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MRI MIC > Chapter 1-Fundamentals > Flashcards

Chapter 1-Fundamentals Flashcards

1
Q

MRI is

A. Non-Ionizing
B. Ionizing imaging

A

A. Non-Ionizing

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2
Q

Explain the process in which we transmit an imaging with MRI.

A

The patients molecules receive an external low-level electromagnetic stimulation and they respond by creating their own signal

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3
Q

MRI uses what type of atom in the body and why?

A

hydrogen due to the abundance of it in our bodies

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4
Q

How many protons does a hydrogen atom have?

A

1 proton which are positively charged and spin on on their own axis.

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5
Q

How come protons are needed to generate a magnetic field??

A

It is due to the positively charged proton that they have. They spin on their own axis. Any charged particle that’s moving can generate a magnetic field

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6
Q

What are the 3 requirements for MRI to work?

A

1) strong magnetic field (aka the magnet
2) external RF energy (the tissue must be stimulated)
3) ODD number of protons (aka like hydrogen which only has one)

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7
Q

The magnetic field is often called the “B O” field.

True or False

A

True.. the BO field is the same as magnetic field

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8
Q

What is the difference in “parallen and anti-parellel” when talking about the protons aligning themselves during MRI?

A

Parallel = “ground -state” aka low energy, they are relaxed
ANTI-parallel- “EXCITED, high energy

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9
Q

What is the “net magnetic moment”

A

the result of the protons aligning is called the net magnetic moment = equilibrium

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10
Q

What occurs when we “TILT” the net magnetization, thus wobbling occurs?

A

that is called precession.

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11
Q

When all the protons are aligned, there is a ______ signal.

A. No signal
B. Strong Signal
C. Weak signal

A

A. when everything is aligned there is no signal, thus why we need to disturb them to create an image.

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12
Q

The precessional frequency is often called the _____ frequency.

A

RESONANT

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13
Q

the precessional frequency/resonant frequency is measured by

A

the strength of the magnetic field and the rate of precessional/wobble

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14
Q

What is the gyromagnetic ratio?

A

it is how the resonant/precessional frequency is affected by the magnetic field strength

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14
Q

What is the gyromagnetic ratio?

A

it is how the resonant/precessional frequency is affected by the magnetic field strength

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15
Q

the ____ the magnetic field the ____ the resonant frequency

A

the HIGHER the magnetic field, the HIGHER the resonant frequency.

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16
Q

What is the gyromagnetic ratio for hydrogen?

A

42.6

Therefore a 1 Tesla strength magnet would be 42.6 million rotations per second

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17
Q

What is the precessional frequency for a 0.5 Tesla magnet?

A

0.5 Tesla = 21.3 MHZ

The math is 42.6 x 0.5 = 21.3

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18
Q

what is the resonant frequency of a 1 Tesla strength magnet?

A

1 Tesla = 42.6 MHZ

The math is 42.6 x 1 = 42.6

19
Q

What is the resonant frequency of a 1.5 Tesla Magnet?

A

1.5 Tesla = 63.9 MHZ

The math is 42.6 x 1.5 = 63.9

20
Q

what is the resonant frequency of a 2.0 Tesla Magnet?

A

2 Tesla = 85.2 MHZ

The math is 42.6 x 2.0 = 85.2

21
Q

What is the resonant frequency of a 3.0 Tesla magnet?

A

3 Tesla = 127.8 MHZ

The math is 42.6 x 3.0 = 127.8

22
Q

When we “disturb” the protons equilibrium, this creates an image. When we “relax, they move back to equilibrium, What causes this disturbance?

A

the RF pulse

23
Q

True or False

The transfer of energy only happens if the frequency of the energy source is the same as the system

A

True

24
Q

What is the direction of the main magnetic field?

transverse or longitudinal?

A

longitudinal

25
Q

True or False

The STRONGER the RF pulse, the LONGER it is applied, and the more it will “WOBBLE”

A

True

26
Q

What is the flip angle?

A

the angle at which the net magnetization is tilted AWAY from the magnetic field

27
Q

When the flip angle is 90 degrees, this is considered a spin echo

True or False

A

True

28
Q

When the flip angle is less than 90 degrees, this is considered a gradient echo

True or False

A

True

29
Q

How is the flip angle determined?

A

it is determined by the RF duration and the amplitude

30
Q

What is the process of “relaxation”?

A

once the RF pulse is turned off, the nuclei returns to the equilibrium, losing the energy to the surrounding environment.

31
Q

T1 Relaxation is also called Spin- _____

A. Spin- Spin
B. Spin-Lattice

A

T1=Spin- Lattice

The relaxation sends the energy into the lattice (enviroment)

32
Q

T1- is often called ______

Transverse or longitundinal?

A

longitudinal

33
Q

T1 is the time for net magnetization to grow to ___ %

A

63

34
Q

T1 is controlled by ___

TR or TE?

A

TR = T1

35
Q

Explain what the white matter, gray matter and CSF will look like in a T1 image

A

White matter= bright (short t1)
Gray matter= slightly bright (long t1)
CSF = DARK (realllllly long t1)

36
Q

T2 is often called spin- _____.

spin spin or spin lattice?

A

Spin- Spin = T2

37
Q

T2 is controlled by

TE or TR?

A

TE=T2

38
Q

T2 is the amount of time it takes to decay ____ %.

A

37

39
Q

When does dephasing occur?

A

When the relaxation occurs and the protons start canceling eachother out.

40
Q

True or False

DEPHASING causes a DROP in net magnetization

A

True

41
Q

Why is T2 called spin-spin?

A

Because instead of spin and leaving the energy to the lattice like t1, the energy goes from one proton to another.

42
Q

What is free induction decay?

A

the signal decay due to dephasing process

43
Q

What will happen to the image if the protons COMPLETELY cancel each other out?

A

There will be no signal

44
Q

What good does the 180 pulse do?

A

By using the 180 pulse, we REPHASE the protons back to “in-phase”

45
Q

T2 is also known as transverse magnetization. True or False

A

True

MRI MIC (1 decks)

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