MRI Pulse Sequence

Question 1

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

Answer 1

pulse sequence

Question 2

Each sequence will have a number of ____

Answer 2

parameters

Question 3

Multiple sequences are grouped together into an

Answer 3

MRI protocol

Question 4

Extrinsic contrast parameters

Answer 4

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

Question 5

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

Answer 5

repetition time (TR)

Question 6

It determines how much longitudinal magnetization recovers between each pulse

Answer 6

repetition time (TR)

Question 7

Repetition time (TR) is measured in

Answer 7

milliseconds

Question 8

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

Answer 8

Echo time (TE)

Question 9

Echo time (TE) is measured in

Answer 9

milliseconds

Question 10

Time of signal acquisition

Answer 10

Echo time (TE)

Question 11

Pulses are characterized by their

Answer 11

flip angles

Question 12

Intrinsic contrast mechanisms

Answer 12

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

Question 13

Relaxation process could:

Answer 13

Transversal relaxation

Longitudinal relaxation

Question 14

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

Answer 14

longitudinal relaxation time / T1 Recovery or Spin-Lattice relaxation

Question 15

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

Answer 15

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

Question 16

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

Answer 16

T1 recovery

Question 17

T1 time of fat is

Answer 17

very short

Question 18

Fat is able to absorb energy quickly, therefore it is

Answer 18

efficient to absorb energy

Question 19

T1 time of water is

Answer 19

quite long

Question 20

Water is

Answer 20

inefficient at receiving energy from nuclei

Question 21

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

Answer 21

Short TRs

Question 22

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

Answer 22

Saturation

Question 23

Allow full recovery of the longitudinal components in fat and water

Answer 23

Long TRs

Question 24

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

Answer 24

T2 decay

Question 25

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

Answer 25

T2 decay in fat and water

Question 26

Fat's T2 time

Answer 26

very short compared with that of water

Question 27

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

Answer 27

Short TEs

Question 28

Allow dephasing of the transverse components in fat and water

Answer 28

Long TE

Question 29

Water/Liquids have

Answer 29

a long T1 and long T2

Question 30

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

Answer 30

T1 weighted image

Question 31

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

Answer 31

short enough

Question 32

Tissue with short T1 relaxation times such as fat, are

Answer 32

bright (high signal)

Question 33

Tissue with long T1 relaxation times such as water, are

Answer 33

dark (low signal

Question 34

Typical parameters for T1 weighting

Answer 34

TR 300-600 ms | TE 10-30 ms

Question 35

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

Answer 35

T2 weighting

Question 36

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

Answer 36

TE

Question 37

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

Answer 37

long enough

Question 38

Tissue with short T2 decay times such as fat, are

Answer 38

dark (low signal)

Question 39

Tissue with long T2 decay times such as water, are

Answer 39

bright (high signal)

Question 40

Typical parameters for T2 weighting

Answer 40

TR 2000 ms + | TE 70 ms +

Question 41

differences in the proton densities must be demonstrated

Answer 41

proton density image

Question 42

Proton density

Answer 42

Long TR, Short TE

Question 43

The heart of MRI

Answer 43

Pulse sequence mechanisms

Question 44

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

Answer 44

Pulse sequence mechanisms

Question 45

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

Answer 45

Pulse sequence mechanisms

Question 46

Main purposes of pulse sequences

Answer 46

to rephase spins and remove inhomogeneity effects ... | to enable manipulation of the TE and TR

Question 47

Spins are rephased in two ways

Answer 47

by using 180 RF pulse | using a gradient

Question 48

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

Answer 48

Conventional spin echo pulse sequence (SE)