Distinguish side lobes from speckle and explain their impact on image quality.

• A. Side lobes are secondary energy lobes from the main beam; speckle is a granular texture from interference of many scatterers; both reduce contrast
• B. Side lobes are random noise; speckle is a fixed pattern that enhances edges
• C. Side lobes occur only in harmonic imaging; speckle occurs only in fundamental imaging
• D. Side lobes are the main beam; speckle is the main lobe

Answer: (A)

Side lobes are secondary energy lobes that extend beyond the main ultrasound beam, while speckle is the granular texture created by the interference of echoes from many tiny scatterers within the tissue. Side lobes can illuminate off-axis structures, producing echoes that mimic real reflectors and degrade image contrast because signals from outside the main beam contribute to the image. Speckle is not a true structure; it’s a random, grainy pattern that arises from coherent summation of many tiny scatterers and tends to mask fine details, reducing apparent contrast and edge definition. Together, these concepts explain why image quality suffers: side lobes introduce off-axis artifacts and speckle blurs fine detail. The other descriptions mischaracterize one or both phenomena—for example,speckle is not a fixed pattern that enhances edges, side lobes are not random noise isolated to a single mode, and side lobes are not the main beam nor is speckle the main lobe.