Which parameter is primarily responsible for determining the depth of ultrasound penetration?

The parameter primarily responsible for determining the depth of ultrasound penetration is frequency. In therapeutic ultrasound, higher frequencies (such as 1 MHz) have a greater rate of absorption in tissues and therefore penetrate to a shallower depth compared to lower frequencies (such as 3 MHz), which penetrate deeper but are less absorbed.

Consequently, when selecting a frequency for ultrasound treatments, therapists consider the target tissue depth; lower frequencies are chosen for deeper tissues because they can travel through more layers without being absorbed as quickly. This understanding is crucial when deciding on the appropriate ultrasound settings for effective treatment.

Intensity relates to the amount of energy delivered but does not affect how deep the ultrasound can penetrate; the duty cycle influences the time the sound is on versus off but does not change penetration depth; and the effective radiating area pertains to the area of the soundhead that effectively transmits energy, but it also does not determine depth. Therefore, frequency is the key factor for depth of penetration in ultrasound therapy.