mirror image artifact
Mirror image artifact in sonography is seen when there is a highly reflective surface (e.g. diaphragm) in the path of the primary beam.
The primary beam reflects from such a surface (e.g. diaphragm) but instead of directly being received by the transducer, it encounters another structure (e.g. a nodular lesion) in its path and is reflected back to the highly reflective surface (e.g. diaphragm). It then again reflects back towards the transducer.
The ultrasound machine makes a false assumption that the returning echo has been reflected once and hence the delayed echoes are judged as if being returned from a deeper structure, thus giving a mirror artifact on the other side of the reflective surface.
It is a friendly artifact that allows the sonographer to exclude pleural effusion by the reflection of the liver image through the diaphragm.
- reflection of a liver lesion into the thorax (the commonest example)
- reflection of abdominal ascites mimicking pleural effusion
- duplication of gestational sac (either ghost twin or heterotopic pregnancy)
- duplication of the uterus
To avoid this artifact, change the position and angle of scanning to change the angel of insonation of the primary ultrasound beam.