Axial resolution is primarily determined by which parameter?

• A. Lateral beam width
• B. Pulse duration
• C. Frame rate
• D. Dynamic range

Answer: (B)

Axial resolution is governed by how long the ultrasound pulse lasts along the direction of the beam. Shorter pulses create shorter spatial pulse lengths, which means two reflectors that are close together along the beam can be distinguished more easily. Since pulse duration directly determines how long the pulse lasts, shorter pulse duration improves axial resolution. Lateral beam width affects resolution across the beam, frame rate relates to how often new images are produced (temporal resolution), and dynamic range deals with contrast sensitivity, not the ability to separate points along the beam. So the pulse duration is the key factor that sets axial resolution.