The impact of insonation angle on four-chamber view image quality: An observational study on 2866 routine scans

Abstract

Objective: To determine insonation angles achieved in routine screening practice and their impact on image quality. Methods: Prospective cross-sectional observational survey of 2866 four-chamber views produced by 287 senor ultrasonographers, from unselected routine second-trimester screening scans. Images were scored from 0 to 5 according to whether two atria, two ventricles, the heart crux, the apex, and the descending aorta were seen. Images were considered adequate if two atria, two ventricles, and the heart crux were seen. The insonation angle was classified as apical, basal, or lateral according to the orientation of the fetal heart to the ultrasound beam. Results: There were 1612 (56.3%) apical, 869 (30.3%) basal, and 385 (13.4%) lateral views. The mean score and the rate of adequate images were significantly greater in the apical group (4.56 and 81.8%) than in the basal group (4.19 and 71.1 %) and were significantly greater in the basal group than in the lateral one (3.6 and 30.9%), p<0.001. Angle of insonation and image quality were not correlated with the experience of the operator. Conclusions: Adequate four-chamber view images are best obtained with an apical or basal insonation angle, which could be achieved in 8 out of 10 scans.