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mri registry > Chapter 2 - Image weighting and contrast > Flashcards

Chapter 2 - Image weighting and contrast Flashcards

1
Q

Intrinsic contrast parameters are those that ____ be changed because they are inherent to the body tissue

can or cannot

A

cannot be changed.

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2
Q

Extrinsic contrast parameters are those that ____ be changed because they are under our control.

can or cannot

A

Can be changed.

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3
Q

Whats an example of intrinsic contrast parameters. Xray for example

A

a parameter that cant be changed is the tissue density of the structure that the xray beam passes thru. It’ll attenuate which is out of our control.

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4
Q

T1 recovery, T2 decay, PD, flow and ADC are all examples of ___ contrast parameters.

A

intrinsic

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5
Q

TR, TE, flip angle, and T1 , turbo, and B value are examples of ____ contrast parameters

A

extrinsic since we have control over those

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6
Q

During relaxation, hydrogen nuclei ___ absorbed RF energy.

give up or take?

A

give up

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7
Q

T2 decay occurs 5-10 faster than T1 recovery does.

A

True

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8
Q

What is T1 recovery caused by?

A

hydrogen nuclei giving up their energy to the surrounding environment.

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9
Q

T1 it is the primary relaxation process.

A

True

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10
Q

Longitudinal magnetization is related exponentially to recovery time.

True or False

A

true

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11
Q

What is the average t1 recovery time in water?

A

2500

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12
Q

What is the average t1 recovery time of fat?

A

200

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13
Q

What is the average t1 recovery time of CSF?

A

2000

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14
Q

What is the average t1 recovery time of white matter>

A

500

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15
Q

the term decay refers to the ____ of coherent transverse magnetization

loss or gain

A

loss

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16
Q

T2 decay is also called what?

A

spin-spin relaxation

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17
Q

transverse magnetization is related exponentially to decay time.

A

True

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18
Q

t2 decay time is the time it takes for 63% of the transverse magnetization to dephase

A

true

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19
Q

What is the average t2 decay time of water?

A

2500

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20
Q

What is the average t2 decay time of fat?

A

100

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21
Q

What is the average t2 decay time of CSF?

A

300

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22
Q

What is the average t2 decay time of white matter?

A

100

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23
Q

What is the difference in T2 and T2* ?

A

not sure

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24
Q

What is spin lattice energy transfer ?

A

a type of relaxation process where spins give up the energy absorbed thru RF exciation to the surrounding molecular lattice of the tissue.

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25
Q

Relaxation basicalled means the loss of energy,

True or False

A

true

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26
Q

What is the proton density of a tissue?

A

means the number of mobile hydrogen protons per unit volume of the tissue.

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27
Q

THe higher the PD of a tissue, the more signal available

True or false?

A

true

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28
Q

Once the b1 Field is removed, the hydrogen nuclei are then only under what influence?

A

the B0

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29
Q

When the RF exciation pulse is switched off the hydrogen nuclei return to their ___-energy state and their magnetic moments _____

High Low
Dephase/Inphase

A

they return to theier LOW energy state and their magnetic moments DEPHASE.

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30
Q

T2 Decay occurs 5-10 times faster than T1 recovery

True or False

A

true

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31
Q

What is spin-lattice energy transfer and does it occur more in t1 or t2/

A

energy released by spins to surrounding molecular lattice (structure), which then causes magnetic moments of hydrogen nuclei to recovery their longitudinal magnetization

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32
Q

How long is the “t1 recovery time?”

A

the time it takes for 63% of the longitudinal magnetization to recover in a tissue which depends on the tissue.

33
Q

What is TR and how does it affect T1 Recovery?

A

TR is the time between one RF pulse to the next. It determines how much T1 occurs.

34
Q

MzT and Mz is part of which recovery curve equation?

t1 or t2?

A

T1 Recovery

35
Q

What is the spin-spin relaxation caused by?

A

Caused by one spin transfering energy into another spin rather than into the lattice like the “spin-lattice” in t1

36
Q

How long is the T2 decay time?

A

the time it takes for 63% of the transverse magnetization to dephase

37
Q

Mxyt and and Mxy are related to which equation ?

t1 or t2

A

t2 decay

38
Q

The T2 decay time is the time between an RF excitation pulse and when the signal is collected in the receiver coil.

True or False

A

True

39
Q

How is T2* different than T2 decay?

A

T2* is dephasing caused by inhomogenities in the B0 field. This produces its own decay curve.

This happens when the RF pulse switches off and the nuclei dephase very quick (10MS)

40
Q

If something is HYPERintense, this will show up ___ on the image

Bright or Dark/Black

A

Bright

41
Q

If something is HYPOintense, it will show up as ___ on image.

Bright or dark/black

A

Dark/black

42
Q

Fat molecules ontain atoms of hydrogen arranged with ____- and Oxygen.

A

carbon and oxygen

43
Q

Fat molecules have large molecules called lipids that are closely packed together.

True or False

A

true

44
Q

Why does water have a faster tumbling rate than fat?

A

because fat has these lipids that are closely packed togehter and water’s molecules are spaced further apart.

45
Q

T1 Recovery time in Fat is short.

True or False

A

True

46
Q

T1 Recovery time in water is short.

True or false

A

FALSE

Recovery time in water in LONG.

47
Q

T2 Decay in fat is short. Why is that?

A

Because T2 decay has todo with the interaction of hydrogen nuclei. Since fat molecules are packed closed together they are more likely to interact.

48
Q

T2 Decay in Water is long. Why is that ?

A

because spin to spin interations are less likely to our due to the water molecules being spaced further apart than it is in fat.

49
Q

T1 contrasts occurs when the vectors do not fully recover from their longitduinal magnetization between each RF excitation.

True or false

A

True .

50
Q

If the TR is SHORT, then what happens to the T1 contrast?

A

the contrast increases since it has to do with the time in-between pulses.

51
Q

When the net magnetization vector (NMV) is pushed beyond 90 degrees, its called _____ saturated.

A

partially

52
Q

When the net magnetization vector (NMV) is pushed to a full 180 degrees, its called _____ saturated.

A

FULLY saturated.

53
Q

What is proton density contrast?

A

differences in signal intensity between tissues depending on their relative number of mobile hydrogen protons per unit

54
Q

A HIGH proton density tissue has a LARGE transverse component of magnetization therefore producing a ____ signal.

High or Low

A

high signal aka they are bright.

55
Q

A low proton density tissue has a SMALL transverse component of magnetization therefore producing a ____ signal.

High or Low

A

Low/ Dark/Black signal.

56
Q

We want the TR to be SHORT in T1-Weighted images. Why is that?

A

This is because we want the TR short enough so that neither the vector in fat nor the water has sufficient time to fully return to B0.

If its too long, both will recovery and therefore we couldn’t demostrate any contrast? Page 42

57
Q

T1 Weighted images are best used to show anatomy.

True or false

A

True

58
Q

For T1 Weighted images, the TR must be ____ and the TE must
be _____.

Short/Long
Short/Long

A

Short and short

59
Q

Name a few types of tissues or pathology that have a high signal with T1?

(aka show up bright)

A 
hemangioma
fat
Lipoma (fat tumor)
Degeneration
Fatty deposits
Slow moving  blood
60
Q

Name a few types of tissues or pathology that have a low signal with T1?

(aka show up Dark)

A 
BONE
Avascular necrosis
Tumors
cysts
calcifications
infection or infarction.
61
Q

For T2s we want the TE to be long. Why is that?

A

We need it long enough to give the vectors in both fat and water time to dephase.

If its too short, neither fat or water has time to dephase.

62
Q

For T2 weighting, the TE must be ___ and the TR must be _____.

Long or short
long or short

A

long TE Long TR

63
Q

Name a few things that would have a high signal in a T2 image.

A 
Water
Fluid
Hemangioma
infection or inflammation
edema
cysts
64
Q

Name a few things that would have a low signal in a T2 image.

A

Bone

calcifications

65
Q

a LONG TR combined with a LONG TE will

____ T1 contrast and ___ T2 contrast

Minimize/maximize.

A

LONG TE and TR will minimize T1 and maximize T2.

66
Q

To achieve proton density (PD) weighting, we need to diminish the effects of T1 and T2, so that PD can dominate.

True oR false

A

True

67
Q

Using a ____ TR and a ____ TE, we can make a PD image.

A

Using a LONG TR and a SHORT TE.

This therefore cancels out the T1 and T2- letting the PD be dominate.

68
Q

Name a few things that would have a high signal in a PD image.

A 
CSF
Fluid
Infection
Edema
Cysts and Fat
69
Q

Name a few things that would have a low signal in a PD image

A 
Air
tendons
bone
scar tissue
calcification
70
Q

If you’re looking at an image and the water is bright, this is likely a ____ image.

t1 t2?

A

T2 using a long TE

71
Q

If you’re looking at an image and the water is dark, this is likely a ____ Image?

T1 or T2

A

T1- using a short TR.

72
Q

What is the difference in T1 CONTRAST and T1 Weighting??

A

T1 contrast is an image where fat is bright and water is dark because the TR is short enough not to have a full recovery

T1 Weighting is an image where the contrast is mostly because of the differenes in t1 Recovery times of the TISSUE.

73
Q

What does diffusion mean?

A

the movement of molecules in the extracellular space due to random thermal motions

74
Q

What does ADC stand for in regards to a DWI (diffusion) image?

A

It is called an apparent diffusion coefficient. page 54 come back to DWI

75
Q

SWI uses the magnetic susceptibilty differences between tissues to generate contrast.

True or false?

A

True

76
Q

SWI consists of a ____ TE and a gradient echo sequence

long or short

A

Long

77
Q

Why is T2 images better at seeing pathology?

A

because most pathology has a high water nuclei content.

78
Q

Gadolinium in its natural form is HIGHLY TOXIC. How is it made safe enough to put in bodies?

A

we make it sife by binding or (chelating) the gad to other molecules such as DTPA.

mri registry (3 decks)

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