4 Intensity Flashcards
What is intensity?
Concentration of the power in a beam
Do ultrasound beams have the same intensity at different locations within the beam?
NO
What is the peak?
Maximum value
Define spatial.
Referring to distance or space
Define temporal.
Referring to all time (transmit & receive)
Define pulsed.
Referring only to the time the pulse exists (transmit only)
Which intensity description is the most important for thermal bioeffects?
SPTA - spatial peak, temporal average
List the 3 commandments of intensity.
- Intensities may be reported in various ways with respect to time and space
- Intensity is the key parameter with regard to bioeffects
- Peak is greater than average
What are decibels?
Logarithmic scale
Relative scale - ratio of final to initial strengths
A comparison
What does a positive decibel describe?
Getting bigger, intensity is increasing
What does 3dB mean?
2 times bigger
What does 10dB mean?
10 times bigger
What does a negative decibel describe?
Getting smaller, intensity is decreasing
What does -3dB mean?
1/2
What does -10dB mean?
1/10
