Pediatric thoracic magnetic resonance imaging: current evidence, technical advances, and clinical integration

This review summarizes established, emerging, and investigational techniques in pediatric thoracic magnetic resonance (MR) imaging (MRI), with emphasis on practical protocol optimization, motion mitigation, clinical implementation, and modality selection relative to computed tomography (CT). Thoracic MRI remains technically challenging because of low proton density, short apparent transverse relaxation time, and continuous cardiorespiratory motion. Conventional fast and motion- robust sequences, including single-shot T2-weighted imaging, three-dimensional T1-weighted spoiled gradient echo imaging, short tau inversion recovery, balanced steady-state free precession, and periodically rotated overlapping parallel lines with enhanced reconstruction/BLADE, are well established and form the basis of routine clinical protocols. Contrast-enhanced MR angiography, perfusion imaging, diffusion-weighted imaging, and dynamic functional imaging are clinically available for selected indications, particularly in experienced centers. In contrast, ultrashort and zero echo time imaging remain emerging techniques because availability, reconstruction, and implementation vary across vendors and institutions. Non-contrast functional approaches, including Fourier decomposition and arterial spin labelling, remain predominantly investigational, and hyperpolarized gas MRI is primarily research-oriented and requires specialized infrastructure. Protocols should be adapted to patient age, cooperation, and the clinical question, using coaching, feed-and-wrap, sedation, or anesthesia when necessary. Magnetic resonance imaging can replace or complement CT in selected settings, including serial assessment of complicated pneumonia, cystic fibrosis, congenital thoracic abnormalities, mediastinal lesions, chest wall disorders, and selected vascular conditions. However, CT remains the reference standard for rapid emergency assessment, subtle interstitial abnormalities, and very small pulmonary nodules. Wider adoption of advanced MRI techniques will require protocol standardization, automated reconstruction and post-processing, cross-platform reproducibility, and prospective multicenter validation.