Ribs AP Oblique is a radiography positioning projection of the Thorax. AP oblique ribs, 45-degree. SID 40". Full inspiration. The centering point is located level of t7. patient in 45-degree oblique position facing tube.. The central ray is perpendicular to ir, horizontal at t7.. Image-quality criteria include posterior ribs of the affected side projected clear of the vertebral column., ribs projected parallel without foreshortening or overlap.. Standard exposure ranges from 65 to 75 kVp, 12 to 20 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Axillary ribs of the affected side 1-12.
- Costochondral junctions.
- Intercostal spaces.
- Thoracic vertebral bodies.
- Mediastinal structures.
- Diaphragm.
Patient preparation
- Verify patient identity using two identifiers.
- Remove all radiopaque objects from the chest and trunk.
- Position patient in 45-degree oblique facing the tube.
- Affected side rotated toward and closest to the IR.
- Instruct patient to take a deep breath in and hold.
Position & centering point
Level of T7. Patient in 45-degree oblique position facing tube.
Central ray
Perpendicular to IR, horizontal at T7.
Exposure / technique
- kVp
- 65–75
- mAs
- 12–20
- SID
- 40" (102 cm)
- Notes
- Grid required. Affected side closest to IR. Full inspiration held.
Image-quality criteria
- Posterior ribs of the affected side projected clear of the vertebral column.
- Ribs projected parallel without foreshortening or overlap.
- All ribs from above diaphragm to below diaphragm visualized.
- Costochondral junctions visible.
- Minimal overlap of ribs from the opposite side.
- Costophrenic angle visible.
Common errors / ARRT traps
- 1 Inadequate obliquity (less than 45 degrees) does not separate ribs from spine.
- 2 Excessive obliquity (more than 45 degrees) foreshortens the ribs.
- 3 Affected side not raised results in overlap and obscuration.
- 4 Breathing instructions not followed causes motion blur.
- 5 Rotation forward or backward aligns ribs instead of projecting clear.
Clinical indications
- Evaluation of posterior rib fractures.
- Assessment of rib pathology not visualized on AP or PA projections.
- Detailed visualization of ribs above and below the diaphragm.
- Trauma follow-up of the posterior ribcage.
Aligned to the 2025 ARRT Content Specifications.