Radiology Patterns

• Radiolucent indicates a dark pattern typically associated with air.
• Radiodense/opacity/radiopaque indicates a white pattern usually associated with solids or fluids, normal in bones and organs.
• Infiltrate refers to an ill-defined radiodensity, such as in atelectasis.
• Consolidation refers to a solid white area, like that seen in pneumonia or pleural effusion.
• Hyperlucency indicates extra pulmonary air, seen in conditions like COPD, asthma, and pneumothorax.
• Vascular markings include lymphatics, vessels, and lung tissue; they increase with CHF and are absent with pneumothorax.
• Diffuse means spread throughout, seen in atelectasis or pneumonia.
• Opaque indicates fluid or solid, as in consolidation.
• Bilateral means both sides, while unilateral means one side.
• Fluffy infiltrates show a diffuse whiteness, often in a butterfly or batwing pattern, indicative of pulmonary edema.
• Patchy infiltrates are scattered densities, seen in atelectasis.
• Platelike infiltrates are thin-layered densities, also seen in atelectasis.
• Ground glass or honeycomb patterns show a reticulogranular distribution through both lung fields, associated with ARDS or fibrosis.

Radiographic Positions

• Posteroanterior (PA), lateral, right anterior oblique, anteroposterior (AP), anteroposterior supine, right lateral decubitus are various radiographic positions.
• In a supine position, the diaphragm is elevated.
• On an AP film, the heart appears larger because it is more anterior.
• Penetration refers to the amount of x-ray exposure.
• Overpenetrated films appear too black, while underpenetrated films appear too white.

Indications for Chest X-Ray (CXR)

• Unexplained dyspnea
• Severe persistent cough
• Hemoptysis
• Fever and sputum production
• Acute severe chest pain
• Positive TB skin test
• ETT placement
• Placement of a pulmonary artery catheter or central venous pressure catheter
• Elevated or changing plateau pressure during mechanical ventilation
• Sudden decline in oxygenation

Analysis of Chest X-Rays:

• Airways: Check trachea midline or for any shifts.
• Bones & soft tissue: Examine vertebral bodies, spinal processes.
• Cardiac Silhouette & mediastinum: Look for enlargement or deviation.
• Diaphragm: Note the gastric bubble, flattening, right side slightly higher than left due to the liver.
• Effusions: Check for pleural effusions, using lateral decubitus to rule out.
• Fields: Examine the lung fields.
• Hilum (right and left): The point where the main bronchus, pulmonary arteries, bronchial arteries, and nerves enter the lung.
• Hydrothorax: More commonly called a pleural effusion.
• A blunted costophrenic angle on a chest x-ray indicates the presence of a pleural effusion.
• About 200 ml of pleural fluid will blunt the costophrenic angle.
• The best chest x-ray view for detecting small pleural effusions is the lateral decubitus.
• Pus in the pleural space is termed empyema.

Pneumothorax

• Refers to a collection of air in the pleural space.
• May occur spontaneously, with trauma, or with an invasive procedure.
• Can occur with mechanical ventilation, in which case it is called barotrauma.
• Pneumothorax causes the lung margin to pull away from the chest wall in the affected region.
• The presence of air can be better visualized by comparing inspiratory vs. expiratory CXRs.

Pulmonary Embolism

• CAT scan is the gold standard for diagnosing a pulmonary embolism.
• V/Q scan can be used to assess pulmonary emboli

Pulmonary Infiltrates

• Seen when alveoli fill with watery fluid (edema), pus (pneumonia), blood (alveolar hemorrhage), or fat-rich material (alveolar proteinosis).
• Appear as white shadows in the lung.
• Air bronchogram refers to the phenomenon of air-filled bronchi (dark) being made visible by the opacification of surrounding alveoli (grey/white).

Pulmonary Edema

• Kerley B-lines are often seen with pulmonary edema due to left heart failure.
• Chest radiograph often shows an enlarged heart and pleural effusion with CHF.

Interstitial Lung Disease (ILD)

• Chest radiograph usually shows diffuse, bilateral infiltrates.
• Infiltrates may look like scattered ill-defined nodules.
• There are many different types of ILDs; the two most common are idiopathic pulmonary fibrosis and sarcoidosis.
• A "honeycomb" appearance can occur.

Other Signs

• Thumb sign indicates epiglottitis, while the steeple sign indicates croup.
• Absence of lung markings on the affected side is consistent with a tension pneumothorax.