Recording-2025-01-28T18_50_46.733Z

Considerations for Foot Imaging

• Source to Image Distance: Minimum of 40 inches for tabletop imaging.

  • Exception for weight-bearing foot X-rays, which may require more than 40 inches.

  • Weight-bearing imaging provides a more accurate representation of the patient's anatomy under normal conditions.

• Shielding: Always shield patients, unless imaging abdomen or pelvis.

• Collimation: Foreseen collimation, possibly two-sided depending on anatomy required.

  • Example: If pain is midfoot, use two-sided collimation to include more anatomy of interest.

• Centering: Use accurate centering to minimize distortion and ensure joint spaces are open.

• Exposure Factors: Follow ALARA (As Low As Reasonably Achievable) principles.

  • For digital, higher kVp range preferred; consider exposure index during post-processing.

  • Each manufacturer has different exposure index ranges; consistency from film days is lost.

• Markers: Mark every image laterally, avoid placing close to midline.

• Adjustments for Casts:

  • Fiberglass Casts: Increase technique by 3-4 kVp.

  • Plaster Casts: Increase by about 5-10 kVp depending on dryness.

• Remove Radiopaque Items: Ensure patients remove shoes, socks, jewelry, pants to reduce artifacts.

AP/AP Axial Projections of the Foot

• Projection Type: Generally use AP axial for toes and foot to accommodate the longitudinal arch.

• CR Angulation: Use 10-15 degrees posterior angulation toward the calcaneus for axial projections.

  • Perpendicular CR is used when checking for foreign bodies.

• Specific Cases: Angulation of 15 degrees for weight-bearing might be adjusted for high arches (use lesser angles for flat feet).

• Image Requirements: Achieve open IP joints and metatarsophalangeal joints in the resulting images.

• Collimation: Use 4-sided collimation to include at least a half-inch soft tissue shadow within the field.

Oblique Projections of toes

• Digital Orientation: Generally done similar to digits in the hand, medial or lateral rotation for toes 1 to 3.

  • 30-45 degree obliquity for the projection with a marker placed beyond the distal tip of the digit.

• Evaluation Criteria: Similar to axial; ensure no superimposition of adjacent digits and include joint spaces. Increased concavity on the side of chefs invite overlapping of soft tissue the digits had a metacarpals should appear directly side-by-side with no or minimal overlapping.

Lateral Projections

• Orientation: Lateral projection, either medial-lateral or lateral-medial, is common for evaluating toes.

• Entry Points:

  • For 2-5, CR is at proximal interphalangeal joint.

  • For the first digit, at the interphalangeal joint.

• Criteria: Ensure open IP joints and appropriate soft tissue visibility on images.

Calcaneus Imaging

• Projections: Plantodorsal axial and lateral projections are standard.

• Positioning: Patient supine, ensure no leg overlap and 90-degree dorsiflexion.

• Angulation: 40-degree cephalic angulation for plantodorsal, CR entry at the base of the third metatarsal.

• Lateral Projection: Maintain true lateral positioning; evaluate for common fractures such as the Jones fracture at the metatarsal tuberosity.

Ankle Projections

• Positioning: Distinction between foot and ankle imaging—lower extremity fully extended when imaging the ankle.

• Projections: Include AP, oblique, and lateral ankle imaging:

  • AP: mid-malleolus as CR entry point; ensure open mortise joint space.

  • Oblique: 45-degree medial rotation of the leg to open the mortise.

• Lateral: Ensure medial-lateral projection; evaluate for alignment and ensure proper dorsiflexion of the foot to assess the ankle joint adequately.

Weight-Bearing Considerations

• Protocols: Bilateral AP axial could be pursued, with careful attention to patient comfort and equipment safety (e.g. protecting the digital detector).

• Entry Point: Center at the level of the base of the third metatarsal, ensuring proper alignment to the IR.

  • Evaluation criteria remain the same as standard imaging.

Tangential Projection of Toes

• Positioning: PC placed in prone position dorsiflex the foot, so the plantar surface of the foot forms a 15 to 20° angle

• CR: is perpendicular and directed 10 tangentially to the posterior aspect of the first MTP joint

Evaluation criteria: sesamoid bones to be a profile for your supreme position, and a minimum of the first three metacarpal should be included in collimation field for possible sesamoids with four sided collimation

Borders of posterior margins of the first and third metacarpals are seen in profile, indicating correct dorsiflexion of the first