Kremkau Chapter 5 key terms

Question 1

autocorrelation

Answer 1

a rapid technique, used in most color Doppler instruments, to obtain mean Doppler shift frequency

Question 2

baseline shift

Answer 2

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

Question 3

Bernoulli effect

Answer 3

pressure reduction in a region of high flow speed

Question 4

bidirectional

Answer 4

indicating Doppler instruments capable of distinguishing between positive and negative Doppler shifts.

Question 5

clutter

Answer 5

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

Question 6

color Doppler display

Answer 6

the presentation of 2D, real time Doppler shift information in color superimposed on real time, gray scale, anatomic, cross sectional image.

Question 7

compliance

Answer 7

distensibility; nonrigid stretchibility of vessels.

Question 8

continuous wave Doppler

Answer 8

a Doppler device or procedure that uses continuous wave ultrasound

Question 9

cosine

Answer 9

the cosine of angle A in figure C-1 is the length of side B divided by the length of side C

Question 10

disturbed flow

Answer 10

flow that cannot be described by straight, parallel streamlines.

Question 11

Doppler angle

Answer 11

the angle between the sound beam and flow direction.

Question 12

Doppler effect

Answer 12

a change in frequency caused by reflector motion

Question 13

Doppler equation

Answer 13

the mathematical description of the relationship between the Doppler shift, frequency, Doppler angle, propagation speed, and reflector speed.

Question 14

Doppler power display

Answer 14

color Doppler display in which colors are assigned according to the strength or the Doppler shifted echoes.

Question 15

Doppler shift

Answer 15

reflected frequency minus incident frequency; the change in frequency caused by motion

Question 16

Doppler spectrum

Answer 16

the range of frequencies present in Doppler shifted echoes.

Question 17

duplex instrument

Answer 17

an ultrasound instrument that combines gray scale sonography with pulsed Doppler and, possibly, continuous wave Doppler

Question 18

eddies

Answer 18

regions of circular flow patterns present in turbulence

Question 19

ensemble length

Answer 19

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

Question 20

fast fourier transform

Answer 20

digital computer implementation of the Fourier transform

Question 21

filter

Answer 21

an electric circuit that passes frequencies within a defined range

Question 22

flow

Answer 22

to move in a stream. volume flow rate.

Question 23

fluid

Answer 23

a material that flows and conforms to the shape of its container; a gas or a liquid

Question 24

frequency spectrum

Answer 24

the range of Doppler shift frequencies present in the returning echoes

Question 25

gate

Answer 25

a device that allows only echoes from a selected depth to pass

Question 26

hue

Answer 26

the color perceived base on the frequency of light

Question 27

inertia

Answer 27

resistance to acceleration

Question 28

laminar flow

Answer 28

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

Question 29

luminance

Answer 29

brightness of a presented hue and saturation

Question 30

parabolic flow

Answer 30

laminar flow with a profile in the shape of a parabola

Question 31

phase quadrature

Answer 31

two signals differing by one fourth of a cycle.

Question 32

plug flow

Answer 32

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

Question 33

poise

Answer 33

unit of viscosity

Question 34

poiseuille equation

Answer 34

the mathematical description of the dependence of volume flow rate on pressure, vessel length and radius, and fluid viscosity.

Question 35

priority

Answer 35

the gray scale echo strength below with color Doppler information is shown preferentially on a display

Question 36

pulsatile flow

Answer 36

flow that accelerates and decelerates with each cardiac cycle

Question 37

pulsed Doppler

Answer 37

a Doppler device or procedure that uses pulsed wave ultrasound

Question 38

range gating

Answer 38

selection of depth from which echoes are accepted based on echo arrival time

Question 39

resistance

Answer 39

pressure difference divided by volume flow rate for steady flow

Question 40

sample volume

Answer 40

the anatomic region from which pulsed Doppler echoes are accepted

Question 41

saturation

Answer 41

the amount of hue present in a mix with white

Question 42

spectral analysis

Answer 42

separation of frequencies in a Doppler signal for display as a Doppler spectrum; the application of the Fourier transform to determine the frequency components present in a Doppler signal.

Question 43

spectral broadening

Answer 43

the widening of the Doppler shift spectrum; that is, 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. this occurs for disturbed and turbulent flow.

Question 44

spectral Doppler display

Answer 44

the presentation of Doppler information in a quantitative form of Doppler shift versus time. visual display of a Doppler spectrum

Question 45

spectrum analyzer

Answer 45

a device that derives a frequency spectrum from a complex signal

Question 46

stenosis

Answer 46

narrowing of a vessel lumen

Question 47

streamlines

Answer 47

a line representing the path of motion of a particle of fluid

Question 48

turbulence

Answer 48

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

Question 49

variance

Answer 49

square or standard deviation; one of the outputs of the autocorrelation process; a measure of spectral broadening.

Question 50

viscosity

Answer 50

resistance of a fluid to flow

Question 51

volumetric flow rate

Answer 51

volume of fluid passing a point per unit of time

Question 52

wall filter

Answer 52

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

Question 53

window

Answer 53

an anechoic region appearing beneath echo frequencies presented on a Doppler spectral display.