Doppler- Effect
What is the audible Doppler range?
-10khz to +10khz
what is the cosine of angle 90?
0
what is the best angle for imaging?
0 , biggest doppler shift
what is the cosine of angle 0?
1
which transducer will have a higher doppler shift? 5Mhz 10Mhz
10Mhz
What angles should you stay between when scanning vessels
30-60
worst angle for doppler* imaging?
90, no doppler shift
What is used to find the max speed of blood flow?
Aliasing
The Doppler shift depends on the _____ of the doppler angle
Cosine
Relationship between Doppler shift and velocity of reflector (blood)
Direct
Cosine of angle measured between what?
Direction of blood flow and axis of beam
This is the difference between the emitted frequency and the echo frequency returning from moving scatterers
Doppler shift
Is an angle greater than 60 good for calculating flow speed ?
No , not reliable
Is an angle less than 30 good for calculating flow speed?
No , sound being totally reflected
If the ------ speed increases the Doppler shift increases
Scatterer and source
The Doppler shift occurs at the interface of each _____ change
Velocity
what is the determining factor in determining flow velocity?
angle of incidence
what is doppler effect?
change in frequency caused by motion of a sound source, receiver, or reflector
as doppler angle increases, the doppler shift _____
deceases
if cosine increases, the calculated scatterer speed ____
decreases
if source frequency increases,the scatterer speed _____
decreases
the doppler shift depends on the cosine of the ____ ____
doppler angle
blood flow and tissue motion are the sources of the ____ ____
doppler effect
the change of frequency caused by motion is called a _____ _____
doppler effect
doppler instruments measure what?
doppler shift
the doppler shift is proportional to _____ ____
flow speed
do higher or lower frequencies produce larger doppler shifts?
higher
if reflector is moving toward the source, then the echo has a _____ frequency
higher
if the doppler angle increases, the scatterer speed ___
increases
the larger the doppler angle, the ___ the doppler shift
less
if motion is away from source, the frequency of echo is _____
lower
for flow away from transducer, the doppler shift is ____
negative
is there a doppler shift if angle is perpendicular to flow?
no ,no doppler shift for 90 degrees
for flow word the transducer,the doppler shift is ____
postive
what does the "2" represent in the doppler equation?
result of 2 doppler shifts for a scatterer
doppler effect happens because of motion of 3 things:
source receiver reflector
