Foot - Composite DP

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Radiographic Positioning


Adult Foot - Composite Dorsoplantar Projection

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Name of projection Foot - Composite Dorsoplantar (Phantom foot)
Area Covered Phalanges, metatarsals, navicular, cuniforms, cuboid, talus, calcaneus. The hindfoot is seen free of superimposition of the tibia and fibula.
Pathology shown Fractures, dislocation, foreign body, joint space abnormalities
Radiographic Anatomy Foot Radiographic Anatomy
IR Size & Orientation 24 x 30 cm
Portrait
Film / Screen Combination Detail
(CR and DR as recommended by manufacturer)
Bucky / Grid No
Filter No
Exposure 57 kVp
1.5 mAs for each exposure
FFD / SID 100 cm
Central Ray 1st Exposure: 15° posterior, directed to the base of the 3rd metatarsal
2nd Exposure: 25° anterior, directed to the level of the lateral maleolus
Collimation Outer skin margins of foot on 4 sides
Markers Distal and Lateral
Marker orientation AP
Shielding Gonadal (check your department's policy guidelines)
Respiration Not applicable
Positioning 1st Exposure
  • Place the cassette on the floor of the exam room
  • Place the foot on the IR parallel to its long axis
  • Place the plantar surface of the foot against the IR
  • The unaffected foot should be a step behind the affected foot
  • Center to the base of the 3rd metatarsal
It is essential that the foot does not move between exposures. Hold the patient's foot firmly and have them take a giant step forward.
2nd Exposure
  • Align the leg to the long axis of the foot
  • The entire plantar surface of the foot against the IR
  • Center to the level of the mid-maleolus
Critique

Positioning
  • No rotation is evidenced by
    • The joint between the medial and intermediate cuneiformsis open (this is closed when the foot is rotated)
    • First metatarsal shaft has equal concavity on both sides
    • Nearly equal spacing between 2nd to 5th metatarsals
    • There should be overlap of 2nd to 5th metatarsal bases.
Area Covered
  • Phalanges, metatarsals, navicular, cuniforms, cuboid, talus, calcaneus, and surrounding foot soft tissue.
Collimation
  • Centre: The base of the third metatarsal
  • Shutter A: Open to include the outer skin margins of the lateral and medial sides of the foot
  • Shutter B: Open to include the soft tissue of the toes and the proximal calcaneus
Exposure
  • Soft tissue visualized
  • All skeletal structures have a similar density
Special Notes The nickname for this projection, "phantom foot", stems from the appearance of the radiograph. The hind foot is demonstrated free of superimposition of the leg, giving the appearance of a phantom foot.

This projection can only be done using film or CR. It cannot be done with DR due to the necessity of two exposures to create one image.

Be sure to have ample room to move the tube around the patient as they must remain stationary during the move.

Permit the patient to hold onto a chair or some type of support because the necessary stance may be difficult for some patients.