Automated Sonography: Defining the Spatial Relationship of Standard Diagnostic Fetal Cardiac Planes in the Second Trimester of Pregnancy

This study defines the spatial relationship of the diagnostic planes of the fetal heart to the 4-chamber view plane in the second trimester of pregnancy as a first step in the automation process. Three-dimensional static volumes of the fetal chest were acquired at the level of the 4-chamber view on 75 fetuses between 18 and 23 weeks' gestation. The spatial relationship of the diagnostic cardiac planes to the 4-chamber view plane were determined for each gestational week by using rotations along the x-, y-, and z-axes and a parallel slide (millimeters) when applicable. The 5-chamber view (cardiac 1 plane) was best obtained by an initial parallel slide of the reference plane (plane A) toward the fetal head followed by a rotation along the y-axis. The right ventricular outflow tract (cardiac 2) and the abdominal circumference (cardiac 3) planes were best obtained by a parallel slide only: toward the fetal head in cardiac 2 and toward the fetal abdomen in cardiac 3. This study shows the spatial relationship of fetal cardiac diagnostic planes to the 4-chamber view plane in the second trimester of pregnancy in 3-dimensional volumes. Testing the clinical applicability of automated software based on these formulas is the next step.