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[Application of spatio-temporal image correlation in normal fetal heart ultrasonography].

OBJECTIVE
To explore the clinical application of real-time three-dimensional ultrasonography in the routine scanning of normal fetal heart.


METHODS
A total of 110 volume datasets of normal fetal hearts in the second trimester were acquired by spatio-temporal image correlation (STIC). An off-line analysis of acquired volume datasets was performed to examine each segment of fetal heart with tomographic ultrasound imaging (TUI) and dynamic multi-planar mode (MP). The re-slice images of four-chamber view, ventricular outflow tract views, and the three vessels plane were viewed with TUI. The quality of images obtained from TUI was compared with the conventional 2D imaging mode. The volume datasets were displayed interactively with MP as a series of three-orthogonal planes. The dynamic loops of one cardiac cycle were preformed by navigating the pivot point and rotational axis and shifting each re-slice image plane inside the volume datasets.


RESULTS
Satisfactory gray-scale volume acquisitions were accomplished in 110 cases. The average STIC scanning time of fetal heart was (55 +/- 15) s. An offline analysis showed that four standard planes of 2D routine screening for fetal hearts were easily obtained by TUI. The quality of the images derived from volume datasets were comparable to that directly obtained from 2D echocardiography. The visualization rate had no significant difference between TUI and routine 2D screening (P > 0.05). In MP mode, 39 cases with the starting plan of apical four-chamber view were obtained. Each segment of fetal heart was almost visualized off line, both in a frozen state and with heart in motion to fulfill sequential segmental analysis in fetal cardiac anatomy. The 72% - 100% main features of atria, ventricles, aorta, and the junction segments were viewed with MP by adjusting the three dimensional volume datasets, whose quality and contents met the expectations of off-line segmental analysis of normal fetal heart. A sagittal section of ventricular septum was obtained in the offline analysis, which was an unconventional view in 2D echocardiography.


CONCLUSION
Real-time three-dimensional ultrasonography can be applied for off-line segmental analysis of normal fetal hearts in the second trimester.