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Objectives: T2*‐weighted magnetic resonance imaging (MRI) sequences have been identified as non‐invasive tools with which to study placental oxygenation in vivo. This study aimed to use these to investigate both static and dynamic responses to hyperoxia of the normal placenta across gestation. Methods: We conducted a single‐center prospective study including 52 uncomplicated pregnancies. Two T2*‐weighted sequences (T2* relaxometry) were performed, one before and one after maternal hyperoxia. The distribution of placental T2* values was modeled by fitting a gamma probability density function (T2* ~Γαβ), describing the structure of the histogram using the mean T2* value, the shape parameter (α) and the rate (β). A dynamic acquisition (blood‐oxygen‐level‐dependent (BOLD) MRI) was also performed before and during maternal oxygen supply, until placental oxygen saturation had been achieved. The signal change over time was modeled using a sigmoid function, to determine the intensity of enhancement (ΔBOLD (% with respect to baseline)), a temporal variation coefficient (λ (min–1), controlling the slope of the curve) and the maximum steepness (Vmax (% of placental enhancement/min)). Results: The histogram analysis of the T2* values in normoxia showed a whole‐placenta variation, with a decreasing linear trend in the mean T2* value (Pearson's correlation coefficient (R) = −0.83 (95% CI, −0.9 to −0.71), P < 0.001), along with an increasingly peaked and narrower distribution of T2* values with advancing gestation. After maternal hyperoxia, the mean T2* ratios (mean T2*hyperoxia/mean T2*baseline) were positively correlated with gestational age, while the other histogram parameters remained stable, suggesting a translation of the histogram towards higher values with a similar appearance after maternal hyperoxia. ΔBOLD showed a non‐linear increase across gestation. Conversely, λ showed an inverted trend across gestation, with a weaker correlation (R = −0.33 (95% CI, −0.58 to −0.02), P = 0.04, R2 = 0.1). As a combination of ΔBOLD and λ, the changes in Vmax throughout gestation were influenced mainly by the changes in ΔBOLD and showed a positive non‐linear correlation with gestational age. Conclusions: Our results suggest that the decrease in the T2* placental signal as gestation progresses does not reflect placental dysfunction. The BOLD dynamic signal change is representative of a free‐diffusion model of oxygenation and highlights the increasing differences in oxygen saturation between mother and fetus as gestation progresses (ΔBOLD) and in the placental permeability to oxygen (λ). © 2024 International Society of Ultrasound in Obstetrics and Gynecology. [ABSTRACT FROM AUTHOR]

This article discusses the potential of "black bone" (BB) MRI imaging sequences as an alternative to conventional radiography for examining the skeleton in fetuses during post-mortem MRI examinations. The study involved 60 fetuses, and skeletal abnormalities were found in 31.6% of cases. The overall sensitivity and specificity of BB MRI for skeletal pathology were 89.4% and 97.5% respectively. The main limitation of fetal BB MRI sequences was the diagnosis of craniosynostosis. The authors conclude that BB MRI imaging sequences offer a radiation-free method for imaging the fetal skeleton and could be a potential alternative to radiography for analyzing bone anomalies. [Extracted from the article]

Diffusion tensor Imaging (DTI) and tractography offer a unique possibility to visualise and evaluate the developing white matter in fetal brain. DTI could be used to explore the normal spinal cord development and to study pathological development of the spinal cord. The aim of this preliminary study was to assess the feasibility of DTI and tractography in the evaluation of the fetal spinal cord. [Extracted from the article]