Which of the following is a characteristic associated with higher axial resolution?

• A. More cycles per pulse (More ringing)
• B. Shorter pulse duration
• C. Fewer cycles per pulse (Less ringing)
• D. Lower frequency

Answer: (C)

Axial resolution depends on how long the ultrasound pulse lasts along the beam axis. A shorter pulse length means the energy occupies less distance, so two reflectors that are close together along the axis can be distinguished rather than blurred into one echo. Fewer cycles per pulse directly shorten the pulse duration and reduce ringing, producing a shorter pulse in time and space. That improvement in pulse length is what boosts axial resolution, making two nearby structures along the beam path more separable.

In contrast, more cycles per pulse lengthen the pulse and degrade axial resolution; lower frequency tends to worsen axial resolution by increasing the wavelength and the axial length of the pulse. Shorter pulse duration helps, but fewer cycles per pulse captures that effect most directly.