4. Mri Pulse Sequences

Front 1

___________ is NOT a characteristic of the steady state gradient echo pulse sequence.

Back 1

A 180 degree RF pulse

*They rephase with gradients

Front 2

Which of the following may be T1 weighted?
1. Spin echo
2. Inversion recovery image
3. Gradient echo image

Back 2

All the above

Front 3

Spin echo and fast spin echo sequences are capable of generating T2 weighted sequences, T/F?

Back 3

True

Front 4

Gradient echo sequences can generate T2 weighted images, T/F?

Back 4

False.

*Gradient echo sequences can generate T2* but not true T2 sequences due to magnetic inhomogenities.

Front 5

As the TE of a gradient echo sequence is varied, ___________ cause fat and water to have signal intensities which cycle from similar to different.

Back 5

Phase effects of chemical shift

Front 6

Depending on the echo time, the signal from fat and water might be in phase or their signals may be out of phase. It may appear that at some echo times two different tissues may appear isointense while at interleaving echo times they may exhibit substantial contrast. This phenomenon is known as:

Back 6

Phase cycling

Front 7

Consider a dual contrast spin echo pulse sequence in which the 90 degree RF pulse is applied at time = 0, the center of the first echo forms at time = 15ms, and the center of the second echo forms at time = 90ms. The 180 degree RF pulse to form the echo used for the T2 weighted image must have been applied at ____ ms.

Back 7

52.5

Front 8

Which of the following sequences is best for performing diffusion weighted imaging?

Back 8

Echo planar imaging

Front 9

Diffusion weighted imaging demonstrates changes in:

Back 9

Cellular metabolism

Front 10

A 180 degree RF pulse followed by a 90 degree RF pulse followed by another 180 degree RF pulse is what type of pulse sequence?

Back 10

Inversion recovery

Front 11

In a fast spin echo pulse sequence with an echo train of 8, if the first four echoes contribute to a proton density image, and the last four echoes contribute to a T2 weighted image, how many repetitions are required to fill the raw data of a 256x256 T2 weighted image?

Back 11

64

*This is because this is a dual contrast sequence so four echoes are being collected for each image.

Front 12

An EPI sequence in which all of the echoes necessary to reconstruct the image are collected following a single RF excitation is the definition of:

Back 12

Single shot EPI

Front 13

Name some facts about magnetic properties of hydrogen protons in water and fat:

Back 13

>In water the hydrogren protons are not as shielded by electrons compared to fat.
>Hydrogen protons in water experience a higher magnetic field and precess at a higher frequency than that of fat.

Front 14

Consider a spin echo pulse sequence in which the 90 degree RF pulse is applied at time = 0 and the maximum signal vof a spin echo forms at time = 15 ms. The 180 degree pulse must have been applied at _______ ms.

Back 14

7.5

Front 15

Which of the following may be seen in a steady state gradient?
1. T1 contrast
2. T2 contrast
3. Magnetic suseptibility

Back 15

Magnetic suseptibility or T2*
(A spoiled gradient echo can generate BOTH T1 and T2*)

Front 16

Which of the following may be seen in a fast gradient echo image?
1. T1 contrast
2. T2 contrast
3. Magnetic susceptibility

Back 16

T1 and T2 contrast

*Although this sequence is considered a gradient the contrast in this sequence is prepared with RF pulses prior to the gradient echo portion of the sequence.
*The contrast is prepared using the same way as spin echo sequence (90 degree RF pulse followed by a 180 degree RF pulse)

Front 17

Which of the following is NOT rephased by the 180 degree RF pulse in a spin echo pulse sequence?
A. Magnetic susceptibility differences between tissues
B. Spin spin interaction
C. Magnetic inhomogeneities
D. Phase effects of chemical shift

Back 17

Spin spin interactions

Front 18

If the TI of an inversion recovery pulse sequence is chosen such that the magnetization of silicone, from a silicone breast implant, is relaxing through zero when the 90 degree RF pulse is transmitted, what type of signal can be expected from the silicone in the resulting image?

Back 18

Dark

Front 19

Which of the following RF flip angles would result in the largest tranverse component, assuming the net magnetization is initially in the longitudinal direction? 30, 45, 60, 75

Back 19

75 degree

Front 20

Which of the following is NOT a characteristic of the spoiled gradient echo pulse sequence?
A. A user selectable RF flip angle
B. The elimination of residual transverse magnetization
C. Steady state transverse magnetizatoin following the formation of the echo
D. An echo formed by gradient refocusing

Back 20

C.

Front 21

Which of the following may NOT be seen in a conventional spin echo image?

Back 21

The phase effects of magnetic susceptibility

Front 22

In a fast spin echo sequence wth an echo train of 12, how many RF pulses are applied for a given slice, during one TR period?

Back 22

13

Front 23

Becuase _________________ the inversion recovery method of fat suppression should NOT be used with MR contrast agents.

Back 23

The enhanced tissues as well as the fat may be suppressed.

Front 24

Which of the following RF flip angles would result in the largest longitudinal component, assuming the net magnetization is initially in the longitudinal direction? 30, 45, 60, 70

Back 24

70

Front 25

In a fast spin echo pulse sequence, the time from the 90 degree pulse to the echo is called:

Back 25

TE

Front 26

During a conventional 10 minute T2 spin echo scan with 1 signal average, most of the contrast information is collected for the image during:

Back 26

Minutes 5 and 6
*The contast information for the image is contained in the central aspects of the raw data and the edge definition is contained in the outer peripheral aspects of the raw data.

Front 27

What is the best sequence for cardiac perfusion studies?

Back 27

EPI

Front 28

In a T2 prepared fast gradient echo sequence which uses a 90 degree, 180 degree, 90 degree preparation scheme, how many 90 degree RF pulses are applied for a single image with 192 phase steps in its matrix?

Back 28

2
* This sequence use only an initial RF pulsing scheme and then collect the entire matrix of MR echoes using only the rephasing capabilities of the gradient system.

Front 29

In which of the following pulse sequences would you expect to find the shortest TR?
1. Spin echo
2. Inversion recovery
3. Fast spin echo
4. Gradient echo

Back 29

Gradient echo
*For T1, T2, and T2* weighted imaging gradient echo sequences require the shortest TR times.
*The longest TR times are used by inversion recovery sequences for T1 weighting and by fast spin echo sequences for T2 weighting.

Front 30

What is the time from an inverting pulse to 90 degree pulse called?

Back 30

TI

Front 31

If a single echo was corrupted, due to a static discharge from the patient's wool socks, during the first 30 sec of 5 minute spin echo knee study, show would you expect the resultant image to appear?

Back 31

There would be a stipe artifact throughout the entire image

Front 32

What is NOT related to the reciever bandwidth?

Back 32

Chemical shift artifact

Front 33

In a gradient echo pulse sequence a system malfunction causes the first pulse of the readout gradient to remain on one milisecond too long. The gradient echo will:

Back 33

Form later than the selected TE

Front 34

In a convential spin echo pulse sequence with a TE of 20 ms and echo duration of 5ms the receiver must turn on ___ ms after the center of the 180 degree pulse.

Back 34

7.5

Front 35

Which of the following is False regarding gradient echo?

Back 35

A gradient echo is the same as FID

Front 36

What are three true statements about gradient echoes?

Back 36

1. gradient echoes are not rephased by an RF pulse
2. gradient echo sequences are not the best choice for identifying metastatic lesions
3. gradient echo sequences generally have shorter TRs than spin echo sequences