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Questions and Answers
What is the IR size for all projections of the digits, thumb, and hand?
18 x 24 cm
What is the typical range for mAs technical factor settings?
At what joint does the CR enter the patient for the PA projection of Digits 2 to 5?
The part position for lateral projection of Digits 2 to 5 requires the phalanges to be rotated from true lateral.
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What is a proper technical factor used for imaging the digits?
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In the PA oblique projection, the digit of interest is extended with the palmar surface resting on a ______ degree wedge sponge.
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What should be included in the evaluation criteria for the PA projection of Digits 2 to 5?
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In the lateral projection of the thumb, where does the CR enter?
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Study Notes
Essential Projections of the Digits, Thumb, and Hand
- All images should be taken with an 18 x 24 cm image receptor (IR).
- Technical factors: mAs 1.6 – 2.5, kVp: 63 – 70.
- Central ray should be perpendicular to the IR for all images.
Digits 2 to 5
- Essential projections: PA, lateral, PA oblique.
- Collimation: 2.5 cm on all sides of the digit, including 2.5 cm proximal to the MCP joint.
PA Digits 2 to 5
-
Part position:
- Extend the digit with the palmar surface in the center of the IR.
- Center the requested digit in the middle of the IR.
- Separate the fingers slightly.
- Long axis of digit aligned parallel.
-
CR:
- Perpendicular to the IR.
- Enters patient at the PIP joint.
-
Evaluation criteria:
- Proper collimation.
- No rotation of the phalanges.
- All three phalanges (distal, middle, proximal) included.
- Distal end of the metacarpal included.
- Open IP and MCP joint spaces.
- No superimposition of digits.
- Proper technical factors (clear soft tissue and bony trabeculae).
- Right or left marker included.
Lateral Digits 2 to 5
-
Part position:
- Separate the digit of interest using cotton swab or tape, and fold other digits into a fist.
- The digit of interest should be centered on the IR.
- The long axis of the digit should be parallel with the IR.
-
Second and third digits positioning:
- Extended with the lateral surface in contact with the IR (mediolateral projection).
- Minimizes object image distance (OID).
-
Fourth and fifth digits positioning:
- Extended with the medial surface in contact with the IR (lateromedial projection).
- Minimizes OID.
-
CR:
- Directed perpendicular to the IR.
- Enters patient at the PIP joint.
-
Evaluation criteria:
- Proper collimation.
- No rotation of the phalanges from a true lateral position.
- All three phalanges (distal, middle, proximal) included.
- Distal end of the metacarpal included.
- Open IP joint spaces.
- No superimposition of digits from the other fingers.
- Proper technical factors (clear soft tissue and bony trabeculae).
- Right or left marker included.
PA Oblique Digits 2 to 5
-
Part position:
- Extend the digit with the palmar surface resting on a 45-degree wedge sponge.
- Separate the digit of interest to prevent soft tissue overlap.
-
CR:
- Perpendicular to the PIP joint of the affected digit.
- Collimation: 2.5 cm on all sides of the digit.
-
Evaluation criteria:
- Proper collimation.
- Phalanges should appear obliqued.
- All three phalanges (distal, middle, proximal) included.
- Distal end of the metacarpal included.
- Open IP and MCP joint spaces.
- No superimposition of digits from the other fingers.
- Proper technical factors (clear soft tissue and bony trabeculae).
- Right or left marker included.
Thumb
- Essential projections: Anteroposterior (AP), lateral, PA oblique.
- Collimation: 2.5 cm on all sides of the digit, including 2.5 cm proximal to the CMC joint.
AP Thumb
-
Part position:
- Place the hand in extreme internal rotation.
- The posterior surface of the thumb should be on the IR.
- Center the MCP joint to the IR.
- Align the long axis of the thumb parallel to the IR.
- Separate other digits from the thumb with tape or the opposite hand.
- Ensure a true AP projection by checking the thumb's position.
-
CR:
- Perpendicular to the MCP joint.
-
Evaluation criteria:
- Proper collimation.
- Entire thumb to the trapezium included.
- Concavity of the phalangeal bodies visible.
- Open IP and MCP joint spaces.
- Proper technical factors (clear soft tissue and bony trabeculae).
- Left or right marker included.
PA Thumb (Alternative)
- Center the thumb and CR appropriately to the IR.
- Evaluation criteria is the same as the AP thumb projection.
- Magnification occurs due to the large OID.
Lateral Thumb
-
Part position:
- Palmar surface on the IR.
- Align the long axis of the thumb parallel to the IR.
- Center the MCP joint to the unmasked portion of the IR.
- Rotate the thumb until the lateral surface is on the IR (mediolateral projection).
-
CR:
- Perpendicular to the MCP joint of the thumb.
-
Evaluation criteria:
- Proper collimation.
- Entire thumb to the trapezium included.
- No rotation of the phalanges.
- Open IP and MCP joint spaces.
- Proper technical factors (clear soft tissue and bony trabeculae).
- Left or right marker included.
PA Oblique Thumb
-
Part position:
- Palmar surface of the thumb on the IR.
- Align long axis of thumb parallel.
- Place a 45-degree wedge sponge under the thumb.
- Center the MCP joint to the IR.
- Rotate the thumb 45 degrees.
-
CR:
- Perpendicular to the IR and the MCP joint.
-
Evaluation criteria:
- Proper collimation.
- Phalanges should appear obliqued.
- Open IP and MCP joint spaces.
- Proper technical factors (clear soft tissue and bony trabeculae).
- Left or right marker included.
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Description
This quiz covers essential projections for digits 2 to 5, focusing on proper collimation, part positioning, and evaluation criteria. It emphasizes technical factors necessary for accurate imaging and the central ray alignment for hand and digit radiography.
