In Utero Diffusion MRI

Abstract

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Spatiotemporal tissue maturation of thalamocortical pathways in the human fetal brain

“…MRI has an inherently low signal:noise ratio as signal attenuation is deliberately introduced and EPI acquisitions are highly susceptible to motion and distortion artefacts. Furthermore, the biophysical properties of the fetal environment introduce a series of additional inter-dependent challenges for acquiring high-quality dMRI data ( Christiaens et al, 2019a ; Christiaens et al, 2019b , Tournier et al, 2020 ). In utero imaging methods must adapt and account for unpredictable, sometimes abrupt motion of fetus, in addition to the motion introduced by maternal breathing.…”

“…Achieving even coverage of the magnetic coil is challenging due to varying fetal and maternal positions inside the scanner, introducing unique bias fields for every subject. The dHCP acquisition protocol and pre-processing pipelines have incorporated dynamic distortion and motion correction algorithms that were designed to specifically tackle the unique artefacts-associated imaging fetuses ( Deprez et al, 2020 ; Cordero-Grande et al, 2018 ; Cordero-Grande et al, 2019 ; Christiaens et al, 2019a ; Christiaens et al, 2019b ; Hutter et al, 2018b ; Price et al, 2019 ). However, even after the extensive correction procedures, there is still some residual motion and distortion in the data.…”

“…However, even after the extensive correction procedures, there is still some residual motion and distortion in the data. For a more extensive and comprehensive review of challenges associated specifically with in utero diffusion imaging and constructive suggestions to address them, readers are directed to Christiaens et al, 2019b .…”

Anisotropy in the Human Placenta in Pregnancies Complicated by Fetal Growth Restriction

“…Specific challenges of in-utero placental MRI include motion, such as maternal breathing and fetal movements, various air-tissue interfaces such as amniotic fluid, abdominal fat and bowel gas, and the suboptimal position of the imaging coil with respect to the organ of interest, especially for placentas located on the posterior wall of the uterus [5]. Another important limitation specifically for diffusion MRI arises Fig.…”

“…Panel B: pathological branching structure, associated with prengancy complications such as fetal growth restriction from the safety requirement to reduce the acoustic sound level of the sequence to protect the fetal hearing. Therefore, typically the gradient slew rate is reduced, in consequence increasing the read-out length and thus the echo time resulting in lower Signal-to-Noise Ratios (SNR) [5,16].…”