Galvin: Lung Imaging as a Bridge to Anatomy, Physiology, and Histology

[x_text]Today we welcome Jeffrey R. Galvin, MD, Professor, Departments of Radiology and Internal Medicine (Division of Pulmonary and Critical Care Medicine) at the University of Maryland Medical System, and Chief, Chest Imaging at the American Institute for Radiologic Pathology. Dr Galvin has the distinct pleasure of being board certified in Internal Medicine, Pulmonary Medicine and Radiology! That background makes him one of the world’s experts in diagnostic imaging of the lung. I cannot stress the importance of adding this lecture to a rotating list of lectures you watch at least once a month! [/x_text]

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Clinical Pearls

Assisted by Sofian Al-Khatib

• #1 key to diagnosis of diffuse lung dz is to identify some key features of the lung disease:
  • lung volumes, disease location in respect to gravity, physiological basis of distribution, CT opacities, and involvement of any secondary nodules.
• No longer should we look at radiographs and talk about “alveolar vs interstitium”
  • Take a methodical approach when it comes to chest imaging
• Simplistic approach
  • Lung Volume?
    • Reduced: (* Fibroblasts contract = fibrosis has reduced lung volume) IPF, Sarcoidosis, Hypersensitivity Pneumonitis
    • Increased: Obstructive lung disease: Asthma, COPD
  • Distribution
    • Effect of Gravity:
      • Blood flow and hydrostatic pressure dictates pathology to the inferior of lungs
      • Air flows superiorly
        • Inhaled diseases affect the lungs in an apical and posterior fashion (Tb, silica…).
    • Lymphatics
      • Sarcoid concentrates around lymphatics
      • Lymphatics have a one-way valve, so the simple motion of the lung parenchyma will clear the periphery by accentuating this one-way movement
    • Metastases- look to the periphery (must be <2-3 μ to get to alveoli past the filtering system)
    • Effect of Stress:
      • Inherit weight of lung causes more stress to the top of lungs
    • Simply approach:
      • upper vs. lower, central vs. peripheral
      • Note the area: vascular, airways, lymphatics
  • Opacity- Terminology is key in diagnosis
    • Basic:
      • Nodule: focal < 10 mm
      • Mass: > 1cm
      • Lines: Uniform in width
      • Ground glass: Still can see parenchyma
      • Consolidation: Unable to see parenchyma/edges of airway/blood vessels
      • “Low attenuation without walls”
      • “Low attenuation with walls”
    • Complex
      • Combined mosaicism attenuation
      • Crazy paving
      • Reticulation: “Net-like”
        • Surrogate for fibrosis
        •  Traction bronchiectasis: fibrosis causing airway dilation
• Note the location of the disease
  • Secondary Lobule
    • Smallest unit, demarcated connective tissue septa
      • Core Structures
        • Bronchiole
          • Pulmonary arteries
          • Lymphatics (none in alveolar walls)
        • Parenchyma
          • Alveoli
          • Alveolar wall
          • Capillary bed
        • Septal Structures
          • Pulmonary veins (live in inter-lobular septa)
          • Lymphatics (again!)
    • When evaluating pathology on the CT scan, try to locate the location
      • Centrilobular: Inflammation, infections
      • Panlobular: Blood, pus, water

 

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[x_text]Suggested Reading

1. Gurney JW, Schroeder BA. Upper lobe lung disease: physiologic correlates. Review. Radiology. 1988 May;167(2):359-66.[PubMed Link]
2. Gurney JW. Cross-sectional physiology of the lung. Radiology. 1991 Jan;178(1):1-10.[PubMed Link]
3. Weibel ER. What makes a good lung? Swiss Med Wkly. 2009 Jul 11;139(27-28):375-86. [PubMed Link]
4. West JB. Distribution of mechanical stress in the lung, a possible factor in localisation of pulmonary disease. Lancet. 1971 Apr 24;1(7704):839-41. [PubMed Link]

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