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Radiation Pneumonitis
 

  • Damage to lungs after radiation therapy
  • Usually requires at least 4500 rads
    • Especially common if >6000 R given in 5-6 weeks
  • Occurs more often if there is concurrent or later chemotherapy
  • Pathologic phases
    • Exudative phase = edema fluid + hyaline membranes
    • Organizing phase
    • Fibrotic phase = interstitial fibrosis
  • Time of onset
    • Usually at least 6 weeks up to 6 months after treatment
  • Location
    • Confined to radiation portal



Radiation portal (left) with subsequent radiation pneumonitis

       Acute Radiation Pneumonitis

o       Occurs within 1-8 weeks after radiation therapy

o       Pathology

         Depletion of surfactant (1 week to 1 month later), plasma exudation, desquamation of alveolar + bronchial cells

o       Usually asymptomatic

o       When symptomatic

         Nonproductive cough, shortness of breath, weakness, fever (insidious onset)

         Acute respiratory failure (rare)

o       Changes usually confined to radiation portal

o       Patchy / confluent consolidation, may persist up to 1 month (exudative reaction)

         Atelectasis + air bronchogram

         Spontaneous pneumothorax (rare)
 

  • CT findings of acute radiation pneumonitis
    • Homogeneous slight increase in attenuation (2-4 months after therapy)
    • Patchy consolidation (1-12 months after therapy)
    • Non-uniform discrete consolidation (most common; 3 months to 10 years after therapy)

 

Sequential transverse images through lung showing radiation pneumonitis in right lung 

  • Prognosis
    • Recovery or progression to death from fibrosis
  • Rx
    • Steroids

       Chronic Radiation Damage

o       9-12 months after radiation therapy

o       Histology

         Permanent damage of endothelial + type I alveolar cells

o       May be associated with:

         Thymic cyst

         Calcified lymph nodes (in Hodgkin disease)

         Pericarditis + effusion (within 3 years)

         Severe loss of volume

         Dense fibrous strands from hilum to periphery

         Thickening of pleura

o       CT findings

         Solid consolidation (radiation fibrosis) + bronchiectasis (stabilized by 1 year after therapy) 

 

Text from Dahnert, 4th Edition

 

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