Side lobe artifact

Quick reference:↑ Cross-cutting acquisition and artifacts

View	Near highly reflective structures: calcified sinotubular junction, pericardium in PLAX, far field of the apical four-chamber (atria).
Timing	Moves with the reflector that produces it, without independent motion.
Caliper / trace	Not measured: look for a linear or arch-shaped echo symmetric about the reflector that crosses anatomic boundaries.

Example

Schematic sector panels: an arch-shaped side-lobe artifact around a strong reflector, and a shadow distal to a calcified structure. — Side lobe arc around a strong reflector (left panel). (Schematic drawing (E/e′ureka), not a patient image)

Correct example

A curvilinear echo in the ascending aorta arising from a calcified sinotubular junction, or linear echoes in the atria, that are symmetric about the reflector and fade with lower gain or harmonic imaging.

Common error

Reporting the arc as a dissection flap, intracardiac mass or thrombus.

Effect on interpretation

False flaps and masses; lowering gain, switching to harmonics, and changing angle or window resolve most side lobes.

Why

Energy outside the main lobe strikes a strong reflector and is displayed as if it came from the main beam, violating the single-main-lobe assumption.