Reflections on the Ultrasound Mirror Image Artifact

A key assumption in ultrasound is that the reflected echoes that return to the transducer travel in a straight line. Mirror image artifacts occur when the transmitted pulse and returning echo reflect off of a highly reflective interface (an acoustic mirror) and change direction before returning to the transducer, thereby breaking this assumption. Mirror image artifacts are seen throughout the body on gray scale, color Doppler, power Doppler, and spectral Doppler. They may closely duplicate the true structure in shape and echo strength, may distort the true structure, may appear weaker than the true structure, or may appear on images that do not simultaneously show the true structure. If not properly recognized, mirror image artifacts can be misinterpreted as true pathology and lead to additional unnecessary tests and potentially harmful interventions.