Results
The feasibility of the algorithm was studied in 123 fetuses. The mean GA was 26 ± 2.3 weeks and the mean BMI was 25 ± 3.6 kg/m2. In total, 6 cardiac planes were included in the current study. The detection rate for each plane is presented in Table 2. The 3VV and 3VT view are in high visualization rate, varying from 88.62% to 97.56%, for the two color imaging modalities. HD-R-flow modality showed a higher detection rate for all the 6 planes than the Color-R-flow method, with significance presenting for the left innominate and azygos vein (LIV and AzV) view (71.54% vs. 35.77%), bilateral subclavian arteries (BSA) view (85.37% vs. 60.16%), and the bilateral internal thoracic arteries (BITA) view (75.61% vs. 50.41%) (Figure).
As Doppler shift could be affected by the angle between the sound beam and the flow direction, we speculated that the detection of these cardiac planes would also be affected by different fetal positions. Since the differences of detection rates of 3VV, BPAB and 3VT views were of no significance, the affection of the fetal position was not under discussion. Then, fetuses were sub-grouped according to different cardiac orientations and comparisons were made between the two color-imaging modalities for the detection of the last three planes. The results demonstrated that HD-R-flow modality showed a significantly higher detection rate than the Color-R-flow modality for the LIV and AzV view (Supine and Lateral position), BSA view (Lateral position), and the BITA view (Supine and Lateral position). However, for the prone position, the detection for each plane was very low and no significance was demonstrated for each of the two modalities (Table 3).