What does 2-dimensional imaging add to 3- and 4-dimensional obstetric ultrasonography?

Abstract

Objective: The purpose of this study was to determine whether 2-dimensional (2D) ultrasonography adds diagnostic information to that provided by the examination of 3-dimensional/4-dimensional (3D/4D) volume data sets alone.

Methods: Ninety-nine fetuses were examined by 3D/4D volume ultrasonography. Volume data sets were evaluated by a blinded independent examiner who, after establishing an initial diagnostic impression by 3D/4D ultrasonography, performed a 2D ultrasonographic examination. The frequency of agreement and diagnostic accuracy of each modality to detect congenital anomalies were calculated and compared.

Results: Fifty-four fetuses with no abnormalities and 45 fetuses with 82 anomalies diagnosed by 2D ultrasonography were examined. Agreement between 3D/4D and 2D ultrasonography occurred for 90.4% of the findings (123/136; intraclass correlation coefficient, 0.834; 95% confidence interval, 0.774-0.879). Six anomalies were missed by 3D/4D ultrasonography when compared to 2D ultrasonography (ventricular septal defect [n = 2], interrupted inferior vena cava with azygous continuation [n = 1], tetralogy of Fallot [n = 1], horseshoe kidney [n = 1], and cystic adenomatoid malformation [n = 1]). There were 2 discordant diagnoses: transposition of the great arteries diagnosed as a double-outlet right ventricle and pulmonary atresia misinterpreted as tricuspid atresia on 3D/4D ultrasonography. One case of occult spinal dysraphism was suspected on 3D ultrasonography but not confirmed by 2D ultrasonography. When compared to diagnoses performed after delivery (n = 106), the sensitivity and specificity of 3D/4D ultrasonography (92.2% [47/51] and 76.4% [42/55], respectively) and 2D ultrasonography (96.1% [49/51] and 72.7% [40/55]) were not significantly different (P = .233).

Conclusions: Information provided by 2D ultrasonography is consistent, in most cases, with information provided by the examination of 3D/4D volume data sets alone.

Figure 1

Retrospective evaluation of the volume dataset shows a dilated azygous vein to the right of the aorta (Ao; “double vessel sign”), demonstrating that the anomaly was actually present in the volume dataset but was overlooked prospectively by the examiner.

Figure 2

3D multiplanar display of the fetal heart. On panel A, the aorta (Ao) overrides the ventricular septum (*). A short axis view of the right ventricle (RV) is shown in panel B and the pulmonary artery (PA) is poorly visualized. The findings are suggestive of a tetralogy of Fallot and were overlooked during the prospective examination of the volume dataset. Panel C: coronal view. LV: left ventricle; RA: right atrium.

Figure 3

4D multiplanar display of the fetal heart. Volume acquired with a transverse sweep through the fetal chest during excessive fetal motion. Panel A: Two vessels (arrows) apparently connect to the right ventricle (RV), suggesting a double outlet right ventricle. Panel B: sagittal view. Panel C: coronal view.

Figure 4

Retrospective review of the volume dataset acquired using sagittal sweeps through the fetal chest reveals two vessels leaving the ventricles in parallel and the correct diagnosis of transposition of the great arteries (Panel A). Panel B: sagittal view. Panel C: coronal view. Ao: aorta; LV: left ventricle; PA: pulmonary artery.