Virtual Bronchoscopy of Neonatal Airway Malacia via High-Resolution, Respiratory-gated Magnetic Resonance Imaging

Central airway malacia is a common complication in preterm infants with bronchopulmonary dysplasia or congenital respiratory disorders and is associated with prolonged hospitalization and other poor outcomes (5). Current assessment methods (e.g., invasive bronchoscopy and ionizing X-ray computed tomography) pose additional risks to vulnerable patients. We demonstrate virtual bronchoscopy of neonatal dynamic airway collapse via minimal-risk magnetic resonance imaging (MRI). Some of the results of these studies have been previously reported in the form of abstracts (6, 7).

With Institutional Review Board approval and parental consent, a male infant with severe bronchopulmonary dysplasia (23 weeks gestation and 590 g weight at birth) underwent ultrashort echo-time airway MRI (8) (three-dimensional resolution = 0.7 mm) during tidal breathing at 41 weeks corrected gestational age. The dynamic airway surface was constructed from static segmentation of respiratory-gated images with interpolation throughout the respiratory cycle (2, 4, 9). The reader is referred to previous publications for technical details on MRI acquisition, gated reconstruction, and quantitative airway analysis (2, 4, 8, 9). Collapse in the middle–lower trachea and right mainstem bronchus was visualized via a virtual “fly-through” of the moving surface (Video 1). This patient was diagnosed with tracheobronchomalacia on clinical bronchoscopy 1 week later, with a good regional agreement to virtual findings.

Video 1.

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The virtual bronchoscopy “fly-through” of the dynamic airway demonstrates malacia in the middle–lower trachea and right bronchus, in agreement with clinical bronchoscopy. The patient’s actual respiratory rate was 66 breaths/min, while the animated virtual view is slowed to 15 breaths/min for display purposes. The virtual fly-through view allows for the assessment of neonatal airway abnormalities that is readily interpretable to clinicians familiar with clinical bronchoscopy by providing sufficient spatiotemporal resolution of the central airway without requiring invasive, ionizing, sedated, or breath-holding procedures. A limitation of imaging-based virtual bronchoscopy can be seen beyond the generation of the main stem bronchi; finite imaging resolution (in this case, 0.7 × 0.7 × 0.7 mm) is not able to capture smaller distal airways and thus precludes the necessary image segmentation for animating the anatomical surface beyond the first few generations.

MRI-based virtual bronchoscopy allows for the novel, safe evaluation of neonatal tracheomalacia with views that are readily interpretable to clinicians. Virtual bronchoscopy may not replace current clinical endoscopy, in particular because the position of the patient cannot be modified during virtual bronchoscopy, nor can the airway tissue be evaluated directly. Even so, this minimal-risk imaging technique is appealing for serial evaluation of disease progression and therapeutic response and for identification of neonates with suspected abnormalities who would benefit from direct airway assessment.