Low-Field Combined Diffusion-Relaxation MRI for Mapping Placenta Structure and Function

Purpose: Demonstrating quantitative multi-parametric mapping in the placenta with combined T2*-diffusion MRI at low-field (0.55T). Methods: We present 57 placental MRI scans performed on a commercially available 0.55T scanner. We acquired the images using a combined T2*-diffusion technique scan that simultaneously acquires multiple diffusion preparations and echo times. We processed the data to produce quantitative T2* and diffusivity maps using a combined T2*-ADC model. We compared the derived quantitative parameters across gestation in healthy controls and a cohort of clinical cases. Results: Quantitative parameter maps closely resemble those from previous experiments at higher field strength, with similar trends in T2* and ADC against gestational age observed. Conclusion: Combined T2*-diffusion placental MRI is reliably achievable at 0.55T. The advantages of lower field strength - such as cost, ease of deployment, increased accessibility and patient comfort due to the wider bore, and increased T2* for larger dynamic ranges - can support the widespread roll out of placental MRI as an adjunct to ultrasound during pregnancy. ### Competing Interest Statement Raphael Tomi-Tricot is an employee of Siemens Healthineers. ### Funding Statement This study was funded by NIH (1U01HD087202-01) Wellcome Trust (201374/Z/16/Z) EPSRC (EP/V034537/1 EP/M020533/1) UKRI (MR/T018119/1) MRC (MR/V002465/1) NIHR Biomedical Research Centre at UCLH NHS Foundation Trust and UCL Core funding from the Wellcome/EPSRC Centre for Medical Engineering at KCL (WT 203148/Z/16/Z) the NIHR Biomedical Research Centre based at Guys and St Thomas NHS Foundation Trust and KCL ### 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: London - Dulwich Research Ethics Committee of NHS Health Research Authority gave ethical approval for this work (19/LO/0852). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the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.