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MRI > MRI Foundation > Flashcards

MRI Foundation Flashcards

1
Q

Why is MR so different from other imaging modalities?

A

MR uses no radiation and does not work based on absorption/reflection

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2
Q

Protons have a _____ charge and spins.

A

positive

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3
Q

The Principle Quantum number:

A

n

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4
Q

The Angular quantum number:

A

l

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5
Q

The Magnetic quantum number:

A

m

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6
Q

The Spin quantum number:

A

s

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7
Q

1 Tesla = _____ G (Gauss)

A

10,000 G

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8
Q

What is the magnetic field intensity of most clinical MR scanners?

A

10,000G (1T) - 30,000 G (3T)

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9
Q

What is resonance?

A

when two or more frequencies perfectly match

they amplify each other

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10
Q

What is the SPIN in MRI?

A

angular momentum and magnetic movement

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11
Q

True or false. Spins align with magnetic field.

A

True

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12
Q

The alignment of the magnets (“in the body”) can have two states:

A

Parallel to the magnetic field & opposite (anti-parallel) to the magnetic field

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13
Q

There are slightly more/less spins parallel to the magnetic field than anti-parallel.

A

There are slightly more spins parallel to the magnetic field than anti-parallel

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14
Q

The difference in the two spins give rise to the ___________.

A

net magnetization

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15
Q

Net magnetization depends on:

A

magnetic field, spin density (# of proton or water molecules), and temperature

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16
Q

Net magnetization increases/decreases with magnetic field.

A

increases

magnetic field & net magnetization are directly proportional

17
Q

Net magnetization increases/decreases with spin density

A

increases

18
Q

Net magnetization increases/decreases with temperature

A

decreases

19
Q

What is relaxation?

A

The return to original status and the approach of and the approach of a total chaos

20
Q

T1-Relaxation occurs on what magnetization?

A

longitudinal magnetization (up & down)

21
Q

T2-Relaxation occurs on what magnetization?

A

transverse magnetization (side to side)

22
Q

The rotation of a transverse magnetization will lead to an induction of a voltage in a ____.

A

receiver coil

23
Q

T2- Spin-Spin Relaxation is also known as ___________.

A

Transverse relaxation

24
Q

T1 Spin-Lattice Interaction is also known as _ .

A

Longitudinal relaxation

25
Q

True or false. Every tissue has its own relaxation curve.

A

True

26
Q

What is the Bloch Equation?

A

The equation for motion (for the magnetization)

27
Q

What happens during T2 relaxation?

A

The “vanishing” of the transverse magnetization back to its original state.

28
Q

What happens during T1-Relaxation?

A

“Recovery” of longitudinal magnetization back to its original state.

29
Q

What happens during excitation?

A

An RF pulse is emitted from the scanner. The longitudinal magnetization decreases and transverse magnetization appears. This makes the protons go to a higher energy state (parallel to anti-parallel)

30
Q

True or false. Normally, protons in the body are oriented randomly. But, when in a MR scanner, they are aligned.

A

True

31
Q

What occurs during recovery?

A

Protons return back to low energy state, restoring longitudinal magnetization

32
Q

What happens during De-phasing?

A

The signal is sent back. T2-relaxation occurs.

33
Q

What is precession?

A

The rotation of a spinning particle upon its axis in the presence of a magnetic field. The speed at which the proton is rotating.

34
Q

Precession can be expressed by what equation?

A

Larmor frequency equation

35
Q

What is Larmor Frequency?

A

The frequency at which a spin precesses about an external magnetic field (Larmor frequency = Precession frequency)

36
Q

Larmor Frequency is dependent on type of ___ and ___.

A

nucleus; strength of magnetic field

37
Q

What is the Larmor Equation?

A

v = y * Bo
Precession Frequency = gyromagnetic ratio * magnetic field

they are directly proportional

38
Q

Why Hydrogen?

A
  • Hydrogen has the highest gyro-magnetic (y) ratio among the nuclei (strong signal)
  • it’s 99.9% abundant
  • Our body constitutes of 60% water
  • Present in nearly all other organic molecules in our body

MRI (13 decks)

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