X-RAY OF THUMB

 

X-RAY OF THUMB

X-ray Thumb P/A View

Region: phalanges of thumb, proximal metacarpal bone

Pathology: fracture and osteoarthritis of thumb

SID: 100 cm (40 inches)

Central Ray: perpendicular beam directed at the first metacarpophalangeal joint

Respiration: unrelated

Position: 

1. The patient is placed in a sitting position.
2. Place the first metacarpophalangeal joint at the center of the image receptor (IR).
3. Use a sponge to support the finger on the IR.
4. Align the major axis of the hand and forearm to the vertical axis of IR.

Collimation: Include all structures from distal phalanx of finger to distal portion of metacarpal bone.

Evaluation: 

1. The entire thumb should be included.
2. The thumb must not be rotated.
3. Metacarpal bones and trapezium should be included.
4. Open distance between interphalangeal joints and the first carpometacarpal joints should be observable

kVp-50, mAs-2

Tip: 

1. Since the distance between image receptor and the subject is bit far when taking posterior-anterior projection (PA projection), its sharpness can be lower than antero-posterior projection (AP projection).
2. In general, unavoidably used to patients who cannot take thumb PA Projection.
3. When high resolution is necessary, low kVp shooting or use of non-screen cassette, etc can be considered.
4. Modified Long and Refert method as 15° is possible to look carpometacarpal joint over in detail.
5. Folio method can be considerable to diagnose rapture of thumb’s metacarpophalangeal.