Quantifying Normal Diaphragmatic Motion and Shape and their Developmental Changes via Dynamic MRI.

Background:The diaphragm is a critical structure in respiratory function, yet in-vivo quantitative description of its motion available in the literature is limited. Research Question:How to quantitatively describe regional hemi-diaphragmatic motion and curvature via free-breathing dynamic magnetic resonance imaging (dMRI)? Study Design and Methods:In this prospective cohort study we gathered dMRI images of 177 normal children and segmented hemi-diaphragm domes in end-inspiration and end-expiration phases of the constructed 4D image. We selected 25 points uniformly located on each 3D hemi-diaphragm surface. Based on the motion and local shape of hemi-diaphragm at these points, we computed the velocities and sagittal and coronal curvatures in 13 regions on each hemi-diaphragm surface and analyzed the change in these properties with age and gender. Results:Our cohort consisted of 94 Females, 6-20 years (12.09 + 3.73), and 83 Males, 6-20 years (11.88 + 3.57). We observed velocity range: ∼2mm/s to ∼13mm/s; Curvature range -Sagittal: ∼3m -1 to ∼27m -1 ; Coronal: ∼6m -1 to ∼20m -1 . There was no significant difference in velocity between genders, although the pattern of change in velocity with age was different for the two groups. Strong correlations in velocity were observed between homologous regions of right and left hemi-diaphragms. There was no significant difference in curvatures between genders or change in curvatures with age. Interpretation:Regional motion/curvature of the 3D diaphragmatic surface can be estimated using free-breathing dynamic MRI. Our analysis sheds light on here-to-fore unknown matters such as how the pediatric 3D hemi-diaphragm motion/shape varies regionally, between right and left hemi-diaphragms, between genders, and with age.