An artefacts is an additional, missing or distorted image which does not conform to the real image of the part being examined. Artefacts does not arise from the primary ultrasound beam, or direct echoes from the part being scanned, but result from distortion or attenuation of the image. There are many different causes. Recognition of such artefacts is important because they can be misleading and may even be mistaken for some important finding that may affect the diagnosis. other artefacts may provide important additional information and should be recognised and used.
Cysts
A Cysts usually appears as an echo-free area and the structures behind the cysts are enhanced: there are no echoes from within cysts because there are no echoes from within cysts because there are no impedance interfaces within the liquid. Because the liquid does not absorb ultrasound to the same extent as tissue, the echoes from behind the cysts are overcompensated by the equipment and appear enhanced- the strong back wall effect.
A cyst is seen as an echo free area with a strong back wall. If there are echoes within a cysts, these may be real or artifactual.
A space, such as a cyst filled with clear fluid, appears to be free of echoes on the screen. The walls of the cyst reflect reflect the ultrasound at an angle so that information does not return to the transducer. This results in acoustic shadows laterally, but behind the cystic area the echoes will be enhanced ( the strong back wall)
Artefacts may be seen in any cystic structure (such as the urinary bladder or gallbladder) and tend to be seen anteriorly, becoming less intense with depth. They may disappear or change in character as the transducer is moved.
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