Tuesday, December 6, 2011

Pathology Demonstrated:

  • Pathology  of  the air filled larynx and trachea, including the region of thyroid and thymus glands and upper esophagus for opaque foreign object or if contrast medium is present.

Technical Factors:
  • IR size - 24 x 30cm (10 x 12 inches), leghtwise
  • Moving or stationary grid
  • 75 to 80 kV range

  • Secure lead shield around waist to protect gonads.

Patient Position:
  • Patient should be upright if possible, seated or standing with back of head and shoulders against IR (may be taken recumbent if necessary).

Part Position:
  • Align midsagital plane with CR and with midline of grid or table.
  • Raise chin so that acanthiomeatal line is perpendicular to the IR (Line from the acanthion or area directed under the nose and the meatus or EAM); have patient look directly ahead.
  • Adjust the IR height to place top of IR about 1 or 1 1/2 inches (3 to 4cm) below EAM. (see note below for explanation of centering.

Central Ray:
  • CR perpendicular to center of IR at level of T1-T2, about 1 inch (2.5cm) above the jugular notch.
  • Minimun SID of 40 inches (102 cm)


  • Collimate to area of interest.


  • Make exposure during a slow, deep inspiration to ensure filling of trachea and upper airway with air.

Note on Exposure:

  • Exposure for this AP projection should be approximately that of an AP of cervical and/ or thoracic spine.

Centering for upper airway and trachea:
  • Centering for this AP projection is similar to that of the lateral distal larynx is not visualized on the AP as a result of the superimposed base of the skul and mandible. Therefore, more of the trachea can be visualized.

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