The red dot represents a (a)   originating sound waves traveling in all directions equally

Since the source is not moving the frequency and wavelength are the (a)   in all directions

Regarding the doppler effect, if the frequency is doubled then the wavelength is (a)  

Regarding the doppler effect, high frequency = (a)   pitch

Regarding the doppler effect, low frequency = (a)   pitch

Short wavelength, high pitch = (a)   frequency

Long wavelength, low pitch = (a)   frequency

Wave forms get closer at the (a)   of the moving source

If the source starts to move the waveform gets (a)  

There is an increase in frequency and a shortening of the wavelength at the (a)   of the moving source

There is a decrease in frequency and a lengthening of the wavelength at the (a)   of the moving source

Source produces the same amount of sound waves. It is the (a)   that produces the change in frequencies at the front and back of the moving source

The (a)   in ultrasound relates to the CHANGE IN FREQUENCY between the emitted and reflected sound

The change in frequency between emitted sound and reflected sound is caused by a change in (a)   between the source and the reflector due to motion

The (a)   is the moving structure and the transducer is the stationary listener

Is a change in the observed or received frequency of a wave because of the motion of the source or observer or receiver

(a)  

Is the difference between the emitted frequency and the echo returning from moving scatterers

(a)  

The change in frequency resulting from motion between transducer and a moving target in the body.

(a)  

Greater velocities = (a)   Doppler shifts

Doppler shift/frequency: Towards the transducer --> (a)   frequency

Doppler shift/frequency: Away from the transducer --> (a)   frequency

The __ __ is a low frequency (10kHz) that ‘rides’ on top of the much higher ‘carrier’ transducer frequency (3MHz).

(a)  

The process of extracting the Doppler frequency from the transducer frequency is called (a)  

(a)   = 2 x reflector speed x incident frequency x Cos angle propagation speed    

Speed = (a)   only

Velocity = __ and __

(a)  

Doppler frequency depends on (a)  

The magnitude of shift depends upon the (a)   of the angle between the sound beam and the direction of motion

Velocity (measured) = true velocity x cos (angle)

(a)  

The Doppler (fd)shift is equal to the received frequency(f2) (a)   the source frequency (f1).

For an approaching reflector (scatterer) Doppler shift is positive when the received frequency is (a)   than the source frequency

For a receding reflector, Doppler shift is (a)  

For a receding reflector, Doppler shift is negative. That is, the received frequency is (a)   than the source frequency

In diagnostic Doppler ultrasound the (a)   reflector is the situation of interest

Is the change in frequency caused by motion

(a)  

This image represents the

(a)  

Based on this equation the doppler sift depends on the (a)   frequency, the velocity of blood, and the angle of intonation

If scatterer speed increases, doppler shift (a)  

If source frequency increases, doppler shift (a)  

The difference between the emitted frequency and the echo frequency returning from moving scatterers

(a)  

What is the disadvantage for pulsed wave doppler?

(a)  

Positive bidirectional Doppler moves (a)   the transducer

Negative bidirectional doppler moves (a)   from the transducer

Bidirectional doppler: Away from the transducer is (a)   the baseline

Quadrature direction or phase quadrature

(a)  

Range ambiguity

Echoes detected come from entire length of overlap between transmit and receive beams.

It does not create an anatomical image.

(a)  

Higher velocities appear negative (below the baseline)

(a)  

It is also called the Nyquist frequency, which is the Doppler frequency at which aliasing occurs.

(a)  

• Change the Nyquist (change the scale).

• Select a transducer with a lower frequency. This shrinks the spectrum

• Select new view with a shallower sample volume. This raises the Nyquist

Using a shllaower sample volume, (a)   the Nyquist

• Use continuous wave Doppler

• Select a new view so that the angle is further away from 0° and closer to 90°. This shrinks the spectrum

• Baseline shift for appearance only

Regarding the nyquist limit, the (a)   refers to the frequency at which a pulsed wave transducer transmits pulses (sampling rates)

Regarding the Nyquist limit, the deeper the target area to investigate, the (a)   the PRF

Regarding the nyquist limit, the deeper the sample volume, the (a)   the transducer has to wait to receive the returning echo

The maximum possible frequency that can be measured. It is equal to one half the PRF

(a)  

Regarding Nyquist limit, if the waiting time between pulses is not sufficient (if another pulse is sent out before all echoes from previous pulses have returned) range (a)   results

Regarding Nyquist limit, to obtain accurate measurement of velocity, the PRF must be at least (a)   the doppler shift frequency

Regarding Nyquist limit, at the very least the PRF has to be (a)   enough to sample the doppler signal at least two times for each cycle.

Regarding Nyquist limit, higher velocities = (a)   PRF

The Nyquist limit (a)   as the sample volume is placed deeper

If the doppler frequency exceeds one half the PRF =

(a)  

This image shows:

(a)  

This image shows:

(a)  

The PRF lowers if the B-mode is updated while doing doppler

(a)  

(a)   doppler can detect broader range of blood flow velocities; more than pulsed wave or color flow

When the velocity is too high to measure accurately with pulsed wave doppler, then (a)   should be used

(a)   has the limitation that it does not provide depth information

(a)   doppler provides depth specificity; but it has limitations on the velocities it can measure accurately

One crystal

Range resolution

Limit on max velocity

Uses damping, Low Q, wide bandwidth

(a)  

Two crystals

Range ambiguity

Unlimited max. velocity

Does not use damping. High Q, narrow bandwidth, higher sensitivity

(a)