The aim of this study was to evaluate real-time MRI (RT-MRI) for the characterization of breathing patterns in patients with late-onset Pompe disease (LOPD) and healthy subjects compared to standard diagnostics.

Respiratory dysfunction has a major impact on morbidity and mortality in patients suffering from neuromuscular diseases. Diagnosis of respiratory muscle weakness can be delayed due to compensatory mechanisms, which might conceal early symptoms of respiratory involvement.

11 patients with LOPD and 11 matched controls underwent 3 Tesla RT-MRI with 20 frames per second. This enabled the assessment of natural breathing mechanisms and dynamic respiratory maneuvers. Quantification of breathing patterns was performed both manually and by automatic segmentation using a U-Net. MRI-assessments were compared to pulmonary function test and ultrasound of the diaphragm. Additionally, fast T1 mapping was performed for tissue analysis of the diaphragmatic crurae. This allowed non-invasive tissue analysis of the diaphragm, thus enabling correlation of morphological and functional diaphragm characteristics.

RT-MRI enabled the exact quantification of reduced diaphragmatic motion in patients with LOPD, compensatory increase of thoracic movements during breathing maneuvers and unmasked paradoxical diaphragm movement during sniff maneuver in 9 out of 11 LOPD patients. Furthermore, U-Net supported lung segmentation allowed the analysis of new aspects of respiratory mechanisms including diaphragmatic/thoracic synchronicity and diaphragmatic/thoracic velocity during sniff maneuver. Additionally, our study showed a significant correlation between the degree of fatty involution of the diaphragm, as assessed by T1 mapping, with functional parameters from RT-MRI and pulmonary function test.

RT-MRI enables efficient and detailed quantification of respiratory muscle function. Quantitative T1-mapping provides a non-invasive approach to assess morphological changes in the diaphragm and relate them to functional parameters. Real-time MRI of the chest is expected to improve future identification and monitoring of breathing impairment in patients with neuromuscular disorders.