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MRI Physics > MRI Equipment and Instrumentation > Flashcards

MRI Equipment and Instrumentation Flashcards

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1
Q

Which magnetic susceptibility is slightly repels the main B0?

A

diamagnetic

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2
Q

Which magnetic susceptibility has a small positive magnetic susceptibility?

A

paramagnetic

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3
Q

Which magnetic susceptibility has a large positive magnetic susceptibility?

A

ferromagnetic

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4
Q

Which magnetic susceptibility has intermediate positive magnetic susceptibility?

A

superparamagnetic

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5
Q

What is another name for the main magnetic field?

A

primary magnetic field

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6
Q

What is the term for evenness or uniformity?

A

homogeneity

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7
Q

What is the homogeneity of B0 measured in?

A

parts per million (PPM)

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8
Q

Which type of shimming adds a secondary electromagnetic field over B0?

A

active shimming

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9
Q

Which type of shimming uses pieces of metal?

A

passive shimming

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10
Q

What is the main magnetic field extends beyond the imaging bore in all directions?

A

fringe field

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11
Q

Which type of shielding uses metal to contain and concentrate B0?

A

passive shielding

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12
Q

Which type of shielding is done with a secondary B0 created by an electromagnet?

A

active shielding

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13
Q

What type of current do primary magnet coils, active shim coils, and active shielding coils use?

A

direct current

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14
Q

Which electromagnet produces heat?

A

resistive magnets

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15
Q

Which electromagnet produces little to no resistance?

A

superconducting magnets

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16
Q

What is the operating temperature for MRI?

A

4 degree kelvin (-452F)

17
Q

What does x represent in horizontal bore?

A

right to left

18
Q

What does y represent in a horizontal bore?

A

anterior to posterior (top to bottom)

19
Q

What does z represent in a horizontal bore?

A

superior to inferior (front to back)

20
Q

What is the center of the gradient coil?

A

isocenter (always B0)

21
Q

What happens when there’s more current?

A

it creates more gradient

22
Q

What’s the term for the strength of gradient?

A

amplitude

23
Q

What is the gradient amplitude measured in?

A

milliTesla/meter

24
Q

What is the time it takes to get to a particular amplitude?

A

rise time (ms)

25
Q

What is the rate that combines amplitude and rise time?

A

slew rate (mT/m/s)

26
Q

What type of current is used for RF transmission?

A

alternating current

27
Q

What is the orientation of RF coils?

A

always parallel to B0

28
Q

What is the orientation of signal being transmitted and received?

A

perpendicular to B0

29
Q

What is the RF shielding with copper in all walls, windows, and doorways?

A

Faraday cage

MRI Physics (8 decks)

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