The average intensity during the pulse duration only is called what?

The average intensity during the pulse duration only is called what?

• A. Peak
• B. Pulse average intensity, or Ipa
• C. Temporal
• D. Isa

Answer: (B)

When dealing with pulsed ultrasound, it’s important to separate the energy delivered during the on-time from the energy (or lack thereof) during the off-time. The average intensity during the actual pulse is a specific, defined measure called pulse-average intensity, abbreviated Ipa. It represents how much energy passes through a point, averaged over the duration the pulse is on. In practical terms, you take the instantaneous intensity during the pulse, average it over the pulse duration, and you get Ipa. This is different from the peak intensity, which is simply the highest instantaneous value within the pulse, and from the temporal-average intensity, which would average over the entire cycle including the off-time and would be lower by the duty factor. Isa, if it refers to a spatial-average quantity, is not the measure described by “average during the pulse duration.” Therefore, the correct concept is pulse-average intensity, or Ipa.

When dealing with pulsed ultrasound, it’s important to separate the energy delivered during the on-time from the energy (or lack thereof) during the off-time. The average intensity during the actual pulse is a specific, defined measure called pulse-average intensity, abbreviated Ipa. It represents how much energy passes through a point, averaged over the duration the pulse is on. In practical terms, you take the instantaneous intensity during the pulse, average it over the pulse duration, and you get Ipa. This is different from the peak intensity, which is simply the highest instantaneous value within the pulse, and from the temporal-average intensity, which would average over the entire cycle including the off-time and would be lower by the duty factor. Isa, if it refers to a spatial-average quantity, is not the measure described by “average during the pulse duration.” Therefore, the correct concept is pulse-average intensity, or Ipa.