24 Questions
What is the purpose of using lead masking in digital IR?
To produce uniform density of phalanges and tarsals
What is the recommended angle of the CR in an AP projection of the foot?
10o posteriorly
What is the minimum SID recommended for an AP projection of the foot?
100 cm
Why is it necessary to flex the opposite knee in an AP projection of the foot?
To support the affected knee
What is the purpose of collimation in an AP projection of the foot?
To restrict the x-ray beam to the area of interest
How should the part be positioned in an AP projection of the foot?
Extend the foot and maintain the plantar surface flat on the IR
What is the recommended kVp range for an AP projection of the foot?
70-75 kV
Why is shielding of the pelvic area recommended in an AP projection of the foot?
To reduce radiation exposure to the pelvic area
What is the required angle for a high arch to be perpendicular to the Metatarsals (MT's)?
15o
What is the direction of the CR in relation to the IR for foreign bodies?
Perpendicular to the IR
What is the primary purpose of the AP oblique projection?
To demonstrate the extent of fractures and fragments
What is the recommended kV range for the AP projection?
70-75 kV
What is the purpose of using lead masking with digital IR?
To increase the detail of the image
What is the recommended position of the patient's knee during the AP oblique projection?
Flexed
What is the direction of the general plane of the dorsum of the foot in relation to the IR?
Parallel to the IR
What is the minimum Source-to-Image Distance (SID) required for the AP oblique projection?
100 cm
What is the typical part position for a mediolateral projection?
Plantar surface ┴ to IR
What is the purpose of shielding the pelvic area?
To reduce radiation exposure to the patient
What is the minimum SID recommended for this procedure?
100 cm
What is the direction of the central ray (CR) in a lateral foot projection?
┴ to the IR, directed to the medial cuneiform
What is the recommended kV for this procedure?
60 ± 5 kV
What is the purpose of collimation in this procedure?
To reduce the radiation dose
Why is the lateromedial projection often used?
Because it may be easier to achieve a true lateral
What is the purpose of flexing the knee of the affected limb about 45 degrees?
To prevent over rotation of the affected leg
Study Notes
AP Projection: Foot (Dorsoplantar)
- Demonstrates location and extent of fractures, fragments, and joint space abnormalities
- Shows soft tissue effusion and foreign bodies
- Technical factors:
- Detail screen and tabletop
- Digital IR with lead masking
- 60 ± 5 kV or 70-75 kV with reduced mAs for uniform density of phalanges and tarsals
- Technique and dose: 70 kV, 2 mAs, 10 cm part thickness, 8 mrad patient dose
- Patient position:
- Supine with pillow under head
- Knee flexed with plantar surface of affected foot flat on IR
- Foot extended and centered to CR and IR
- CR angle: 10° posteriorly (toward heel) directed to base of 3rd MT
- Collimation: four sides of digit of interest
AP Oblique Projection – Medial Rotation: Foot
- Demonstrates location and extent of fractures, fragments, and joint space abnormalities
- Shows soft tissue effusion and foreign bodies
- Technical factors:
- Detail screen and tabletop
- Digital IR with lead masking
- 60 ± 5 kV or 70-75 kV with reduced mAs for uniform density of phalanges and tarsals
- Technique and dose: 70 kV, 2 mAs, 7 cm part thickness, 11 mrad patient dose
- Patient position:
- Supine or sitting with knee flexed and plantar surface of affected foot flat on IR
- Body turned slightly away from side in question
- Foot rotated medially 30°-40° to plane of IR
- CR angle: perpendicular to IR, directed to base of 3rd MT
- Collimation: four sides of digit of interest
Lateral – Mediolateral or Lateromedial Projections: Foot
- Demonstrates location and extent of fractures, fragments, and joint space abnormalities
- Shows soft tissue effusion and foreign bodies
- Technical factors:
- Detail screen and tabletop
- Digital IR with lead masking
- 60 ± 5 kV
- Technique and dose: not specified
- Patient position:
- Lateral recumbent with pillow for head
- Knee flexed at 45° and opposite leg behind injured limb
- Foot dorsiflexed to assist in positioning
- Plantar surface perpendicular to IR
- CR angle: perpendicular to IR, directed to medial cuneiform (at level of base of 3rd MT)
- Collimation: four sides of foot to include 2-3 cm proximal to ankle joint
This quiz focuses on the AP projection of the foot in radiography, covering the pathology demonstrated, including fractures, foreign bodies, and joint space abnormalities.
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