Ribs (AP view)

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The ribs AP view is a specific projection employed in the assessment of the posterior ribs. Unlike a standard chest radiograph, this projection applies a lower kV higher mAs technique to highlight bony structures.

It often involves two projections, one of the supradiaphragmatic ribs and two of the subdiaphragmatic ribs.

Indications

The AP view specifically focuses on the posterior ribs. The rib series is often considered to be an unnecessary, unjustified projection in many radiology departments. Indeed the Royal College of Radiologists (UK) iRefer guidelines state "Demonstration of a simple rib fracture does not usually alter management but if a complication such as pneumothorax or infection is suspected, chest radiograph would be appropriate" . Thus if the projection might change the patient management it may still be considered pertinent and worthy of discussion.

Patient position

  • the patient is erect facing the x-ray tube, posterior portion resting on the upright detector 
  • the chin is raised as to be out of the image field 
  • hands are placed by the patient's side

Technical factors

  • anteroposterior projection
  • suspended inspiration (ribs above the diaphragm)  
  • suspended inspiration (ribs below the diaphragm) 
  • centering point (above the diaphragm) 
    • 10 cm below the jugular notch at the midsagittal plane 
  • centering point (below the diaphragm)
    • midway between the xiphoid process and the 12 rib
  • collimation (ribs above the diaphragm)  
    • superior to the 1rib 
    • inferior to the extent of the detctor 
    • laterally to the skin borders 
  • collimation (ribs below the diaphragm)  
    • superior to T9
    • inferior to the 12rib (above illiac crest) 
  • orientation  
    • portrait 
  • detector size
    • 35 cm x 43 cm or 43 cm x 35 cm
  • exposure
    • 60-70 kVp
    • 30-40 mAs
  • SID
    • 100 cm
  • grid
    • yes

Image technical evaluation

The entire rib cage should be visible from the 1 to the 12.

  • the chin should not be superimposing any structures
  • minimal to no superimposition of the scapulae borders on the lung fields
  • sternoclavicular joints are equal distant apart
  • the clavicle is in the same horizontal plane
  • a minimum of ten posterior ribs is visualized above the diaphragm
  • the ribs and thoracic cage are seen only faintly over the heart
  • clear vascular markings of the lungs should be visible

Practical points

The isolated referral of a rib series in the assessment of rib trauma is controversial  however, still widely used. Ensure the projection is not performed under a chest examination AEC setting, this will not achieve the correct exposure to adequately present the bony structures of the thoracic cage.