Assessment of uterine artery geometry and hemodynamics in human pregnancy with 4d flow mri and its correlation with doppler ultrasound

Abstract

Background: Uterine artery (UtA) hemodynamics might be used to predict risk of hypertensive pregnancy disorders, including preeclampsia and intrauterine growth restriction. Purpose or Hypothesis: To determine the feasibility of 4D flow MRI in pregnant subjects by characterizing UtA anatomy, computing UtA flow, and comparing UtA velocity, and pulsatility and resistivity indices (PI, RI) with transabdominal Doppler ultrasound (US). Study Type: Prospective cross-sectional study from June 6, 2016, to May 2, 2018. Population or Subjects or Phantom or Specimen or Animal Model: Forty-one singleton pregnant subjects (age [range] = 27.0 ± 5.9 [18–41] years) in their second or third trimester. We additionally scanned three subjects who had prepregnancy diabetes or chronic hypertension. Field Strength/Sequence: The subjects underwent UtA and placenta MRI using noncontrast angiography and 4D flow at 1.5T. Assessment: UtA anatomy was described based on 4D flow-derived noncontrast angiography, while UtA flow properties were characterized by net flow, systolic/mean/diastolic velocity, PI and RI through examination of 4D flow data. PI and RI are standard hemodynamic parameters routinely reported on Doppler US. Statistical Tests: Spearman’s rank correlation, Wilcoxon signed rank tests, and Bland-Altman plots were used to preliminarily investigate the relationships between flow parameters, gestational age, and Doppler US. Results: 4D flow MRI and UtA flow quantification was feasible in all subjects. There was considerable heterogeneity in UtA geometry in each subject between left and right UtAs and between subjects. Mean 4D flow-based parameters were: mean bilateral flow rate = 605.6 ± 220.5 mL/min, PI = 0.72 ± 0.2, and RI = 0.47 ± 0.1. Bilateral flow did not change with gestational age. We found that MRI differed from US in terms of lower PI (mean difference −0.1) and RI (mean difference < −0.1) with Wilcoxon signed rank test P = 0.05 and P = 0.13, respectively. Data Conclusion: 4D flow MRI is a feasible approach for describing UtA anatomy and flow in pregnant subjects. Level of Evidence: Technical Efficacy: Stage 1

Uterine artery and umbilical vein blood flow are unaffected by moderate habitual physical activity during pregnancy

“…PC‐MRI permits the quantification of the faster (center of the vessel) and slower (vessel wall) velocities within a vessel, and good spatial resolution allows for accurate vessel cross‐sectional area measurements throughout the cardiac cycle. Our measurements of UTA blood flow were considerably higher than those derived using a similar technique, four‐dimensional (4D) flow MRI, which measured bilateral flow of 606 mL/min . The considerably lower UTA blood flow by 4D flow MRI can be attributed to measurements made earlier in pregnancy, at around 26 weeks' gestation, and lower spatial resolution.…”

Cross‐modality and in‐vivo validation of 4D flow MRI evaluation of uterine artery blood flow in human pregnancy

“…While it is possible that US overestimated mean velocity over the cross‐sectional area by sampling the center of the vessel, we may have underestimated flow rate due to the lower spatial and temporal resolution of a 1.5‐T MRI scanner compared with the 3‐T magnetic field strength used for two‐dimensional phase‐contrast MRI 42 . However, we believe this would have been a systematic bias affecting measurements in both COMP and no‐COMP subjects and we have demonstrated repeatability of these measurements in a previous study 14 . Fortunately, substantial progress in 4D flow MRI is being made to decrease scan time and improve temporal and spatial resolution 43,44 .…”

“…A key advantage of 4D flow MRI during pregnancy is its large spatial coverage, which allows evaluation of the entire course of the UtA. We have demonstrated that use of this modality is technically feasible in pregnant women 14 , but did not correlate UtA flow measurements with pregnancy outcome. In this study, therefore, we sought to further validate 4D flow MRI measurement of UtA blood flow by exploring the association with adverse pregnancy outcome and comparing it with Doppler US measurement of UtA blood flow.…”

“…UtA flow rate (MRI‐flow, in mL/min) was computed from the spatial mean MRI velocity waveforms and vessel cross‐sectional area and averaged across the four planes for each vessel (Figure 1). Further details about the MRI acquisition procedure, postprocessing, repeatability of 4D flow MRI scans and interobserver reproducibility of postacquisition measures have been described previously 14 .…”

The application of in utero magnetic resonance imaging in the study of the metabolic and cardiovascular consequences of the developmental origins of health and disease

“… 121 Flow through the uterine arteries was also measured in human pregnancies, with velocity measurements agreeing with those obtained with Doppler US. 122 A strength of PC-MRI is the ability to assess blood flow in a 3D volume, which could allow assessment of placental and cardiovascular adaptations throughout gestation as a result of fetal programming.…”