Wrist Tangential (Carpal Canal) is a radiography positioning projection of the Upper Extremity. Seated, wrist hyperextended. CR angled 25–30° to long axis of hand. The centering point is located approximately 1 inch distal to the base of the third metacarpal. wrist hyperextended, palm flat on ir.. The central ray is cr angled 25–30 degrees to long axis of hand, entering 1 inch distal to 3rd metacarpal base.. Image-quality criteria include hook of hamate shown in profile without foreshortening., pisiform visible as a distinct structure.. Standard exposure ranges from 60 to 70 kVp, 2 to 4 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Hook of hamate in profile without overlap.
- Pisiform clearly visible as a separate structure.
- Carpal tunnel space defined by hook and pisiform.
- Capitate and other distal carpals.
- Second through fifth metacarpal bases.
- Scaphoid tubercle and trapezium.
Patient preparation
- Verify patient identity using two identifiers.
- Remove watches, bracelets, and radiopaque items from the arm.
- Seat the patient at the end of the table.
- Place forearm on the IR with palm down.
- Hyperextend the wrist as far as comfortably possible.
Position & centering point
Approximately 1 inch distal to the base of the third metacarpal. Wrist hyperextended, palm flat on IR.
Central ray
CR angled 25–30 degrees to long axis of hand, entering 1 inch distal to 3rd metacarpal base.
Exposure / technique
- kVp
- 60–70
- mAs
- 2–4
- SID
- 40" (102 cm)
- Notes
- Tabletop technique. Hyperextension is critical to opening the carpal canal.
Image-quality criteria
- Hook of hamate shown in profile without foreshortening.
- Pisiform visible as a distinct structure.
- Carpal tunnel space open and clearly defined.
- Second through fifth metacarpal bases included.
- No motion blur; hook borders sharp.
- Collimation: 1 inch on all sides of the carpal tunnel region.
Common errors / ARRT traps
- 1 Insufficient wrist hyperextension flattens the carpal canal.
- 2 CR angle less than 25 degrees overlaps hamate and pisiform.
- 3 CR angle greater than 30 degrees projects the canal off-axis.
- 4 Centering off the distal third metacarpal clips the hook.
- 5 Pronation or supination distorts the carpal anatomy.
Clinical indications
- Suspected hook of hamate fracture.
- Pisiform fracture evaluation.
- Carpal tunnel syndrome assessment.
- Post-operative carpal canal or hamate fixation follow-up.
Aligned to the 2025 ARRT Content Specifications.