Which ultrasound frequency is appropriate for targeting tissue at depths of about 1–2 cm?

• A. ~2–5 cm
• B. ~1–3 cm
• C. ~1–2 cm
• D. ~0.5–1 cm

Answer: (C)

Ultrasound frequency is chosen to balance how deeply the sound penetrates with how clear the image is. Higher frequencies give sharper detail but don’t travel as far; lower frequencies travel deeper but with less detail. For tissue around 1–2 cm beneath the surface, you want enough penetration to reach that depth while still maintaining good resolution, which means using a mid-range frequency. The option that corresponds to imaging at about 1–2 cm depth matches the target depth best, and would be the appropriate choice. Deeper targets would need lower frequencies, while shallower targets would use higher frequencies. In practice, imaging around 1–2 cm is typically done with mid-range frequencies in the few-megahertz range.