HDlive Flow silhouette mode and spatiotemporal image correlation for diagnosing congenital heart disease

Abstract

Recent advances in three-/four-dimensional (3D/4D) ultrasound, such as HDlive Flow, provide the potential to evaluate more precisely the fetal and placental circulations1-5 and gynecological disorders6-10. HDlive Flow silhouette mode is the latest technology to demonstrate blood flow with vitreous-like clarity. This technique has the ability to delineate the blood vessel walls, while presenting the vessel lumen as semitransparent. We present our experience of imaging normal and abnormal fetal cardiac structures, reconstructed using HDlive Flow, HDlive Flow silhouette mode and spatiotemporal image correlation (STIC), and evaluate the visualization rate of cardiac structures in normal fetuses using spatial three-vessel and panoramic views. One hundred and seven normal fetuses and three with congenital heart defects (transposition of the great arteries (TGA), hypoplastic left heart syndrome (HLHS) and pulmonary valve stenosis (PS)) were studied at 18–34 weeks of gestation using HDlive Flow, HDlive Flow silhouette mode and STIC (Voluson E10, GE Healthcare Japan, Tokyo, Japan). Normal fetuses were enrolled consecutively for assessment. In normal fetuses, in the spatial three-vessel view, the relationships and course of the outflow tracts (criss-cross arrangements of the pulmonary artery and aorta) and superior vena cava were identified (Figure 1 and Videoclips S1–S3). This view provided a superior or anterior view of the fetal heart, and criss-cross spatial arrangements of the aorta, pulmonary artery and superior vena cava could be recognized clearly. The panoramic view showed the spatial arrangements of the cardiac chambers and vessels, facilitating visualization of the relationships and course of the outflow and inflow tracts (Figure 2 and Videoclips S4 and S5). This view provided a left, oblique and lateral view, in which the two ventricles, two great arteries and the descending aorta could be seen clearly. The visualization rate of cardiac structures with the spatial three-vessel view was 91.6% and that with the panoramic view was 81.3% in normal fetuses. In the fetus with TGA, ultrasound assessment was performed at 32 + 1 weeks' gestation. HDlive Flow identified clearly the spatial parallel arrangement of the aorta, positioned on the left of the right ventricle, and the pulmonary artery, positioned on the left of the left ventricle (Figure 3a and Videoclip S6). HDlive Flow silhouette mode revealed hidden vessels, such as pulmonary veins, that were concealed by the cardiac chambers (Figure 3b and Videoclips S7 and S8). In the fetus with HLHS, ultrasound assessment was performed at 30 + 1 weeks' gestation. HDlive Flow and HDlive Flow silhouette mode in the spatial three-vessel view showed a significant difference in size between the pulmonary artery and aorta (Figure 4a and b and Videoclips S9 and S10). An extremely small ascending aorta and teardrop-shaped heart were also evident in the panoramic view (Figure 4c and d and Videoclips S11 and S12). Moreover, the large difference in size between the aortic arch and descending aorta was evident. HDlive Flow silhouette mode depicted clearly the contour of right atrium, right ventricle, pulmonary artery and the extremely small aorta. In the fetus with PS, ultrasound assessment was performed at 31 + 5 weeks' gestation. The diameter of the pulmonary artery was 10.9 mm, whereas that of the aorta was 5.7 mm. The pulmonary artery peak velocity was 246.5 cm/s and aortic peak velocity was 89.3 cm/s. A markedly large main pulmonary artery due to post-stenotic dilatation was demonstrated clearly using HDlive Flow (Figure 5a and Videoclip S13). HDlive Flow silhouette mode showed a holographic image of the fetal heart with a dilated pulmonary artery and hidden vessels, including the descending aorta and several veins (Figure 5b and Videoclip S14). There have been several investigations into conventional 3D/4D power Doppler ultrasound for evaluation of the normal fetal heart and congenital heart anomalies12-15. This imaging technique has enabled visualization of the main parts of the fetal cardiovascular system in normal and abnormal conditions. However, the resolution and image quality of conventional 3D/4D power Doppler remain low and may not offer a better understanding of the precise fetal cardiovascular structures. HDlive Flow uses an adjustable light source to create light and shadow effects, increasing the depth perception of 3D/4D color/power Doppler ultrasound2. Moreover, the resolution of HDlive Flow is significantly higher than that of conventional 3D/4D power Doppler11. In the present study, HDlive Flow could depict clearly the spatial relationships of fetal cardiac structures, enabling comparison of their dimensions between the normal fetal heart and those with congenital heart anomalies. The most unique characteristic of HDlive Flow silhouette mode is the holographic-like imaging of blood flow to the fetal heart. In the present study, HDlive Flow silhouette mode showed clearly the complicated overlapping cardiac structures in the normal fetal heart and in congenital heart anomalies. The three-vessel view is one of the key diagnostic planes for detection of congenital heart anomalies using two-dimensional (2D) fetal echocardiography16. An abnormal three-vessel view is defined as one that depicts abnormal vessel size, abnormal alignment, abnormal arrangement or abnormal vessel number. However, the three-vessel view depicted by 2D echocardiography is only a snapshot and an additional sweeping technique for assessment of the relationships among ventricles, outflow tracts, great arteries and the superior vena cava is mandatory. Use of the spatial three-vessel view resolved this problem as the spatial relationships between the outflow tracts, the connection between arteries and ventricular chambers and the size of the great vessels visualized are readily discernible11. In the present study, the visualization rate of cardiac structures with the spatial three-vessel view was 91.6% in normal fetuses. Possible reasons for unsuccessful visualization might be fetal malpresentation, an inappropriate position or increased maternal body mass index. Another explanation could be fetal movement and acoustic shadows requiring repeat examination to acquire satisfactory data. The panoramic view is a novel diagnostic imaging plane for observing the whole fetal heart. This imaging plane facilitates visualization of the relationships and course of the outflow and inflow tracts, especially the thoracic descending aorta. In the present study, the visualization rate of cardiac structures with the panoramic view was 81.3% in normal fetuses. The main cause of the slightly lower visualization rate with this view compared with the spatial three-vessel view may be acoustic shadows of the spine and ribs near the descending aorta and inferior vena cava. In conclusion, HDlive Flow silhouette mode and STIC provide a novel technique for imaging the fetal heart that can determine the spatial relationships among cardiac chambers, great arteries and veins. The extent to which this technology can provide diagnostic information additional to that of 2D fetal echocardiography has to be determined. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. 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