Editor's Highlight: In Utero Exposure to Gadolinium and Adverse Neonatal Outcomes in Premature Infants

Two-Compartment Perfusion MR IVIM Model to Investigate Normal and Pathological Placental Tissue

BACKGROUND

Perfusion and diffusion coexist in the placenta and can be altered by pathologies. The two-perfusion model, where f1 and, f2 are the perfusion-fraction of the fastest and slowest perfusion compartment, respectively, and D is the diffusion coefficient, may help differentiate between normal and impaired placentas.

PURPOSE

Investigate the potential of the two-perfusion IVIM model in differentiating between normal and abnormal placentas.

STUDY-TYPE

Retrospective, case-control.

POPULATION

43 normal pregnancy, 9 fetal-growth-restriction (FGR), 6 small-for-gestational-age (SGA), 4 accreta, 1 increta and 2 percreta placentas.

FIELD STRENGTH/SEQUENCE

Diffusion-weighted-echo planar imaging sequence at 1.5 T.

ASSESSMENT

Voxel-wise signal-correction and fitting-controls were used to avoid overfitting obtaining that two-perfusion model fitted the observed data better than the IVIM model (Akaike weight: 0.94). The two-perfusion parametric-maps were quantified from ROIs in the fetal and maternal placenta and in the accretion zone of accreta placentas. The diffusion coefficient D was evaluated using a b ≥ 200 sec/mm2 -mono-exponential decay fit. IVIM metrics were quantified to fix f1  + f2  = fIVIM .

STATISTICAL-TESTS

ANOVA with Dunn-Sidák's post-hoc correction and Cohen's d test were used to compare parameters between groups. Spearman's coefficient was evaluated to study the correlation between variables. A P-value<0.05 indicated a statistically significant difference.

RESULTS

There was a significant difference in f1 between FGR and SGA, and significant differences in f2 and fIVIM between normal and FGR. The percreta + increta group showed the highest f1 values (Cohen's d = -2.66). The f2 between normal and percreta + increta groups showed Cohen's d = 1.12. Conversely, fIVIM had a small effective size (Cohen's d = 0.32). In the accretion zone, a significant correlation was found between f2 and GA (ρ = 0.90) whereas a significant negative correlation was found between fIVIM and D (ρ = -0.37 in fetal and ρ = -0.56 in maternal side) and f2 and D (ρ = -0.38 in fetal and ρ = -0.51 in maternal side) in normal placentas.

CONCLUSION

The two-perfusion model provides complementary information to IVIM parameters that may be useful in identifying placenta impairment.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY STAGE: 1.

Associations of maternal urinary rare earth elements individually and in mixtures with neonatal size at birth

Prenatal rare earth elements (REEs) exposure is linked to unfavorable health consequences. Epidemiologic research on repeated measurements of REEs during gestation correlated with fetal growth is exiguous. Until now, few studies have characterized exposure characteristics of REEs in pregnant women. We aimed to ascertain the characteristics and predictors of REEs exposure over three trimesters among pregnant women and examine the possible effects of prenatal REEs exposure on size at birth. Urinary REEs concentrations exhibited considerable within-subject variation with intraclass correlation coefficients ranging from 0.16 to 0.58. Maternal age, household income, gestational weight gain, passive smoking during pregnancy, parity, and neonatal gender were associated with maternal urinary REEs concentrations. Elevated maternal urinary holmium and thulium concentrations in the 3rd trimester were significantly related to reductions in birth weight. Weighted quantile sum (WQS) regression model identified that urinary REEs mixture in the 3rd trimester were negatively related to birth weight (WQSREEs β = -26.22; 95% confidence interval [CI]: -47.62, -4.82), with holmium (40%) and thulium (24%) receiving the highest weights. Male infants received the most weight (>50%) related to decreased birth weight. This study revealed a significant association between individual and mixture REE exposure in late pregnancy with a reduction in birth weight.

Gadolinium during human pregnancy following administration of gadolinium chelate before pregnancy

Gadolinium (Gd), a toxic rare earth element, has been shown to dissociate from chelating agents and bioaccumulate within tissues, raising concerns about the possibility of their remobilization during pregnancy with subsequent free Gd exposures to developing fetuses. Gd chelates are among the most commonly used magnetic resonance imaging (MRI) contrast agents. This investigation was undertaken after the detection of elevated Gd (800-1000× higher than the usual rare earth element levels) in preliminary unpublished studies from the placentae of subjects in the NIH ECHO/UPSIDE Rochester Cohort Study and unpublished studies from placentae analyzed in formalin-fixed placental specimens from Surgical Pathology at the University of Rochester. Fifteen pregnancies with elevated Gd were studied (12 first pregnancies and 3 second pregnancies). Maternal bloods were collected from all three trimesters, maternal, and cord (fetal) bloods at delivery as well as placental tissue. Breastmilk was also collected from selected mothers. It was determined that Gd was present in maternal bloods from all three trimesters, and in cord bloods and breastmilk in both first and second pregnancies. These results emphasize the need to fully appreciate the implications of pre-pregnancy exposure to Gd chelates and its potential effects on maternal and fetal health.

Functional diagnosis of placenta accreta by intravoxel incoherent motion model diffusion-weighted imaging

OBJECTIVES

To investigate the diagnostic value of intravoxel incoherent motion (IVIM) DWI for placenta accreta by comparing diffusion and perfusion characteristics of placentas with accreta lesions (APs) with those of normal placentas (NPs).

METHODS

Twenty-five pregnant women with AP and 24 with NP underwent 3-T magnetic resonance examinations with IVIM-DWI. The perfusion percentage (f), pseudo-diffusion coefficient (D*), and diffusion coefficient (D) values were calculated from different ROIs: the entire-plane of the AP (AP-ROI) and NP (NP-ROI) and the implanted (IR-ROI) and non-implanted region (NIR-ROI) of the AP. The AP-ROIs and NP-ROIs were compared using covariance analysis; the IR-ROIs and NIR-ROIs were compared using the Wilcoxon signed-rank test. ROC curves were produced to evaluate the parameters for predicting placenta accreta.

RESULTS

The f and D* values for the AP-ROIs ([45.0 ± 7.63]%, [11.64 ± 2.15]mm²/s) were significantly higher than those for the NP-ROIs ([31.85 ± 5.96]%, [9.04 ± 3.13]mm²/s) (both p < 0.05); the IR-ROIs (54.8%, 14.03 mm²/s) were also significantly higher than the NIR-ROIs (37.4%, 11.4 mm²/s) (both p < 0.05). No significant differences were found between the D values of the AP-ROIs and NP-ROIs (p > 0.05) or of the IR-ROIs and NIR-ROIs (p > 0.05). The areas under the curve for f and D* of the ROC curves were 0.93 and 0.79, respectively.

CONCLUSIONS

These results suggest that the IVIM parameters f and D* can be used to quantitatively evaluate the higher perfusion of AP when compared with NP. Furthermore, IVIM may be a useful functional diagnostic technique to predict placenta accreta.

KEY POINTS

• Intravoxel incoherent motion (IVIM) may be a useful diagnostic technique to quantitatively estimate the perfusion of the placenta. • The perfusion percentage (f) and pseudo-diffusion coefficient (D*) values differed significantly between placentas with accreta lesions and normal placentas. • ROC curves showed that perfusion percentage (f) and pseudo-diffusion coefficient (D*) values could accurately predict placenta accreta.

Neuroimaging and radiation exposure in pregnancy

Physiologic changes occurring in pregnancy and postpartum can have secondary effects on the maternal nervous system. While most alterations to neurologic function during pregnancy are transient, there is an elevated risk for more serious complication in the peripartum period, such as cerebrovascular events or exacerbation of preexisting neurologic conditions. Due to the morbidity and mortality associated with these neurologic manifestations in some cases, timely diagnostic evaluation is essential. In the pregnant population, the use of diagnostic techniques such as computed tomography (CT) and magnetic resonance imaging (MRI), commonly employed to evaluate emergent neurologic abnormalities, requires special consideration of the potential risks associated with prenatal exposure. This review discusses several neurologic conditions affecting women during pregnancy for which diagnostic imaging may be warranted. Concerns relating to CT and MRI procedures, radiation exposure in utero, and exposure to intravenous contrast by placental transfer and breastfeeding are also reviewed.

Measurements of signal intensity of globus pallidus and dentate nucleus suggest different deposition characteristics of macrocyclic GBCAs in children

Introduction

The safety of using GBCAs to enhance the visibility of body structures is currently discussed due to possible gadolinium retention in brain structures. The aim of the study was to evaluate the effect of multiple exposures to macrocyclic GBCAs in children.

Materials and methods

This retrospective, single-center study included data from 43 patients who had received ≥4 injections of macrocyclic GBCAs during MRI examinations over performed over 8 to 84 months. Signal intensity was measured on unenhanced T1-weighted MRI, and globus pallidus to thalamus (GP/Th) and dentate nucleus to pons (DN/P) ratios were calculated. The differences in ratios were tested with the Student’s t-test or the Wilcoxon rank sum test. For categorical data, Pearson's chi-squared test was used. Relationships were analyzed with the Spearman's rank correlation coefficient.

Results

Patients with the mean age of 7.5 years (SD = 4.2) received 8.19 (SD = 3.63) injections of GBCAs on average. Differences in GP/Th and DN/P ratios between the first and the last measurement were insignificant. Children before the end of myelination process (≤2 years of age) had the first GP/Th ratio values significantly lower than those >2 years of age (p = 0.0284), which than increased at the final scan and reached the level similar to values obtained in the group of >2 years of age.

Conclusions

Maturation of the brain may affect both signal intensity of brain structures and susceptibility to GBCAs; thus, assessment of signal intensity of the brain structures should be conducted taking into account the age of a child.

Elemental content of the placenta: A comparison between two high-risk obstetrical populations, adult women carrying multiples and adolescents carrying singletons

BACKGROUND

The placenta is responsible for the exchange of nutrients and for preventing harmful compounds from entering the fetal circulation. With increasing industrialization, exposures to commercial and toxic metals become a concern for both pregnant women and those planning a pregnancy. The understanding of transport mechanisms and pharmacokinetics for most inorganic elements is incomplete and limited to normal term deliveries.

OBJECTIVES

To obtain novel data on 46 inorganic elements in placentae from two high-risk obstetric populations, women carrying multiples and adolescents carrying singletons, evaluating differences, if present, and identifying predictors of placental content.

METHODS

Placental tissue was collected from adolescents carrying singletons and adults carrying multiples. Elemental content was analyzed using inductively coupled plasma-mass spectrometry (ICP-MS). Multivariate regression and factor analyses were used.

RESULTS

With the exception of Au and Pt, almost all placentae contained quantifiable concentrations of each element analyzed. All placentae contained the essential elements Ca, Fe, Mg, Se and Zn, which clustered together onto the same factor. Most elements were higher in placentae from women carrying multiples. Differences in placental content disappeared after adjusting for maternal age. Rare earth elements (REEs) clustered together and remained higher in the multiples even after adjusting for maternal age.

CONCLUSION

Human placentae contain a wide range of elements, including REEs. Ranges differed considerably between cohorts. Elements with similar chemical properties, like REEs or nutritionally essential elements, clustered together. Maternal age, and therefore longer environmental exposure, was significantly associated with elevated element concentrations in the placenta. Placental concentrations of several metals that are known to be nutritionally essential (e.g., Fe, Ca, Mg, and Zn) did not differ significantly between cohorts, suggesting tight regulation, whereas concentrations of environmental contaminants differed significantly between groups, even after adjusting for maternal age.