Measuring 3D flow in the fetal heart with motion corrected Doppler ultrasound gated MRI

Congenital heart disease (CHD) affects approximately 1% of live births. Detection of CHD through routine fetal ultrasound screening continues to rise, however accurate identification of babies who require life-saving surgical intervention immediately after birth remains challenging for many complex cardiac anomalies. Prenatal diagnosis, reliant predominantly on 2D ultrasound, is often incomplete, even in expert hands, due to difficulties in visualising the 3D structure of the heart and vessels. Additionally, 2D Doppler ultrasound provides only a limited understanding of blood flow in fetal heart and vessels. In the postnatal life ultrasound limitations have been addressed by cardiac MRI, which provides 3D visualisation, volumetric and vascular flow measurements. Fetal MRI has seen a growing role in diagnosis of fetal anomalies, but it is susceptible to corruption by fetal motion and maternal breathing. To address this, we have developed motion corrected 3D MRI, by composing multiple fast 2D acquisitions into a consistent 3D volume for static structures. Imaging the beating fetal heart, however, presents additional challenges: not only does it beats three times faster than in adults, but until recently there was no practical method that could measure fetal heart rate during acquisition in real time. In our previous work we proposed motion-corrected 3D+time fetal cardiac MRI with the fetal heart rate estimated after acquisition directly from the imaging data, but this did not accurately capture beat-to-beat heart rate variation, resulting in errors which have so far prevented clinical adoption of these techniques. Recently, a CE-marked, MRI-compatible Doppler ultrasound gating device has become available. This device can accurately measure the fetal heart rate and provide an external gating signal directly to MRI scanner in real time. This recent technology provides new exciting opportunities for development of high temporal resolution imaging of the fetal heart. To date, due to lack of motion compensation, the Doppler gating has been limited mainly to 2D anatomy and flow imaging, which is still highly susceptible to fetal motion. In this project we propose to develop Doppler-gated motion-compensated 3D+time MRI of moving fetal cardiac anatomy and flow. This new technology will unlock opportunities for large clinical studies to enable accurate diagnosis, discovery of novel biomarkers and understanding of pathological in-utero development in different forms of CHD. We will close the current technological gap by combining new Doppler ultrasound gating device with our motion corrected fetal 3D MRI technique. Our preliminary results show that Doppler-gated 3D+time imaging of moving fetal cardiac anatomy is not only feasible and efficient, but also provides accurate measurements of fetal cardiac function superior to image-gated 3D+time MRI. We now intend to further develop this technique to generate motion corrected Doppler-gated 3D+time flow and evaluate 3D+time anatomical and flow imaging on a large dataset of 300 fetal subjects. We aim to develop a practical vendor independent acquisition and software tools for accurate volumetric measurements of fetal heart function, based on Doppler-gated “off-the-shelf” MRI sequences that can be easily deployed in any centre with an existing fetal MRI programme. The proposed technology has potential to improve clinical management of fetuses with suspicion of severe forms of CHD, by ensuring that babies who require urgent postnatal surgery are more accurately diagnosed before birth. Additionally, confident exclusion of severe lesions will reduce pressure on NHS resources and the emotional burden on affected families.