Chapter 5 Flashcards
Parallel imaging is usually used to increase resolution or decrease scan time. (T or F)
true
What do T1 images typically best demonstrate?
Anatomy
What does STIR stand for? Short ___ Inversion Recovery.
tau
SSFP sequences usually produce images that are ___ weighted.
T2
What are the advantages of propeller K Space filling?
Rapid imaging, increased SNR and CNR, reduced motion artifact.
Which sequence is considered the gold standard for MR imaging
Spin Echo
How is time reduced in fast spin echo?
Use a turbo factor, Use an echo train
What is Double IR prep used to accomplish?
Used to null blood for cardiac imaging
What type of echoes are sampled during SS-FSE?
Spin echoes
What artifact can occur as a result of using long echo trains?
Image Blurring
When would we be most likely to use a FLAIR sequence?
Head or spine studies (to look for periventricular lesions)
Which Fast Inversion Recovery sequence(s) do we often use?
FLAIR, STIR
What is the approximate T1 relaxation time of fat at 1T?
200 ms
Which of the following statements is true in an incoherent gradient echo sequence?
The system discriminates between residual and the most recently created transverse magnetization because it has a different phase value
look at q 16 (quiz)
_
look at q 14 (quiz)
_
How is K space filled in Fast Gradient Echo Sequences?
Keyhole filling,
Centric filling
When would we be most likely to use a STIR sequence?
MSK studies (i.e. knee, wrist)
Spin echo pulse sequences are classified according to whether the residual transverse magnetization is in phase (coherent) or out of phase (incoherent). (T or F)
False
GRADIENT ECHO sequences are classified according to whether the residual transverse magnetization is in phase (coherent) or out of phase (incoherent). See page 167 in the text for more information.
What is the approximate T1 relaxation time of CSF at 1T?
2000 ms
In which of the following sequences is all the transverse magnetization rewound at the end of each TR period?
Coherent gradient echo
An inversion recovery pulse sequence begins with which of the following?
180 degree inverting pulse
FLAIR stands for Fluid Low Attenuation Inversion Recovery
T or F
False
FLAIR stands for Fluid Attenuated Inversion Recovery
STIR sequences should NOT be used in conjunction with contrast enhancement. (T or F)
True
STIR sequences should NOT be used in conjunction with contrast enhancement, which shortens the T1 times of enhancing tissues, making them bright. The T1 times of these structures are shortened so that they approach the T1 time of fat. In a STIR sequences therefore, enhancing tissue may also be nulled. See page 158 in the text for more information.
During EPI all the lines of K space are filled during one repetition. (T or F)
true
Using a long echo train decreases the SAR. (T or F)
False
Using a long echo train significantly increases the SAR by applying so many successive 180 degree pulses. See page 150 in the text for more information.
look at q 1, 2, 9, (study guide)
_
what order is centric filling in K space
center lines first, outer last
what order is keyhole filling in K space
outer first, center after contrast injection
what order is EPI k space filling
readout gradient switches from pos to neg, phase polarity does not change
what order is spiral k space filling
readout and phase both switch polarity
Generally speaking, gradient echo sequences are faster than spin echo sequences. (T or F)
true
Which pulse sequence is the gold standard?
spin echo
What are the two fast inversion recovery sequences that we often use?
STIR. Nulls the signal from fat.
FLAIR. Nulls CSF.
what are the uses of STIR
musculoskeletal
what are uses for FLAIR
periventricluar lesions
coherent gradient echo
rewinding. transverse is rewound at end of each TR
incoherent gradient echo
spoilers. differentiates between residual and most recently created transverse magnetization
which is True T2* - angiographic, myelographic or arthrographic effect
coherent gradient echo
which demonstrate T1 anatomy and pathology and after gadolinium?
incoherent gradient echo
During which k-space filling are lines filled as a block and rotated about the central axis of k-space, decreasing scan time, increasing the SNR and decreasing motion?
propeller
Which of the following describes a “steady state” in MRI?
Created when the TR is shorter than the relaxation time of tissues. Energy “in” by the FA = energy “out” during the TR
Residual builds in the transverse plane
resultant image is a ratio of T1 to T2
What is used to rephase the FID in gradient sequences?
a gradient
Which type of imaging fills multiple lines of k-space per TR by assigning lines of k-space to coils coupled together, thus acquiring data simultaneously.
Parallel imaging. Can be used to reduce scan time or improve resolution.
What does this statement describe?
As the area of the gradient under the line equals that above the line, moving spins accumulate a zero change as they pass along the gradients.
balanced gradient system
double IR prep
black blood
triple IR prep
nulls fat and blood
RF spoiling
only info from the most recently created magnetization to affect image contrast
gradient spoiling
residual magnetization is dephase so it is incoherent at beginning of next repition
advantage of spin echo
good quality, true T2
disadvantage of spin echo
long scan times
T1 most useful to
demonstrate anatomy
T2 most useful to
demonstrate pathology
effective TE
weighting in fast spin echo bc echoes are generated at different TE times
T2*
always present to some degree
True T2
steady state free precession (SSFP)
Relaxation times of water
2500 ms (for T1 and T2 times)
relaxation T1 time of fat
200 ms
relaxation T2 time of fat
100
relaxation T1 time of CSF
2000 ms
relaxation T2 time of CSF
300 ms
Which pulse sequence are classified according to whether the residual transverse magnetization is in-phase (coherent) or out-of-phase (incoherent)?
gradient
___: Partial Fourier + fast spin echo. Half the lines are acquired and half are transposed. Reduces SAR but has SNR penalty.
single-shot fast spin echo
