Test 2 Flashcards
What is the readout gradient is also known as?
a. RF encoding gradient
b. Frequency encoding gradient
c. Phase encoding gradient
d. Slice select gradient
B
What is the center of the bore in all planes is known as?
a. Claustrocenter
b. Hypercenter
c. Isocenter
d. Hypocenter
C
When does the frequency encoding gradient turn on in a CSE pulse sequence?
a. Between the 90º and 180º pulses
b. During the 90º and 180º pulses
c. During the FID
d. During the spin echo
D
What is the range of frequencies sampled during the read out gradient (sampling window) known as?
a. Spatial encoding
b. Spin echo
c. Transmit bandwidth
d. Receive bandwidth
D
In general, what do small FOVs and thin slices require?
a. Steep gradients
b. Short TRs
c. Wide bandwidths
d. Long RF pulses
A
During the scan, where is data stored?
a. Hard drive
b. k-Space
c. Chest of drawers
d. Spin echo
B
What is the mathematical process that converts frequency amplitudes from the time domain to the frequency domain in order to locate them spatially?
a. FID
b. Fast Fourier Transform
c. Readout gradient
d. k-Space
B
What determines which line of k-space get filled?
a. k-Space gradient
b. Slice select gradient
c. Readout gradient
d. Phase encoding gradient
D
Data in the outer lines of k-space contribute to ________ information.
a. Signal and contrast
b. Distal pixels
c. Resolution
d. T1 or T2
C
A single data point of k space contains information from the entire slice.
True
False
T
FLAIR is a fast IR sequence that nulls signal from what tissue?
a. White matter
b. Water/CSF
c. Fat
d. Muscle
B
In order to null the signal from a tissue using an IR sequence, the TI must be what?
a. at the larmor frequency
b. 0.69 times the T1 time of the tissue
c. 0.69 times the T2 time of the tissue
d. In steady state
B
What pulse sequence is a 90º pulse followed by a 180º pulse?
a. FIESTA
b. SSFSE
c. CSE
d. FSE
C
In a Fast/Turbo spin echo sequence, data from echoes farther away from the effective TE will be placed where?
a. In a shallow readout gradient
b. In noise
c. In the central lines of K space
d. In the outer lines of K space
D
A sequence that uses a reverse flip angle at the end of the echo train to restore residual transverse magnetization into the longitudinal plane is known as what?
a. Single Shot Fast Spin Echo/SSFSE/HASTE
b. FIESTA/Balanced gradient echo
c. Incoherent Gradient Echo/SPGR
d. DRIVE/FR-FSE/Driven equilibrium Fourier transform
D
Which inversion recovery sequence has the shortest TI?
a. FSE
b. FLAIR
c. STIR
d. SSFSE
C
What is TI?
a. Time from 180º inversion pulse to the 90º excitation pulse
b. Time from the 90º excitation pulse to the 180º rephasing pulse
c. Time from 90º inversion pulse to the 90º excitation pulse
d. Time from 90º excitation pulse to the 180º inversion pulse
A
What is Tau?
a. Time from 180º inversion pulse to the 90º excitation pulse
b. Time from the 90º excitation pulse to the 180º rephasing pulse
c. Time from 90º inversion pulse to the 90º excitation pulse
d. Time from 90º excitation pulse to the 180º inversion pulse
B
What is TE?
a. Time from 180º inversion pulse to the 90º excitation pulse
b. Time from the 90º excitation pulse to the 180º rephasing pulse
c. Time from 90º inversion pulse to the 90º excitation pulse
d. Time from 90º excitation pulse to the peak of echo
D
Increasing ETL will result in
I. Increased T1 weighting
II. Reduced scan time
III. Increased heating
a. II and III
b. I and II
c. I and III
d. I, II, and III
A
The technologist selects a TR of 600ms and a TE of 30ms for a CSE sequence. What weighting should they expect?
a. T1
b. T2
c. Diffusion
d. PD
A
How does a CSE pulse sequence compensate for T2*?
a. Long TR
b. Two rephasing pulses
c. Short TR
d. 180º rephasing pulse
D
What pulse sequence acquires all lines of k-space in one TR using FSE in combination with partial averaging?
a. CSE/FSE
b. SSFSE/HASTE
c. FRFSE/DRIVE
d. STIR/FLAIR
B
What changes during every 180° rephasing echo in a Fast/Turbo spin echo?
a. Phase encoding gradient
b. Effective TE
c. Center frequency
d. Phase direction
A
What occurs when a gradient is applied to B0?
a. The precessional frequencies of H increases at one end and decreases at the other
b. T2 weighting increases
c. T2 weighting decreases
d. Resonance occurs as long as it is at the Larmor frequency
A
GRE pulse sequences have more T2* than SE.
True
False
T
A pulse sequence with a TR of 50ms, a TE of 5ms, and a flip angle of 70 would result in what weighting?
PD weighting
T2* weighting
T2 weighting
T1 weighting
T1
In general, GRE pulse sequences are faster than SE.
True
False
T
With a short TR, what determines the optimum flip angle to give the highest signal for a tissue?
a. Larmor equation
b. DRIVE
c. Steady State
d. Ernst angle
D
What processes affect weighting in GRE?
a. All of the above
b. Flip angle
c. Steady State
d. Residual transverse magnetization
A
What is the difference between SE and GRE
I. GRE has a variable flip angle II. SE uses a 180º rephasing pulse
III. GRE uses a rephasing gradient.
a. I, II, and III
b. I and III
c. II only
d. II and III
A
In incoherent gradient echo, the spoilers can be ____.
a. Only RF pulses
b. Only gradients
c. Frequency modulation
d. Gradient or RF pulses
D
Decreasing pixel size will increase resolution.
True
False
T
The technologist doubles the NEX. What happens to SNR?
I. The SNR doubles II. The SNR increases by √2 III. The SNR increases by 1.4
a. II and III
b.I only
c. II only
d. II and III
A
What results when slice thickness is increased?
a. Decreased SNR
b. Increased partial voluming
c. Increased chemical shift
d. Decreased coverage
B
Doubling NEX will double scan time.
True
False
T
Coil placement and selection is important for image quality
True
False
T
What results when FOV is increased?
I. SNR increases
II. Resolution decreases
III. Coverage increases
a. II and III
b. I and III
c. I, II, and III
d. I and II
C
What results when receiving bandwidth increases?
I. Resolution increases II. Minimum TE decreases III. SNR decreases
a. II and III
b. I, II, and III
c. III only
d. I and III
A
which of the following pulse sequences does not use a 180 refocusing RF pulse
a. spin echo
b. gradient echo
c. inversion recovery
d. fast spin echo
B
What does STIR stand for?
a. sequence time in relaxation
b. safe time in recovery
c. short tau inversion recovery
d. soft tune inversion RF
C
the highest signal amplitude is stored in which area of space
a. central line
b. outer line
c. top half
d. bottom half
A
what do data near periphery of kspace determine?
a. contrast
b. details and resolution
c. weighting
d. slice thickness
B
a long TI required for which pulse sequence
a. STIR
b. FLAIR
c. CSE
d. DRIVE
B
what determines the number of lines of k-space
a. phase matrix
b. phase encoding gradient
c. frequency matrix
d. frequency encoding gradient
A
What is the term for the number of times data is collected with the same phase encoding gradient slope?
a. TR
b. NEX/NSA
c. frequency matrix
d. Receive bandwidth
B
adjust which parameter will have smallest effect on scan time
a. TR
b. TE
c. NEX/NSA
d. slice thickness
e. phase matrix
D
increasing what parameter will increase SNR?
a. TR
b. frequency matrix
c. TE
d. slice gap
A
increasing bandwidth will affect all of the following except:
a. decrease chemical shift
b. decrease SNR
c. decrease resolution
d. decrease minimum TE
C
decreasing slice thickness will result in all of the following except
a. decrease SNR
b. decrease coverage
c. decrease resolution
d. increase partial voluming
D
what GRE pulse sequence use oscillating readout gradient to produce a train of echo
a. Fast GRE
b. EPI
c. FIESTA
d. FSE
B
doubling NEX will double __
a. scan time
b. SNR
c. resolution
d. T1-W
A
what is gradient amplitude
rate of change of mag field strength
___ gradient amplitude will have big differences in frequencies
a. steep
b. shallow
A
what is purpose of gradient axes
spatially locate signal along 3 gradients
what determine slice thickness ? (2)
slope of gradients
range of frequencies (transmit bandwidth)
to achieve thin slice we need ___ & ___
steep slope and narrow transmit bandwidth
what is sampling window
amount of time the frequency encoding gradient is turned on
sampling interval has a ____ relationship with digital sampling frequency
inverse
sampling interval = ____/___
sampling window (s)
sampling frequency (Hz)
incorrect frequency sampled is due to ____ which lead to artifact called ___
sampling frequency < Nyquist frequency
aliasing
sampling frequency > Nyquist frequency = ____
more noise
time insufficient
Receive bandwidth = ____ because both has 2 x Nyquist frequency
sampling frequency
to achieve small fFOV, we need ____
steep frequency encoding gradient
data in COLUMN determine ___ in ____ direction
size of FOV
phase
data in ROW determine ___ in ____ direction
size of FOV
frequency
duration of ____ affect minimum TE
sampling window
phase FOV expressed as ____
% of frequency FOV
what is frequency matrix
Number of pixels in frequency direction
phase FOV is used in ____ , ____, ____
rectangular FOV
antialiasing
parallel imaging
what determine frequency matrix
amount of time signal is sampled
duration of sampling window affect___
minimum TE
what happened when phase encoding gradient is ON
affect frequency of magnetic moments
what happened when phase encoding gradient is OFF
frequency back to normal & phase position remains
phase encoding gradient can be used to avoid ___
aliasing/wrap
what is phase matrix
number of time phase encoding is turned on
high amplitude signal = ____
which location in k-space
decrease resolution
central
low amplitude signal = ___
which location in k-spce
increase resolution
outer
2D scan time = _____ x ____ x_____
phase matrix
TR
NEX/NSA
what is needed to create a large change in phase
steep slope
small pixel = _____ phase encoding gradient
steep
steep phase encoding fill ___ lines
outer
shallow phase encoding fill ___ line
central
we can take advantage of which fact abt k-space to reduce scan time
conjugate symmetry
how pulse sequence fill k-space
- Bss pick an area of k-space
- phase encoding pick which line of k-space to fill
- frequency encoding determine how each line is filled
what determine how each line of k-space is filled
frequency encoding
what are the options to fill k-space
- partial averaging
- partial echo
- parallel imaging
4 . single shot
5.spiral k-space - acquisition
- propeller/BLADE
which options only fill half of k-space and has symmetrical top and bottom
1. partial averaging
2. partial echo
3. parallel imaging
4 . single shot
5.spiral k-space
6. acquisition
7. propeller/BLADE
1
which option allow central line to get sample first
1. partial averaging
2. partial echo
3. parallel imaging
4 . single shot
5.spiral k-space
6. acquisition
7. propeller/BLADE
5
which option fill many lines per TR and require special coil
1. partial averaging
2. partial echo
3. parallel imaging
4 . single shot
5.spiral k-space
6. acquisition
7. propeller/BLADE
3
which option fill all data in k-space in a single TR with echo train
1. partial averaging
2. partial echo
3. parallel imaging
4 . single shot
5.spiral k-space
6. acquisition
7. propeller/BLADE
4
which option has symmetrical echo that doesnt need to sample
1. partial averaging
2. partial echo
3. parallel imaging
4 . single shot
5.spiral k-space
6. acquisition
7. propeller/BLADE
2
which option sample center every TR but has long scan time and reduce resolution
1. partial averaging
2. partial echo
3. parallel imaging
4 . single shot
5.spiral k-space
6. acquisition
7. propeller/BLADE
7
FFT converts ____ from the __ domain to the ____ domain
frequency amplitude
time
frequency
low amplitude signal generated ___
steep phase gradient + large phase change
For nyquist theorum, what must be sampled and how many times for accuracy
highest frequencies
twice
each chest = ___
slice in the image
Number of chests = ___
Number of slice
each drawer = ____ of k-space
line
each sock = ___
data point
what determine what data to put in which line
frequency coding gradient
the number of data point is determined by ____
frequency matrix
Thru ADC, echo received at time ___ is digitized
TE
amplitude is to figure out _____
if a pixel is bright or dark
frequency is to figure out ____
which pixel
what is spatial encoding
calculate how much signal from each voxel
SE use a ___ pulse to rephase echo
180
CSE give ____ weighting
True T2
pattern for CSE
1. 90-180
2. 90-180-180-180-
3. 180-90-180-180-
1
pattern for FSE
1. 90-180
2. 90-180-180-180-
3. 180-90-180-180-
2
FSE use ____ and has ____
while EPI use ___ & ___
ETL
effective TE
RF pulse and oscillating readout gradient
DRIVE use _____ pulse
reverse flip pulse
IR sequence use ____
TI
pattern for IR
1. 90-180
2. 90-180-180-180-
3. 180-90-180-180-
3
what pulse sequence is 90-180
CSE
what pulse sequence is 180-90-180-180-
IR
what pulse sequence is 90-180-180-180-
FSE
STIR has ____ TI
short
why STIR need a short TI
T1 time of fat is shorter than water
FLAIR has ____ TI
long
which pulse sequence null signal from fat
1. STIR
2. FLAIR
3. DIR
4. TIR
1
which pulse sequence null signal from BLOOD
1. STIR
2. FLAIR
3. DIR
4. TIR
3
which pulse sequence null signal from WATER
1. STIR
2. FLAIR
3. DIR
4. TIR
2
which pulse sequence add another inversion pulse to null signal from FAT AND BLOOD
1. STIR
2. FLAIR
3. DIR
4. TIR
4
what is the null point of fat
0.69 x T1 time
what is the definition of null point
time it takes a certain tissue to recover from full inversion to the transverse plane
