Tangential Projection of the Carpal Bridge
- Calcification or other pathology of the dorsal aspect of the carpal bones is shown.
Technical Factor:
- IR size - 18 x 24 cm (8 x 10 inches)
- Detail screen, tabletop
- Digital IR - use lead masking
- 64 or add upto 6 kV range
Shielding:
- Secure lead shield around waist to shield gonads.
Patient Position:
- Have patient stand or sit at end of table and then lean over and place dorsal surface of hand, palm upward, on cassette.
Part Position:
- Center dorsal aspect of carpals to IR.
- Gently flex wrist as far as patient can tolerate, or until hand and forearm form as near 90degrees (right angle) as possible.
Central Ray:
- Angle the CR 45degrees to the long axis of the forearm.
- Direct CR to a midpoint of the distal forearm about 4cm (1 1/2 inches) proximal to the wrist joint.
- Minimum SID is 40 inches (100cm)
Collimation:
- Collimate all four sides to area of interest.
Radiographic Criteria of Tangential View of the Carpal Bridge
Structure Shown:
- A tangential view of the dorsal aspect of the scaphoid, lunate, and triquetrum is visible.
- An outline of the capitate and trapezium superimposed is visible.
Position:
- Dorsal aspect of the carpal bones should be visualized clear of superimposition and centered to IR.
Collimation and CR:
- Collimation should be visible on four sides of affected wrist
- CR and center of the collimation should be to the area of dorsal carpal bones.
Exposure Criteria:
- Optimal density and contrast with no motion should demonstrate the dorsal aspect of the carpal bones, with sharp borders and clear, sharp bony trabecular markings.
- Outline of the proximal metacarpals should be visualized through superimposed structures without overexposure of the dorsal aspects of carpals seen in profile.
