Chapter 3 & 4 Flashcards
Spin-echo & gradient-echo pulse sequnces
The following are all part of a pulse sequence EXCEPT:
a. intervening time periods
b. maximum intensity projections
c. a series of RF pulses
d. gradient applications
b. maximum intensity projections
Which of the following is NOT true of spin echo pulse sequences:
a. very versatile
b. good image quality
c. true T2 weighting sensitive to pathology
d. scan times relatively short
d. scan times relatively short
In fast spin echo, scan time is reduced by:
a. filling more than one line of K space per TR
b. increasing the number of phase encodings
c. increasing the TR
d. increasing the NEX
a. filling more than one line of K space per TR
An Inversion Recovery pulse sequence can be which of the following:
a. T1 weighted
b. water suppressed
c. fat suppressed
d. all of the above
d. all of the above
The echoes collected around the effective TE in fast spin echo have the most impact on:
a. decreased signal amplitude
b. image contrast
c. image resolution
d. steep phase encoding slopes
b. image contrast
Which of the following is true regarding single shot fast spin echo (SS-FSE):
a. all the lines in K space are acquired in many TR periods
b. the SNR is increased
c. the SAR is increased
d. the SAR is decreased
c. the SAR is increased
Inversion recovery is a pulse sequence that begins with a:
a. 90 degree excitation pulse
b. 90 degree inverting pulse
c. variable excitation pulse
d. 180 degree inverting pulse
d. 180 degree inverting pulse
STIR is an important pulse sequence because it suppresses:
a. fat
b. water
c. blood
d. CSF
a. fat
The inversion recovery sequence FLAIR is especially useful in visualizing:
a. musculoskeletal structures
b. multiple sclerosis plaques
c. bone tumors
d. bone bruising
b. multiple sclerosis plaques
The time between the 180 degree pulse and the peak of the echo is the:
a. TR
b. TAU
c. TE
d. TAU/2
b. TAU
In a spin echo sequence TAU represents:
a. The time from the inversion pulse to the recovery pulse
b. The time from the excitation pulse to the echo
c. The time from the beginning of the excitation pulse to the phase encoding gradient
d. The time from the beginning of the excitation pulse to the 180 degree rephasing pulse
d. The time from the beginning of the excitation pulse to the 180 degree rephasing pulse
The 180 degree RF pulse in a spin echo sequence is used to:
a. Rephase the spinning nuclei
b. Dephase the spinning nuclei
c. Improve T1 contrast
d. Eliminate T2 information
a. Rephase the spinning nuclei
The Null point is:
a. the point at which there is no longitudinal magnetization in a tissue in an inversion recovery sequence
b. the point where K-space is filled with the steepest phase encoding gradient slopes
c. a technique that uses multiple coils to fill segments of K-space
d. a point where an 180 degree pulse is applied
a. the point at which there is no longitudinal magnetization in a tissue in an inversion recovery sequence
If a conventional SE takes 12 minutes to acquire, with all other factors remaining the same, an FSE using an ETL of 6 will take:
a. 1 minute
b. 2 minutes
c. 4 minutes
d. 6 minutes
b. 2 minutes
For FSEs acquired with long effective TEs, scan time can be reduced by selection of:
a. shorter ETL
b. longer ETL
c. ETL doesn’t affect scan time
d. Larger FOV
b. longer ETL
Which of the following best describes an FSE sequence?
a. a 90 degree pulse followed by a 180 degree pulse
b. a 180 degree pulse followed by a 90/180 degree pulse combination
c. a “train” of gradient echoes
d. a “train” of spin echoes
d. a “train” of spin echoes
Which of the following best describes an IR sequence?
a. a 90 degree pulse followed by a 180 degree pulse
b. a 180 degree pulse followed by a 90/180 degree pulse combination
c. a “train” of gradient echoes
d. a “train” of spin echoes
b. a 180 degree pulse followed by a 90/180 degree pulse combination
Which sequence is used to suppress signal from fatty marrow so that pathology in
musculoskeletal imaging can be seen clearly?
a. TAU
b. SSFP
c. FLAIR
d. STIR
d. STIR
Fat remains bright on T2 weighted images due to multiple RF pulses, which reduce the
effects of spin-spin interactions in fat called:
a. J coupling
b. J spacing
c. Z coupling
d. Z spacing
a. J coupling
The TI required to null the signal from a tissue is ____ times its T1 relaxation time.
a. 0.85
b. 0.41
c. 0.69
d. 0.31
c. 0.69
Which sequence is used to suppress CSF signal in T2 weighted images so that pathology adjacent to CSF is seen more clearly?
a. TAU
b. STIR
c. FLAIR
d. SSFP
c. FLAIR
In a fast spin echo pulse sequence, if the echo train length is increased by a factor of four, the scan will be:
a. One times as fast
b. Two times as fast
c. Three times as fast
d. Four times as fast
d. Four times as fast
In a fast spin echo sequence, the effective TE is the echo that is performed with the:
a. Outer views of K space
b. High amplitude phase encoding gradients
c. Low amplitude phase encoding gradients
d. First phase encoding steps
c. Low amplitude phase encoding gradients
In an IR pulse sequence, what TI will produce a STIR fat suppressed pulse sequence?
a. 100 - 175ms
b. 300 - 500ms
c. 500 - 800ms
d. 1700 - 2200ms
a. 100 - 175ms
TI in an IR pulse sequence, is the time interval between the:
a. 90 and 180 degree pulses
b. 90 degree pulse and the echo signal
c. 180 degree pulse and the echo signal
d. 180 and 90 degree pulses
d. 180 and 90 degree pulses
Driven equilibrium or DRIVE is a pulse sequence that:
a. is a specific type of fast spin echo
b. uses a reverse flip angle excitation pulse at the end of the echo train
c. has high signal of water and CSF when using a short TR
d. all of the above
d. all of the above
Which of the following is not a gradient echo pulse sequence:
a. steady state free precession
b. echo planar imaging
c. inversion recovery
d. incoherent gradient echo
c. inversion recovery
Gradient echo sequences allow for a reduction in the scan time as the TR:
a. is greatly reduced
b. is increased
c. is slightly increased
d. remains constant
a. is greatly reduced
Gradients that dephase are called:
a. degraders
b. spoilers
c. zero gradients
d. obsolete factors
b. spoilers
Gradients that rephase are called:
a. backtrackers
b. rewinders
c. backward gradients
d. reversers
b. rewinders
Gradient echoes can produce which kind of weighted images?
a. T2* only
b. T1, T2, PD only
c. T2, T1, T2, PD
d. T1, T2, PD only
c. T2*, T1, T2, PD
T1 weighting in gradient echoes uses a large flip angle.
a. True
b. False
a. True
Proton density weighting in gradient echoes uses a large flip angle.
a. True
b. False
b. False
Proton density weighted images are achieved by manipulating the TR and TE to remove any T1 and T2 weighting in gradient echoes.
a. True
b. False
b. False
Gradient echoes use:
a. Larger flip angles
b. Variable flip angles
c. 180 degree flip angles
d. 90 degree flip angles
b. Variable flip angles
One disadvantage of gradient echo imaging is there is no compensation for inhomogeneities in the magnetic field. The result is that:
a. T2* effects are not eliminated
b. T2* effects are eliminated
c. T2* effects are non-existent
d. T1 effects are eliminated
a. T2* effects are not eliminated
Which of the following best describes an EPI sequence?
a. a 90 degree pulse followed by a 180 degree pulse
b. a 180 degree pulse followed by a 90/180 degree pulse combination
c. a “train” of gradient echoes
d. a “train” of spin echoes
c. a “train” of gradient echoes
Balanced gradient echo sequences maintain the steady state using:
a. A 45 degree pulse followed by 180 degree pulses with alternating polarity
b. A 45 degree pulse followed by 90 degree pulses with alternating polarity
c. A 45 degree pulse followed by 270 degree pulses without alternating polarity
d. A 45 degree pulse followed by 90 degree pulses without alternating polarity
b. A 45 degree pulse followed by 90 degree pulses with alternating polarity
In a steady state GRE acquisition, the contrast weighting is:
a. T1 weighted
b. Based on the differences between relaxation rates of different tissues
c. T2* weighted
d. Weighted for the ratio of T1 to T2
d. Weighted for the ratio of T1 to T2
In the steady state, there is coexistence of both longitudinal and transverse magnetization.
a. True
b. False
a. True
Incoherent gradient echoes spoil residual transverse magnetization so that only transverse magnetization from the previous excitation is used.
a. True
b. False
a. True
There are two methods to achieve spoiling: RF spoiling and gradient rewinding.
a. True
b. False
b. False
Any two 90 degree RF pulses produce:
a. an FID
b. no signal
c. a Hahn echo
d. none of the above
c. a Hahn echo
Hybrid sequences, such as GRASE, contain:
a. gradient rephasing
b. RF rephasing
c. compromised image quality
d. both a and b
d. both a and b
In gradient echo pulse sequences, the FID is rephased by the:
a. 180 degree rephasing pulse
b. phase encoding gradient
c. frequency encoding gradient
d. 90 degree rephasing pulse
c. frequency encoding gradient
The following is true regarding coherent gradient echo sequences EXCEPT:
a. rewinders are used to keep residual magnetization in phase
b. the echo samples both the FID and stimulated echo
c. spoilers are used to dephase residual magnetization
d. mostly used with a long TE to produce T2* weighting
c. spoilers are used to dephase residual magnetization
Advantages of coherent gradient echo pulses include the following EXCEPT:
a. flow sensitive, good for angiography
b. fast scans, breath-holding possible
c. magnetic susceptibility increases
d. can be acquired in a volume acquisition
c. magnetic susceptibility increases
The following is true regarding incoherent gradient echo sequences EXCEPT:
a. gradient and RF rewinders are used
b. only the FID and not the stimulated echo is sampled
c. produces mainly T1 images
d. good SNR and anatomical detail in volume
a. gradient and RF rewinders are used
To maintain the steady state, flip angles are usually:
a. 30 to 45 degrees
b. 90 degrees
c. 90 to 110 degrees
d. 180 degrees
a. 30 to 45 degrees
Balanced gradient echo sequences utilize:
a. large flip angle, 90 degrees
b. short TR, 10ms to reduce scan time and flow artifact
c. long TE, 5-10ms to enhance T2*
d. all of the above
d. all of the above
Steady state free precession (SSFP) sequences produce information that is mainly:
a. T2*
b. T2
c. T1
d. Proton density
b. T2
