Forearm Radiography : AP Projection

Sunday, March 30, 2014

Forearm (Radius and Ulna) - AP Projection

AP projection of the forearm is normally taken with arm extended and hands supinated, which means palm surface of the hand is facing up. Pronated or PA Projection of the forearm crosses the radius and ulna at its proximal third and rotates the humerus medially, resulting in an oblique view of the forearm. The elbow joint, the radius and ulna, and the proximal row of the slightly distorted carpal bones are demonstrated. Fractures and/or dislocations of the radius or ulna and some pathologic processes, such as osteomyelitis or arthritis or arthritis if present is also demonstrated.

Technical Factors and Shielding

IR size - 30 x 35 cm (11 x14 inches) for smaller patients; 35 x 43 cm (14 x 17 inches) for large patients
Division in half, lengthwise
Detail screen, tabletop
Digital IR - use lead masking
60 or add upto 6 kV range
Place lead shield over patient's lap to shield gonads.

Patient and Part Position

Drop shoulder to place entire limb on same horizontal plane.
Align anfd centere forearm to long axis of IR, ensuring that both wrist and elbow joints are included. (Use as large an IR as necessary.)
Instruct patient to lean laterally as necessary to place entire wrist, forearm, and elbow in as near a true frontal position as possible. (Medial and lateral epicondyles should be the same distance from IR.)
Seat patient at end of table, with hands and arm fully extended and palm up (supinated).

Central Ray and Collimation

CR perpendicular to IR, directed to midforearm
Minimum SID of 40 inches (100cm)
Collimate lateral borders to the actual forearm area with minimal collimation at both ends to avoid cutting off anatomy at either joint. Considering divergent of x-ray beam, ensure that a minimum of 3 to 4 cm (1 to 1 1/2 inches) distal to wrist and elbow joints is included on the IR.


Radiographic Criteria : AP Projection of the Forearm

Structure Shown:

AP projection of the entire radius and ulna is shown, with minimum of proximal row carpals and distal humerus, as well as pertinent soft tissues, such as fat pads and stripes of the wrist and elbow joints.

Correct Part Positioning:

Long axis of forearm should be aligned with long axis of IR.
No rotation is evidence by humeral epicondyles visualized in profile, with the radial head, neck, and tuberosity slightly superimposed by the ulna.
Wrist and elbow joint spaces are only partially open because of beam divergence.

Collimation and CR:

Collimation borders are visible at the skin margins along the length of the forearm, with only minimal
collimation at both ends to ensure the essential joint anatomy is included.
CR and center of collimation field should be to the approximate midpoint of the radius and ulna.

Exposure Criteria:

Optimal and similar density and contrast with no motion should visualized.
Soft tissue and sharp, cortical margins and clear, bony trabecular markings.

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