Two specific intensity values are cited in relation to unfocused transducers: 100 mW/cm2 and 1 W/cm2.

Two specific intensity values are cited in relation to unfocused transducers: 100 mW/cm2 and 1 W/cm2.

• A. 10 mW/cm2 and 100 mW/cm2
• B. 100 mW/cm2 and 1 W/cm2
• C. 1 mW/cm2 and 10 mW/cm2
• D. 1 W/cm2 and 10 W/cm2

Answer: (B)

Two intensity measures are used to describe ultrasound safety exposure: the peak intensity during a pulse (SPPA) and the time-averaged intensity over the pulsed train (SPTA). For unfocused transducers, safety standards set these limits at 1 W/cm^2 for the peak and 100 mW/cm^2 for the time-averaged. The higher peak limit reflects energy delivered in short bursts, while the lower average limit accounts for potential heating over time. Therefore, the pair 100 mW/cm^2 and 1 W/cm^2 corresponds to the SPTA and SPPA safety limits for unfocused beams. If a transducer emits pulses with a peak of 1 W/cm^2 and a duty cycle of 10%, the time-averaged intensity would be 0.1 W/cm^2 (100 mW/cm^2), staying within those limits.

Two intensity measures are used to describe ultrasound safety exposure: the peak intensity during a pulse (SPPA) and the time-averaged intensity over the pulsed train (SPTA). For unfocused transducers, safety standards set these limits at 1 W/cm^2 for the peak and 100 mW/cm^2 for the time-averaged. The higher peak limit reflects energy delivered in short bursts, while the lower average limit accounts for potential heating over time. Therefore, the pair 100 mW/cm^2 and 1 W/cm^2 corresponds to the SPTA and SPPA safety limits for unfocused beams. If a transducer emits pulses with a peak of 1 W/cm^2 and a duty cycle of 10%, the time-averaged intensity would be 0.1 W/cm^2 (100 mW/cm^2), staying within those limits.