High resolution isotropic diffusion imaging in post-mortem neonates: a feasibility study

To investigate the potential of advanced diffusion weighted imaging (DWI) in post-mortem MRI (PMMR) at 3T.

We acquired PMMR brain and body imaging in 12 neonates, mean gestational age 33.4 weeks (range 29-37 weeks) at 3T and 1.5T. Head and body diffusion imaging at 1.5T consisted of bipolar diffusion encoding and single-shot spin-echo echo-planar imaging (SE-EPI) for acquisition (echo time (TE) 96 ms; repetition time (TR) 2700 ms; voxel size 1.8 x 1.8 mm in-plane with slice thickness 5 mm; b-values of 500 and 1000 s/mm² applied in three orthogonal directions; total acquisition time 2:12). A whole-body 3T diffusion imaging protocol using monopolar diffusion encoding and simultaneous multislice EPI acquisition with gradients applied in 12 uniformly distributed directions was obtained (TE 53.4 ms; TR 5600 ms; 1.8 mm isotropic; multiband factor 2; b-values of 250, 750, 1250 and 1750 s/mm²; acquisition time 2:09 for a single b-value).

There was significant improvement in image quality in multiband, multislice diffusion PMMR protocol. On visual assessment of image quality, 1.5T DWI scored poorly (mean 2.4 SD ± 0.47), and all 3T b-values individually scored significantly higher (p < 0.001) apart from b = 250 s/mm² which was not significantly different.

Recent advances in diffusion sequences and hardware utilising higher field strengths and gradient performance allows whole-body diffusion PMMR imaging at high resolution with improved image quality compared to the current clinical approach.

We have demonstrated feasibility of a multislice, multiband quantitative diffusion imaging sequence in the perinatal post-mortem setting. This will allow more detailed and quantitative clinical PMMR investigations using diffusion MRI in the future.