Physics Review #5

Front 1

What is volume flow rate?

Back 1

Volume flow rate is the volume of flow passing through a vessel or location per unit time.

Front 2

VFR formula/Pousille's equation

Back 2

Q= Delta P x Pie x Radius cubed/8nl

Front 3

What are the 4 factors that affect volume flow rate?

Back 3

The 4 factors affecting volume flow rate are:
Pressure difference, tube diameter, tube length, viscosity

Front 4

Define the relationship of VFR with resistance.

Back 4

VFR and resistance have an inverse relationship. If resistence goes up then VFR will go down.

Front 5

Resistence formula

Back 5

Resistance ...
8nl/pie x radius cubed

Front 6

What is the most important component that affects the VFR in Poiseuille's equation?

Back 6

The most important component affecting VFR in poiseuille's equation is vessel size (diameter/radius). This is because it is cubed so any change in diameter/radius will have a big effect.

Front 7

What is plug flow?

Back 7

Plug flow is flow at the vessel origin or enterance. The viscosity is constant across the width of the vessel.

Front 8

What is laminar/parabolic flow?

Back 8

Laminar/parabolic flow is stead flow. Flow is fastest in the center due to low resistence and slower near the walls due to friction from the walls (higher resistence). Flow is in straight and parallel lines running in layers. Laminar flow is used for velocity check (sample)

Front 9

What is disturbed flow?

Back 9

Disturbed flow is when parallel streamline flow is altered or "disturbed" from their straight form. In natural setting it is seen at bif and in pathology it is seen pre-stenosis.

Front 10

What is turbulent flow?

Back 10

Turbuelent flow is random and chaotic flow. Speed AND direction are chaotic. Flow creates circles/swirling patterns known as Eddie currents. Turbulent flow is seen post-stenosis.

Front 11

What is reynolds number?

Back 11

Reynolds number predicts the onset of turbulence. If reynolds number exceeds 2000 turbulence occurs.
** 1800 - 2000 = disturbed flow

Front 12

Reynolds number formula

Back 12

reynolds number formula
Velocity x density x diameter/viscosit

Front 13

Define continuity rule.

Back 13

According to continuity rule, volume flow must be CONSTANT pre- at and post- stenosis. Blood is neither created nor destroyed as it flows through stenosis.

Front 14

Define Bernoulli's effect.

Back 14

Bernoulli's effect ... There is a drop in pressure at stenosis associated with increased flow speed. This decreased pressure in regions of high flow speed is known as bernoulli's effect.

Front 15

What happens to pressure and velocity at stenosis?

Back 15

At stenosis, pressure decreases and velocity increases in order to maintain continuity rule.

Front 16

If the pressure gradient increases, flow _____

Back 16

If the pressure gradient increases, flow INCREASES

Front 17

If the resistence increases, VFR ________

Back 17

If the resistence increases, VFR DECREASES

Front 18

List the variables on which flow resistence depends upon.

Back 18

Flow resistence depends on...
Length (increasing) Viscosity (increasing) Diameter (decreasing) all resulting in INCREASED resistence

Front 19

Flow resistence decreases with an _____ in vessel radius.

Back 19

Flow resistence decreases with an INCREASE in vessel radius

Front 20

What happens to energy at stenosis?

Back 20

At stenosis, pressure energy is converted into kinetic energy.

Front 21

List the variables increase which decrease VFR (those with inverse relationship)

Back 21

Viscosity increased and/or length increased results in a decrease in VFR

Front 22

What happens to the speed of flow at stenosis?

Back 22

At stenosis velocity INCREASES, the flow speeds up

Front 23

At stenosis the pressure is _____ than the proximal and distal locations

Back 23

At stenosis the pressure is LOWER than the proximal and distal locations

Front 24

What happens to the VFR at Stenosis?

Back 24

At stenosis VFR stays CONSTANT (continuity rule)

Front 25

Define velocity.

Back 25

Velocity is the speed and direction of flow.

Front 26

Define doppler effect.

Back 26

Doppler effect is a change in received frequency as a result of relative motion (motion can be with the receptor, reflector or sound source)

Front 27

Define doppler shift.

Back 27

Doppler shift is the difference between emitted frequency and received frequency.

Front 28

When the received frequency is smaller than the initial frequency, what kind of doppler shift happend?

Back 28

In doppler shift, if the received frequency is smaller than the initial frequency, the result is NEGATIVE doppler shift. Flow is going AWAY from the Tx.

Front 29

Define positive doppler shift.

Back 29

Positive doppler shift is when the received frequency is greater than the initial frequency (flow is coming TOWARDS the Tx

Front 30

Smaller angle results in what kind of doppler shift?

Back 30

Smaller angle results in BIGGER doppler shift. (0 degrees is the max and 90 degrees is nothing)

Front 31

What happens when you scan at 90 degree angle?

Back 31

At 90 degree there is NO doppler shift. You are inside the vessel

Front 32

Doppler equation formula

Back 32

Fd= 2 x operating frequency x velosity x cosine theta/ prop speed

Front 33

Define doppler equation and their relationship with one another

Back 33

Doppler equation relates to the variables that result in doppler shift and is related to flow speed and frequency. When speed and frequency increase doppler shift increases.

Front 34

What kind of relationship do doppler shift and angle have?

Back 34

Doppler shift and angle have an inverse relationship.

Front 35

What kind of relationship do angle and cosine theta have?

Back 35

Angle and cosine theta are homies, what one does the other does too.

Front 36

A stationary sound source and a stationary listener _____ result in doppler shift.

Back 36

A stationary sound source and a stationary listener DO NOT result in doppler shift.
**THERE IS NO MOVEMENT. Doppler shift requires movement.

Front 37

A doppler shift is a change in ______ of the ____ or ______ as a result of relative motion.

Back 37

A doppler shift is a change in received frequency of the SOURCE or RECEPTOR as a result of relative motion.

Front 38

A 3 MHZ transducer produces 2 Khz doppler shift frequency. If all parameters remain the same and we double operating frequency, what will be the new doppler shift?

Back 38

Doubling operating frequency will double doppler shift.

Front 39

Maximum negative doppler shift will be caused by the reflecftor which is ____ from the source

Back 39

Maximum negative doppler shift will be caused by the reflector which is MOVING AWAY from the source

Front 40

Maximum positive doppler shift will be caused by the reflector which is moving _____ the trandsducer

Back 40

Maximum positive doppler shift will be caused by the reflector which is moving TOWARDS the transducer

Front 41

The reflector which is ____ to the sound source will not produce any doppler shift.

Back 41

The reflector which is PERPINDICULAR (90 degrees) to the sound souce will not produce any doppler shift

Front 42

What are the limitations for color doppler?

Back 42

Color doppler limitations are ...
Increased dwell time due to multiple pulses per scan line
Decreased frame rate to increase packet size
aliasiing seen in form of mosaics

Front 43

What is aliasing?

Back 43

Aliasing is color artifact due to improper settings. Aliasing occurs when doppler shift exceeds the nyquist limit (1/2 PRF). Aliasing is AKA undersampling

Front 44

List the reasons for aliasing

Back 44

Aliasing occurs due to ...
Scanning deep samples
Higher frequency selected than necessary
Improper doppler shift (results in low angle)
Undersampling
Exceeding nyquist limit

Front 45

List the ways to reduce aliasing

Back 45

Reduce aliasing by...
Scanning shallower
increase scale (PRF)
Lower frequency
Increase scanning angle
Use a smaller sample size (will increase frame rate)
Switch to CW doppler (requires no PRF)

Front 46

What is auto correlation?

Back 46

Auto correlation is the automatic assignment of color according to strength. Done by the machine.

Front 47

What is power doppler used for?

Back 47

Power doppler is used to indicate the prescence or abscence of flow in small.tiny vessels (does not alias)

Front 48

List the limitations of power doppler.

Back 48

Power doppler cannot tell you the type of flow, direction of flow or velosity (speed) of flow

Front 49

List the differences between PW and CW

Back 49

PW has 1 crystal, CW has 2
PW has damping and PRF, CW does not
PW has aliasing @ high velocity, CW has NO aliasing
PW has image and waveform, CW has waveform only
PW has a duty factor of 1%, CW is 100%
PW has range resolution, CW has range ambuiguity

Front 50

What are the drawbacks of CW?

Back 50

Drawback of CW...
No Image
Blind modality
Too much information/overlapping

Front 51

Do you see any color at 90 degrees? which one?

Back 51

At 90 degrees you do not see red or blue, you will only see black

Front 52

What does lack of color indicate?

Back 52

Lack of color indicates ...
Abscence of flow
poor probe position
occulded vessel
poor color gain
high wall filter setting
poor angle (90 degree)

Front 53

Define spectral broadening.

Back 53

Spectral broadening are wide spectral traces indicating multiple velocities are present in the sample. Vertical thickening of spectral trace. Spectral broadening is seen at stenosis and is AKA window filling.

Front 54

What is Fast Fourier Transform?

Back 54

FFT is the mathematical technique the ultrasound machine uses to calculate the doppler shift in spectral instruments. It shows the individual velosities in the signal. It is the PW & CW demodulation for spectral analysis

Front 55

What is the unit for Viscosity?

Back 55

The unit for viscosity is POISE

Front 56

Pulsatile flow is controlled by ______

Back 56

Pulsatile flow is controlled by the HEART

Front 57

Phasic flow is controlled by _____

Back 57

Phasic flow is controlled by RESPIRATION