Four-dimensional volume-rendered imaging of the fetal ventricular outflow tracts and great arteries using inversion mode for detection of congenital heart disease

Aim:  Using four-dimensional (4D) sonography with an inversion mode, we evaluated fetal ventricular outflow tracts and great vessels for the detection of congenital heart disease. Methods:  Volume datasets of the fetal heart were acquired with spatiotemporal image correlation (STIC), which uses automated transverse and longitudinal sweeps of the anterior chest wall. A total of 12 normal fetuses and seven fetuses with congenital heart disease (one case of double-outlet right ventricle, one case of tetralogy of Fallot, one case of transposition of the great arteries, one case of hypoplastic pulmonary artery with a large ventricular septal defect, and three cases of hypoplastic left heart syndrome) at 16–37 weeks of gestation were studied using transabdominal 4D sonography with an inversion mode. 4D inversion mode images of great arteries were evaluated. Results:  4D ultrasound with an inversion mode demonstrated real-time 3D angiographic features of fetal cardiac outflow tracts in both normal and abnormal fetal hearts. This modality facilitated visualization of the relationships, size, and course of the outflow tracts, thus helping the examiner to more effectively understand the spatial relationships between the vessels. In normal fetal hearts, it was clearly shown that the pulmonary artery crosses in front of the aorta. In the three cases of hypoplastic left heart syndrome, an extremely small ascending aorta was evident. In the one case of tetralogy of Fallot, a relatively small pulmonary artery was noted. In the one case of hypoplastic pulmonary artery with a large ventricular septal defect, a markedly small main pulmonary artery was depicted. In the case of transposition of the great arteries, the vessels left the ventricles parallel to each other. In the case of double-outlet right ventricle, great arteries leaving the right ventricle in parallel were shown. Conclusion:  4D ultrasound in the inversion mode provides a means of evaluating fetal cardiac outflow tracts in 3D in real time. This technique may assist in the evaluation of spatial relationships between the great vessels and both ventricles, and the difference in the size of great vessels. Moreover, the inversion mode images should be more readily discernible than those obtained by conventional ultrasonography. 4D ultrasound in the inversion mode may be an important modality in future fetal cardiac research and in the evaluation of fetal congenital heart disease.