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Physics > Chp 4 - Hemodynamics and Doppler > Flashcards

Chp 4 - Hemodynamics and Doppler Flashcards

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1
Q

What does Bernouillis Principle describe?

A

the inverse relationship between velocity and pressure

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2
Q

What is the continuity equation

A

Q = VA - change in velocity must occur in a change of area to maintain the volume of blood flow

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3
Q

What is directional PD

A

uses CD and PD - sensitivity of PD but direction of flow from CD

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4
Q

What is duplex imaging

A

real time 2D imaging with SD

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5
Q

What is the ensemble length?

A

the number of pulses per SL in CD (aka packet size)

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6
Q

What is FFT?

A

Fast Fourier transform - process for processing doppler signal to produce SD

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7
Q

What is the flow equation?

A

Q = volume of blood/time

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8
Q

What is the frequency shift?

A

the difference between the transmitted and received frequencies

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9
Q

What is Ohm’s law?

A

A law used in electronics where flow = pressure differential / resistence
V=IR

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10
Q

What does the phase quadrature do?

A

determines positive and negative frequency shifts in doppler therefore direction of flow

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11
Q

What is the vasa vasorum?

A

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

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12
Q

When do we have energy loss related to inertia?

A

every time blood changes direction

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13
Q

Where is plug flow found?

A

in large BV and at the entrance of vessels

it is a result of systole

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14
Q

What Reynolds number represents true turbulence

A

greater than 2000

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15
Q

Reynolds number equation

A

Re = v X 2r X p / viscosity

v = velocity of blood

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16
Q

What AR and DR = hemodynamically significant

A

75% decrease in area and 50% decrease in diameter

17
Q

Where is the highest hydrostatic pressures typically located

A

at more distal parts of the body like feet and ankles

18
Q

What is transmural pressure

A

the difference between the pressure inside the vein and surrounding tissue

19
Q

What happens with an increased transmural pressure?

A

flow inside the vein is higher than the surrounding tissue - the vein get sthe circular shape (it will collapse when lower)

20
Q

What does it mean if there is pulsatility in the peripheral veins?

A

may indicate problems with the right side of the heart

21
Q

When is tardus parvus seen?

A

when there is a proximal obstruction

22
Q

What is the doppler effect?

A

When frequencies of sound hit a moving object the frequencies come back higher

23
Q

What is the relationship between frequency and scatter?

A

as frequency increases, scatter increases to the fourth power

24
Q

What is the RI formula?

A

RI = PSV - EDV / PSV

25
Q

PI formula?

A

PI = PSV-EDV / mean velocities

26
Q

Nyquist limit formual:

A

1/2 of the PRF

27
Q

In CD what does increasing the persistence setting do?

A

it reduces the effect of noise and makes it easier to follow small vessels
but decreases FR

28
Q

What is tissue doppler used for?

A

cardiac imaging

high amplitude, low velocity

29
Q

What provides the potential energy in the cardiovascular system?

A

The beating heart

30
Q

When is the Doppler shift highest?

A

When the beam is parallel to the direction of flow

31
Q

When a reflector moves toward the transducer, what will happen to the
reflected frequency?

A

It will be increased

32
Q

In the exercising patient, what is the response to peripheral resistance with arteriolar dilatation?

A

the peripheral resistence decreases

33
Q

What will happen with under sampling of the blood flow?

A

aliasing

34
Q

What is the spectral amplitude/brightness that make up SD represent?

A

the amount of RBC

35
Q

The doppler shift is lowest at what angle?

A

90 deg

36
Q

What is the fewest number of crystals a PW Doppler device may have?

A

one

37
Q

Which type of Doppler does not rely on the frequency shift but instead
relies on the strength of the shift?

A

Power Doppler

38
Q

What is the duty factor of CW Doppler?

A

1

39
Q

What is seen proximal to a low resistence bed?

A

monophasic flow

Physics (12 decks)

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