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Physics 1 > Lesson 11 > Flashcards

Lesson 11 Flashcards

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1
Q

What does the reflection between 2 different boundaries depend on?

A

Media impedance

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2
Q

What is the result of a large difference between impedances?

A

A large reflection

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3
Q

What would happen if you injected air into a liver?

A

You would get a large reflection

- air vs solid

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4
Q

What are 2 examples of contrast agents?

A
  1. Levovist

2. SonoVue

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5
Q

What are 4 characteristics of contrast agents?

A
  1. Easy administration
  2. Nontoxic
  3. Stable
  4. Small enough to perfuse through blood vessels (capillaries)
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6
Q

What do most contrast agents contain?

A

Microbubbles of air

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7
Q

What stabilizes contrast agents? (3)

A
  1. Protein
  2. Lipid
  3. Polymer shell
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8
Q

What are contrast agents?

A

Dye that get injected to be bale to make structures more visible

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9
Q

How do reflections from blood show up as?

A

Weak echoes

- increases with contrast agents

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10
Q

What will high IRC show up as on an ultrasound?

A

As bright echoes

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11
Q

What do contrast agents produce?

A

Strong harmonics

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12
Q

When are harmonics produced?

A

When sound is produced non-linearly

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13
Q

What will introduction of contrast agents do with tissues?

A

Increase the echogenicity

- normally makes the tissue brighter and lesion darker, but can sometimes be the other way around

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14
Q

What is another use of contrast agents?

A

Perfusion rate

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15
Q

What can the ultrasound do at higher amplitudes to the bubbles?

A

Pop them

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16
Q

How is perfusion rate used in U/S?

A

Using high U/S to pop the bubbles and then using low amplitude to watch the organ fill back up

17
Q

Perfusion rate

A

How fast the organ is getting blood back

18
Q

What 2 pieces of information does the machine need to position the echo on display?

A
  1. The direction the echo came from

2. The distance to the reflector/structure that created the echo

19
Q

What can the transducer no do directly?

A

Measure distance

20
Q

What does the transducer measure?

A

The travel time

- round trip

21
Q

What is speed assumed to be?

A

1540m/s

- 1.54mm/us

22
Q

What is the formula for distance?

A

Speed x Time

23
Q

What is the formula for time?

A

Distance/Speed

24
Q

What is the formula for speed?

A

Distance/Time

25
Q

What is the formula for distance for range?

A 
d = 1/2 v x t 
d = 1/2 c x t
26
Q

What is the round trip travel time in soft tissues?

A

13us/cm

Physics 1 (42 decks)

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