Which statement about ultrasound frequency and resolution is true?

• A. Higher frequency improves penetration but worsens resolution
• B. Higher frequency improves axial resolution and penetration
• C. Higher frequency improves axial resolution but reduces penetration
• D. Frequency has no effect on resolution

Answer: (C)

Higher frequency shortens the ultrasound wavelength, which improves axial resolution because the system can distinguish two closely spaced interfaces along the beam path. At the same time, higher frequency is more strongly attenuated by tissue, so imaging depth (penetration) decreases. This trade-off—better axial resolution with higher frequency but reduced penetration—explains why the true statement is that increasing frequency improves axial resolution while reducing penetration.