Doppler Effect Flashcards

1
Q

What is the doppler effect?

A

the change in frequency of sound as the source and observer move towards (or away from) each other.

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2
Q

What does flow towards the transducer indicate?

A

Increased echo frequency

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3
Q

What does flow away from the transducer indicate?

A

Decreased echo frequency

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4
Q

What is the continuous doppler?

A

Continuously transmits and receives sound waves

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5
Q

What are the advantages of continuous wave doppler?

A

Detection of high velocity signals

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6
Q

Is there aliasing in continuous wave doppler?

A

No

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7
Q

Is there different or the same elements for the transmit/receive in continuous wave?

A

Different

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8
Q

What is pulsed doppler?

A

Sends out small pulses in short bursts

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9
Q

What is an advantage of pulsed doppler?

A

Collects info about velocities from well defined volume at a chosen depth

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10
Q

Is there the same or different elements for send/receive in pulse doppler?

A

Same

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11
Q

What is aliasing?

A

occurs when signal is not sampled at a sufficiently high sampling frequency and the signal frequencies are misrepresented

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12
Q

What is the nyquist sampling theorum?

A

A signal can be accurately reconstructed if the sampling frequency is at least twice the highest frequency component in the signal

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13
Q

List three types of spectral doppler

A

-pulsed
-continuous
-tissue doppler

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14
Q

What is spectral doppler?

A

Displays info on time, velocity and amplitude

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15
Q

What is spectral broadening?

A

occurs when sample volume is too large or too close to vessel wall/valve

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16
Q

What is tissue doppler?

A

Specialised pulse-wave doppler that allows for the detection of low velocity, high amplitude signals from moving tissues