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 acquisition plane. Fetal tibia/fibula and radius/ulna pairs were assessed for completeness of imaging. A further 20 fetuses (gestational age 20–26 weeks) were scanned in both axial and sagittal planes and the results compared to verify 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 from more 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 different. 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. Copyright © 2000 International Society of Ultrasound in Obstetrics and Gynecology