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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
Relaxation basicalled means the loss of energy, True or False
true
26
What is the proton density of a tissue?
means the number of mobile hydrogen protons per unit volume of the tissue.
27
THe higher the PD of a tissue, the more signal available True or false?
true
28
Once the b1 Field is removed, the hydrogen nuclei are then only under what influence?
the B0
29
When the RF exciation pulse is switched off the hydrogen nuclei return to their ___-energy state and their magnetic moments _____ High Low Dephase/Inphase
they return to theier LOW energy state and their magnetic moments DEPHASE.
30
T2 Decay occurs 5-10 times faster than T1 recovery True or False
true
31
What is spin-lattice energy transfer and does it occur more in t1 or t2/
energy released by spins to surrounding molecular lattice (structure), which then causes magnetic moments of hydrogen nuclei to recovery their longitudinal magnetization
32
How long is the "t1 recovery time?"
the time it takes for 63% of the longitudinal magnetization to recover in a tissue which depends on the tissue.
33
What is TR and how does it affect T1 Recovery?
TR is the time between one RF pulse to the next. It determines how much T1 occurs.
34
MzT and Mz is part of which recovery curve equation? t1 or t2?
T1 Recovery
35
What is the spin-spin relaxation caused by?
Caused by one spin transfering energy into another spin rather than into the lattice like the "spin-lattice" in t1
36
How long is the T2 decay time?
the time it takes for 63% of the transverse magnetization to dephase
37
Mxyt and and Mxy are related to which equation ? t1 or t2
t2 decay
38
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
True
39
How is T2* different than T2 decay?
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
If something is HYPERintense, this will show up ___ on the image Bright or Dark/Black
Bright
41
If something is HYPOintense, it will show up as ___ on image. Bright or dark/black
Dark/black
42
Fat molecules ontain atoms of hydrogen arranged with ____- and Oxygen.
carbon and oxygen
43
Fat molecules have large molecules called lipids that are closely packed together. True or False
true
44
Why does water have a faster tumbling rate than fat?
because fat has these lipids that are closely packed togehter and water's molecules are spaced further apart.
45
T1 Recovery time in Fat is short. True or False
True
46
T1 Recovery time in water is short. True or false
FALSE Recovery time in water in LONG.
47
T2 Decay in fat is short. Why is that?
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
T2 Decay in Water is long. Why is that ?
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
T1 contrasts occurs when the vectors do not fully recover from their longitduinal magnetization between each RF excitation. True or false
True .
50
If the TR is SHORT, then what happens to the T1 contrast?
the contrast increases since it has to do with the time in-between pulses.
51
When the net magnetization vector (NMV) is pushed beyond 90 degrees, its called _____ saturated.
partially
52
When the net magnetization vector (NMV) is pushed to a full 180 degrees, its called _____ saturated.
FULLY saturated.
53
What is proton density contrast?
differences in signal intensity between tissues depending on their relative number of mobile hydrogen protons per unit
54
A HIGH proton density tissue has a LARGE transverse component of magnetization therefore producing a ____ signal. High or Low
high signal aka they are bright.
55
A low proton density tissue has a SMALL transverse component of magnetization therefore producing a ____ signal. High or Low
Low/ Dark/Black signal.
56
We want the TR to be SHORT in T1-Weighted images. Why is that?
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
T1 Weighted images are best used to show anatomy. True or false
True
58
For T1 Weighted images, the TR must be ____ and the TE must be _____. Short/Long Short/Long
Short and short
59
Name a few types of tissues or pathology that have a high signal with T1? (aka show up bright)
``` hemangioma fat Lipoma (fat tumor) Degeneration Fatty deposits Slow moving blood ```
60
Name a few types of tissues or pathology that have a low signal with T1? (aka show up Dark)
``` BONE Avascular necrosis Tumors cysts calcifications infection or infarction. ```
61
For T2s we want the TE to be long. Why is that?
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
For T2 weighting, the TE must be ___ and the TR must be _____. Long or short long or short
long TE Long TR
63
Name a few things that would have a high signal in a T2 image.
``` Water Fluid Hemangioma infection or inflammation edema cysts ```
64
Name a few things that would have a low signal in a T2 image.
Bone | calcifications
65
a LONG TR combined with a LONG TE will ____ T1 contrast and ___ T2 contrast Minimize/maximize.
LONG TE and TR will minimize T1 and maximize T2.
66
To achieve proton density (PD) weighting, we need to diminish the effects of T1 and T2, so that PD can dominate. True oR false
True
67
Using a ____ TR and a ____ TE, we can make a PD image.
Using a LONG TR and a SHORT TE. This therefore cancels out the T1 and T2- letting the PD be dominate.
68
Name a few things that would have a high signal in a PD image.
``` CSF Fluid Infection Edema Cysts and Fat ```
69
Name a few things that would have a low signal in a PD image
``` Air tendons bone scar tissue calcification ```
70
If you're looking at an image and the water is bright, this is likely a ____ image. t1 t2?
T2 using a long TE
71
If you're looking at an image and the water is dark, this is likely a ____ Image? T1 or T2
T1- using a short TR.
72
What is the difference in T1 CONTRAST and T1 Weighting??
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
What does diffusion mean?
the movement of molecules in the extracellular space due to random thermal motions
74
What does ADC stand for in regards to a DWI (diffusion) image?
It is called an apparent diffusion coefficient. page 54 come back to DWI
75
SWI uses the magnetic susceptibilty differences between tissues to generate contrast. True or false?
True
76
SWI consists of a ____ TE and a gradient echo sequence long or short
Long
77
Why is T2 images better at seeing pathology?
because most pathology has a high water nuclei content.
78
Gadolinium in its natural form is HIGHLY TOXIC. How is it made safe enough to put in bodies?
we make it sife by binding or (chelating) the gad to other molecules such as DTPA.

MRI Registry (3 decks)

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