Which intensity is measured at the location where intensity is maximum and at the instant when the pulse is strongest?

Which intensity is measured at the location where intensity is maximum and at the instant when the pulse is strongest?

• A. Isppa
• B. Itp
• C. Isptp
• D. Ita

Answer: (C)

Intensities in ultrasound are described by where you measure them in space and when you measure them in time. The highest instantaneous energy occurs at the spatial peak—the point in the beam where the intensity is greatest—and at the temporal peak—the moment when the pulse reaches its maximum amplitude. Combining these two peaks gives the spatial-peak temporal-peak intensity, Isptp, which represents the maximum instantaneous exposure at the location of greatest intensity. Isppa would be the spatial-peak value averaged over the pulse duration, smoothing out the temporal fluctuations; Itp is the temporal-peak value at the measurement location but isn’t guaranteed to be at the spatial peak; Ita is the temporal-average over time, not the instantaneous maximum. Thus, the measure that matches being at the location of maximum intensity and at the moment of strongest pulse is Isptp.

Intensities in ultrasound are described by where you measure them in space and when you measure them in time. The highest instantaneous energy occurs at the spatial peak—the point in the beam where the intensity is greatest—and at the temporal peak—the moment when the pulse reaches its maximum amplitude. Combining these two peaks gives the spatial-peak temporal-peak intensity, Isptp, which represents the maximum instantaneous exposure at the location of greatest intensity.

Isppa would be the spatial-peak value averaged over the pulse duration, smoothing out the temporal fluctuations; Itp is the temporal-peak value at the measurement location but isn’t guaranteed to be at the spatial peak; Ita is the temporal-average over time, not the instantaneous maximum. Thus, the measure that matches being at the location of maximum intensity and at the moment of strongest pulse is Isptp.