Artifacts in Sonography - Part 3.

As a continuation of parts 1 1 and 2 2, this article discusses artifacts as caused by insufficient temporal resolution, artifacts in color and spectral Doppler sonography, and information regarding artifacts in sonography with contrast agents. There are artifacts that occur in B-mode sonography as well as in Doppler imaging methods and sonography with contrast agents, such as slice thickness artifacts and bow artifacts, shadows, mirroring, and artifacts due to refraction that appear, for example, as double images, because they are based on the same formation mechanisms. In addition, there are artifacts specific to Doppler sonography, such as the twinkling artifact, and method-based motion artifacts, such as aliasing, the ureteric jet, and due to tissue vibration. The artifacts specific to contrast mode include echoes from usually highly reflective structures that are not contrast bubbles ("leakage"). Contrast agent can also change the transmitting signal so that even structures not containing contrast agent are echogenic ("pseudoenhancement"). While artifacts can cause problems regarding differential diagnosis, they can also be useful for determining the diagnosis. Therefore, effective use of sonography requires both profound knowledge and skilled interpretation of artifacts.

Ultrasound Artifacts - Part 2.

Part 2 discusses important artifacts in addition to those presented in part 1. Shadows and acoustic enhancement are based on regional differences in sound attenuation and are connected with the mode of action of depth gain compensation. They are not caused solely by the reflection properties of structures in terms of strong echoes → shadows, anechoic structure → acoustic enhancement. Anisotropy provides further evidence that echo strength is to be considered relative and is always linked to the equipment being used. Algorithms for "image improvement" can also result in artifacts as shown by black lines caused by image sharpening. Depending on the shape and position of the relevant structure, deviations from the assumed sound velocity result in incorrect positioning on the x-axis or refraction, which causes incorrect positioning on the y- and/or z-axis and may contribute significantly to shadows and acoustic enhancement.