Which artifact arises from energy emitted from outer portions of the array producing secondary beams and spurious structures away from the main image?

Which artifact arises from energy emitted from outer portions of the array producing secondary beams and spurious structures away from the main image?

• A. Side lobes
• B. Grating lobes
• C. Reverberation
• D. Speckle

Answer: (B)

Grating lobes arise when the spacing between array elements is large compared to the wavelength. The outer portions of the array can emit energy that, through constructive interference at specific off-axis angles, forms additional, secondary beams. These grating lobes appear as spurious structures away from the main image, mimicking echoes from locations outside the intended imaging direction. In contrast, side lobes are secondary maxima near the main beam within the same general direction, not distant off-axis artifacts. Reverberation comes from multiple reflections within tissue creating repeated echoes, and speckle is the grainy pattern from coherent scattering; neither is about energy from outer array regions forming separate, off-axis beams.

Grating lobes arise when the spacing between array elements is large compared to the wavelength. The outer portions of the array can emit energy that, through constructive interference at specific off-axis angles, forms additional, secondary beams. These grating lobes appear as spurious structures away from the main image, mimicking echoes from locations outside the intended imaging direction.

In contrast, side lobes are secondary maxima near the main beam within the same general direction, not distant off-axis artifacts. Reverberation comes from multiple reflections within tissue creating repeated echoes, and speckle is the grainy pattern from coherent scattering; neither is about energy from outer array regions forming separate, off-axis beams.