Free-breathing Dynamic MRI Analysis of Three-dimensional Diaphragm Curvatures in Pediatric Patients with Thoracic Insufficiency Syndrome.

Purpose To quantify regional respiratory function using four-dimensional free-breathing dynamic MRI (dMRI) and evaluate vertical expandable prosthetic titanium rib surgery impact on diaphragm curvature in pediatric thoracic insufficiency syndrome (TIS) using pre- and postoperative and control comparisons. Materials and Methods Curvature was retrospectively analyzed in 149 pediatric patients with TIS from May 2010 to November 2022 (49 pre- and postoperative, 70 preoperative-only, 30 postoperative-only dMRI) and compared with 190 controls. Mean follow-up ± SD was 2.4 years ± 1.8. Diaphragm contours were delineated at end-expiration and end-inspiration, and curvature was quantified across 13 regions per hemidiaphragm. Analyses included paired t tests, one-way analysis of variance to compare with controls, and correlation analyses relating postoperative curvature to ventilatory status and thoracic Cobb angle. Results Patients with TIS (mean age, 3.5 years ± 3.5; 27 male) demonstrated region-, plane-, and phase-dependent preoperative curvature differences compared with controls (mean age, 11.9 years ± 3.6; 92 male). Significant pre- to postoperative curvature changes were limited to five region-plane-phase combinations. The right hemidiaphragm anterior-lateral region at end-expiration showed the only sagittal-plane change (6.3 m-1 ± 0.7 to 8.2 m-1 ± 0.6, P = .02), approaching control values (9.3 m-1 ± 2.6). Several regions were no longer different from controls, most prominently in the right hemidiaphragm coronal plane at end-inspiration, whereas others, particularly sagittal end-inspiration regions, remained different (P < .05). Postoperative curvature correlated with ventilatory status, strongest in central sagittal regions (ρ ≤ 0.392, P < .001), and with thoracic Cobb angle in posterior sagittal regions (ρ ≤ 0.385, P < .001). Conclusion Surgery resulted in plane- and phase-specific improvements in diaphragm curvature, with partial normalization toward control values predominantly in coronal-plane regions. Keywords: Pediatrics, MR-Functional Lung Imaging, MR-Imaging, Pulmonary, Diaphragm, Anatomy, Treatment Effects, Outcomes Analysis, Comparative Studies, Curvature, Dynamic MRI, Quantitative Radiology, Shape, Thoracic Insufficiency Syndrome (TIS) Supplemental material is available for this article. © RSNA, 2026.