Which statement describes the effect of increasing transducer diameter on lateral resolution?

Which statement describes the effect of increasing transducer diameter on lateral resolution?

• A. Lateral resolution worsens
• B. Lateral resolution improves
• C. Lateral resolution stays the same
• D. Lateral resolution is unrelated to diameter

Answer: (B)

Increasing transducer diameter narrows the ultrasound beam, which directly improves lateral resolution. Lateral resolution depends on how wide the beam is as it travels through tissue; a larger aperture allows the emitted waves from more elements to interfere and focus into a tighter beam, especially in the focal zone. The beamwidth can be approximated by a relation where beamwidth is proportional to wavelength times focal length divided by the aperture diameter, so increasing the diameter reduces beamwidth. A smaller beam lets you distinguish two closely spaced structures side by side, yielding better lateral detail. (Axial resolution, by contrast, is set by wavelength and pulse length, not diameter.)

Increasing transducer diameter narrows the ultrasound beam, which directly improves lateral resolution. Lateral resolution depends on how wide the beam is as it travels through tissue; a larger aperture allows the emitted waves from more elements to interfere and focus into a tighter beam, especially in the focal zone. The beamwidth can be approximated by a relation where beamwidth is proportional to wavelength times focal length divided by the aperture diameter, so increasing the diameter reduces beamwidth. A smaller beam lets you distinguish two closely spaced structures side by side, yielding better lateral detail. (Axial resolution, by contrast, is set by wavelength and pulse length, not diameter.)