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Flashcards in Study guide test 3 Deck (41):
1

What is the movement of fluid from one location to another?

velocity

2

Fluid moving with a variable velocity, that accelerates and decelerates; what is it?

pulsatile flow

3

What is fluid moving from one location to another that accelerates and decelerates from respiration called?

phasic flow

4

What type of flow pattern will be seen with normal physiological states? 

laminar flow

5

Chaotic flow with many directions and speeds, whay type of flow is this?

turbulent flow

6

Frictional loss occurs when one object rubs against another. Blood sliding across vessel walls would be considered what? 

frictional loss

7

Know the Reynolds numbers

< 1500= laminar

1500-2000= ????

>2000= turbulent

8

What are the effects of stenosis?

change in flow direction

increased velocity as vessel narrows

turbulence downstream from the stenosis

pressure gradient across the stenosis

loss of pulsatility

9

What is hydrostatic pressure?

pressure related to the weight of blood pressing on a vessel measured at a height above or below heart level

 

10

Hydrostatic pressure in a supine patient with a blod pressure  of 140mmHg

all measurement sites= 0mmHg

11

Hydrostatic pressure while standing upright in a patient with a blood pressure of 140mmHg:

ankle: level-far below heart level, hydrostatic pressure-100mmHg, measured pressure-240mmHg

knee: level-somewhat below heart, hydrostatic pressure-75mmHg, measured pressure-215mmHg

waist: level-slightly below heart, hydrostatic pressure-50mmHg, measured pressure-190mmHg

mid chest: level-heart level, hydrostatic pressure-0mmHg, measured pressure-140mmHg

top of head: level-above heart, hydrostatic presure--30mmHg, measured pressure-110mmHg

12

What does the Doppler shift provide information about?

measures the velocity of blood in the circulation

13

What is a positive Doppler shift?

blood moves towards transducer (arteries)

14

What is a negative Doppler shift?

blood moves away from transducer (veins)

15

What is the typical range of a Doppler shift?

20Hz to 20,000Hz (range of audible sound)

16

What is the phenomenon where high velocities appear as negative?

aliasing

17

When the sample volume is deep, the PRF is what? Nyquist limit?

low

18

What are the 5 ways to eliminate aliasing?

adjust the scale to its maximum-increases Nyquist limit

select a new ultrasonic view with a shallower sample volume-increases Nyquist limit

select a lower frequency transducer-decreases Doppler shift

use baseline shift-aliasing remains but display more appealing

use continuous wave Doppler-never aliases, but range ambiguity

19

Know about large and small sample volumes. Which one will fill in on Doppler?

large spectral broading

20

What do the X and Y axis stand for on the Doppler spectrum?

X=time

Y=shift or velocity

21

What 2 things are related to Doppler spectrum?

amplitude of the reflected signal

number of blood cells creating the reflection

22

When we look at our Doppler Spectrums and we see our wave form, if you have a higher waveform, is a higher freq or lower freq being used?

higher frequency

23

What is Doppler shift inversely related to?

propagation speed

24

What is the basic Doppler system that simply identifies blood flow by the pressence of the frequency shift?

25

What is the Doppler effect?

frequency shift

26

What is the difference betwen speed and velocity?

speed measures distance

velocity measures magnitude and direction

27

Know about angles with Doppler:

when the angle between the direction of motion and sound is 0º or 180º, flow is parallel to the sound beam

the measured and true velocities are equal: Cosine 0º=1 (flow toward transducer), Cosine 180º=-1 (flow away from transducer)

Cosine 90º=0 (perpindicular/normal incidence can not measure Doppler shifts and velocities

28

What's a primary advantage for pulsed wave Doppler?

range resolution (being able to select the exact location where velocities are measured)

29

What's the primary advantage to continuous wave Doppler?

ability to accurately measure very high velocities

30

What kind of processing does bidirectional Doppler use?

phase quadrature

31

Fast Fourier Transform (FFT) is used in what type of process?

used to process both pulsed and continuous wave Doppler signals

32

What type of velocities does color flow measure?

negative and positive shifts

slower and faster velocities

laminar and turbulent flow

33

What is autocorrelation?

a digital technique used to analyze color flow Doppler

34

What are the personal limitations to color flow imaging?

more time needed to aquire data

reduced frame rate

decreased temporal resolution

35

What is the area of interrogation in a Pulsed Doppler jam called?

sample volume

36

What are the advantages and disadvantages of large Doppler packets?

Advantages:

more accurate velocity measurement, increased sensitivity to low flow

Disadvantages:

more time needed to aquire data, reduced frame rate, decreased temporal resolution

37

How do you measure low flow rates?

38

Know about inspiration:

diaphragm moves upward toward abdomen

thoracic pressure decreases

abdominal pressure increases

venous return to the heart increases

venous flow in legs decreases

39

Know about expiration:

diaphragm moves upward into thorax

thoracic pressure increases

abdominal pressure decreases

venous return to the heart decreases

venous flow in legs increases

40

When venous pressure is low, what is the volume of pressure in the veins?

low

41

What happens to the shape of veins when the venous pressure increases?

becomes more circular