Comparative study of placental T2* and intravoxel incoherent motion in the prediction of fetal growth restriction

Preeclampsia Associated Differences in the Placenta, Fetal Brain, and Maternal Heart Can Be Demonstrated Antenatally: An Observational Cohort Study Using MRI

BACKGROUND

Preeclampsia is a multiorgan disease of pregnancy that has short- and long-term implications for the woman and fetus, whose immediate impact is poorly understood. We present a novel multiorgan approach to magnetic resonance imaging (MRI) investigation of preeclampsia, with the acquisition of maternal cardiac, placental, and fetal brain anatomic and functional imaging.

METHODS

An observational study was performed recruiting 3 groups of pregnant women: those with preeclampsia, chronic hypertension, or no medical complications. All women underwent a cardiac MRI, and pregnant women underwent a placental-fetal MRI. Cardiac analysis for structural, morphological, and flow data were undertaken; placenta and fetal brain volumetric and T2* (which describes relative tissue oxygenation) data were obtained. All results were corrected for gestational age. A nonpregnant cohort was identified for inclusion in the statistical shape analysis.

RESULTS

Seventy-eight MRIs were obtained during pregnancy. Cardiac MRI analysis demonstrated higher left ventricular mass in preeclampsia with 3-dimensional modeling revealing additional specific characteristics of eccentricity and outflow track remodeling. Pregnancies affected by preeclampsia demonstrated lower placental and fetal brain T2*. Within the preeclampsia group, 23% placental T2* results were consistent with controls, these were the only cases with normal placental histopathology. Fetal brain T2* results were consistent with normal controls in 31% of cases.

CONCLUSIONS

We present the first holistic assessment of the immediate implications of preeclampsia on maternal heart, placenta, and fetal brain. As well as having potential clinical implications for the risk stratification and management of women with preeclampsia, this gives an insight into the disease mechanism.

Placental differences between uncomplicated and complicated monochorionic diamniotic pregnancies on diffusion and multicompartment Magnetic Resonance Imaging

INTRODUCTION

Twin-twin transfusion syndrome (TTTS) and selective fetal growth restriction (sFGR) are common complications in monochorionic diamniotic (MCDA) pregnancies. The Diffusion-rElaxation Combined Imaging for Detailed Placental Evaluation (DECIDE) model, a placental-specific model, separates the T2 values of the fetal and maternal blood from the background tissue and estimates the fetal blood oxygen saturation. This study investigates diffusion and relaxation differences in uncomplicated MCDA pregnancies and MCDA pregnancies complicated by TTTS and sFGR in mid-pregnancy.

METHODS

This prospective monocentric cohort study included uncomplicated MCDA pregnancies and pregnancies complicated by TTTS and sFGR. We performed MRI with conventional diffusion-weighted imaging (DWI) and combined relaxometry - DWI-intravoxel incoherent motion. DECIDE analysis was used to quantify different parameters within the placenta related to the fetal, placental, and maternal compartments.

RESULTS

We included 99 pregnancies, of which 46 were uncomplicated, 12 were complicated by sFGR and 41 by TTTS. Conventional DWI did not find differences between or within cohorts. On DECIDE imaging, fetoplacental oxygen saturation was significantly lower in the smaller member of sFGR (p = 0.07) and in both members of TTTS (p = 0.01 and p = 0.004) compared to the uncomplicated pairs. Additionally, average T2 relaxation time was significantly lower in the smaller twin of the sFGR (p = 0.004) compared to the uncomplicated twins (p = 0.03).

CONCLUSION

Multicompartment functional MRI showed significant differences in several MRI parameters between the placenta of uncomplicated MCDA pregnancies and those complicated by sFGR and TTTS in mid-pregnancy.

Value of placental virtual magnetic resonance elastography and intravoxel incoherent motion-based diffusion and perfusion in predicting adverse outcomes of small-for-gestational-age infants

OBJECTIVE

It is critical to early monitor and manage small-for-gestational age (SGA) infants with truly adverse outcomes not detected by conventional methods. We aimed to explore the value of diffusion-weighted imaging (DWI)-based virtual magnetic resonance elastography (vMRE) and intravoxel incoherent motion (IVIM)-based biexponential and stretched exponential parameters in predicting adverse outcomes of SGA infants.

METHODS

Twenty SGA infants with adverse outcomes and forty without adverse outcomes were included in this prospective study. One DWI-based vMRE parameter [the stiffness value (μdiff)], five IVIM-based parameters [true diffusion coefficient (D), pseudo-diffusion coefficient (D*), perfusion fraction (f), diffusion distribution coefficient (DDC), and diffusion heterogeneity index (Alpha)] and apparent diffusion coefficient (ADC) were calculated and compared between groups. The predictive efficiency was compared by the logistic regression analysis and receiver operating characteristic curve analysis. The relationship between the μdiff value with gestational age was also evaluated.

RESULTS

The placental μdiff value was remarkably higher, and the f, DDC, and ADC values were considerably lower in the SGA infants with adverse outcomes compared with those without adverse outcomes. The μdiff and f value were predictive risk factors for SGA infants with adverse outcomes. A combined predictive model (μdiff and f) improved the predictive efficacy. Moreover, there was no statistically significant correlation between the placental stiffness value and gestational age.

CONCLUSIONS

Functional MRI parameters to quantify placenta elastography and microcirculation in SGA patients. This might be a useful tool to assess placental function and a vital non-invasive supplement for predicting adverse outcomes of SGA infants.

CRITICAL RELEVANCE STATEMENT

This prospective study shows DWI-based virtual magnetic resonance elastography and intravoxel incoherent motion-based functional parameters to quantify placenta elastography and microcirculation in small-for-gestational-age patients, which could complement existing non-invasive methods for monitoring and predicting neonatal perinatal adverse outcome.

KEY POINTS

• vMRE is an emerging non-invasive imaging technique for evaluating placenta stiffness. • SGA infants with adverse outcome have stiffer placental elasticity and lower microcirculation. • Risk factors combination displayed better efficacy in predicting adverse outcomes of SGA.

Assessing within-subject rates of change of placental MRI diffusion metrics in normal pregnancy

PURPOSE

Studying placental development informs when development is abnormal. Most placental MRI studies are cross-sectional and do not study the extent of individual variability throughout pregnancy. We aimed to explore how diffusion MRI measures of placental function and microstructure vary in individual healthy pregnancies throughout gestation.

METHODS

Seventy-nine pregnant, low-risk participants (17 scanned twice and 62 scanned once) were included. T2 -weighted anatomical imaging and a combined multi-echo spin-echo diffusion-weighted sequence were acquired at 3 T. Combined diffusion-relaxometry models were performed using both aT 2 * $$ {\mathrm{T}}_2^{\ast } $$ -ADC and a bicompartmentalT 2 * $$ {\mathrm{T}}_2^{\ast } $$ -intravoxel-incoherent-motion (T 2 * IVIM $$ {\mathrm{T}}_2^{\ast}\;\mathrm{IVIM} $$ ) model fit.

RESULTS

There was a significant decline in placentalT 2 * $$ {\mathrm{T}}_2^{\ast } $$ and ADC (both P < 0.01) over gestation. These declines are consistent in individuals forT 2 * $$ {\mathrm{T}}_2^{\ast } $$ (covariance = -0.47), but not ADC (covariance = -1.04). TheT 2 * IVIM $$ {\mathrm{T}}_2^{\ast}\;\mathrm{IVIM} $$ model identified a consistent decline in individuals over gestation inT 2 * $$ {\mathrm{T}}_2^{\ast } $$ from both the perfusing and diffusing placental compartments, but not in ADC values from either. The placental perfusing compartment fraction increased over gestation (P = 0.0017), but this increase was not consistent in individuals (covariance = 2.57).

CONCLUSION

Whole placentalT 2 * $$ {\mathrm{T}}_2^{\ast } $$ and ADC values decrease over gestation, although onlyT 2 * $$ {\mathrm{T}}_2^{\ast } $$ values showed consistent trends within subjects. There was minimal individual variation in rates of change ofT 2 * $$ {\mathrm{T}}_2^{\ast } $$ values from perfusing and diffusing placental compartments, whereas trends in ADC values from these compartments were less consistent. These findings probably relate to the increased complexity of the bicompartmentalT 2 * IVIM $$ {\mathrm{T}}_2^{\ast}\;\mathrm{IVIM} $$ model, and differences in how different placental regions evolve at a microstructural level. These placental MRI metrics from low-risk pregnancies provide a useful benchmark for clinical cohorts.

Characterisation of placental, fetal brain and maternal cardiac structure and function in pre-eclampsia using MRI

Background

Pre-eclampsia is a multiorgan disease of pregnancy that has short- and long-term implications for the woman and fetus, whose immediate impact is poorly understood. We present a novel multi-system approach to MRI investigation of pre-eclampsia, with acquisition of maternal cardiac, placental, and fetal brain anatomical and functional imaging.

Methods

A prospective study was carried out recruiting pregnant women with pre-eclampsia, chronic hypertension, or no medical complications, and a non-pregnant female cohort. All women underwent a cardiac MRI, and pregnant women underwent a fetal-placental MRI. Cardiac analysis for structural, morphological and flow data was undertaken; placenta and fetal brain volumetric and T2* data were obtained. All results were corrected for gestational age.

Results

Seventy-eight MRIs were obtained during pregnancy. Pregnancies affected by pre-eclampsia demonstrated lower placental and fetal brain T2*. Within the pre-eclampsia group, three placental T2* results were within the normal range, these were the only cases with normal placental histopathology. Similarly, three fetal brain T2* results were within the normal range; these cases had no evidence of cerebral redistribution on fetal Dopplers. Cardiac MRI analysis demonstrated higher left ventricular mass in pre-eclampsia with 3D modelling revealing additional specific characteristics of eccentricity and outflow track remodelling.

Conclusions

We present the first holistic assessment of the immediate implications of pre-eclampsia on the placenta, maternal heart, and fetal brain. As well as having potential clinical implications for the risk-stratification and management of women with pre-eclampsia, this gives an insight into disease mechanism.

Differences in placental oxygenation and perfusion status between fetal growth-restricted and small-for-gestational-age pregnancies: a functional magnetic resonance imaging study

OBJECTIVE

Functional magnetic resonance imaging (MRI) can assess oxygenation and perfusion status in the placenta. We aimed to explore the differences in functional parameters between pregnancies complicated by fetal growth restriction (FGR) and small-for-gestational-age (SGA).

METHODS

This was a prospective study. A pregnancy complicated by SGA was defined by prenatal ultrasonic estimated fetal weight (EFW) and a final birthweight < the 10th percentile. A pregnancy complicated by FGR was defined as a more severe subtype (ultrasonic EFW < the 3rd percentile or abnormal Doppler results). All pregnant women underwent T2* and intravoxel incoherent motion (IVIM) scans using a 3.0-T MRI scanner. Functional parameters in the control, SGA, and FGR groups, namely, the T2* Z score, apparent diffusion coefficient (ADC), diffusion coefficient (D), pseudodiffusion coefficient (D*), and perfusion fraction (f), were calculated and compared.

RESULTS

In total, 30 pregnancies complicated by SGA, 24 pregnancies complicated by FGR, and 28 control pregnancies were included in the final analysis. Oxygenation status, as assessed by the T2* Z score, was significantly lower in pregnancies complicated by FGR than in pregnancies complicated by SGA (p < 0.001). However, diffusion and perfusion parameters, including the ADC, D, D*, and f, were similar between pregnancies complicated by SGA and FGR (p > 0.05 for all). Compared to the control pregnancies, all the parameters were significantly decreased in the SGA and FGR groups, except for the D* value. The T2* Z score, ADC, and D values were negatively correlated with birthweight.

CONCLUSION

Although both pregnancies complicated by SGA and FGR were associated with significantly lower oxygenation and perfusion than normal control pregnancies, placental hypoxia seemed to be more predominant in pregnancies complicated by FGR than in pregnancies complicated by SGA.

KEY POINTS

• Pregnancy complicated by FGR was associated with a more severe type of hypoxia than pregnancy complicated by SGA. • The diffusion and perfusion parameters of pregnancies complicated by SGA and FGR were similar. • SGA may represent another growth disorder that is not entirely healthy.

Placental perfusion using intravoxel incoherent motion MRI combined with Doppler findings in differentiating between very low birth weight infants and small for gestational age infants

INTRODUCTION

Abnormalities in placental morphology and function can lead to small for gestational age infants (SGA) and very low birth weight infants (VLBWI). In this study, we explored the value of intravoxel incoherent motion (IVIM) histogram parameters, MRI morphological parameters, and Doppler findings of the placenta in differentiating between VLBWI and SGA.

METHODS

Thirty-three pregnant women who were diagnosed with SGA and met the inclusion criteria were enrolled in this retrospective study and divided into two groups: 22 with non-VLBWI and 11 with VLBWI. The IVIM histogram parameters (perfusion fraction (f), true diffusion coefficient (D), and pseudo-diffusion coefficient (D*)), MRI morphological parameters, and Doppler findings were compared between groups. The diagnostic efficiency was compared by receiver operating characteristic (ROC) curve analysis.

RESULTS

The D_mean, D_90th, D*_90th, f_max, and placental area of the VLBWI group were significantly lower than those of the non-VLBWI group (p < 0.05). The values of umbilical artery pulsatility index, resistance index (RI), and peak systolic velocity/end-diastolic velocity were significantly higher in the VLBWI group than in the non-VLBWI group (p < 0.05). D_90th, placental area, and umbilical artery RI had the highest areas under the curve (AUCs) of the ROC curves, at 0.787, 0.785, and 0.762, respectively. A combined predictive model (D_90th, placental area, and umbilical artery RI) improved the performance in differentiating between VLBWI and SGA compared with the single model (AUC = 0.942).

DISCUSSION

IVIM histogram (D_90th) and MRI morphological (placental area) parameters and a Doppler finding (umbilical artery RI) may be sensitive indicators for differentiating between VLBWI and SGA.

Differentiating between normal and fetal growth restriction-complicated placentas: is T2∗ imaging imaging more accurate than conventional diffusion-weighted imaging?

AIM

To compare the performance of T2∗ imaging and apparent diffusion coefficient (ADC) in differentiating normal placentas from those complicated by fetal growth restriction (FGR).

MATERIALS AND METHODS

This prospective study included 28 control and 30 FGR placentas. Gradient-echo magnetic resonance imaging (MRI) at 16 different echo times and diffusion-weighted imaging (b-value of 0 and 800 s/mm²) were performed on all pregnant women using a 3 T MRI system.

RESULTS

Both T2∗ imaging Z-score and ADC were significantly lower in the FGR placentas (ADC, (1.69 ± 0.19) × 10^-3 versus (1.42 ± 0.28) × 10^-3 mm²/s, p<0.001; T2∗ imaging Z-score, -0.004 ± 0.95 versus -2.441 ± 1.48, p<0.001). The area under the curve for T2∗ imaging Z-score and ADC was 0.917 (95% confidence interval [CI] = 0.842-0.991) and 0.788 (95% CI = 0.655-0.887), respectively. The performance of T2∗ imaging in differentiating FGR placentas was significantly better than that of ADC (Z = 2.043, p=0.041).

CONCLUSION

Placental T2∗ imaging was found to be more reliable than ADC in differentiating between normal and FGR placentas.

Use of intravoxel incoherent motion MRI to assess placental perfusion in normal and Fetal Growth Restricted pregnancies on their third trimester

INTRODUCTION

Intravoxel Incoherent Motion (IVIM) MRI is a non-invasive, in vivo techniques which can assess placental perfusion quantitatively, and be useful for evaluating placental microcirculation. Our primary aim was to investigate whether fetal growth restriction (FGR) pregnancies have different placental perfusion and diffusion compared with normal pregnancies using IVIM. A secondary aim was to investigate correlations between placental IVIM parameters and gestational age in normal pregnancy.

METHODS

This study population included 17 FGR pregnancies and 36 normal pregnancies between 28 + 3 to 38 + 0 weeks. All women underwent a MRI examination including an IVIM sequence with 9 b-values on a 3.0 T MRI system. The standard diffusion coefficeint (D), pseudodiffusion (D*) and perfusion fraction (f) were calculated.

RESULTS

Placental f was significantly lower in the FGR group than that in the normal group (33.96 ± 2.62(%) vs 38.48 ± 5.31(%), p = 0.002). Placental D and D* in two groups showed no statistical significance (P > 0.05). Placental f moderately increased with increasing gestational age in normal pregnancies (r = 0.411, p = 0.013), and there existed a negative correlation between D values and gestational age (r = -0.390, p = 0.019).

DISCUSSION

The f values are able to distinguish FGR from normal pregnancies. It can be uses as a feasible index to evaluate placenta perfusion. Gestational age-associated changes in placental IVIM parameters likely reveal trajectories of microvascular perfusion fraction and diffusion characteristics in the normal developing placenta.