How sonographic tomography will change the face of obstetric sonography: a pilot study

This study was undertaken to determine whether 3-dimensional (3D) volume sonography (sonographic tomography) can yield a far quicker and equally accurate anatomic examination of the second-trimester fetus compared with traditional 2-dimensional (2D) scanning.

Twenty-five consecutive second-trimester fetuses with normal structural surveys on standard 2D imaging underwent 5 standard 3D volume acquisitions each (in the regions of the head, chest, abdomen, face, and lower extremities) immediately after the 2D scan. The 2D and 3D images were subsequently compared in relation to the completeness of the fetal survey, measurements of the biparietal diameter and femur length, and time required to obtain the fetal survey.

The structural surveys were complete in 20 of 25 cases using 3D reconstructed volumes. One fetus had an incomplete evaluation of the face on 3D volumes (and limited on 2D imaging because of the prone position of the fetus). The other 4 fetuses with incomplete surveys done on 3D volumes had missing images of a hand or foot. Three-dimensional reconstructions slightly overmeasured the biparietal diameter compared with the 2D reference standard (mean difference, 1.1 mm; P < .001). For femur length, the mean difference was not statistically significant. It took a mean time of 1.1 minutes to obtain the 3D volumes and 5.5 minutes to reconstruct the complete surveys by the 3D volume method. With the standard 2D technique, the structural surveys were done in a mean time of 13.9 minutes. The mean time difference between both methods was 7.3 minutes (P = 2.4 x 10(-9)).

Using 3D volume acquisition, it is feasible to perform and interpret a structural survey in half the time in which a 2D survey is performed. Further research is necessary to standardize the acquisition of volumes to minimize artifacts and produce uniform images.