Quantitative Assessment of Regional Dynamic Airway Collapse in Neonates via Retrospectively Respiratory-Gated 1 H Ultrashort Echo Time MRI.

<bold>Background: </bold>Neonatal dynamic tracheal collapse (tracheomalacia, TM) is a common and serious comorbidity in infants, particularly those with chronic lung disease of prematurity (bronchopulmonary dysplasia, BPD) or congenital airway or lung-related conditions such as congenital diaphragmatic hernia (CDH), but the underlying pathology, impact on clinical outcomes, and response to therapy are not well understood. There is a pressing clinical need for an accurate, objective, and safe assessment of neonatal TM.<bold>Purpose: </bold>To use retrospectively respiratory-gated ultrashort echo-time (UTE) MRI to noninvasively analyze moving tracheal anatomy for regional, quantitative evaluation of dynamic airway collapse in quiet-breathing, nonsedated neonates.<bold>Study Type: </bold>Prospective.<bold>Population/subjects: </bold>Twenty-seven neonatal subjects with varying respiratory morbidities (control, BPD, CDH, abnormal polysomnogram).<bold>Field Strength/sequence: </bold>High-resolution 3D radial UTE MRI (0.7 mm isotropic) on 1.5T scanner sited in the neonatal intensive care unit.<bold>Assessment: </bold>Images were retrospectively respiratory-gated using the motion-modulated time-course of the k-space center. Tracheal surfaces were generated from segmentations of end-expiration/inspiration images and analyzed geometrically along the tracheal length to calculate percent-change in luminal cross-sectional area (A % ) and ratio of minor-to-major diameters at end-expiration (r D,exp ). Geometric results were compared to clinically available bronchoscopic findings (n = 14).<bold>Statistical Tests: </bold>Two-sample t-test.<bold>Results: </bold>Maximum A % significantly identified subjects with/without a bronchoscopic TM diagnosis (with: 46.9 ± 10.0%; without: 27.0 ± 5.8%; P < 0.001), as did minimum r D,exp (with: 0.346 ± 0.146; without: 0.671 ± 0.218; P = 0.008). Subjects with severe BPD exhibited a far larger range of minimum r D,exp than subjects with mild/moderate BPD or controls (0.631 ± 0.222, 0.782 ± 0.075, and 0.776 ± 0.030, respectively), while minimum r D,exp was reduced in CDH subjects (0.331 ± 0.171) compared with controls (P < 0.001).<bold>Data Conclusion: </bold>Respiratory-gated UTE MRI can quantitatively and safely evaluate neonatal dynamic tracheal collapse, as validated with the clinical standard of bronchoscopy, without requiring invasive procedures, anesthesia, or ionizing radiation.<bold>Level Of Evidence: </bold>2 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2019;49:659-667. [ABSTRACT FROM AUTHOR]