Chest AP supine is a radiography positioning projection of the Thorax. Bedside supine chest. ICU/trauma. SID 40". The centering point is located approximately 3" (7.5 cm) inferior to the jugular notch, equivalent to t7 in the supine position.. The central ray is vertical, perpendicular to ir. centered ~3" below the jugular notch.. Image-quality criteria include both lungs entirely visualized, including apices and costophrenic angles., no rotation: sc joints equidistant from spine.. Standard exposure ranges from 80 to 100 kVp, 2 to 6 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Entire lung fields, apices through costophrenic angles.
- Clavicles in the same horizontal plane, apical region unobstructed.
- Eight or nine posterior ribs above the diaphragm.
- Heart and mediastinum, magnified relative to an erect PA.
- Trachea and carina.
Patient preparation
- Verify patient identity using two identifiers.
- Remove ECG leads if possible (or pull off chest); remove jewelry, gowns with snaps.
- Confirm pregnancy status.
- Slide IR under the upper torso, positioned 1.5"-2" above the shoulders so apices are included.
- Instruct full inspiration; hold (note: many bedside patients are intubated, coordinate with respiratory therapist).
Position & centering point
Approximately 3" (7.5 cm) inferior to the jugular notch, equivalent to T7 in the supine position.
Central ray
Vertical, perpendicular to IR. Centered ~3" below the jugular notch.
Exposure / technique
- kVp
- 80–100
- mAs
- 2–6
- SID
- 40" (102 cm)
- Notes
- Portable units typically max at SID 40-48". Heart appears even larger than upright AP because of magnification + supine cardiac position.
Image-quality criteria
- Both lungs entirely visualized, including apices and costophrenic angles.
- No rotation: SC joints equidistant from spine.
- Pleural effusion appears as hazy hemithorax graying on supine, not as a costophrenic-angle meniscus.
- Pneumothorax may show as deep sulcus sign rather than apical lucency.
- Diaphragm appears higher than upright (less gravity).
- Marker clearly indicates "Supine" or "AP".
Common errors / ARRT traps
- 1 Reading the enlarged heart as cardiomegaly; shorter SID and greater OID magnify it.
- 2 Expecting air-fluid levels without a horizontal beam.
- 3 Omitting the slight caudad angle, so the clavicles obscure the apices.
- 4 Judging inspiration against the ten-rib erect standard rather than eight or nine.
- 5 Failing to mark the image as supine or semierect and to note the SID.
Clinical indications
- ICU patient, line/tube placement check (ET tube, central line, NG tube, chest tube).
- Trauma patient unable to stand.
- Post-operative bedside follow-up.
- Daily ICU rounds chest for evaluating pulmonary status changes.
Aligned to the current ARRT Radiography Content Specifications.