Chapter 4 Penny Flashcards by Billie Harney

the wraparound of the spectral of color Doppler display that occurs when the frequency shift exceeds the Nyquist limit; occurs only with pulsed-wave Doppler

aliasing

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the tool used to inform the machine what the flow is to that the velocities can be accurately calculated

angle correction

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the color Doppler processing technique that assesses pixels as stationary or in motion

autocorrelation

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the acronym used to describe color-Doppler display; “blue away, red toward’

BART

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the operator-adjustable dividing line between positive frequency shifts and negative frequency shifts on spectral and color Doppler

baseline

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the principle that describes the inverse relationship between velocity and pressurew

Bernouli’s principle

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the Doppler device that can detect positive and negative Doppler shifts

bidirectional Doppler

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the stationary layer of blood cells immediately adjacent to the vessel wall

boundary layer

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the term describing the intensity or luminance of the color Doppler display

brightness

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the muscles in the calf that, upon contraction, propel venous blood toward the heart

calf muscle pump

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the ability of veins to store blood

capacitance

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acoustic noise in the color and/or spectral Doppler signal

clutter

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accessory vessels that connect portions of the same blood vessel together

collateral blood vessels

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Doppler shift information presented as a color (hue) superimposed over the grayscale image

color Doppler imaging

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the setting for color Doppler that allows the operator to select frequency shift threshold, it determines whether color pixels should be displayed preferentially over grayscale pixels

color priority

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the equation that describes the change in velocity as the area changes in order to maintain the volume of blood flow

continuity equation

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Doppler device that uses continuous-wave ultrasound transmission; a device that consists of two elements, one element is used by the system to constantly transmit sound and the other is used to constantly receive sound

continuous-wave Doppler

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the point at which a stenosis is hemodynamically significant with a pressure drop distal to the stenosis

critical stenosis

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the inability to determine the depth of the reflector if the pulses are sent out too fast for them to be timed

depth ambiguity

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the relaxation of the heart following contraction

diastole

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the change in the frequency of the received signal related to the motion of reflector

Doppler effect

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the equation that explains the relationship of the Doppler frequency shift to the frequency of the transducer, the velocity of the blood, the angle of blood flow, and the propagation speed

Doppler equation

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real-time two-dimensional imaging combined with the spectral Doppler display

duplex

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the sum of the individual resistances when multiple vessels are connected in series

effective resistance

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the difference in energy between two points

energy gradient

the number of pulses per scan line in color Doppler; also referred to as packet size

ensemble length

pressure applied to the outside of an object

extrinsic pressure

a mathematical process used for analyzing and processing the Doppler signal to produce the spectral waveform

fast Fourier transform

a motion artifact caused by the movement of tissue when using power Doppler

flash artifact

the volume of blood per unit time; typically measured in liter per minute or milliliter per second, represented the symbol Q

flow

the difference between the transmitted and received frequencies

frequency shift

a form of resistance, caused by two materials rubbing against each other, thereby converting energy to heat

friction

critical stenosis

hemodynamically significant stenosis

the study of blood flow through the blood vessels of the body

hemodynamics

a term used to describe displayed colors

hue

describes the relationship between gravity, density of the blood, and distance between an arbitrary reference point

hydrostatic pressure

Newton's principle that states that an object at rest stays at rest and an object in motion stays in motion unless acted on by an outside force

inertia

supplied with nerves

innervated

the energy form of flowing blood

kinetic energy

the flow profile represented by blood that travels in nonmixing layers of different velocities, with the fastest flow in the center and the slowest flow near the vessel walls

laminar flow

the total amount of energy in a system never changes, although it might be in a different form from which it is started

law of conservation of energy

the brightness of the color Doppler image

luminance

millimeters of mercury

mmHg

low-level echoes on the display that do not contribute useful diagnostic information

noise

Doppler device that cannot differentiate between positive and negative frequency shifts

nondirectional Doppler

a stenosis that does not necessarily compromise blood flow to organs or structures

nonhemodynamically significant stenosis

the maximum frequency shift sampled without aliasing; equal to one half the pulse repetition frequency

Nyquist limit

a law used in electronics in which flow is equal to the pressure differential divided by resistance

Ohm's law

the component of a continuous-wave Doppler devices that produces the voltage that drives the transducer

oscillator

the number of pulses per scan line; also called ensemble length

packet size

the averaging of color frames in order to display blood flow with a long signal-to-noise ratio

persistence

the component of the Doppler device that determines positive opposed to negative frequency shifts and, therefore, direction of blood flow

phase quadrature

the characteristic waveform of peripheral veins; flow is determined by respiratory variations as a result of intrathoracic pressure changes

phasic flow

in arteries, the phasicity describes the shape of the waveform based on the resistiveness of the distal bed in veins, phasicity describes the flow pattern that results from respiratory variation

phasicity

the flow profile represented by blood typically flowing at the same velocity

plug flow

the law that describes the relationship of resistance, pressure, and flow

Poisuilles law

pressure energy created by the beating heart

potential energy

Doppler mode in which the signal is determined by the amplitude (strength) of the shift, not the shift itself. Amplitude is directly proportional to the number of red blood cells; also referred to as amplitude Doppler

power Doppler

the difference between pressures of two points of a blood vessel

pressure gradient

blood that flows in a pattern representative of the beating heart, with increases and decreases in pressure and blood flow velocity

pulsatility

Doppler measurement used to determine how pulsatile a vessel is over time

Pulsatility index

the number of pulses of sound produced in one second

pulse repetition frequency

the Doppler technique that uses pulses of sound to obtain Doppler signals from a user specified depth

pulsed-wave Doppler

the gate placed by the operator in the region where Doppler sampling is desired; used with pulsed-wave Doppler

range gate

the ability to determine the depth of echoes by timing how long it takes for the echoes to go from the transducer to the reflector and back; utilized by pulsed-wave devices

range resolution

very small reflectors, like red blood cells

Rayleigh scatterers

the downstream impedance to flow; determined by vessel length, vessel radius, and viscosity of blood

resistance

Doppler measurement used to quantitate the resistiveness of the distal bed

resistive index

the formula used to quantitate the presence of turbulence; Reynolds number greater than 2000 typically indicate turbulence

Reynolds number

the area within the range gate where the Doppler signals are obtained

sample volume

the amount of white added to a hue; the more white there is, the less saturated the color

saturation

the spectral Doppler and color Doppler tool that controls the number of pulses transmitted per second to obtain the Doppler information; also known as pulse repetition frequency in spectral Doppler and color Doppler

scale

the method used to obtain the strain information

speckle tracking

the filling of the spectral window

spectral broadening

the area underneath the envelope on the spectral display

spectral window

pathologic narrowing of a blood vessel

stenosis

the changing of the shape of the muscle as it lengthens and contracts

strain

the operator-adjustable spectral Doppler control that increases or decreases the number of heartbeats visualized on the spectral display

sweep speed

the time period of the cardiac cycle when the heart is contracting

systole

an arterial waveform shape with a delayed peak systolic upstroke that indicates proximal obstruction

Tardus parvus

combination of platelets, red blood cells, and fibrin that make up a blood clot

thrombus

color Doppler imaging technique used to document wall motion

tissue Doppler imaging

the difference of pressure inside a vessel compared to the pressure outside of the vessel

transmural pressure

the ability to visualize real-time grayscale, color Doppler, and spectral Doppler simultaneously

triplex

the outer layer of a blood vessel

tunica adventitia

the inner layer of a blood vessel which is closest to the flowing blood

tunica intima

the middle, muscular layer of a blood vessel

tunica media

chaotic, disorderly flow of blood

turbulent flow

the color Doppler scale with mean velocities displayed vertically on the scale and turbulence displayed horizontally

variance mode

a network of small blood vessels that supply blood to the walls of arteries and veins

vasa vasorum

the narrowing of a blood vessel caused by the contraction of the vessel wall

vasoconstriction

the widening of a blood vessel caused by the contraction of the vessel wall

vasodilatation

the color Doppler scale with mean velocities displayed vertically

velocity mode

the energy loss caused by friction

viscous energy

the operator control that eliminates low-frequency, high amplitude signals caused by wall or valve motion; also called high-pass filter

wall filter

the brightness or amplitude of the dots on a B-mode display; the brighter the dots of the spectral waveform, the more red blood cells that make up the signal

z-axis