MRI Physics 3 Flashcards
Why is EPI the sequence of choice for functional MRI
a. High SNR
b. high resolution
c. ultra fast sequence
d. all of the above
c. ultra fast sequence
In Gradient Recalled Echo (GRE) the main reason for using partial flip angles is to
a. lower TE
b. Lower TR
c. increase SNR
d. b and c
b. lower TR
the Flow Related Enhancement Effect (FRE) is associated with which pulse sequence
a. GRE
b. EPI
c. SE
d. FSE
a. GRE
In an FSE sequence as the echo train length of turbo factor increases, the number of slices per TR
a. decreases
b. increases
c. stays the same
d. depends on the flip angle
a. decreases
Magnetization Transger (MR) suppresses signal from
a. protein bound water
b. protein bound fat
c. free water
d. free fat
a. protein bound water
MRI signal data placed in outer edges of K space has a greater effect on
a. image contrast
b. image spatial resolution
c. image SNR
d. b and c
b. image spatial resolution
Which kind of scan uses the B parameter with units [s/mm^2]
a. diffusion
b. perfusion
c. a and b
d. none of the above
a. diffusion
A short TE time in a GRE sequence is typically
a. less than 10 ms
b. 15-25 ms
c. 30-40 ms
d. none of the above
a. less than 10ms
The TI required to null the signal from a tissue in an IR sequence is given by
a. .37T1
b. .63T1
c. .69 T1
d. T1
c. .69 T1
T1 weighted images are generally useful for demonstrating anatomy in MRI because they have a high SNR. T2 weighted images are generally useful for demonstrating pathology because
a. they have a low SNR
b. the TR is long
c. diseased tissue is accompanied by edema
d. none of the above
c. diseased tissue is accompanied by edema
If the spacing between the echoes (ESP) in the FSE echo train is reduced from a time of 15ms to 10ms, then the contrast blurring will be
a. decreased
b. the same
c. increased
d. b or c
a. decreased
The TE time in a GRE sequence is measured from the start of the RF pulse to
a. the starting time of the dephasing gradient
b. the midpoint time of the dephasing gradient
c. the starting time of the rephasing gradient
d. the midpoint time of the rephasing gradient
d. the midpoint time of the rephasing gradient
For balanced gradient lobes, what must be equal
a. gradient amplitude
b. gradient time
c. (gradient amplitude) x (gradient time)
d. all of the above
c. (gradient amplitude) x (gradient time)
If Gmax is the maximum gradient and Tr is the rise time, then the slew rate SR is given by
a. SR=Gmax x Tr
b. SR=Gmax/Tr
c. SR=Tr/Gmax
d. none of the above
b. SR = Gmax / Tr
reversing the phase encoding gradient after readout in a coherent gradient echo is a process known as
a. spoiling
b. rewinding
c. blipping
d. fractional echo
b. rewinding
If the ETL or TF for a FSE sequence is 4, how much faster would the FSE sequence be compared to a similar CSE sequence
a. 2
b. 4
c. 16
d. none of the above
b. 4
In a dual echo FSE scan with ETL = 8, using the first four echoes for a PD image and the last four echoes for a T2W image would be an example of what method
a. Full Echo Train
b. Split Echo Train
c. Shared Echo
d. none of the above
b. Split Echo Train
Which of the following statements about EPI are true
I. EPI uses gradient blipping to fill K space
II. the weighting of EPI images is given by an effective TE
III. EPI imaging is often used for fMRI
a. I only
b. I and III only
c. II and III only
d. I II and III only
d. I II and III
A SE produced by 2 90deg RF pulses is called
a. CSE
b. Hahn Echo
c. stimulated Echo
d. b and c
d. b and c
Incoherent GRE sequences can use
a. RF spoiling
b. gradient spoiling
c. a and b
d. none of the above
c. a and b
In a dual SE sequence, the weighting of the image associated with the first echo is
a. PD weighting
b. T1W
c. T2W
d. a or c
a. PD Weighting
To achieve full recovery of the longitudinal magnetization in a FLAIR sequence, the TR should be
a. 400-800ms
b. 2000+ms
c. 6000+ms
d. none of the above
c. 6000+ms
fMRI uses a rechnique knows as
a. FLAIR
b. STIR
c. BOLD
d. SSFSE
c. BOLD
The central park of K space conrols ____, while the peripheral part of K space controls ____.
a. image contrast, spatial resoluion
b. spatial resolution, image contrast
c. image window, image level
d. image level, image window
a. image contrast, spatial resolution
In order to rewind a gradient, what factor must be balanced between positive and negative gradient lobes
a. amplitude * rise time
b. amplitude * gradient time
c. slew rate * rise time
d. slew rate * gradient time
b. amplitude * gradient time
The percentage of time during a TR period that a gradient is at maximum amplitude is known as
a. rise time
b. slew rate
c. gradient balance
d. duty cycle
d. duty cycle
A typical rise time for gradients on high field MRI systems is several hundred
a. picoseconds
b. microseconds
c. milliseconds
d. seconds
b. microseconds
The gradient coils are powered by the
a. RF amplifiers
b. RF coils
c. gradient amplifiers
d. none of the above
c. Gradient amplifiers
SSFSE is an acquisition that
a. fills multiple lines of K space in one TR
b. is acquired in one TR
c. can fill half of K space and transpose the other half
d. all of the above
d. all of the above
In IR pulse sequences, what is the proper ordering of the initial two RF pulses
a. 90, 90
b. 90, 180
c. 180, 90
d. 180, 180
c. 180, 90
Which MRI images are acquired to diagnose stroke after onset of symptoms
a. T1W
b. T2W
c. PD
d. Diffusion Weighted
d. Diffusion Weighted
Partial Saturation pulse sequence have what kind of MRI contrast weighting
a. T1W
b. T2W
c. PD
d. T1/T2W
a. T1W
If after a sequence of RF pulses, the longitudinal magnetization is Mz= 0 then we say that Mz is
a. saturated
b. partially saturated
c. unsaturated
d. fully magnetized
a. saturated
Saturation REcovery pulse sequences have what kind of MRI contrast weighting
a. T1W
b. T2W
c. PD
d. T1/T2W
c. PD
In a 2D CSE sequence, what is the slice select gradient turned on?
I. During the 90deg pulse
II. During the 180 deg Pulse
III. During the Phase Encode gradient?
a. I only
b. I and II only
c. I and III only
d. I II and III only
b. I and II only
For breath hold T1W imaging, which sequence would be the best choice?
a. Coherent GRE
b. Incoherent GRE
c. CSE
d. All of the above
b. Incoherent GRE
Magnetization Transfer Contrast (MTC) is what kind of technique?
a. spatial saturation
b. spectral saturation
c. inversion recovery
d. driven equilibrium
b. spectral saturation
If the equilibrium value of the longitudinal magnetization Mz = M0 then what value would the longitudinal magnetization of a tissue have at the null point
a. Mz = 0
b. Mz = .693 M0
c. Mz = M0
d. none of the above
a. Mz = 0
IR pulse sequences can produce MR images that are strongly ___
a. T1W
b. T2W
c. PD
d. T1/T2W
a. T1W
A fast FLAIR combines which two pulse sequences
a. CSE and IR
b. FSE and IR
c. GRE and IR
d. FSE and GRE
b. FSE and IR