Lecture 5 Flashcards
Definition of amplitude
The maximum variation in acoustic variable
(T/F) Amplitude is not the peak to peak difference, it is the maximum to the average, and the minimum to average difference.
True
(T/F) As sound travels, it increases in amplitude
False
(T/F) Bioeffects can be altered by the sonographer adjusting gain
False, adjusting POWER can alter bioeffects
Definition of Power
Rate of energy transference
Definition of Intensity
Concentration of power in an area
Equation for Intensity
I = P/A
Relationship between intensity and power
Directly related
If power increases, intensity..
Increases
If area decreases, intensity..
Increases
Relationship between intensity and amplitude
Intensity is proportional to amplitude squared
Ex. If amplitude is doubled, intensity is multiplied 4x
Relationship between power & amplitude
Power is proportional to amplitude squared
Ex. If amplitude is tripled, power is multiplied 9x
Intensities vary in _____ & _____
Time & space
Highest intensity attained is called
Peak intensity
Second highest intensity attained is the
Pulse average intensity
Lowest intensity is the
Average intensity
Highest intensity in time & space
SPTP
Lowest intensity in time & space
SATA
Intensity related to tissue heating (exposure time)
SPTA
Intensity related to cavitation
SPTP
Definition of Attenuation
The weakening of sound as it travels
Definition of Reflection
Redirection of sound back into a transducer
How is the amount of reflection indicated on the display?
Brightness or pixel
Definition of Absorption
Conversion of sound energy into heat
Absorption occurs because
Sound is a mechanical wave
Definition of Scatter
Redirection of sound into all directions
Dominant factor in attenuation
Absorption
Definition of Attenuation Coefficient
Amount of attenuation of sound per centimeter of travel
Equation for AC
AC = f/2
Total attenuation is dependent on ____ & ____
Frequency & path length
2 Equations for Attenuation
A = 1/2 freq. x path length A = AC x path length
Definition of Half Value Layer Thickness
Depth in tissue where intensity of sound is half the original value
Equation for Half Value Layer Thickness
HVL = 3/AC
If HVL increases, what happens to frequency?
Decreases