CXR interpretation

Question 1

What patient scenarios might justify a CXR?

Answer 1

• PNA
• Immunocompromised pt
• COPD with acute exacerbation
• Foreign body
• CHF
• Aspiration pneumonia
• Blunt trauma
• Rib fracture
• Lun tumor
• CP
• Suspected pneumothorax
• SOB (severe)
• Hemoptysis
• Pulmonary HTN
• Pulmonary embolism
• Interstitial lung dx
• ICU pt (adm, invasive lines, ETT)

Question 2

What are some basic tissue densities noted on a CXR?

Answer 2

• Black- air
• Dark gray- SQ tissue, fat
• Light gray- soft tissue
  
  • Muscle, heart, blood vessels, pus, blood, watery stuff
• Off White- bone
• Bright White- metal
  
  • Pacemakers, surgical clips, bullets

Question 3

What are some limitations of a supine CXR?

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Answer 3

• Supine limits full inspiration
  
  • Cephalic push noted→ liver and ABD contents pushing up on lungs/diaphragm
• Small pleural effusion will stay in posterior pleural space and can be missed
• Pneumothorax
  
  • Air would go to anterior portion of chest and may not be able to see it as well
• Be careful interpreting supine films!

Question 4

What are some differences of AP versus PA CXR?

Answer 4

• AP
  
  • Xray beam entering anterior thorax/exiting posterior thorax
  • Pt position- supine
  • Detector position- under them, below them, or on back
  • Heart size- magnified, accentuated
  • Diaphragm- cephalad push
• PA
  
  • Xray beam entering posterior/exiting anterior
  • Pt position- upright, sitting
  • Detector position- in front of chest
  • Heart size- truer to size
  • Diaphragm- caudal push

Question 5

When might an expiration CXR be useful?

Answer 5

• Small pneumothorax
  
  • Expiration will make lung smaller and denser→ makes pneumothorax appear larger
• Lodged foreign body
  
  • “Ball-valve phenomenon”
  • On inspiration, air can move past the object, but during expiration, the bronchus gets smaller, and air cannot exit around the object
    
    • The expiration image will show air trapping in affected lung and mediastinal shift toward unaffected side.

Question 6

What conditions might cause a pneumothorax and what might be seen on the Cxr?

Answer 6

• Pneumothorax- air positioned between visceral and parietal pleura
  
  • Trauma, SCL catheter
  • Liver bx
  • spontaneous→ bleb rupture
  • Mets
• Take with upright film preferred
• Deep sulcus sign present
  
  • If pt supine- air will be anterior portion chest
    
    • Costophrenic angle- air travels and goes to sulcus (deep groove) and push/migrates caudal
      
      • Costophrenic angle looks longer, deeper, more acute

Question 7

What is a pleural effusion, some causes, and what will you look for on a CXR?

Answer 7

• Pleural effusion- collection of fluid between the visceral and parietal pleura
  
  • 100 mLs to be detected on upright CXR
• Look for:
  
  • Blunting of costophrenic angles
    
    • CLASSIC place to look in upright position
    • Fluid will go down and angle will not be sharp, acute, demarcated
  • Increased basilar density (whiteness)
  • loss of normal lung- Hemidiaphragm is noted
  • IF SUPINE- see effusion horizontally in posterior pleural space (increased density/whiteness)
    
    • When in doubt→ get decubitus (on their side)
• Causes:
  
  • Malignancies
  • Pancreatitis (left side)
  • Cirrhosis (right side)
  • CHF (bilateral)
  • PNA

Question 8

Describe some causes for a mediastinal shift, and which way the shift would be.

Answer 8

• Tension pneumothorax- mediastinum shifted toward UNAFFECTED side
• Atelectasis- collapse of entire lung segment result in severe volume loss
  
  • See mediastinal shift toward AFFECTED side
• Airway obstruction- mediastinal shift toward UNAFFECTED side

Question 9

What is overexposure and underexposure on a CXR? What might be easier or harder to see on each exposure?

Answer 9

Overexposure

• Image is dark
  
  • Easy to see
    
    • Thoracic spine
    • Medistinal strucutre
    • Clavicles (bone)
    • Behind the heart (retrocardiac)
    • NG and ETT placement
  • Cannot see
    
    • Pulmonary vessels
    • Small nodules
    • Fine structures

Underexposure

• Image is white
  
  • Easy to see
    
    • Pulm vasculature (don’t mistake for infiltrate)
  • Cannot see:
    
    • Behind the heart
    • Spinal anatomy
    • Behind hemidiaphragms

Question 10

What is the silhouette sign?

Answer 10

• Useful in interpreting CXR
• Determine location of abnormality in relation to normal structures
• RML vs RLL
  
  • Loss of right heart border= infiltrate in RML
  • Loss of right hemidiaphragm= infiltrate in RLL
  • Loss o left heart border= infiltrate in LUL
  • Loss of left hemidiaphragm= infiltrate in LLL

Question 11

What are mediastinal masses and where can certain pathological processes be seen?

Answer 11

Mediastinal mass→ widening or bulge in central soft tissue of the chest

• Anterior (tumors) (4T’s)
  
  • Thymoma
  • Thyroid lesions
  • Teratoma- germ cell
  • T cell lymphoma
• Middle
  
  • Thoracic aorta aneurysms
  • Neoplasms
  • Adenopathy
  • Diaphragmatic hernias
• Posterior
  
  • Neurogenic (90%)
  • Neuroblastomas
  • Neurofibromas
  • Schwannomas
  • Ganglioneuromas

Question 12

What is a systematic approach to analyzing CXR?

Answer 12

• Who
• What (orientation)–> AP, PA, Supine, upright
• When
• Why→ hx and PE important!
• Exposure
• Airway→ trachea dark (air), appears midline
• Bone→ see spinous process, clavicles, appear flat, ribs good
• Cardiac→ see all boarders, see aortic knob, measure how big (no > ½ chest)
• Diaphragm/medistinum- hila composed of pulm arteries and major bronchi, no widening (masses)
• Everything Else- markings all the way out to ⅓ of lung fields, address NG tube, ETT

Question 13

How can you tell if there is good inspiration or hypinflation on a CXR?

Answer 13

• Good inspiration= hemidiaphragm down to level of posterior 10th/11th rib
  
  • standing–> 10th rib
  • sitting/lying–> between 8-10th rib
• Hypoinflation- dome at 7th rib

Question 14

Why is position important on CXR? What might be affected based on position?

Answer 14

• Magnification
• organ position
• blood flow
• gravitational pull