Ch. 5 - Intensity Flashcards
The concentration of the power in a beam is the
intensity
The equation for intensity is
Power
————– = Intensity (W/cm2)
Beam Area
The units for intensity are
w/cm2 (watts/square cm)
Intensity is not uniform across a _____ _____. With Pulsed U/S, intensity is not uniform throughout _____.
sound beam
time
5 Key words for intensity are
Peak Average Spatial Temporal Pulsed
The maximum value, when referring to Intensity, is called
Peak
The mean value, when referring to Intensity, is
Average
The Distance or Space, when referring to Intensity, is
Spatial
The Time (all time, transmit and receive) when referring to Intensity, is
Temporal
The Time that the Pulse exists (transmit only), when referring to Intensity, is
Pulsed
What does SPTP stand for?
spatial peak temporal peak (highest value)
What does SATP stand for?
spatial average
temporal peak
What does SPTA stand for?
spatial peak temporal average (most important for thermal bioeffects)
What does SATA stand for?
spatial average
temporal average
What does SPPA stand for?
spatial peak
pulse average
What does SAPA stand for?
spatial average
pulsed average
All Intensities have a unit of
W/cm2
T or F? An U/S beam does not have the same intensity at different locations within the beam.
(Spatial)
True
T or F? An U/S does not have the same intensity at different times.
(Temporal)
True
The 1st Commandment of Intensity is
1) Intensities may be reported in various ways with respect to time and space.
The 2nd Commandment of Intensity is
2) Intensity is the key parameter with regard to bioeffects. The different Intensities are important in the study of bioeffects. SPTA Intensity is the most relevant Intensity with respect to tissue heating.
The 3rd Commandment of Intensity is
3) Peak is greater than Average.
Thus, SPTP is the highest Intensity, and SATA is the lowest Intensity
A novel way of rating numbers. The _____ of any number represents the number “10s” that are multiplied together to create the original number.
logarithm
What is the log of 100?
10 x 10 = 100, the log of 100 is 2
Definition: a logarithmic scale. A relative scale - ratio of the final to the initial strengths. A comparison, therefore, two intensities are needed to calculate.
Decibels
What are the units of relative amplitude?
dB
Positive decibels means getting _____ (smaller/bigger). The Intensity is _____ (increasing/decreasing).
bigger
increasing
3dB means _____ (number) times bigger.
2
10dB means _____ (number) times bigger.
10
6dB means _____ x _____. Final is _____ (number) times bigger than the original.
2 x 2
4
Negative Decibels means getting _____ (smaller/bigger). The Intensity is _____ (increasing/decreasing).
smaller
decreasing
-3dB means _____ (number). We have fallen to _____ (fraction) of the original value.
one-half
half
-10dB means _____ (number). We have fallen to _____ (fraction) of the original value.
one-tenth
one-tenth
What is the meaning of -10dB? 10dB means _____ (number) times _____ (smaller/bigger). Therefore, -10dB means _____ (fraction) of the original.
10 times bigger
1/10
_____ Intensity is the most relevant Intensity with respect to tissue heating.
SPTA
