    lateral skull with label
  • Superimposed cranial halves with superior detail of the lateral cranium closest to the IR are demonstrated.
  • The entire sella turcica, including anterior and posterior clinoids and dorsum sallae, is also shown.
  • The sella turcica and clivus are demonstrated in profile.

  • For better visualization of central skull anatomy for determining tilt or rotation.
  • No rotation or tilt of the cranium is evident.
  • Rotation is evident by anterior and posterior separation of symmetric vertical bilateral structures such as the EAMs, mandibular rami, and mastoid processes.
  • Tilt is evident by superior and inferior separation of symmetric horizontal structures such as the orbital roofs (plates), and mandibular bodies.

Collimation and CR:
  • Entire skull visualized on the image, with the region 2 inches (5 cm) superior to the EAM in the approximate center.
  • Collimation borders to outer margin of skull.

Exposure Criteria:
  • Density and contrast are sufficient to visualize bony detail of sellar structures and surrounding skull
  • Sharp bony margins indicate no motion.

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