Pulse Sequence test
Which of the following pulse sequences allow tissues to relax over twice the dynamic range possible with SE pulse sequence?
IR
A gradient echo sequence in which any residual transverse magnetization is removed prior to the next excitation pulse is known as:
Incoherent
What is the term for the number of times data is collected with the same phase encoding gradient amplitude slope?
NEX or number of averages
The contrast of an image acquired with a T2-prepared fast gradient echo sequence is most similar to an image acquired with which of the following types of sequences?
fast spin echo
What function does the initial 180° RF pulse have in an IR pulse sequence?
flips the net magnetization into the negative longitudinal plane for greater TI relaxation range
In which of the following pulse sequences would you expect to find the shortest TR?
gradient echo
The highest amplitude signal is stored in which area of k-space?
on the central lines of k-space
The highest spatial resolution of the image is located where in k-space?
on the outer lines of k-space
What is it called when only half the area of the k-space is filled along the frequency axis?
partial averaging
In a fast spin echo sequence with an echo train of 12, how many RF pulses are applied for a given slice during one TR period?
0.
In a fast spin echo sequence with an echo train of 12, how many RF pulses are applied for a given slice during one TR period?
1
Which of the following may be T1 weighted:
1 & 2
The presence of random noise means that doubling the NEX increases the SNR by what factor? 1- square root of 2 2- 1.41 3- 2
1 2 3
What will be the effect of shortening the TE time? 1. increases signal-to-noise ratio (SNR) 2. increases the spin density contrast weighting 3. reduces contrast based on T2 relaxation times
1 2 3
What is 10 mT/m, the typical gradient strength, equal to in G/cm?
1 G/cm
Which of these statements are true regarding rephased GRE pulse sequences? 1- rephased GRE sequences preserve transverse signal 2- both longitudinal and transverse signals contribute to the next RF pulse 3- rephased GRE sequences increase T1 dependence
1 and 2 only
Which of these statements are true regarding rewound GRE pulse sequences? 1. rewound GRE sequences preserve transverse signal 2. both longitudinal and transverse signals contribute to the next RF pulse 3. rewound GRE sequences increase Tl dependence
1 and 2 only
Coherent, incoherent, and steady state free precession (SSFP) pulse sequences can be differentiated according to whether or not they use the FID or spin echo signals. Which statement is correct? 1- Coherent pulse sequences use a gradient reversal to rephase both the FID and the dephasing portion of the spin echo. 2- Incoherent pulse sequences use a gradient reversal to rephase both the FID and rephasing portion of the spin echo. 3- SSFP uses an RF pulse to initiate the rephrasing process and a rewinder to move the spin echo to occur before the RF pulse.
1 and 3 only
Which of these statements is true regarding spoiled GRE sequences? 1- spoils the transverse signal 2- increases T2* dependence 3- only longitudinal signals contribute to next RF pulse
1 and 3 only
Which of these statements is true regarding spoiled GRE sequences? 1. spoils the transverse signal 2. increases T2* dependence 3. only longitudinal signals contribute to next RF pulse
1 and 3 only
If the TR is reduced, how is the image quality affected? 1- SNR decreases. 2- T2 contrast increases. 3- Spin density weighting is increased.
1 only
Which of the following may be T1 weighted:
1, 2, & 3
T2* dephasing is caused by which of the following: 1. magnetic field inhomogeneities 2. susceptibility artifacts 3. spin spin interactions
1, 2, and 3
What will be the effect of shortening the TE time? 1- increases signal-to-noise ratio (SNR) 2- increases the spin density contrast weighting 3- reduces contrast based on T2 relaxation times
1, 2, and 3
f the TR is reduced, how is the image quality affected? 1. SNR decreases. 2. T2 contrast increases. 3. Spin density weighting is increased.
1. SNR decreases.
When using a spin echo pulse sequence if the echo forms at 20 ms, the 180 degree pulse must have been transmitted at:
10 ms
If you're running a FSE pulse sequence with an echo train length of 4, which of the following echoes should be placed closest to the center of K-space in order to acquire a T2 weighted image?
100 ms
Which of the following RF patterns best represents an inversion recovery pulse sequence:
180 - 90 - 180
An inversion recovery pulse sequence spin echo sequence begins with a:
180 degree RF pulse
What mechanism rephases the dephasing hydrogen nuclei in a SE sequence?
180° RF pulse
If a phase resolution of 256 is desired, and 1 NEX is selected, then the TR must be repeated:
192 times
If the shown pulse sequence was a fast spin echo sequence, how many lined of K space would be filled during each TR?
2
If a given spin echo pulse sequence takes 12 minutes to acquire, a fast spin echo sequence using an ETL of six, with all other factors remaining the same, will take:
2 minutes
What is the time interval between the 90° RF pulse and a subsequent 90° RF pulse applied to the same slice?
2 only
For a GRE pulse sequence with a 45° flip angle, what is the total power deposited per TR compared with a CSE pulse sequence?
25%
What is the steady state?
A condition where TR is shorter than the T1 & T2 times of the tissues
To produce the echo, a gradient echo pulse sequence uses
A gradient magnetic field only
Coherent, incoherent, and steady state free precession (SSFP) pulse sequences can be differentiated according to whether or not they use the FID or spin echo signals. Which statement is correct? 1. Coherent pulse sequences use a gradient reversal to rephase both the FID and the dephasing portion of the spin echo. 2. Incoherent pulse sequences use a gradient reversal to rephase both the FID and rephasing portion of the spin echo. 3. SSFP uses an RF pulse to initiate the rephasing process and a rewinder to move the spin echo to occur before the RF pulse.
3 only
If the TR is reduced, how is the image quality affected? 1- SNR decreases. 2- T2 contrast increases. 3- Spin density weighting is increased.
3 only
Place the following SE pulse sequence events in the correct order. 1. signal measurement 2. 180° RF pulse 3. 90° RF pulse
3, 2, 1
Place the following SE pulse sequence events in the correct order. 1- signal measurement 2- 180° RF pulse 3- 90° RF pulse
3,2,1
If you have a standard spin echo pulse sequence and the first 90 degree RF pulse occurs at 0 ms, and the 180 degree RF pulse occurs at 15 ms, when will the center of the echo occur?
30 ms
If a TSE/FSE pulse sequence has an echo train length of 32, how many lines of k-space will be filled per TR?
32
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 = 15 ms, and the center of the second echo forms at time = 90 ms. The 180 degree RF pulse to form the echo used for the T2 weighted image must have been applied at ______ ms.
52.5
Which of the following RF flip angles would result in the largest transverse component, assuming the net magnetization is initially in the longitudinal direction?
75 degree
What term describes the signal that follows the application of the initial 90° RF pulse?
FID
The gradient that is on during the production of the echo is the:
Frequency
Due to the decreased efficiency in refocusing spins, this pulse sequence is extremely sensitive to magnetic field homogeneity:
GRE
Which of these pulse sequences is the most "flow sensitive"?
GRE
What is the term for an echo formed by the application of two successive 90° RF pulses?
Hahn echo
What is the term for an echo formed by the application of two successive 90° RF pulses? What is the term for an echo formed by the application of two successive 90° RF pulses?
Hahn echo
Which of the following pulse sequences samples only the FID and is primarily used for T1 image weighting?
Inversion recovery pulse sequences
Phase encoding is performed:
Phase encoding is performed:
Due to the decreased efficiency in refocusing spins, this pulse sequence is extremely sensitive to magnetic field homogeneity
SE
____________ is NOT a characteristic of the steady state gradient echo pulse sequence.
Spin-spin interactions
If the TR of a gradient echo pulse sequence is considerably less than the T2 (and T2*), the condition that will exist is known as:
Steady State
RF spoiled pulse sequences produce ______ or _____ and demonstrate good anatomy.
T1 & PD
Flip angle controls the amount of _______________ and ________________ weighting
T1 & proton density
The peak signal strength of a spin echo is less than the initial strength of the FID because of _____
T2 relaxation
The peak signal strength of a spin echo is less than the initial strength of the FID because of ______.
T2 relaxation
What is the time interval between the 90° RF pulse and the first echo?
TE
In an IR pulse sequence, what is the term for the time between the initial 180° and the 90° RF pulse?
TI
The time between the initial 180 degree RF pulse and the 90 degree RF pulse in an IR pulse sequence is called the:
TI
What is the time interval between the 90° RF pulse and a subsequent 90° RF pulse applied to the same slice?
TR
What is the correct formula for determining the total scan time, in minutes, for a 3DFT image?
TR (sec) x Npe x NEX x Nslices/60 (sec)
The time from the 180 degree RF pulse to the 90 degree RF pulse can be called:
Tau time
In a fast spin echo sequence, the effective TE is the echo that is performed with:
The low amplitude phase encoding gradients
Which RF pulse series produces several true T2-weighted SE images with each TR?
a 90° RF pulse, a series of 180° RF pulses and the collection of echoes
Which of the following statements is FALSE regarding a gradient echo sequence?
a long TE improves the T1 contrast
What do spin density images measure?
a subset of all protons in fat and water molecules
Changing the TR will directly affect which of the following?
acquisition time
Which of these statements is NOT true regarding steady state?
all of the above are true statements
Regarding T2 and T2*, which of the following effects is compenstated for by the 180 degree RF pulse?
all the above
If the TI of an inversion recovery pulse sequence is selected so that the magnetization 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?
dark
Which of the following statements is FALSE?
gradient echoes are not rephased by a RF pulse
What is the image quality result on SE images if the TE is lengthened?
increases the contrast based on the T2 of the tissues
What is the image quality result on SE images if the TE is lengthened?
increases the contrast based on the T2 of the tis¬sues
Using flip angles of 10° or less in a GRE pulse sequence will result in what effect on the image?
less SNR
Gradient recalled echo (GRE) pulse sequences are accomplished using the following events:
less than 90° RF pulse, gradient reversal
What parameters are used to create spin echo (SE) T2-weighted images?
long TE and long TR
hat parameters are used to create spin echo (SE) T2-weighted images?
long TE and long TR
A long TR msec (3000 msec or greater) and a short TE (shorter than 40 msec) would acquire an image that would produce which type of image contrast?
not T 2 weighted
In a CSE pulse sequence, a 90° RF pulse is followed by a 180° RF pulse. How much more power does it take to de liver a 180° RF pulse compared with the 90° RF pulse?
not all of the above or
The 180 degree RF pulse that follows the initial 90 degree pulse in a spin echo sequence will cause the NMR signal to reappear while correcting for:
not chemical or all the above
What type of pulse sequence begins with a 90° RF pulse and is immediately followed by the collection of the echo?
partial saturation
What are the additional RF pulses called that are used to saturate out hydrogen nuclei prior to excitation?
presaturation
Where in the pulse sequence are presaturation pulses usually placed?
prior to the excitation pulse
In a FSE pulse sequence, a 90° RF pulse is followed by a 180° RF pulse. How much more power does it take to deliver a 180° RF pulse compared with the 90° RF pulse?
quadruple
What is a way to reduce the scan time without directly affecting image contrast?
reduce the number of phase encodings (Npe)
In a GRE sequence, if the flip angle is lowered while holding the TR constant, which of the following would be reduced?
saturation
Which of the following is NOT rephased by the 180 degree RF pulse in a standard spin echo pulse sequence?
spin spin interactions
In a CSE pulse sequence, the 180° RF pulse flips the net magnetization 180 degrees into the opposite direction. In a GRE pulse sequence, what effect does a gradient reversal have on net magnetization?
spins that have slowed down speed up, and vice versa, allowing remaining net magnetization to rephase
Which of the following pulse sequences uses the least amount of RF energy?
spoiled gradient echo
Which of the following is NOT a characteristic of the spoiled gradient echo pulse sequence?
steady state transverse magnetization following the formation of the echo
In a spin echo pulse sequence, what is the term for the time between the 90° RF pulse and the 180° RF pulse? 1- TE 2- tau 3- TE/2
tau
What is the term for the time from the excitation pulse to the refocusing pulse and from the refocusing pulse to the echo?
tau time
Why are presaturation pulses useful?
to reduce flow artifacts
To acquire a set of T1 weighted images, the spoiled gradient echo sequence __________ work and the steady state gradient echo sequence _______ work.
would, would not
