The doppler effect MUT

Objects in motion will produce echoes that come back at a slightly different __ than what was sent out

frequency

Moving __ the sound source = higher received frequency

towards

Moving towards the sound source = __ received frequency

higher

Moving __ from the sound source = lower received frequency

away

Moving away from the sound source = __ received frequency

lower

The difference between the reflected and transmitted frequencies is called the __ or __

frequency shift or doppler shift

If the frequency is __ than the transmitted, Its a positive shift

greater

if the frequency is greater than the transmitted, Its a __ shift

positive

if the frequency is __ than the transmitted, its a negative shift

less

if the frequency is less than the transmitted, Its a __ shift

negative

What three things does doppler shift tell you?

presence, direction, and magnitude

Doppler shift equation =

__

2 x freq x V x cos / C

What three things affect the doppler shift?

velocity, frequency, and angle

Velocity is __ related to shift

directly

velocity

Increase in blood velocity = __ doppler shift

increase

frequency is __ related to shift

directly

Increase in transducer frequency = __ doppler shift

increase

Angle is __ related to shift

inversely

Increase in angle (closer to 90) = __ doppler shift

decrease

At __ degrees/perpendicular = NO shift

90

At 90 degrees/perpendicular = __ shift

NO

At __ degrees/parallel or __ degrees = greatest shift

0 or 180

At 0 degrees/parallel or 180 degrees = __ shift

greatest

Doppler shift info __ and superimposed or ‘pasted’ onto B-mode image (duplex).

colorized

Color only displays __ and average __

direction, velocities

__ is displayed and the range it’s able to detect (maximum velocity)

PRF

Slow flow = __

low scale

Fast flow = __

high scale

Closer to __ = higher doppler shift and therefore, brighter color

parallel

Closer to parallel = higher doppler shift and therefore, __

brighter color

__ = NO doppler shift and so black

perpendicular

Flow separations and any vessel that __ or __ will show both red and blue part of the flow moves towards and then away

loops, curves

Blue on top and red on bottom

__ means away or downhill

red

Correctly use color doppler

__ the box in the direction of the vessel angle

steer

Correctly use color doppler

The size of the box should just cover the area of __

interest

Correctly use color doppler

Adjust the scale to fit the type of __ you are evaluating

flow

Correctly use color doppler

Adjust __ so color fills in the vessel but down not __ out of the vessel walls

gain, bleed

Pulsed doppler

What are the benefits to pulsed doppler

position and size

Pulsed doppler is specific and __ can be measured

velocities

Pulsed doppler is __

quantitative

__ - which breaks down the signal into separate components according to velcoity (magnitude of shift) and time (location)

spectral analysis

spectral analysis which breaks down the signal into separate components according to __ (magnitude of shift) and __ (location)

velocity, time

How to correctly use PW doppler

Sample at __ of flow/vessel with sample angle steered in direction of vessel and __ to vessel walls

center, parallel

How to correctly use PW doppler

If the angle is not parallel, __ measurement will be inaccurate

velocity

How to correctly use PW doppler

Generally, ideal angles are __ degrees

45-60

How to correctly use PW doppler

Sample gate should be approximately __ the size of the vessel

1/3

Power doppler

AKA __ or __ doppler

energy, amplitude

Power doppler

Only __ color

one

What three things does power doppler map?

magnitude, power, and amplitude of doppler signal

Power doppler

Only detects and displays the __ of flow NOT __

presence, direction

Power doppler

what is the benefit of power doppler?

sensitive to slow flow

Continuous wave doppler = __

non-imaging

Continuous wave doppler

Requires __ crystals

2

Continuous wave doppler

one for __ and other for __

transmitting, receiving

Continuous wave doppler

only used as flow detector or to measure severely __ velocities

elevated

Continuous wave doppler

__ - unable to determine depth or location

range ambiguous

Continuous wave doppler

Cannot choose a __

location

Doppler optimization

Scale

__ the scale = not sensitive enough

decrease

Doppler optimization

Scale

__ the scale = aliasing

increase

Doppler optimization

Wall filters and high pass filters - __/__

low frequency/high amplitude

Doppler optimization

__ wall filter = not sensitive enough

decrease

Doppler optimization

Gain

__ gain to enhance the strength of the doppler signal

increase

Doppler optimization

Gain

__ if bleeding out of vessel

decrease

Doppler optimization

Problem - Aliasing

Shift exceeds the __ limit

nyquist

Doppler optimization

Problem - Aliasing

nyquist limit - __

½ PRF

Doppler optimization

Problem - Aliasing

Increase __ or __

scale or PRF

Doppler optimization

Problem - Aliasing

Lower __

baseline

Doppler optimization

Problem - Aliasing

Decrease __

transducer frequency

Doppler optimization

Problem - Aliasing

Increase __

doppler angle

Doppler optimization

Problem - SLOW FLOW

Low velocity flow will produce a small doppler shift. The opposite of __

aliasing

Doppler optimization

Problem - SLOW FLOW

Lower __ and __

scale and wall filter

Doppler optimization

Problem - SLOW FLOW

Increase three things

frequency, color gain, and packet size

Doppler optimization

Problem - SLOW FLOW

decrease __

angle (closer to parallel)

Doppler optimization

Problem - SLOW FLOW

Use __

power doppler