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Z MRI Physics > Module 2 > Flashcards

Module 2 Flashcards

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1
Q

occurs when an object with a certain precessional frequency is subjected to a force that has the same precessional frequency

A

resonance

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2
Q

excitation that matches the precessional frequency of hydrogens atoms at a certain filed strength

A

RF pulse

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3
Q

can cause some energy of low spin up to change to high spin up

A

application of RF pulse

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4
Q

higher RF pulse to match processional frequency

A

higher strength magnet

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5
Q

RF pulse does not match larmor frequency of hydrogen atom

A

no resonance occurs

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6
Q

Resonance occurs, NMV moves out of alignment with B(o)

at angle with B(o)

A

flip angle

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7
Q

most common fip angle

A

90

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8
Q

main magnetic filed plane

A

longitudinal

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9
Q

fip angle plane

A

transverse plane

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10
Q

when magnetic moments are on same point in precessional path

maximum signal

A

in phase

coherent

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11
Q

magnetic moments are not on teh same point in precessional path

minimal or no signal

A

out of phase

in-coherent

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12
Q

RF pulse turned off NMV realigns with B(o)

A

relaxation

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13
Q

process when hydrogen loses energy

atoms that moved to high state will return to low state

A

relaxation

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14
Q

longitudianl plane

A

recovery

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15
Q

transverse plane

A

decay

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16
Q

occurs simultaneously but independently as relaxation

takes place in transverse magnetization

A

decay

17
Q

hydrogen nuclei start to realign with B(o) in teh longitudinal plane

out of phase

transverse magnetization begins to decay

logitudinal regrowth

transverse dephasing

A

effects of RF pulse removal

18
Q

relaxation time for 63% of NMV of tissue to recover

A

T1 recovery

spin lattice relaxation

19
Q

relaxation time for transverse plane to decay to 37%

A

T2 decay

spin spin relaxation

20
Q

relaxation due to nuclei giving up energy to surrounding environment

A

spin lattice relaxation

T1 recovery

21
Q

interaction of spins nuclei with each other

A

spin spin relaxation

T2 Decay

22
Q

independent of each other

T2 never exceeds T1

A

relaxation time

23
Q

decay of FID signal

shorter than T2 because of dephasing due to magnetic field inhomogenities and T2 decay

A

T2*

24
Q

signal induced in coil from patients tissues (hydrogen atoms)

measure in coulombs

A

free induction decay

FID

25
Q

plot of MR signal intensity as a functino of time

spatially reconstructed into an image though a mathmatical function

2D or 3D fourier transformation

A

FID

free induction decay

26
Q

results in a nuclear magnetic spectrum in the frequency domain

A

Fourier transformation of FID

Z MRI Physics (12 decks)

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