Ch. 5 Vocab Review

Question 1

Flow

Answer 1

to move in a stream continually changing position and possibly direction.

Question 2

Fluids

Answer 2

a material that flows and conforms to the shape of its container (gas or liquid).

Question 3

Flow Resistance

Answer 3

pressure difference divided by volume flow rate for steady flow. R(g/cm⁴-s)=8xL(cm)x viscosity(poise)/Pi x[r⁴(cm⁴)]

Question 4

Volumetric Flow Rate

Answer 4

volume of fluid passing a point per unit of time (per second or minute). Q(mL/s)=changeP(dyne/cm²)/R(poise)

Question 5

Pressure Gradient (slope)

Answer 5

pressure difference divided by distance between the two pressure locations.

Question 6

Viscosity

Answer 6

resistance of fluid to flow. R(poise)=changeP(dyne/cm²)/Q(mL/s)

Question 7

Plug flow

Answer 7

flow with all fluid portions traveling with the same flow speed and direction.

Question 8

Laminar flow

Answer 8

flow in which fluid layers slide over each other in a smooth, orderly manner, with no mixing between layers.

Question 9

Parabolic flow

Answer 9

laminar flow with a profile in the shape of a parabola.

Question 10

Disturbed flow

Answer 10

flow that cannot be described by straight parallel streamlines.

Question 11

Turbulent flow

Answer 11

random, chaotic, multidirectional flow of a fluid with mixing between layers; flow that is not laminar.

Question 12

Pulsatile flow

Answer 12

flow that accelerates and decelerates with each cardiac cycle.

Question 13

Continuity Rule

Answer 13

blood is neither created nor destroyed as it flows through a vessel.

Question 14

Bernoulli Effect

Answer 14

pressure reduction in a region of high-flow speed. Pressure Drop (where V₂=flow speed at stenosis): △P=4(V₂)²

Question 15

Doppler effect

Answer 15

a change in frequency caused by the motion of reflectors.

Question 16

Doppler shift

Answer 16

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

Question 17

Doppler angle

Answer 17

the angle between the sound beam and the flow direction.

Question 18

Spectral analysis

Answer 18

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

Question 19

Aliasing

Answer 19

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

Question 20

Nyquist limit

Answer 20

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

Question 21

Color Doppler display

Answer 21

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

Question 22

Autocorrelation

Answer 22

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

Question 23

Wall filter

Answer 23

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

Question 24

Clutter

Answer 24

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

Question 25

Priority

Answer 25

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

Question 26

Baseline shift

Answer 26

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

Question 27

Ensemble length

Answer 27

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

Question 28

Variance

Answer 28

a measure of spectral broadening.

Question 29

Power Doppler Display

Answer 29

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

Question 30

Hue

Answer 30

the color perceived based on the frequency of light.

Question 31

Saturation

Answer 31

the amount of hue present in a mix of white.

Question 32

Luminance

Answer 32

brightness of a presented hue and saturation.

Question 33

Continuous Wave

Answer 33

a wave in which cycles repeat indefinitely; not pulsed.

Question 34

CW Doppler

Answer 34

a Doppler device or procedure that uses CW ultrasound.

Question 35

Bidirectional Instrument

Answer 35

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

Question 36

Sample Volume

Answer 36

the anatomical region from which pulsed Doppler echoes are accepted.

Question 37

Doppler Spectrum

Answer 37

the range of frequencies present in Doppler-shifted echoes.

Question 38

Spectral Doppler Display

Answer 38

the presentation of Doppler information in a quantitative form. Visual display of a Doppler spectrum.

Question 39

Range Gate

Answer 39

a device that allows only echoes from a selected depth (arrival time) to pass.

Question 40

Duplex Instrument

Answer 40

an ultrasound instrument that combines gray-scale sonography with pulsed Doppler and possibly, CW Doppler.

Question 41

Fast Fourier Transform (FTT)

Answer 41

a mathematical technique used to generate Doppler shift spectral displays.

Question 42

Spectral Broadening

Answer 42

the widening of the Doppler-shift spectrum or the increase in the range of Doppler-shift frequencies present that occurs because of a broadened range of flow velocities encountered by the sound beam.