Uterine artery pulsatility and resistivity indices in pregnancy: comparison of MRI and Doppler US

Abstract

Objective

The aim of this work was to evaluate whether the uterine arteries (UA) could be identified and their flow profiles measured during a fetal MRI examination. A comparison was performed against same day routine sonographic Doppler assessment.

Methods

35 normal, healthy, singleton pregnancies at 28-32 weeks gestation underwent routine Doppler examination, followed by MRI examination. The resistivity index (RI) and pulsatility index (PI) of the left and right UA were measured using phase contrast MRI. Bland Altman statistics were used to compare MRI with the ultrasound results.

Results

Sixty-nine comparable vessels were analysed. Six vessels were excluded due to artefact or technical error. Bland-Altman analysis demonstrated the ultrasound indices were comparable, although systematically lower than the MRI indices; Right UA RI bias -0.03 (95% limits of agreement -0.27 to +0.20), and left UA RI bias -0.06 (95% limits of agreement -0.26 to +0.14); Right UA PI bias -0.06 (95% limits of agreement -0.50 to +0.38), Left UA PI bias -0.11 (95% limits of agreement -0.54 to +0.32). The inter-rater agreement for the MRI derived PI and RI analysis was good.

Conclusion

This study demonstrates that in the majority of early third trimester pregnancies, the uterine arteries can be identified, and their flow profiles measured using MRI, and that the derived PI and RI values are comparable with Doppler ultrasound values. MRI may prove a useful future technique to complement the use of ultrasound in the assessment of fetal well-being.