WRIST X RAY : PA Projections and Alternative AP

Thursday, March 20, 2014

PA or Alternative AP Projection of the Wrist

Pathology Demonstrated in PA or AP wrist x-ray are fractures of distal radius or ulna or isolated fracture of radial or ulna styloid processes, as well as fractures of individual carpal bones, are demonstrated. Some pathologic processes, such as osteomyelitis and arthritis, also maybe seen.

Technical Factors:

IR size- 18 x 24 cm (8 x 10 inches)
Division in half, crosswise
Detail screen, table top
Digital IR- use lead masking
60 or add more or less 6 kV depending on patient hands

Shielding, Patient Position and Part Position:

pa wrist
PA Wrist
Place lead shield over patient's lap to shield gonads.
Seat patient at end of table with elbow flexed about 90degrees and hand and wrist resting on casette, palm down. Drop shoulder so that shoulder, elbow, and wrist are on same horizontal plane.
Align and center long axis of hand and wrist to portion of IR that are being exposed, with carpal area centered to CR.
With hand pronated, arch hand slightly to place wrist and carpal area in close contact with cassette.

Central Ray and Collimation

CR perpendicular to IR, directed to midcarpal area
Minimum SID of 40 inches (100cm)
Collimate to wrist on all four sides; include distal radius and ulna and mid-metacapal area.

Alternative AP Projection Wrist X-Ray:

An AP wrist may be taken, with hands slightly arched to place wrist and carpals in close contact with cassette, to better demontrate intercarpal spaces and wrist joint, and to place the intercarpal spaces more parallel to the divergent rays. This wrist projection is good for visualizing the carpals if the patent can assume this position easily.


Structure Shown and Proper Part Position:

Midmetacarpal and proximal metacarpal; carpals; distal radius, ulna, and associates joints; and pertinent soft tissues of the wrist joint, such as fat pads and fat stripes, are visible.The intercarpal spaces do not all appear open because of irregular shapes that result in overlapping.
Long axis of the hand, wrist, and forearm is aligned with IR.
wrist xray
PA Wrist Radiograph

True PA is evidenced by the following:

Equal concavity shapes are on each side of the shafts of the  proximal metacarpals
Near equal distances exist among the proximal metacarpals.
Separation of distal radius and ulna is present, except for possible minimal superimposition at the distal radioulnar joint.

Collimation, Central Ray and Exposure Criteria:

Collimation should be visible on four sides to area of affected wrist.
CR and center of collimation field should be to the midcapal area.
Optimal density and contrast with no motion should visualized soft tissue, such as pertinent fat pads, and sharp, bony margins of the carpals and clear trabecular markings.

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