Axial resolution is chiefly determined by which parameter?

Axial resolution is chiefly determined by which parameter?

• A. Beam width
• B. Pulse duration
• C. Transducer diameter
• D. Line density

Answer: (B)

Axial resolution is about distinguishing two structures that lie along the direction the ultrasound waves travel. It depends on how long the emitted pulse is along that axis. A shorter pulse creates a shorter spatial pulse length, so echoes from closely spaced interfaces don’t blur together as easily. Spatial pulse length equals the number of cycles in the pulse times the wavelength, so reducing the pulse duration directly lowers the length of the pulse in space and improves axial resolution. The other options affect other aspects of image quality: beam width mainly governs lateral resolution, transducer diameter influences beam size and focusing, and line density affects sampling along the image, not how closely two structures can be separated along the beam.

Axial resolution is about distinguishing two structures that lie along the direction the ultrasound waves travel. It depends on how long the emitted pulse is along that axis. A shorter pulse creates a shorter spatial pulse length, so echoes from closely spaced interfaces don’t blur together as easily. Spatial pulse length equals the number of cycles in the pulse times the wavelength, so reducing the pulse duration directly lowers the length of the pulse in space and improves axial resolution. The other options affect other aspects of image quality: beam width mainly governs lateral resolution, transducer diameter influences beam size and focusing, and line density affects sampling along the image, not how closely two structures can be separated along the beam.