With continuous-wave ultrasound, SATA equals which intensity?

With continuous-wave ultrasound, SATA equals which intensity?

• A. SPTA
• B. SAPA
• C. SPPA
• D. SATA

Answer: (B)

Continuous-wave ultrasound has a constant amplitude with no pulses, so averaging over time and averaging over a pulse duration are the same at every point in the beam. SAPA is the spatial-average of the pulse-average across the beam, while SATA is the spatial-average of the temporal-average. Since pulse-average equals temporal-average in CW, SAPA reduces to SATA. Therefore, in continuous-wave conditions, SATA and SAPA describe the same intensity. The other descriptors rely on either pulsed structure (SPPA) or on a spatial peak rather than a spatial average (SPTA), so they don’t match the continuous-wave equivalence.

Continuous-wave ultrasound has a constant amplitude with no pulses, so averaging over time and averaging over a pulse duration are the same at every point in the beam. SAPA is the spatial-average of the pulse-average across the beam, while SATA is the spatial-average of the temporal-average. Since pulse-average equals temporal-average in CW, SAPA reduces to SATA. Therefore, in continuous-wave conditions, SATA and SAPA describe the same intensity. The other descriptors rely on either pulsed structure (SPPA) or on a spatial peak rather than a spatial average (SPTA), so they don’t match the continuous-wave equivalence.