Low field combined diffusion-relaxation MRI for mapping placenta structure and function

Combined diffusion-relaxation MRI shows potential for improved characterisation of pregnancy complications. All existing diffusion-relaxation studies in the placenta are at high field strength, mostly 3T. Here we demonstrate quantitative multi-parametric mapping in the placenta with combined T2*-diffusion MRI at low-field strength (0.55T). We present 56 placental MRI scans performed on a commercially available 0.55T scanner. We acquired the images using a combined T2*-diffusion technique 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. Quantitative parameter maps show similar spatial patterns, but different absolute values, to previous experiments at high field strength, with similar trends in T2* and ADC against gestational age observed. Combined T2*-diffusion placental MRI is reliably achievable at 0.55T. The advantages of low-field imaging - such as reduced cost, ease of deployment, improved accessibility, greater patient comfort due to the wider bore, and longer T2* values enabling greater absolute range - can support the broader adoption of quantitative placental MRI techniques, such as combined T2*-diffusion, as a complementary tool to ultrasound during pregnancy. • Demonstrate combined T2*-diffusion MRI in the placenta at low field strength (0.55T), using a commercially available scanner. • Present quantitative T2* and ADC maps from 56 scans, showing spatial patterns and gestational trends consistent with high-field studies. • Show repeatability of the technique with a test–retest scan. • Highlight the potential to combine the practical benefits olow-field MRI – including lower cost, wider bore, and longer T2* – with the clinical value of combined T2*-diffusion imaging to improve access and utility.