Artifacts and the visualization of fetal distal extremities using three-dimensional ultrasound

Objectives To demonstrate that acoustic shadowing in 3D US may give rise to artifacts simulating limb defects and provide a solution to eliminate its occurrence. Methods Twenty second trimester fetuses (gestational age 15-24 weeks) were scanned with three-dimensional ultrasound (3D US) using a sagittal acquisit ion plane. Fetal tibial fibula and radius/ulna pairs were assessed for comp leteness of imaging. A further 20 fetuses (gestational age 20-26 weeks) wer e scanned in both axial and sagittal planes and the results compared to ver ify clear visualization of both bones. Results Shadowing from adjacent structures produced an apparent limb defect in 55% of the first 20 fetuses imaged only sagittally (18% of limb pairs). Acquiring data front move than one orientation avoided this artifact. Conclusions The 3D US is subject to the same artifacts as two-dimensional ( 2D US) in terms of acoustic shadowing, although their presentation may be d ifferent. Awareness of this fact is essential for correct interpretation of 3D US studies. Three-dimensional scanning protocols should be modified to ensure that fetal structures are adequately visualized by acquiring volume data in more than one acquisition orientation.