Purpose or Case Report: Dynamic and four-dimensional computed tomography (4D-CT) of the airways and lungs is an advanced imaging technique designed to identify dynamic pathologies across various levels of airway, including the oropharynx, larynx, trachea, bronchi, and lungs. This modality enables detailed assessment of airway motion and functional abnormalities that are intermittently absent on conventional static imaging. At the oropharyngeal level, Robin sequence (Pierre Robin syndrome) represents congenital anomalies resulting from abnormal development of the first pharyngeal arch, leading to mandibular hypoplasia, failure of normal tongue descent, non-fusion of the palatal shelves, and resultant upper airway obstruction. At the laryngeal level, vocal cord dysfunction is a cause of feeding difficulties and vocal dysfunction in the pediatric population, most frequently resulting from prolonged intubation or iatrogenic injury to the recurrent laryngeal nerve following cardiac surgery. In such cases, dynamic CT serves as a valuable, non-invasive alternative to nasal endoscopy for evaluating glottic motion. Tracheomalacia, defined as excessive expiratory collapse of the tracheal lumen, may be congenital—such as with cystic fibrosis or Mounier-Kuhn syndrome—or acquired secondary to prolonged intubation, chronic or recurrent infections, or idiopathic. Similarly, bronchomalacia refers to the weakening of bronchial cartilage, resulting in airway collapse or significant luminal narrowing during expiration, and may also occur congenitally or as a sequela of chronic inflammation. Dynamic CT of the lung parenchyma can demonstrate areas of air trapping during the expiratory phase, such as with bronchiolitis obliterans secondary to recurrent inflammation, although the precise clinical implications of the CT findings remain undefined. Importantly, many of these entities are challenging to detect on traditional inspiratory and expiratory CT imaging. Dynamic low-dose CT protocols not only enhance diagnostic accuracy by providing real-time functional assessment but also reduce overall radiation exposure by eliminating the need for separate phase acquisitions. This pictorial essay aims to review the spectrum of airway and lung pathologies detectable by dynamic and 4D-CT, emphasizing optimal imaging techniques, interpretative considerations, and risk-based diagnostic strategies relevant to pediatric radiologists.
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