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Basic Chest X-ray Interpretation

An X-ray is a density-gram where “white” is “dense” and “black” is “not dense.” Determine a systematic method you use every time you interpret a CXR to ensure you don’t miss anything

  • Start every CXR you interpret by assessing the quality of the film:
  • Penetration:
    • Should see vertebral bodies through the cardiac silhouette but not into the abdomen
    • If you cannot see them through the heart, the film is “under-penetrated,” and everything will appear more “white.”
    • If you can see them through the abdomen the film is “over-penetrated” and everything will appear more “black.”
  • Rotation: Spinous processes should be in the middle of the clavicular heads
  • Two Different Systematic Methods:
  • ABCDE method

    • Airway – Trachea midline and patent
    • Bones – Bone density and obvious fractures
    • Cardiac Silhouette – Should see L & R heart border, if not there may be an adjacent opacity (Right Middle Lobe, Lingula)
      • Cardiomegaly = heart size ≥ ½ the width of the hemithorax on a PA film
    • Diaphragm – Look for pleural effusions at the costo-phrenic angle. If you cannot see the diaphragm along the way, there may be an adjacent opacity (Lower Lobe)
    • “Everything else” – Refers to the lung fields
      • Extra-Thoracic Soft Tissue – Subcutaneous emphysema
      • Fields and Fissures –lung fields should appear symmetric and “black”
      • Great Vessels – Tortuosity of the aorta and the outlines of the pulmonary vessels
      • Hilum – Hilar masses, LAD and pulmonary arteries
  • Working around the film method:

    • Imagine the entire CXR film as a square and an inner “box” as the pleural lining
    • Outside the box: Lines/tubes, subq emphysema, gastric bubble, subdiaphragmatic air
    • Edge of the box: Look for pleural thickening, pleural effusion, pneumothorax, visualization of the diaphragm
    • Middle of the box: Trachea, vascular pedicle, hila, heart borders, great vessels, retrocardiac space
    • The lung fields

Silhouette sign

  • Two things of different densities will show a clear border on a chest x-ray
  • Loss of a border you expect to see suggests a change in density of one of the structures.
  • Ex: heart &l lung have different densities with sharp border. Loss of this border suggests that the lung “increased” in density
    • Ex: Pneumonia (fluffy opacities, air bronchograms, asymmetric) and pulmonary edema (linear opacities, fluid in fissures, Kerley B lines, cephalization)

CXR example

CXR example
  • 1,2-10: first rib, posterior aspect of ribs 2 to 10
  • AK: aortic knob
  • APW: aortopulmonary window
  • BS: breast shadow
  • C, T: carina, tracheal air column
  • CA, GA: colonic air, gastric air
  • CPA: costophrenic angle
  • DA: descending aorta
  • LHB: left heart border (most of which represents the left ventricle, the superior aspect represents the left atrial appendage)
  • LPA: left pulmonary artery
  • RC: right clavicle
  • RHB: right heart border (represents the right atrium)
  • PHB: posterior heart border
  • RHD, LHD: right hemidiaphragm, left hemidiaphragm
  • RPA: right pulmonary artery
  • S: scapula
  • RA: retrosternal space
  • RMF: right lung fissure (left major and minor fissures are not always visualized)

Chapter 15. Imaging Studies. Gomella L.G., & Haist S.A. (Eds.), (2007). Clinician's Pocket Reference: The Scut Monkey, 11e. McGraw Hill.