In therapeutic ultrasound, which frequency and depth correspond to a superficial treatment (approximately 1–2 cm)?

In therapeutic ultrasound, which frequency and depth correspond to a superficial treatment (approximately 1–2 cm)?

• A. 2.5 MHz; 3 centimeters
• B. 3.0 MHz; 1–2 centimeters
• C. 1.0 MHz; 5 centimeters
• D. 5.0 MHz; 0.5 centimeters

Answer: (B)

Penetration depth in therapeutic ultrasound is governed mainly by the frequency. Higher frequency waves are absorbed more quickly by tissue and don’t travel far, while lower frequencies penetrate deeper. To target tissues about 1–2 cm beneath the skin, you use a higher frequency such as 3 MHz, which typically reaches roughly that superficial depth. The other options pair frequencies with depths that don’t align with the 1–2 cm range: a lower frequency like 1 MHz would reach deeper (around 4–5 cm), a much higher frequency like 5 MHz would stay very shallow (about half a centimeter), and 2.5 MHz with a 3 cm depth exceeds the superficial target. So the 3 MHz frequency with a 1–2 cm depth best matches the superficial treatment goal.

Penetration depth in therapeutic ultrasound is governed mainly by the frequency. Higher frequency waves are absorbed more quickly by tissue and don’t travel far, while lower frequencies penetrate deeper. To target tissues about 1–2 cm beneath the skin, you use a higher frequency such as 3 MHz, which typically reaches roughly that superficial depth. The other options pair frequencies with depths that don’t align with the 1–2 cm range: a lower frequency like 1 MHz would reach deeper (around 4–5 cm), a much higher frequency like 5 MHz would stay very shallow (about half a centimeter), and 2.5 MHz with a 3 cm depth exceeds the superficial target. So the 3 MHz frequency with a 1–2 cm depth best matches the superficial treatment goal.