What is the purpose of subdicing?

• A. To focus the beam upon transmit
• B. To reduce grating lobes
• C. To increase transmitted intensity
• D. To alter the transmitted frequency

Answer: (B)

Grating lobes are unwanted off-axis beams that appear when element spacing in an ultrasound array is too large relative to the wavelength. Subdicing splits each element into many tiny subelements, creating a finer, more continuous aperture and breaking up the regular spacing that feeds those lobes. With the reduced effective spacing and the more aperiodic aperture, the grating lobes are suppressed, improving image quality. This technique doesn’t change the transmitted frequency or inherently increase transmitted intensity, and it doesn’t directly provide beam focusing.