Diffusion-weighted post-mortem magnetic resonance imaging of the human fetal brain in situ

Purpose: To evaluate perinatal brain apparent diffusion coefficient (ADC) values at postmortem MRI (PMMR) in order to evaluate post mortem changes.

Materials and methods: Postmortem brain MRI was performed with diffusion gradient values b=0, 500, and 1000s/mm(2) on 43 fetal cases. Mean ADC values were calculated from 7 regions of interest (ROIs) throughout the brain.

Results: 43 fetuses were evaluated with median gestational age 36 weeks (range 21-41). Overall, fetal brain ADC varied with maceration score, but not with gestational age or post mortem interval. The best single predictor of brain ADC was maceration score, which accounted for 52% of data variation for frontal cortex (p<0.001) and 44% in basal ganglia (p<0.001), and between 24% and 32% in all five of the other included brain areas. Gestation was only significantly associated with occipital ADC changes and post mortem interval only significantly associated with basal ganglia ADC changes. Median intra-observer and inter-observer variability was 6.0% (95% range 1.0%-18.1%) and 8.0% (95% range 0.2%-33.9%) respectively.

Conclusion: DWI characteristics in different fetal brain areas following death are multifactorial, with maceration the strongest predictor in most anatomical areas. Deep grey matter areas are also affected by gestation and post mortem interval. With better models, brain ADC may be useful to estimate the degree of maceration where gestation and post mortem interval is unknown.