Following the first demonstration of the fetal face in 1989 and the advent of fast processors around 2000, 3D and 4D ultrasound have become important tools in obstetric imaging over the past decade. Unlike 2D imaging, 3D ultrasound provides a volume of a region of interest that contains an infinite number of 2D planes. Mechanical and electronic transducers have the ability to acquire volumes of target organs through sweeps, and fast processors are able to display the acquired information within seconds. The operator can then choose to display this information in a multiplanar format of 2D images or as a spatial volume projecting the external or internal anatomic features on the screen.

Static 3D, spatiotemporal image correlation (STIC), or 4D imaging can be used to acquire a cardiac volume with a mechanical or electronic transducer. The best cardiac volumes are acquired using the STIC technique. Ideally, it can be used for offline assessment of cardiac structures and movements. Color Doppler, power Doppler, bidirectional power Doppler (high-definition flow), and B-flow modes can be combined with STIC acquisitions.

These volumes can be displayed with the color information alone, the grayscale information alone, or a combination of both, referred to as “glass-body” mode. A light source can emphasize the effect of depth.

If anomalies involving the four-chamber anatomy can be visualized similarly to the 2D image with color Doppler, anomalies involving the great vessels clearly demonstrate the superiority of 3D. Size difference, flow direction, and spatial relationship of the great vessels are some of the information that can be visualized with 3D color Doppler and “glass-body” mode. 3D imaging can, therefore, be used to explain anomalies to future parents and explore treatment options with colleagues.

The major limitations of the STIC technique include delayed acquisition time and movement artifacts due to fetal movements or maternal breathing movements.

Here are two examples where 3D color Doppler and “glass-body” mode are superior to 2D imaging in the assessment of fetal heart anomalies. 

A double aortic arch results from the persistence of right and left aortic arches. The left ductus arteriosus persists while the right ductus arteriosus regresses. Each aortic arch gives rise to a subclavian and a common carotid artery. A double aortic arch forms a tight vascular ring around the trachea and esophagus. This condition requires surgical intervention postnatally.

The part of the complete ring behind the trachea is not seen in this plane. It is better demonstrated with 3D color Doppler.

A coronary artery fistula (CAF) is an abnormal connection between a coronary artery and a cardiac chamber or a great vessel.

3D color Doppler and “glass-body” mode allowed the visualization of the CAF over an entire cardiac cycle.

References:

Chaoui R, Heling K-S. 3D Ultrasound in Prenatal Diagnosis: A Practical Approach. 2nd ed. Berlin, Germany: DeGruyter; 2024.

Abuhamad A, Chaoui R. A Practical Guide to Fetal Echocardiography: Normal and Abnormal Hearts. 4th ed. Philadelphia, PA: Lippincott-Williams Wilkins; 2022.

Tekesin I, Uhlemann F. Prenatal diagnosis of coronary artery fistula using 2D and 3D/4D ultrasound. Ultrasound Obstet Gynecol 2017; 51:274-275.

Vladimir Lemaire, MD, RDMS (Ob/Gyn, FE), is a Maternal-Fetal Medicine Sonographer at UT Southwestern Medical Center in Dallas, Texas.

This posting has been edited for length and clarity. The opinions expressed in this posting are the author’s own and do not necessarily reflect the view of their employer or the American Institute of Ultrasound in Medicine.