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

Background: The diaphragm is a critical structure in respiratory function; however, in vivo quantitative description of its motion available in the literature is limited. Research Question: How do we quantitatively describe regional hemidiaphragmatic motion and curvature via free-breathing dynamic MRI (dMRI)? Study Design and Methods: In this prospective cohort study, we gathered dMRI images of 177 healthy children and young adults and segmented hemidiaphragm domes in end-inspiration and end-expiration phases of the constructed 4-dimensional image. We selected 25 points uniformly located on each 3-dimensional (3D) hemidiaphragm surface. Based on the motion and local shape of hemidiaphragm at these points, we computed the velocities and sagittal and coronal curvatures in 13 regions on each hemidiaphragm surface and analyzed the change in these properties with age and sex. Results: This cohort consisted of 94 female patients (range, 6-20 years; mean ± SD, 12.09 ± 3.73 years) and 83 male patients (range, 6-20 years; mean ± SD, 11.88 ± 3.57 years). We observed the following: velocity range: approximately 2 to approximately 13 mm/s; and curvature range: sagittal: approximately 3 to approximately 27 m Interpretation: Regional motion/curvature of the 3D diaphragmatic surface can be estimated using free-breathing dMRI. Our analysis sheds light on heretofore unknown matters such as how the pediatric 3D hemidiaphragm motion/shape varies regionally, between right and left hemidiaphragms, between sexes, and with age.