Which statement correctly describes how ultrasound frequency relates to tissue depth?

• A. Higher frequency penetrates deeper into tissue
• B. Lower frequency penetrates deeper into tissue
• C. Frequency has no effect on depth; depth is determined by gel type
• D. Depth depends only on intensity

Answer: (B)

Ultrasound depth is determined by how far the sound waves can travel before they’re significantly attenuated. Lower frequencies experience less attenuation, so they can propagate deeper into tissue and image deeper structures. Higher frequencies provide clearer, more detailed images but lose energy more quickly and therefore don’t reach as far. That’s why clinicians choose lower-frequency transducers for deep organs (like the liver or pelvic structures) and higher-frequency transducers for superficial structures (such as thyroid or breast tissue).

Gels mainly aid coupling and don’t set how deep ultrasound can image. Intensity affects image brightness and heating risk but doesn’t overcome the fundamental limit set by frequency and tissue attenuation. So the correct idea is that lower frequency penetrates deeper into tissue.