The importance of ultrasonic side-lobe artifacts.

Transducer side lobes consist of multiple low-intensity sound beams located outside of the main ultrasound beam. Although the echoes generated by side lobes originate outside of the main beam, they appear as specular or diffuse artifactual echoes within the beam. They are visible with both static and real-time equipment. Specular side-lobe artifacts occur near strong, curved, highly reflecting surfaces such as the diaphragm, or near large cystic masses such as the urinary bladder or gallbladder. Diffuse artifacts originate from bowel gas adjacent to cystic structures. These echoes can be confused with particulate material or sludge in organs such as the urinary bladder and gallbladder, or in abnormal cystic masses. We illustrate the genesis of these artifactual echoes and provide clinical examples of commonly visualized side-lobe artifacts.