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DSM PHY > Physics 2 Test Ch 18, 19, 20 > Flashcards

Physics 2 Test Ch 18, 19, 20 Flashcards

1
Q

What kind of flow is moving with a variable velocity from cardiac contractions?

A

Pulsatile Flow

pg 286

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2
Q

What kind of flow is moving with a variable velocity from respirations?

A

Phasic Flow

pg 286

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3
Q

What is laminar flow?

A

Flow streamlines are alined and parallel. Characterized by layers of blood that travel at individual speeds. Laminar flow patters are commonly found in normal physiologic States. Two types of flow are plug(all layers of blood travel at the same velocity). Parabolic (bullet shaped with velocity highest in the center)
Pg 287

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4
Q

What is chaotic flow?

A

Turbulence

pg 288

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5
Q

What are frictional losses?

A

Viscous(thickness), frictional (heat), inertial(tendency of fluid to resist changes in velocity)

Occurs when flow energy is converted to heat as one object rubs against another.
pg 290/291

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6
Q

What is the Reynolds number for turbulent flow?

A

Greater than 2000

pg 288

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7
Q

What are the effects of a stenosis?

A 
Change in flow direction
increased velocity as vessel narrows
turbulence downstream from the stenosis
pressure gradient across the stenosis
loss of pulsatility
pg 292
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8
Q

What is hydrostatic pressure in a supine position?

A

All parts of the body are at the same level as the heart so… The hydrostatic pressure is zero.
Pg 297

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9
Q

What is hydrostatic pressure in a standing position?

A 
Finger in air -50 
Heart 0
 Waist 50
 Knee 75
  Ankle 100
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10
Q

What is coaptation?

A

When you can compress the vein.

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11
Q

When you breath in, what happens to the pressure in the legs, abdomen, and chest?

A

Inspiration

Diaphragm moves downward
Thoracic pressure decreases
Abdominal pressure increases
Venous return to the heart increases
Venous flow in legs decreases

pg 301

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12
Q

When you breath out, what is happening to the pressure of the legs, abdomen, and chest?

A

Expiration

Diaphragm moves upward
Thoracic pressure increases
Abdominal pressure decreases
Venous return to the heart decreases
Venous flow  in legs increases
pg 301
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13
Q

What is a positive Doppler shift?

A

When blood moves toward the transducer. The reflected frequency is higher than the transmitted frequency.
Pg 304

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14
Q

What is a negative Doppler shift?

A

When blood moves away from transducer. The reflected frequency is lower than transmitted frequency.
pg 304

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15
Q

What information does a Doppler shift tell us?

A

the velocity of blood cells in circulation (venous going away or arterial coming toward).
Doppler shift is directly related to frequency of transmitted sound.
pg 303

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16
Q

What is the normal Doppler shift range in diagnostic imaging

A

20 Hz and 20kHz
audible range
pg 338

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17
Q

What is aliasing?

A

Most common error with Doppler. Very high velocities in one direction are incorrectly displayed as going in the opposite direction.Wrap around appearance.
pg 315

The phenomenon where high velocities appear in the opposite direction
pg 338

18
Q

When the sample volume is deep, PRF is _____ and the Nyquist limit is _____.

A

low / low

pg 317

19
Q

What are the 5 ways to eliminate the effects of aliasing?

A 
Adjust scale to maximum
Select a new view with shallower volume
Lower frequency
Change the base line
Use a continuous wave Doppler
pg 319
20
Q

The sample volume should always be at 2 mm; however if you are using a larger gate the Doppler will look different, will it be larger or smaller?

A

larger (aliasing)

pg 317

21
Q

What is the y-axis on the Doppler spectrum?

A

velocity

pg 307

22
Q

What is the x-axis on the Doppler spectrum?

A

time

pg 307

23
Q

What are the gray shades on the Doppler spectrum related to?

A

Amplitude of the reflected signal.
Number of blood cells creating the reflection.
pg 324

24
Q

A higher frequency transducer creates a Doppler spectrum that is _____.

A

High, because they are directly related

p. 308

25
Q

Doppler shift is inversely related to _____.

A

Propagation speed

pg 306

26
Q

What kind of processing is used in bidirectional Doppler?

A

Phased quadrature

P.311

27
Q

What is the difference between speed and velocity?

A

Speed is magnitude 50 mph
velocity is magnitude plus direction 50 mph to the south
pg 305

28
Q

What kind of Doppler shift will be recorded at a 90 degree angle?

A

No Doppler shift

pg 338

29
Q

Higher frequency transducers will produce a Doppler shift that is _____ than a lower frequency transducer.

A

higher
Doppler shift is directly related to frequency of transducer.
pg 308

30
Q

What is the primary advantage for pulsed wave?

A

Being able to see the exact location where the velocity is being measured. Range resolution, range specificity, and freedom from range ambiguity.
pg 314

31
Q

What is the primary advantage of continuous wave?

A

Accurately measuring very high velocities

pg 312

32
Q

What is Fast Fourier Transform?

A

A digital system used to process both pulsed and continuous wave Doppler signals. 2 advantages are exceedingly accurate and displays all individual velocity components that make up the complex reflected signal. It distinguishes laminar from turbulent flow.
Laminar flow well cleaned windows.
Turbulent flow broadening spectrum and filled in windows.
pg 336

33
Q

What is Autocorrelation?

A

A digital system that is used to analyze color flow Doppler. This process is less accurate but faster to perform than FFT.
pg 337

34
Q

What is color Doppler looking for?

A

It provides us with the direction of flow. Color Doppler gives us mean velocity were as pulsed and continuous wave measure the peak velocity.
pg 325

35
Q

What are we measuring with continuous wave Doppler?

A

We are measuring all the moving blood cells in the overlap region.

High velocities
pg 312

36
Q

What is a limitation for color Doppler?

A

creates aliasing?

37
Q

What are Doppler packets?

A

With color multiple U/S pulses are used to accurately determine blood velocities. 2 advantages of larger packets are more accurate velocity measurement and increased sensitivity to low flow. 3 disadvantages are more time needed to acquire data, reduced time frame, and decreased temporal resolution.
pg 332

38
Q

What is sensitive to low flow states?

A

Power Doppler

pg 333

39
Q

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

A

energy gradient
pg 289

Possibly velocity Pg. 285

40
Q

What is the shape of the venous structure at high pressure?

A

circle

pg 295

41
Q

What is the shape of the venous structure at intermediate pressure?

A

oval

pg 295

42
Q

What is the shape of the venous structure at low pressure?

A

hourglass

pg 295

DSM PHY (14 decks)

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