[Artifacts in ultrasonic diagnosis]

Due to facts of the wave theory, to properties of ultrasound-systems and to peculiarities of the examined organs and tissues artifacts may influence the image-formation in diagnostic sonography. In diagnostic ultrasound five types of artifacts are common: --Displaying of nonstructural echo signals (reverberation and reflection) --Removal of real structural echo signals from the display (tissue-attenuation and acoustic shadowing) --Displacement of echo signals on the display (refraction and beamwidth-artifact) --Distortion of echo signals (shape distortion-artifact, bands, gray-scale-contouring and blobby dots) --Distortion of the organ dynamics on the display (reverberation or "ring-around" and "herbie") The understanding of the mechanisms behind their production allows recognition of artifacts and avoids misinterpretations and incorrect diagnoses. Moreover, it helps to prevent the production of artifacts, e.g. by proper gain-control-setting, adjusted focussing, etc.; it also may, if properly evaluated, reveal further information which can be used for diagnostic purposes (e.g. nature and geometry of interfaces, content of cysts, etc.).