12.INTENSITY Flashcards
What is intensity?
Answer: Intensity is the concentration of power within a particular cross-sectional area of an ultrasound beam. Intensity is a measure of how much energy the ultrasound beam carries per unit area, and it plays a significant role in both image quality and patient safety during ultrasound imaging.
Intensity is equal to power divided by the beam area.
Intesity = power/beam area
Intensity is measured in units of watts/cm2.
For a focused transducer, will the beam intensity remain constant through the scan field?
Answer: Intensity depends upon beam diameter which is not constant through the scan field that’s why beam intensity does not remain constant through the scan field.
Intensity is equal to power divided by the beam area.
Intesity = power/beam area
How is the intensity measured for continuous wave ultrasound?
Answer: For continuous wave ultrasound, the intensity is measured where it is maximum.
This is called the spatial peak intensity. For continuous wave ultrasound, the beam is always on and the pulse average and temporal average intensities are the same.
Which pair of intensities has the same value for continuous wave ultrasound?
Answer: pulse average & temporal average
Pulse average & temporal average intensities have the same value for continuous wave ultrasound.
How is the intensity measured for pulsed wave ultrasound?
Answer: The intensity of pulsed wave ultrasound is more complex to measure compared to continuous wave ultrasound because the ultrasound energy is not continuously delivered, but rather in short bursts or pulses.
For pulsed wave ultrasound, several specific intensity measurements are used to describe how the energy is distributed over time and space.There are many options for measuring the intensity of pulsed ultrasound.
The intensity of pulsed ultrasound can be measured as peak intensity, average intensity, intensity in time, and intensity in space.
What is the importance of describing sound beam intensities with regard to time and space?
Answer: Calculating sound beam intensities in a variety of ways with regard to time and space are important in studying bioeffects.
Describing sound beam intensities with regard to time and space is crucial in ultrasound because both dimensions significantly affect how energy is distributed within tissues, influencing image quality and patient safety.
Describing sound beam intensities in terms of time and space allows clinicians to balance safety, diagnostic effectiveness, and patient comfort during ultrasound procedures.
Which intensity is closely correlated to tissue heating?
Answer: SPTA intensity is most closely correlated to tissue heating.
With regards to bioeffects, the most relevant intensity measurement for pulsed ultrasound is the SPTA or spatial peak, temporal average intensity.
If the SPTA for pulsed ultrasound is less than 100 mW/cm, the risk of bioeffects of ultrasound is considered negligible.
If the SPTA intensities are equal for both continuous wave and pulsed ultrasound, the continuous wave will have the lowest SPPA.
Answer: True. If the SPTA intensities are equal, the continuous wave will have the lowest SPPA.
If the SPTA (Spatial Peak Temporal Average) intensities are equal for both continuous wave (CW) and pulsed ultrasound, the continuous wave will indeed have the lowest SPPA (Spatial Peak Pulse Average) intensity.
Continuous wave ultrasound has lower SPPA when SPTA is the same for both continuous and pulsed waves because continuous wave ultrasound emits energy constantly, while pulsed wave ultrasound only emits energy intermittently during the pulse duration.
Put these intensities in decreasing order SPTP, SATA, SPPA, SPTA
Answer: SPTP, SPPA, SPTA, SATA
The rank of intensities from largest to smallest is:
SPTP > Im > SPPA > SPTA > SATA SPTP intensity has the highest value.
SATA intensity has the lowest value.
What is beam uniformity coefficient?
Answer: The beam uniformity coefficient measures the spatial distribution of acoustic energy. It indicates the degree that intensity of an ultrasound beam is distributed in space. It is calculated by dividing the spatial peak intensity by the spatial average intensity.
The other name for beam uniformity coefficient is SP/SA factor.
What is the minimum value of the SP/SA factor?
The minimum value of the SP/SA factor is 1.0
Beam uniformity coefficient also called SP/SA factor describes the spread of a beam in space. It is a unitless number and has a value of 1 or greater.
Two sound beams have same SPTP intensities of 300 mW/cm?.
One beam is pulsed wave while the other is continuous wave. Which beam has a higher SPTA intensity?
Answer: The continuous wave will have the higher SPTA intensity.
Pulsed wave ultrasound has longer receive time which reduces the SPTA intensity.
Continuous wave ultrasound emits energy constantly, while pulsed wave ultrasound only emits energy intermittently during the pulse duration.
What is intensity reflection coefficient?
Answer: Intensity reflection coefficient is defined as the percentage of intensity of an ultrasound beam that is reflected as the sound wave passes through a boundary between the two media.
Intensity reflection coefficient is the reflected intensity divided by the incident intensity.
intensity
intensity reflection coefficient (IRC) = reflected intensity /
incident intensity
The intensity reflection coefficient is a unitless number.
What is the maximum possible value for both the intensity reflection coefficient and the intensity transmission coefficient?
Answer: The maximum percentage of the incident intensity that either reflects or transmits is 1 or 100%.
When total reflection occurs the intensity reflection coefficient is 1.0 or 100%.
When complete transmission occurs the intensity transmission coefficient is 1.0 or 100%.
What is the minimum possible value for both the intensity reflection coefficient and the intensity transmission coefficient?
Answer: The minimum percentage of the incident intensity that either reflects or transmits is 0 or 0%.
When no reflection occurs the intensity reflection coefficient is 0 or 0%.
When no transmission occurs the intensity transmission coefficient is 0 or 0%.
It is possible to have total transmission and no reflection or total reflection and no transmission.
A sound beam with an intensity of 55 W/cm strikes a boundary and 60% of the wave’s intensity is reflected. How much the intensity of the wave is transmitted?
Answer: 40% intensity of the wave is transmitted.
The law of conservation of energy states that the sum of the intensity reflection coefficient and intensity transmission coefficient equals 100% or 1.
IRC + ITC = 1 or 100%
ITC = 100% - IRC
ITC = 100% - 60%
ITC = 40%
