Effect of spectacular reflection on out-of-plane ultrasonographic images reconstructed from three-dimensional data sets.

The effect of specular reflection on ultrasonographic images reconstructed out of plane to the plane of acquisition of a three-dimensional volumetric data set was studied using two in vitro phantoms that incorporated structures exhibiting specular reflection. The phantoms were scanned transversely (axially) to form three-dimensional data sets, with coronal cross-sectional images reconstructed perpendicular to the plane of acquisition of the data sets. Directly scanned, nonreconstructed coronal images of the phantoms also were obtained in the same planes and from the same areas as the reconstructed coronal images. The direct and reconstructed coronal images were compared. Owing to the inherent directionality of specular reflectors, the reconstructed coronal images differed from the directly scanned images in two ways, containing some hyperechoic regions that were not present at direct coronal scanning and failing to contain other hyperechoic areas that were present at direct coronal imaging. We conclude that sonographic images reformatted from volumetric data sets may have a different appearance than images scanned directly in the same plane, independent of other factors such as resolution. This should be taken into account when such reformatted images are interpreted. KEY WORDS: Three-dimensional ultrasonography; Artifact; Reflection, specular.