Decreasing ultrasound frequency is used to improve visualization of deep vessels because it:

• A. Increases frame rate
• B. Increases depth penetration
• C. Improves spatial resolution
• D. Reduces noise

Answer: (B)

Lowering the frequency improves depth penetration because tissue attenuation is frequency-dependent: higher frequency waves are absorbed and scattered more quickly, so they don’t travel as far. Using a lower frequency lets the ultrasound energy reach deeper vessels with enough strength to form a usable image. The trade-off is that lower frequency reduces spatial resolution, since longer wavelengths give less detail. Options about frame rate or noise aren’t the primary reason for better visualization of deep vessels; frame rate is affected more by depth and the number of scan lines, and lowering frequency doesn’t inherently reduce noise.