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Physics > Module 4 Physics > Flashcards

Module 4 Physics Flashcards

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1
Q

What is the average flow speed across a laminar parabolic flow vessel?

A

It is one half of the max flow speed (at the centre)

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2
Q

What is the entrance affect?

A

this is when we see plug flow - typically when we are entering a larger artery into a smaller radius or ascending aorta

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3
Q

When does turbulent flow occur

A

In an area of stenosis or bifurcation

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4
Q

What does a waveform of turbulent fllow look like

A

ragged edges and SB

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5
Q

What is the Windkissel effect?

A

During systole, the LV contracts pushing blood into the aorta and larger arteries causing expansion of walls with increased pressure, then when diastole occurs the LV relaxes and release ith elastic recoil of the arteries allowing for blood to push through during diastole too

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6
Q

What type of arteries perform the windkissel effect?

A

aorta and larger arteries because they have more elastic components to stretch and recoil

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7
Q

Kinetic energy formula”

A

velocity squared

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8
Q

What is hydrostatic pressure?

A

it is the force of fluid, proportional to the density of fluid, height of fluid and gravity

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9
Q

Hydrostatic pressure formula

A

density x gravity x height

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10
Q

What is the resistance equation

A

8ln/pier^4
n - viscosity
r- radius

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11
Q

What is the flow equation?

A

Q = pressure difference / resistence

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12
Q

BP equation

A

CO x TPR

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13
Q

Where is the highest pressure in the body?

A

left ventricle 100 mmHg

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14
Q

Which have lower pressures? Arteries or veins?

A

Veins - arterial side is higher because of the pumping of heart

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15
Q

Where is the lowest pressure in the body

A

the right atrium 0mmHG

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16
Q

Most energy loss happens where?

A

at the capillaires

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17
Q

What is Poiseuilles Equation

A

Q = change in pressures x pie x r^4 / 8 x l x n

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18
Q

What is the continuity rule

A

flow rate must remian constant regardless so if area changes velocity must change and vise sersa
Q = v x area
this is why in a stenosis (decrease area) the velociuty increases

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19
Q

Where are the highest velocities typically

A

just beyond the point of max narrowing

20
Q

What is the bernouilli effect

A

increase in flow speed = decrease in pressure

21
Q

What is the Doppler Effect?

A

The Doppler Effect is a change in frequency due to change in wavelength from a change in motion

22
Q

Wavelength formula

A

wavelength = c/f

23
Q

Increasing wavelength will ___ frequency?

A

decrease freq

24
Q

What causes the best change in frequency with Doppler imaging?

A

when the angle is 0 deg

25
Q

What is the Doppler Shift (DS)?

A

A measure of doppler effect - how much the frequency has changed

it is the difference between transmitted vs recieved frequency

DS = F recieved - F transmitted

26
Q

What is indicative of a higher DS?

A

faster moving blood

27
Q

How to calculate the doppler shift (simplified doppler equation)

A

Change in freq = 2 X Ft X velocity / C

28
Q

What angle do we want to be at when using Doppler?

A

Want to be perfectly parallel (0 deg) but often impossible - best to be less than 60 deg or else large error

29
Q

Is CD a qualitative or quantitative assessment?

A

qualitative

30
Q

Does CD show velocities of flow?

A

Yes but theyre only estimates, SD shows absolutes

31
Q

What is the packet size? What does a higher packet size indicate? What is the packet size of CD ?

A

the amount of pulses per SL (CD has about 3-12)

higher packet size = more accurate estimate of DS freq

32
Q

What is flow seperation?

A

Can look like aliasing but has a black line surrounding the change in colour - it is the reversal of blood flow (aliasing is not tis just an artifact)

33
Q

What is the highest detectable mean velocities in CD

A

63.6 cm/s away or towards

34
Q

What must the PRF scale equal in CD?

A

must be 2x higher than the highest DS freq

35
Q

How to determine the Nyquist Limit

A

Max DS = PRF/2 or PRF = 2x the max DSF

36
Q

What does power doppler display

A

The density of moving RBC (amplitude of rayleigh scatter)

doesnt display DSF

37
Q

What does SD display?

A

a visual spectrum of DS frequencies over time

direction, velocity (absolute), amplitude, quality of flow

38
Q

When is Fast Fourier Transformation used?

A

FFT only used with SD - like autocorrelation for CD, displays wide variety of DS into their individual frequency components to plot on graph

39
Q

How does FFT work?

A

Sorts the many DSF into groups called bins of similar DSF
each bin corresponds to a spot on the Y axis
more DS in a bin = brighter

40
Q

how does the SVB size affect the SPL?

A

increase SVB increases the SPL whihc decreases Axial Res

41
Q

Relationship between PD and BW

A

longer ringing period (PD) results in less frequencies/bandwidth but greater sensitivity

42
Q

What should the spectral trace height be?

A

about 2/3 of the y axis

43
Q

What is the angle for the most accurate measurement in SD

A

0 deg (cosine for 0 is 1)

44
Q

Other names for AC?

A

angle of insonation and angle of incidence

45
Q

What is the returnign signal from blood like?

A

low amplitude but high DSF

46
Q

What is the returning signa from tissue?

A

high amplitude but low DSF

Physics (12 decks)

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