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MRI > MRI Pulse Sequence > Flashcards

MRI Pulse Sequence Flashcards

1
Q

the combination of the characteristics and timing of the radio pulses and magnetic field gradients

A

pulse sequence

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2
Q

Each sequence will have a number of ____

A

parameters

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3
Q

Multiple sequences are grouped together into an

A

MRI protocol

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4
Q

Extrinsic contrast parameters

A

Time to Repetition/Repetition Time (TR)
Time to Echo/Echo Time (TE)
Flip Angle

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5
Q

time from the application of an excitation pulse to the application of the next pulse

A

repetition time (TR)

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6
Q

It determines how much longitudinal magnetization recovers between each pulse

A

repetition time (TR)

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7
Q

Repetition time (TR) is measured in

A

milliseconds

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8
Q

time between the application of radiofrequency excitation pulse and the peak of the signal induced in the coil

A

Echo time (TE)

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9
Q

Echo time (TE) is measured in

A

milliseconds

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10
Q

Time of signal acquisition

A

Echo time (TE)

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11
Q

Pulses are characterized by their

A

flip angles

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12
Q

Intrinsic contrast mechanisms

A 
T1 recovery
T2 decay
Proton density
flow
apparent diffusion coefficient (ADC)
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13
Q

Relaxation process could:

A

Transversal relaxation

Longitudinal relaxation

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14
Q

Time that it takes for the longitudinal magnetization to recover, to go back to its original value, is described by

A

longitudinal relaxation time / T1 Recovery or Spin-Lattice relaxation

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15
Q

Nuclei/Proton lose precessional coherence or dephase and the NMV decays in the transverse plane, this dephasing relaxation process is called

A

Transverse Relaxation times or T2 decay or spin-spin energy transfer

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16
Q

It is caused by the exchange of energy nuclei to their surrounding environment or lattice

A

T1 recovery

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17
Q

T1 time of fat is

A

very short

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18
Q

Fat is able to absorb energy quickly, therefore it is

A

efficient to absorb energy

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19
Q

T1 time of water is

A

quite long

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20
Q

Water is

A

inefficient at receiving energy from nuclei

21
Q

Do not permit full longitudinal recovery in either fat or water so that there are different longitudinal components in fat and water

A

Short TRs

22
Q

As the NMV does not recover completely to the positive longitudinal axis, they are pushed beyond the transverse plane by the succeeding 90 degrees RF pulse

A

Saturation

23
Q

Allow full recovery of the longitudinal components in fat and water

A

Long TRs

24
Q

It is caused by the exchange of energy from one nucleus to another

A

T2 decay

25
Q

occurs as a result of the spins of adjacent nuclei interacting with each other and exchanging energy

A

T2 decay in fat and water

26
Q

Fat’s T2 time

A

very short compared with that of water

27
Q

Do not permit full dephasing in either fat or water so their transverse components are similar

A

Short TEs

28
Q

Allow dephasing of the transverse components in fat and water

A

Long TE

29
Q

Water/Liquids have

A

a long T1 and long T2

30
Q

It is one where the contrast depends predominantly on the differences in the T1 times between tissues

A

T1 weighted image

31
Q

To achieve T1 weighting, the TR must be ______ so that neither fat nor water has sufficient time to fully return to B0

A

short enough

32
Q

Tissue with short T1 relaxation times such as fat, are

A

bright (high signal)

33
Q

Tissue with long T1 relaxation times such as water, are

A

dark (low signal

34
Q

Typical parameters for T1 weighting

A

TR 300-600 ms

TE 10-30 ms

35
Q

It is one where the contrast depends predominantly on the differences in the T2 times between tissues

A

T2 weighting

36
Q

controls the amount of T2 decay that is allowed to occur before the signal is received

A

TE

37
Q

To achieve T2 weighting, the TE must be ______ to give both fat and water time to decay

A

long enough

38
Q

Tissue with short T2 decay times such as fat, are

A

dark (low signal)

39
Q

Tissue with long T2 decay times such as water, are

A

bright (high signal)

40
Q

Typical parameters for T2 weighting

A

TR 2000 ms +

TE 70 ms +

41
Q

differences in the proton densities must be demonstrated

A

proton density image

42
Q

Proton density

A

Long TR, Short TE

43
Q

The heart of MRI

A

Pulse sequence mechanisms

44
Q

They are the computer software executing a series of commands to apply an rf pulses, gradients, data sampling windows

A

Pulse sequence mechanisms

45
Q

Enable to control of the way in which the system applies RF pulses and gradients

A

Pulse sequence mechanisms

46
Q

Main purposes of pulse sequences

A

to rephase spins and remove inhomogeneity effects …

to enable manipulation of the TE and TR

47
Q

Spins are rephased in two ways

A

by using 180 RF pulse

using a gradient

48
Q

are used to produce T1, T2 or proton density weighted images and are one of the most basic pulse sequences used in MRI

A

Conventional spin echo pulse sequence (SE)

MRI (1 decks)

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