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.

Examples:

  • 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.

See also