PLANTODORSAL (AXIAL) PROJECTION: LOWER LIMB-CALCANEUS

Tuesday, September 18, 2012

Pathology Demonstrated:
  • Pathologies or fractures with medial or lateral displacement are demonstrated.

Technical Factors:

  • IR size - 18 x 24 cm (8 x 10 inches)
  • devide in half, crosswise
  • Detail screen
  • Digital IR-use lead masking
  • 70 +- 5 kV range
  • Increase by 8 to 10 kV over other foot projections
  • mAs 5


Shielding:
  • Place lead shield over pelvic area to shield gonads.


Patient Position:

  • Take radiograph with patient supine or seated on table with leg fully extended.
Plantodorsal (axial) calcaneus


Part Position:

  • Center and align ankle joint to CR and to portion of IR being exposed.
  • Dorsiflex foot so plantar surface is near perpendicular to IR.
  • Loop gauze or a toourniquet around foot, and ask patient to pull gnetly but firmly and hold the plantar surface of foot as near perpendicular to IR as posible. (Do not keep patient in this position any longer than is necessary because it may be very uncomfortable.)


Central Ray:

  • Direct CR to base of third metatasal to emerge at a level just distal to lateral malleolus.
  • Angle CR 40degree cephalad from long axis of foot (which also would be 40degree from vertical if long axis of foot is perpendicular to IR).
  • Minimum SID is 40 inches (100 cm).


Collimation:

  • Collimate closely to area of calcaneus.


CR and DR:

  • Close collimation and lead masking are important over unused portions of image plate to prevent fogging from scatter radiation to the hypersensitive image plate or receptor.


Note: CR collimation must be increased if long axis of plantar surface of foot is not perpendicular to IR.

Radiographic Criteria:

Structure Shown:

  • Entire calcaneus should be visualized from the tuberosity posteriorly to the talocalcaneal joint anteriorly.


Position:

  • No rotation; a portion of the sustentaculum tali should appear in profile medially.


Collimation and CR:

  • CR and center of collimation field should be midway between the distal lateral malleolus and the sustentaculum tali.
  • With the foot in proper 90 degree flexion, correct alignment and angulation of the CR are evidenced by an open talocalcaneal joint space, no distortion of the calcaneal tuberosity, and adequate elongation of the calcaneus.


Exposure Criteria:

  • Optimal density and contrast with no motion will demonstrate sharp bony margins and trabecular markings and will at least faintly visualize the talocalcaneal joint without overexposing the distal tubersosity area.

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