Estimating lung volumetric parameters via rapid, limited-slice, free-breathing thoracic dynamic MRI

Purpose: We present an observational study involving free-breathing short-scan-time dynamic MRI (dMRI) method that can be routinely used for computing dynamic lung volumes accurately. Materials and Methods: (i) Full-resolution free-breathing sagittally-acquired 2D dMRI scans are gathered from 45 normal children via True-FISP sequence. Sparse dMRI (s-dMRI) scans are simulated from these datasets by subsampling in the spatio-temporal domains via a limited number NSS of selected sagittal locations and TSS of time instances (respectively, NFS and TFS for full scan). (ii) A 4D image is constructed from both full and sparse scans. Lungs are segmented from 4D image, and their volumes from full (VF) and sparse dMRI (VS) scans are computed. (iii) A regression model is fit for VF as a function of VS on a training set, and the full-resolution volume VP predicted by the model is estimated from VS. (iv) The deviation of VP from VF is analyzed on both synthesized sparse dMRI scans from a separate full-resolution test set and actual s-dMRI scans prospectively acquired from 10 normal children. Results: With NSS=5 (per lung) and TSS=40, the deviation of VP from VF was ~2% with a total scan-time of ~9 min (45-60 min for the full scan with NFS=15-22 (per lung) and TFS=80). These metrics become 0.4%, and <20 min for s-dMRI with NSS=15-22 (per lung) and TSS=40. Conclusion: s-dMRI is a practical approach for computing dynamic lung volumes that can be used routinely with no radiation concern, especially on patients who cannot tolerate long scan times. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study was funded by a grant from the National Institutes of Health R01HL150147. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethics committee/IRB of the Children's Hospital of Philadelphia (CHOP) and University of Pennsylvania gave ethical approval for this work. Written consent was obtained by the study team from the parents/guardians of the participating children to take part in the study and to have the results published. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors