Forearm Radiography : Lateral Projection

Saturday, December 24, 2011

Forearm (Radius and Ulna) : Lateromedial Projection

Radiograph of a lateral (lateromedial) projection of forearm will clearly demonstrate the bones of the forearm (radius and ulna), the elbow and the proximal row of the carpal bones. Fractures and/or dislocations of the radius and ulna, pathologic processes, such as osteomyelitis and arthritis, are shown if present.

Technical Factor

IR size - 30 x 35 cm ( 11 x 14 inches) or 35 x 43 cm (14 x 17 inches)
Division in half, lengthwise
Detail screen, tabletop
Digital IR - use lead masking
64 or add upto 6 kV range (+4 kV from AP)
To make best use of the anode heel effect, place elbow at cathode end of x-ray beam.

Patient Position and Shielding

Seat patient at end of table, with elbow flexed 90degree.
Place lead shield over patient's lap to shield gonads.

Part Position

The elbow is flexed 90°, and align forearm on the unmasked surface of the IR
Forearm is parallel with the long axis of the IR.
Drop shoulder to place entire upper limb on same horizontal plane.
Ensure both wrist and elbow joints are included on radiograph.
Rotate hand wrist into true lateral position.and support hand to prevent motion, if needed. (Ensure that distal radius and ulna are superimposed directly.)
For heavy muscular forearms, place support under hand and wrist as needed to place radius and ulna parallel to IR.

Central Ray and Collimation

CR perpendicular to IR, directed to mid-forearm
Minimum SID of 40 inches (100cm)
Collimate both lateral borders to the actual forearm area. Also collimate on both ends to avoid cutting off anatomy at either joint. Considering divergence of the 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 of Forearm :  Lateral View

Structure Shown

Lateral projection of entire radius and ulna, proximal row of carpal bones, elbow, as well as pertinent soft tissue,such as fat pads and stripes of the wrist and elbow joints.
Superimposition of the radius and ulna at their distal end.
Superimposition of the radial head over the coronoid process.

Proper Part Positioning

Long axis of forearm should be aligned to long axis of IR.
Elbow should be flexed 90degrees

True Lateral / No Rotation when:

The head of the ulna is superimposed over the radius,
Humeral epicondyles is superimposed.
Radial head is superimposed with coronoid process, with radial tuberosity demonstrated.

Collimation and Central Ray

Light Border should be visible at skin margins along the length of forearm, with minimal collimation on both ends.
Essential joint anatomy is included on radiograph .
CR and center of the collimation field is at the midpoint of the radius and ulna.

Exposure Criteria:

Optimal density and contrast with no motion should visualize sharp cornical margins.
Clear and sharp soft tissue and bony trabecular markings along the entire length of the radial and ulnar shaft
Fat pads and stripes of the wrist and elbow joint is also clearly demonstrated.

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