Ch. 5 wkst 3 - 6 Flashcards

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1
Q

Doppler effect

A

a change in frequency caused by the motion of reflectors.

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2
Q

Doppler shift

A

reflected frequency minus incident frequency; a change in frequency that occurs as a result of motion.
fD(kHz)-fR-fT OR
DopplerShift = [2 x v of blood x freq of transducer x cosΘ] / propagation speed

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3
Q

Doppler angle

A

the angle between the sound beam and the flow direction.

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4
Q

Spectral analysis

A

separation of frequencies in a Doppler signal for display as a Doppler spectrum.

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5
Q

Aliasing

A

improper Doppler-shift information from a pulsed-wave Doppler or color Doppler instrument when the true Doppler shift exceeds one half the PRF.

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6
Q

Nyquist limit

A

the Doppler-shift frequency above which aliasing occurs. (PRF/2) MHz

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7
Q

Color Doppler display

A

the presentation of two-dimensional, real-time Doppler-shift information superimposed on a real-time, gray-scale, anatomical, cross-sectional image.

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8
Q

Autocorrelation

A

a rapid technique, used in most color Doppler instruments, for obtaining mean Doppler-shift frequency.

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9
Q

Wall filter

A

an electric filter that passes frequencies above a set level and eliminates strong, low-frequency Doppler shifts from pulsating heart or vessel walls.

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10
Q

Clutter

A

noise in the Doppler signal that generally is caused by high-amplitude, Doppler-shifted echoes from the heart and vessel walls.

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11
Q

Priority

A

the gray-scale strength below which color Doppler information is shown preferentially on a display.

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12
Q

Baseline shift

A

movement of the zero Doppler-shift frequency or zero flow speed line up or down on a spectral display.

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13
Q

Ensemble length

A

number of pulses used to generate one color Doppler image scan line.

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14
Q

Variance

A

a measure of spectral broadening.

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15
Q

Power Doppler Display

A

color Doppler display in which colors are assigned according to the strength (amplitude, power, intensity, energy) of the Doppler-shifted echoes.

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16
Q

Hue

A

the color perceived based on the frequency of light.

17
Q

Saturation

A

the amount of hue present in a mix of white.

18
Q

Luminance

A

brightness of a presented hue and saturation.

19
Q

Power Doppler Display

A

color Doppler display in which colors are assigned according to the strength (amplitude, power, intensity, energy) of the Doppler-shifted echoes.

20
Q

Continuous Wave

A

a wave in which cycles repeat indefinitely; not pulsed.

21
Q

CW Doppler

A

a Doppler device or procedure that uses CW ultrasound.

22
Q

Bidirectional Instrument

A

is an instrument that is capable of distinguishing between positive and negative Doppler shifts (forward and reversed flow).

23
Q

Sample Volume

A

the anatomical region from which pulsed Doppler echoes are accepted.