Intensity - EXAM II Flashcards
What is energy?
The ability to do work.
What is power?
Energy per unit time.
What are the units for sound intensity?
power per unit area
or
Power / Area
What are the units for power?
watts
What are the units for intensity?
W/m2
What are the usual units for intensity in ultrasound?
mW/cm2
Intensity =
Intensity = amplitude2 / 2pV
p=density
V=speed
What happens to intensity if you double the amplitude?
it is increased x4 because of the exponent (power of 2)
What happens to intensity if amplitude is increased x3?
Intensity = x9
What is the relationship between Amplitude and Frequency?
They are independent of each other.
There can be the same frequency, but different amplitude.
What are the two basic parameters in measurements of intensity?
Space and Time
What are the two types of measurement of intensity?
Peak and Average
What is the highest instantaneous intensity measurement at a given moment?
TP - Temporal Peak
What is the average intensity over time?
TA - Temporal Average
What is the highest intensity in the area?
SP - Spatial Peak
What is the average intensity over the area?
SA - Spatial Average
If TP = TA What kind of ultrasound is it?
CW, Always on
Peak Intensity = Average Intensity
What is another type of intensity measurement?
Im: Average intensity measured at the most intense half-cycle.
What is the final type of intensity measurement?
PA - Pulse average
The average intensity for the duration of the pulse itself.
What type of measurement is PA?
Time
What type of measurements can PA be combined with?
Spatial:
SPPA
SAPA
List the Intensities in order of highest to lowest
SPTP Im SPPA SPTA SATP SAPA SATA
What do all of the letters mean in reference to intensity?
They are different ways of measuring energy.
Over space and time.
What is BUC?
Beam uniformity coefficient.
It suggests the level of uniformity across the area.
