If the number of cycles in the transmitted pulse increases, which property is most affected?

• A. Axial resolution is degraded
• B. Lateral resolution is degraded
• C. Spatial pulse length becomes shorter
• D. Rate of attenuation is increased

Answer: (A)

Increasing the number of cycles in the transmitted pulse lengthens the spatial pulse length. Axial resolution, which is the ability to distinguish two reflectors along the beam path, improves with shorter spatial pulse length. So, when more cycles are used, the spatial pulse length grows and axial resolution worsens.

Lateral resolution depends mainly on beam width and focusing, not on how many cycles are in the pulse. The spatial pulse length would not become shorter with more cycles; it becomes longer. Attenuation is governed mostly by frequency content and tissue properties, not the cycle count, so that’s not the primary effect here.