The effects of Position on Appearance in Chest Imaging

Chest X-Ray

Standard Views Film Appearances with Position

1.  
   1. Standing (Upright Chest X-Ray)
      1. Posteroanterior (PA) Film
      2. Left Lateral X-Ray
         1. Request right lateral film if right-sided finding
         2. More sensitive than PA for abdominal free air
   2. Supine (Portable Chest X-Ray)
      1. Anteroposterior (AP) Film
         1. Magnifies heart and anterior mediastinum
         2. Emphasizes rib and calcium contrast
         3. Lung parenchyma may appear washed out
2. Special Views
   
    
   1. Inspiration and Expiration Film Indications
      1. Pneumothorax accentuated on expiration
      2. Unilateral diaphragmatic paralysis
      3. Unilateral obstruction of major bronchus
          
   2. Lordotic View Indications
      1. Posterior Apical Disease
      2. Middle Lobe disease
         
          
   3. Reverse Lordotic View Indications
      1. Anterior apical disease
         
          
   4. Oblique Film
      1. Peripheral small lesions
         1. Separated from overlying chest shadows
         2. Lesions poorly seen on lateral chest X-Ray
      2. Rib fractures (at axillary lines)
         
          
   5. Lateral decubitus Film
      1. Detect small areas of air at uppermost pleural space
      2. Detect small areas of dependent pleural fluid
         1. Measure size and mobility of fluid collection
         2. Accessible with sampling needle (>1 cm size)
      3. Uncover Lung tissue obscured by pleural fluid
         1. Place side of interest up
      4. Mobility of mediastinal or pleural masses
      5. Assess mobility of solids and fluids within cavities
      6. Assist with maximizing inspiration of uppermost lung
          
   6. High Penetration Film with moving grid (Bucky Film)
      1. Obesity
      2. Dense pleural or pulmonary opacities
      3. Calcified lesions
      4. Lesions obscured by heart or diaphragms
      5. Air Bronchograms in densely infiltrated areas
         
          
   7. Intrathoracic Pressure Manoeuvres
      1. Valsalva Manoeuvre: shrinks pulmonary vessels
      2. Muller Manoeuvre: distends pulmonary vessels
      3. Indications
         1. Distinguish blood vessel from lymph node
         2. Distinguish A-V malformation from solid lesion
   8. Barium Swallow
      1. Enlarged retro-mediastinal nodes
      2. Define Posterior intrathoracic mass
      3. Confirm ruptured diaphragm or Diaphragmatic Hernia
      4. Impaired swallowing with aspiration
   9. Diagnostic Pneumothorax (instill air in pleural space)
      1. Distinguish peripheral lung mass from pleural lesion
      2. Define mesothelioma
      3. Parenchymal disease extending towards chest wall
         
          
3. Circumstances that decrease Chest X-Ray quality
   
    
   1. Semi-upright position (neither standing nor supine)
      1. May enlarge normal structures
      2. Changes air-fluid levels
   2. Lordosis or vertical axis rotation
      1. Widens heart and mediastinum
   3. Inadequate sustained inspiration
      1. Breathing film
         1. Lung structures and diaphragm blurred
      2. Expiration film
         1. Basilar infiltrates accentuated
         2. Interstitial structures accentuated
            1. Vessels
            2. Pleural fluid
         3. Increased heart size
   4. Supine Film
      1. Decreases Lung Volume
         1. Highlights infiltrates and interstitium
      2. Increases venous return to heart
         1. Distends azygous vein and pulmonary vein
      3. Diaphragm rises and intracardiac pressure increases
         1. Heart and mediastinal structures enlarge
      4. Fluid and air migrate
         1. Pleural Effusions disappear
         2. Small Pneumothorax disappears
         3. Air-Fluid levels (e.g. Lung Abscess) disappear
      5. Pneumothorax signs on supine film
         1. Deep Sulcus sign
            1. Costophrenic angle sharply outlined by air
            2. Diaphragm-mediastinal junction sharply outlined
         2. Hyperlucency superimposed over liver shadow

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