MRI Physics 3 Flashcards by Elad Nevo

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

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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

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the Flow Related Enhancement Effect (FRE) is associated with which pulse sequence

a. GRE
b. EPI
c. SE
d. FSE

a. GRE

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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

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Magnetization Transger (MR) suppresses signal from

a. protein bound water
b. protein bound fat
c. free water
d. free fat

a. protein bound water

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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

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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

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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

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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

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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

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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

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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

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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)

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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

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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

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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

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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

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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

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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

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Incoherent GRE sequences can use

a. RF spoiling
b. gradient spoiling
c. a and b
d. none of the above

c. a and b

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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

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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

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fMRI uses a rechnique knows as

a. FLAIR
b. STIR
c. BOLD
d. SSFSE

c. BOLD

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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

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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

Which transverse dephasing effect cannot be removed by the SE pulse sequence a. Spin lattice coupling b. spin spin coupling c. magnetic inhomogeneity dephasing d. none of the above

b. spin spin coupling

which sequence tends to have the higher SNR a. GRE b. CSE c. EPI d. b and c

b. CSE

Interventional MRI is usually performed with a. superconducting magnets b. open magnets c. a and b d. none of the above

b. open magnets

not including the dephasing lobe, for how long is the readout gradient turned on during a single phase encoding step a. BW = receiver bandwidth b. 1/BW c. Ts = sample time d. b and c

c. Ts = sample time

what effectively limits teh length of the Echo Train in a FSE sequence a. T1 decay b. T2 decay c. T2* decay d. b and c

b. T2 decay

If ETL is the echo train length, then the scan time for CSE compared to FSE is a. CSE = FSE x ETL b. CSE = FSE x ETL ^1/2 c. CSE = FSE/ETL d. CSE = FSE/ ETL^1/2

a. CSE = FSE x ETL

If one cannot obtain enough coverage for a FSE T2W scan in a single acquisition then the proper action is to a. take two acquisitions b. adjust TR c. adjust TE d. a and b

b. adjust TR

A long ETL (e.g. ETL = 16) would probably be associated with which kind of scan? a. T1W b. T2W c. PD d. a and c

b. T2W

In order to increase SNR while maintaining resolution in a FSE scan which parameter should be adjusted a. TR b. TE c. Ny d. NEX

d. NEX

What is the main advantage of 3D FSE scans compared to 3D GRE scans a. 3D FSE Faster b. 3D FSE has higher spatial resolution c. 3D FSE can produce T2W images d. all of the above

c. 3D FSE can produce T2W images

if TR = 400ms for a GRE scan, thsi would be a ____ TR a. short b. medium c. long d. cannot say depends on steady state magnetization

c. long

In order to enhance T1W in a GRE scan which FA would be the best choice a. 90 b. 45 c. 10 d. none of the above T1W does not depend on FA

a. 90

compared to CSE on FSE images with PD contrast what will CSF look like a. brighter b. same c. darker d. b or c

a. brighter

Which of the following are true statements about coherent gradient echoes I. they are T2* weighted II. they have dark fluid MRI signals III. they have low susceptibility artifacts a. I only b. II. I and II only c. III only d. I II and III

a. I only

In order to resent the phase to zero before the next phase encoding in a 3D scan one must insert ___ gradients into the pulse sequence a. Slice Selective b. Crusher c. Rewinder d. Spoiler

c. Rewinder

what must be accomplished in a GRE pulse sequence before performing readout a. Phase encoding b. phase rewinding c. spoiling d. none of the above

a. phase encoding

if TR = repetition time, Ny = # phase encodes, Nz = # slice encodes, and NEX = # of excitations, then the scan time for a 3D GRE scan is a. TR*Ny*NEX b. TR*Ny*Nz*NEX* #Slices c. TR*Ny*Nz*NEX d. TR*Nz*NEX

c. TR*Ny*Nz*NEX

Consider a 2D GRE scan that is not MP. Suppose that the TR = 50ms, TE= 25ms, FA = 15deg, Ny = 256, NEX = 4 #Slices = 20. what is the scan time. a. 128s b. 256s c. 512s d. 1024s

d.1024s

If TE =25ms for a GRE scan this would be a ____ TE a. short b. medium c. long d. can't say depends on steady state magnetization

c. long

Which effects are larger in FSE compared to CSE I. Magnetic susceptibility II. Magnetization transfer III. Image Contrast Blurring a. I only b. II only c. II and III only d. I II and III

c. II and III only

The scan time in FSE is reduced compared to taht on CSE by a. using a dual echo to obtain two images b. filling more than one line of K space per TR c. performing more than one phase encoding step per TR d. b and c

d. b and c

After the initial RF excitation pulse, if TE = 11.25ms at a static field of 1.5T then the fat and water transverse magnetization verctors are a. in phase b. out of phase c. in and out of phase d. none of the above

b. out of phase

Unlike standard GRE, SSFP can produce _____ image contrast, using small FAs and small TRs a. T1W b. T2W c. PD d. T2*W

b. T2W

Which method(s) use the top/bottom symmetry of K space I. 1/2 NEX II. 1/2 Fourier III. partial echo a. I only b. I and II only c. III only d. I II and III

b. I and II only

The driven equilibrium (DE) magnetization preparation sequence can allow for more T2W contrast if what initial tissue preparation pulse sequence is used a. 180 b. 90-180 c. 90-180-90 d. none of the above

c. 90-180-90

Which sequence permits dynamic imaging with contrast in a single breath hold a. GRE b. IR c. SE d. Fast GRE

d. Fast GRE

FLAIR sequences are typically used in brain imaging for a. anatomy b. edema c. MS plaques d. none of the above

c. MS plaques

What determines the value of TE/Effective in FSE a. echo spacing (ESP) b. ETL c. central K space line contrast d. FA

c. Central K Space line contrast

A sequence that uses a variable FA for the initial RF pulse is a. CSE b. FSE c. GRE d. all of the above

c. GRE

At 2.0 T the fat and water peaks are separated by what frequency interval a. 147Hz b. 165 Hz c. 220 Hz d. 293 Hz

d. 293 Hz

which fat sequence is best if T2W is desired a. Coherent GRE b. Incoherent GRE c. FSE d. none of the above

c. FSE

A GRE sequence with a steady state residual transverse magnetization has a repetition time TR that is a. shorter than both T1 and T2 b. longer than both T1 and T2 c. shorter than T1 but longer than T2 d. longer than T1 but shorter than T2

a. shorter than both T1 and T2

Which method will not spoil steady state transverse magnetization a. increasing TR b. decreasing TR c. RF pulse d. Gradient Pulse

b. Decreasing TR

the sequence MP-RAGE is a. coherent GRE b. incoherent GRE c. multiplanar d. magnetization prepared

d. magnetization prepared

dynamic gadolinium scanning would be accomplished with which pulse sequence a. coherent GRE b. incoherent GRE c. CSE d. none of the above

b. incoherent GRE

Which of the following gradient amplitudes is the largest one a. 1G/cm b. 10mT/m c. 10G/cm d. b and c

c. 10G/cm

Fluid filled lesions generally appear _____ on T1W images and _____ on T2W images a. hypointense, hypointense b. hypointense, hyperintense c. hyperintense, hypointense d. hyperintense, hyperintense

b. hypointense, hyperintense

Accumulated phase errors are worst in ____ EPI while motion artifacts are worst in _____ EPI a. single shot, single shot b. single shot, multi shot c. multi shot, single shot d. multi shot, multi shot

b. single shot, multi shot

In order to make the echo sample time in EPI small, what must be done a. increase receive bandwidth b. increase transmit bandwidth c. decrease receive bandwidth d. decrease transmit bandwidth

a. increase receive bandwidth

which pulse sequence will have the greatest dB/dt in the patient a. CSE b. FSE c. GRE d. EPI

d. EPI

which pulse sequence will have the greatest power deposition in the patient a. CSE b. FSE c. GRE d. EPI

b. FSE

In order to avoid chemical shift artifacts in EPI what should be enabled a. spatial sat pulses b. spectral sat pulses c. FATSAT d. b and c

d. b and c

Using no phase wrap (NPW) the FOV and Ny are both doubled, while NEX is reduced by 1/2. This means that SNR is ____, while spatial resolution is _____. a. decreased, unchanged b. decreased, decreased c. unchanged, increased d. unchanged, unchanged

d. unchanged, unchanged

Suppose a T2W SE scan has an optimized TR. That is TR is as small as possible to maintain the desired coverage. If spatial sat pulses are now prescribed by the operator, then what must be done to the TR in order to maintain coverage a. TR increased b. TR decreased c. TR unchanged d. either a or b depending on the situation

a. TR increased

Which is the proper ordering from shortest to longest a. TI for STIR, TI for FLAIR, TI for water b. TI for FLAIR, TI for STIR, TI for water c. TI for water, TI for STIR, TI for FLAIR d. TI for water, TI for FLAIR, TI for STIR

a. TI for STIR, TI for FLAIR, TI for water

Which processes could best be eliminated by spatial sat pulses I. swallowing II. carotid flow III. retro orbital fat a. I only b. I and II only c. II and III only d. I II and III

b. I and II only

FATSAT is what kind of technique a. spatial sat b. spectral sat c. frequency selective sat d. b and c

d. b and c

Magnetization Transfer (MT) uses a. ramp sampling b. balanced gradients c. off resonant pulses d. none of the above

c. off resonant pulses

Diffusion imaging techniques are used to measure a. blood volumes b. random water motion c. a and b d. none of the above

b. random water motion

Which pulse sequence is most likely to be used for diffusion scans a. SE b. GRE c. IR d. EPI

d. EPI

Diffusion in a particular spatial direction is detectable using a. a sensitizing gradient b. an RF refocusing pulse c. tagging d. a and c

a. a sensitizing gradient

Compared to a T2W image created with a CSE sequence, in a T2W image created with FSE sequence, fat tends to appear a. darker b. brighter c. the same d. either a or c

b. brighter

In order to achieve the contrast desired in an FSE sequence, what kind of phase encoding gradient slopes are used to form echoes at the effective TE a. shallow b. steep c. a and b d. none of the bove

a. shallow

Fractional Echo allows for ____ TE values using the ____ symmetry of K space a. shorter, left/right b. shorter, top/bottom c. longer, left/right d. longer, top/bottom

a. shorter, left/right

A sequence that can demonstrate true T2W is a. coherent GRE b. incoherent GRE c. Steady State Free Precession d. none of the above

c. Steady State Free Precession

For an FSE scan with PD contrast, the ETL is more likely to be a. 1 b. 4 c. 16 d. none of the above

b. 4

With the static magnetic field 1.5T the TI for a FLAIR sequence is typically in the range a. 100-200 ms b. 400-800 ms c. 1700-2200 ms d. 5000-6000 ms

c. 1700-2200 ms

The BOLD effect makes fMRI possible in which organs a. brain b. muscle c. a and b d. none of the above

a. brain

Which of the following can be used in perfusion imaging I. gadolinium II. inversion pulses III. saturation pulses a. I only b. I and II only c. II and III only d. I II and III

d. I II and III

If the static magnetic field is decreased, then the spectral bandwidth of a FATSAT pulse should be a. narrower b. the same c. broader d. none of the above

a. narrower

MRI Physics 3 Flashcards

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