The term 'effective radiating area' refers to what?

The term 'effective radiating area' refers to what?

• A. Area of the sound head
• B. Area of the device
• C. Area of the patient
• D. Area of the treatment zone

Answer: (A)

In therapeutic ultrasound, the important idea is that the energy you deliver comes from a specific emitting surface. The term effective radiating area refers to the portion of the ultrasound transducer that actually emits energy—the sound head’s radiating face. Because intensity is calculated as power per unit area, the ERA is the area you use for dose calculations. It isn’t the whole device footprint, nor is it the patient’s area, and while you irradiate tissue within a certain treatment zone, the dose depends on the emitting surface itself. If the device produces a certain power, a smaller ERA yields a higher intensity, and a larger ERA yields a lower intensity.

In therapeutic ultrasound, the important idea is that the energy you deliver comes from a specific emitting surface. The term effective radiating area refers to the portion of the ultrasound transducer that actually emits energy—the sound head’s radiating face. Because intensity is calculated as power per unit area, the ERA is the area you use for dose calculations. It isn’t the whole device footprint, nor is it the patient’s area, and while you irradiate tissue within a certain treatment zone, the dose depends on the emitting surface itself. If the device produces a certain power, a smaller ERA yields a higher intensity, and a larger ERA yields a lower intensity.