Ultrasound Physics Ch 5 (Intensities)

What does the following describe

. refers to distance or space

. ultrasound beam doesn't have the same intensity at different locations

Spatial

What is Peak?

the maximum value

What is Average?

the mathematical middle value

What does the following describe?

. refers to all time, transmit (pulse duration) and receive.

. A pulsed ultrasound beam doesn't have the same intensity at different times

Temporal

What does the following describe?

. refers only to the transmit time (pulse duration).

. A pulsed ultrasound beam does not have the same intensity at different times during the pulse.

. Pulsed is the average intensity for the pulse duration only (ignore listening time)

Pulsed

The strength of a sound beam varies depending on the _________________.

measurement point within the beam

Intensity varies over time with pulsed ultrasound, depending on whether ____________________.

the system is transmitting or receiving

The center of a beam is _________ than the edges.

more intense

When asked to measure the intensity of a beam what could you report?

. The spatial peak intensity or the spatial average intensity

What is spatial peak intensity I sp?

The beams intensity at the location where it is maximum

What is spatial average intensity I sa?

The average intensity across the beam's entire cross-sectional area.

Spatial peak intensity is always _____ than the spatial average intensity.

higher

What are the 4 different methods of measuring intensity?

. temporal peak intensity, I tp

. I max, I m

. pulse average intensity, I pa

. temporal average intensity, I ta

What is temporal peak intensity?

measuring the intensity of the beam at the instant in time of its maximal value

What is I max or Im?

the avg intensity during the most intense half cycle

What is pulse average intensity or I pa?

the average intensity during the pulse duration- the transmit time-

What is temporal average intensity or I ta?

Averaging the intensity during the entire pulse repetition period-both the transmit and receive times-

What is the most relevant intensity with respect to tissue heating?

SPTA (spatial peak temporal average)

A number called the beam uniformity coefficient (also called SP/SA factor) describes the _________________.

spread of a beam in space, spatial distribution of energy

The SP/SA factor is ______________.

unitless, with a value of 1 or greater?

For continuous wave ultrasound, the beam is always "on" so the _____ and _____ average intensities are the same.

pulse , temporal

. Thus, SPTA=SPPA and SATA=SAPA

When pulsed and continuous wave sound beams have the same SPTP intensities which has the higher SPTA intensity?

the continuous wave beam has the higher SPTA intensity?

When pulsed and continuous wave sound beams have the same SATP intensities, which has the higher SATA intensity?

The continuous wave beam has the higher SATA intensity

What is the rank of intensities from largest to smallest?

SPTP--> I m --> SPPA --> SPTA --> SATP --> SAPA -->SATA