SNAC CH.3
129. First-order GMN corrects only for __________. a. constant velocity b. accelerated flow c. pulsitile flow d. c & b
a
Reducing the number of phase and/or frequency encodings increases voxel volume and __________ SNR. a. increases b. decreases c. stays the same d. doubles
a
SNR is __________ proportional to the voxel volume . a. directly b. inversely c. quadratic d. square root
a
STIR sequences are generally used to suppress the signal from __________. a. fat b. water c. CSF d. b & c
a
Signal comes only from the patient, or more specifically, the tissue in the __________. a. voxel b. scanner c. scan room d. live
a
Since noise occurs randomly and since motion artifact is merely unwanted "noise" signals, then and increase in NSA averages out __________. a. "noise" or motion artifact b. SNR c. Gibbs or truncation artifact d. Time
a
TE is the time __________. a. between the initial RF excitation pulse and the echo b. between 90' RF pulses c. between the initializing 180' RF pulse and the 90' pulse d. time between the 90' pulse and the 180' pulse
a
TR is generally chosen by the amout of __________ desired on the image. a. T1 contrast b. T2 contrast c. T1 contrast or T2 contrast d. none of the above
a
TR is the time between successive __________. a. 90° RF pulses b. 180° pulses c. 360° pulses d. none of the above
a
For T1 information in the brain at 1.5 T, TR times of __________ are usually desired. a. 250 msec-400 msec b. 400 msec-500 msec c. 1000 msec-15000 msec d. 2000 msec-4000 msec
b
124. As the bandwidth is reduced and sampling time is __________, gradient amplitude or slope is __________. a. Increased / reduced b. Reduced / reduced c. Increased / increased d. Reduced / Increased
A
127. STIR sequences with a TI time of 150 ms, suppress __________ based on the T1 recovery time. a. fat b. water c. liver d. silicone
a
121. A voxel that is isotropic is __________ in __________ dimensions and shaped like a __________. a. equal / all / cube b. equal / two / parallelogram c. equal / two / rectangle d. unequal / all / hexagram
a
122. Reducing the receiver bandwidth, __________ the signal-to-noise ratio (SNR). a. increases b. decreases c. does not effect d. doubles
a
130. If the patient has a heart rate of 60 beats per minute, the scan would be triggered 60 times per minute or every __________. The effective TR would therefore be __________. a. 1 second / 1000 msec b. 1 minute / 1000 msec c. 1 minute / 100 msec d. b & c
a
137. Truncation and Gibbs artifact appear as striations or "lines" in the __________ direction. a. phase b. frequency c. right d. k-space
a
138. Truncation and Gibbs artifact can be minimized by __________ encoding steps. a. increasing the phase b. increasing the frequency c. increasing the right d. increasing the k-space
a
139. Magnetic susceptibility artifact appears as a __________ in the area of the metal. a. "signal void" b. "zipper artifact" c. "herringbone" d. "corduroy"
a
52. For conventional imaging scan time for a 2D acquisition can be calculated as follows: a. TR x Ny x NSA b. TR x Ny x NSA x # slices (partitions) c. TR x Ny x NSA/ ETL d. TR x NSA x #shots
a
79. Using a short effective TE places the early echoes in the train in __________ of k-space. a. central portion b. top line c. bottom line d. anywhere
a
93. In gradient echo sequences, __________ is manipulated to maintain image contrast. a. Flip angle b. TI c. Contrast agent d. None of the above
a
An inversion sequence that utilizes a short TI is often referred to as __________. a. STIR b. FLAIR c. FSE d. EPI
a
As TR increases, the available imaging time (within the sequence) __________ and therefore, the number of slices allowed during the sequence __________. a. increases / increases b. increases / decreases c. decreases / decreases d. decreases / increases
a
As the flip angle is reduced (assuming constant TR), spins with longer T1 times exhibit greater longitudinal recovery and the image becomes __________. a. less T1 weighted b. more T1 weighted c. only T1 weighted d. None of the above
a
As the main field increases, the SNR __________. a. increases b. decreases c. stays the same d. doubles
a
As the phase matrix increases scan time __________. a. increases b. decreases c. stays the same d. none of the above
a
As the voxel volume increases the SNR __________. a. increases b. decreases c. stays the same d. doubles
a
As we increase TR, scan time __________. a. increases b. decreases c. reduces by half d. stays the same
a
At 1.5T, STIR sequences generally use TI times of __________. a. 150 ms b. 750 ms c. 2000 ms d. none of the above
a
Conventional SE sequences can acquire T2 or PD contrast with __________ selections. a. long TR b. short TR c. large flip angle d. long TI times
a
For T1 information in the brain at lower field strengths, 0.2 T-0.5 T, lower TR times __________ are usually desired. a. 250 msec-400 msec b. 400 msec-500 msec c. 1000 msec-15000 msec d. 2000 msec-4000 msec
a
For bandwidth the SNR is proportional to __________. a. one over the square root of the BW b. the bandwidth c. the bandwidth2 d. quadratic to the bandwidth
a
For the area of the pixel __________. a. multiply one side by the other side b. divide one side by the other side c. add one side to the other side d. subtract one side from the other side
a
For the voxel volume __________. a. multiply one side by the other side then multiply that answer by the slice thickness b. divide one side by the other side by the thickness c. add one side to the other side + thickness d. subtract one side from the other side - thickness
a
If the matrix is reduced by 2 (going from 256 x 256 to 128 x 256) the voxel size is doubled and SNR would increase by a factor of __________. a. 2 b. 4 c. 6 d. 8
a
In general, the smaller the voxel, the __________ the resolution. a. better b. worse c. lower d. more constant
a
In most cases, to demonstrate anatomy, high SNR __________ are selected. a. (T1 weighted) images b. (T2 weighted) images c. inversion recovery d. gradient echo Chapter 3
a
In order to increase the signal-to-noise ratio (SNR), one must __________ the signal and/or __________ the noise. a. Increase / reduce b. Reduce / Increase c. Increase / Increase d. Reduce / Reduc
a
Increasing the FOV __________. a. increases voxel volume and increases SNR b. increases voxel volume and reduces SNR c. reduces voxel volume and increases SNR d. reduces voxel volume and reduces SNR
a
Increasing the FOV increases voxel volume and __________ SNR. a. increases b. decreases c. stays the same d. doubles
a
Increasing the number of phase and/or frequency encodings __________. a. reduces voxel volume and reduces SNR b. increases voxel volume and reduces SNR c. increases voxel volume and increases SNR d. reduces voxel volume and increases SNR
a
Increasing the slice thickness will __________ SNR . a. increase b. decrease c. not change d. double
a
Inversion recovery sequences were initially utilized to acquire images with very strong __________. a. T1 weighting b. T2 weighting c. T2* weighting d. PD weighting
a
Narrowing the receiver bandwidth, __________ the chemical shift artifact. a. increases b. decreases c. does not effect d. doubles
a
Narrowing the receiver bandwidth, __________ the minimum allowable TE. a. increases b. decreases c. does not effect d. doubles
a
Optimization of image quality in MRI generally represents a compromise between __________. a. image contrast, SNR and acquisition time b. height, width and depth of the voxel c. patient age and time of day d. none of the above
a
Reducing the TR increases the __________ on the image. a. T1 weighting b. T2 weighting c. PD weighting d. None of the above
a
The increase in TE, and resultant increase in dephasing results in (a/an) __________ in susceptibility artifact, especially on gradient echo images. a. increase b. doubling c. reduction d. no change
a
To determine the pixel size __________. a. FOV divided by Matrix along one side by...FOV divided by Matrix along the other b. FOV divided by slice thickness c. Matrix divided by matrix d. Thickness divided by FOV
a
When T2 contrast is required, SNR is __________ and scan time is often __________. a. reduced / increased b. increased / reduced c. unchanged / unchanged d. increased / increased
a
When a long effective TE is used, it can be used in combination with a __________ however, when a short TE is used, it should be used in combination with a __________. a. long ETL / short ETL b. short ETL / short ETL c. long ETL / long ETL d. short ETL / short ETL
a
When the SNR is adequate the image quality is generally good, however, when the SNR is bad, image quality is poor or the image can appear __________. a. "grainy" b. "blurry" c. "streaky" d. all of the above
a
115. As an example, if the slice thickness is increased from 3 mm to 6 mm, the voxel volume will __________ and thus the SNR will increase by a factor of __________. a. Stay the same / 0 b. double / 2 (double) c. double / 22 = 4 (quadruple) d. quadruple / 4 (quadruple)
b
120. A 2D acquisition selectively excites a __________ of tissue while a 3D acquisition excites a __________. a. slice / slice b. slice / slab c. proton / slab d. atom / molecule
b
134. A "leak" in the RF shielding can result in extraneous signals entering the scan room and manifesting themselves as __________ on images. a. "fold-over" b. "zipper artifact" c. "chemical shift" d. "herringbone
b
71. Increasing the TE increases the __________ on the image. a. T1 weighting b. T2 weighting c. PD weighting d. None of the above
b
72. Longer TE allows for __________ slices. a. more b. less c. no change d. None of the above
b
91. Long TR sequences yield __________. a. short scan times b. long scan times c. T1 weighted images d. Suppressed images
b
As TR is increased, the image reflects __________. a. More T1 contrast b. Less T1 contrast c. More T2 contrast d. Less T2 contrast
b
At 1.5T, IR sequences used for the evaluation of pediatric brains generally use TI times of __________. a. 150 ms b. 750 ms c. 2000 ms d. none of the above
b
FSE image blurring increases as the effective TE __________. a. increases b. decreases c. stays the same d. doubles
b
FSE images are acquired by filling __________ of k space in each TR period. a. one line b. multiple lines c. no lines d. all lines
b
For #slices in the 3D acquisition, the SNR is proportional to __________. a. the number of slices b. the square root of the number of slices c. the number of slices2 d. the inter-slice gap
b
For a 3D, or volume acquisition or a single slice acquisition, scan time can be calculated as follows: a. TR x Ny x NSA b. TR x Ny x NSA x # slices (partitions) c. TR x Ny x NSA/ ETL d. TR x NSA x #shots
b
For the area of the pixel, the answer will be in units of __________. a. mm b. mm2 c. mm3 d. cm
b
If FOV is doubled (going from 12cm to 24cm) the voxel size is increased in two dimensions and therefore the voxel size is increased by __________. a. 2 b. 4 c. 6 d. 8
b
If proton density (PD) weighting is desired, a short TE is selected (20 msec or less) to reduce the __________ and a long TR is then selected (2000 msec or higher) to reduce __________. a. T2 weighting / T2 weighting b. T2 weighting / T1 weighting c. T1 weighting / T1 weighting d. T1 weighting / T2 weighting
b
If the NSA is increased by 2 the SNR increases by __________. a. 2 b. square root of 2 c. 22 d. 100%
b
In 3D or single slice acquisitions, scan time is determined by the __________. a. TR x #PE's x NSA b. TR x #PE's x NSA x # slices c. TR x #PE's x NSA / ETL d. TR x # shots x NSA
b
In general, the __________ the RF coil, the __________ the SNR. a. bigger / better b. smaller / better c. smaller / lower d. bigger / lower
b
In most cases, to demonstrate pathology, high contrast __________ are selected. a. (T1 weighted) images b. (T2 weighted) images c. inversion recovery d. gradient echo
b
In most instances, increasing signal-to-noise, depending on the method chosen by the operator, can result in a (an) __________ in spatial resolution. a. increase b. reduction c. stablilzation d. doubled
b
In most instances, when spatial resolution is increased, signal-to-noise is __________. a. increased b. reduced c. unchanged d. doubled
b
Increasing the matrix, increases the number of phase and frequency steps and therefore __________. a. increases the voxel size b. decreases the voxel size c. has no effect on the voxel size d. increases the pixel size
b
Increasing the number of phase encodings (samplings) __________. a. increases samples and therefore increases truncation artifact b. increases samples and therefore reduces truncation artifact c. reduces samples and therefore reduces truncation artifact d. reduces samples and therefore increases truncation artifact
b
Motion artifacts occur along the __________ on MR images. For this reason the direction of __________ generally defaults along the short axis of the anatomy. a. Frequency direction / frequency encoding b. Phase direction / phase encoding c. Frequency direction / phase encoding d. Phase direction / frequency encoding
b
Pixel size is synonymous with the term __________. a. "spatial resolution" b. "in-plane" resolution. c. "temporal resolution" d. a & b
b
Reducing the TR will increase the saturation of tissues and therefore will result in (a/an) __________ in the SNR. a. increase b. decrease c. variation d. stability
b
The FOV controls the __________ in two (2) dimensions. a. Pixel size b. voxel volume c. slice thickness d. a & b
b
The SNR is proportional to __________. a. Total sampling time2 b. √Total sampling time c. Total sampling time x 2 d. Total sampling time
b
The __________ is the ability to "resolve" one structure from another on the image. a. Signal- to-noise b. Spatial resolution c. Contrast-to-noise d. Temporal Resolution
b
The matrix is the __________ chosen to make up the image. a. voxel size b. number of phase and frequency encoding steps c. the FOV and slice thickness d. none of the above
b
The number of frequency encodings __________ affect the scan time a. does b. does not c. doubles d. none of the above
b
Using a larger FOV and then magnifying the image for photographic purposes (makes the image bigger on the film), __________. a. and increases spatial resolution. b. does not increase spatial resolution. c. and decreases voxel volume d. and decreases pixel size
b
Using a long TR does not make an image __________, it makes it less __________. a. T2 weighted / T2 weighted b. T2 weighted / T1 weighted c. T1 weighted / T1 weighted d. T1 weighted / T2 weighted
b
At 1.5T images are out of phase at __________ TE and in phase at roughly __________ TE. a. 2.2 ms / 2.2 ms b. 4.4 ms / 4.4 ms c. 2.2 ms / 4.4 ms d. 4.4 ms / 2.2 ms
c
By the relationship between SNR and NSA, since noise increases randomly, the SNR is proportional to the __________. a. NSA2 b. NSA c. √NSA d. 1/√NSA
c
106. As the frequency matrix increases scan time __________. a. increases b. decreases c. stays the same d. none of the above
c
116. In a FSE acquisition the number of echoes produced in a single repetition is an operator selectable parameter known as the __________. a. "Echo Train Length" (ETL) b. Turbo Factor c. a & b d. None of the above
c
132. Calculate the possible cardiac phases that could be acquired in the cine acquisition, if the heart-rate is 60 BPM and the TR is 25 ms. a. 1500 phases b. 150 phases c. 40 phases d. 25 phases
c
136. Hydrogen in fat and hydrogen in water precess at different frequencies, this shift in resonant frequency is referred to as __________. a. "fold-over" b. "zipper artifact" c. "chemical shift" d. "herringbone
c
88. At 1.5T, FLAIR sequences generally use TI times of __________. a. 150 ms b. 750 ms c. 2000 ms d. none of the above
c
97. Increasing the NSA by a factor of four results in a __________ increase in sampling time, and the SNR increases by a factor of __________. a. 4x / 4 b. 2x / 2 c. 4x / 2 d. 2x / 4
c
As TE is reduced, the image reflects __________. a. More T1 contrast b. Less T1 contrast c. More T2 contrast d. Less T2 contrast
c
During MR image acquisition, signal that is detected includes those signals that are desired known as "signal" and unwanted signal known as __________. a. debris b. waste c. noise d. radar
c
For an isotropic voxel: __________. a. one side should equal the other side should be greater than the slice thickness b. one side should be greater than the other side should equal the slice thickness c. one side should equal the other side should equal the slice thickness d. all sides are different
c
For fast spin echo imaging scan time for a 2D acquisition can be calculated as follows: a. TR x Ny x NSA b. TR x Ny x NSA x # slices (partitions) c. TR x Ny x NSA/ ETL d. TR x NSA x #shots
c
For the voxel volume, the answer will be in units of __________. a. mm b. mm2 c. mm3 d. cm
c
Generally SNR parameters can be broken into several categories. These categories include: __________. a. Hardware and contrast parameters b. voxel size and sampling c. a & b d. none of the above
c
Generally, the resolution is determined by the __________. a. TR & TE b. NSA & BW c. voxel size d. all of the above
c
If a 256 frequency encoding is selected, the system will sample the echo __________ in the presence of the frequency encoding gradient. a. 128 times b. 192 times c. 256 times d. 512 times
c
If a phase resolution of 256 is desired, then the pulse sequence must be repeated a minimum of __________, and with each repetition, the phase encoding gradient will be applied with a different amplitude and/or polarity. a. 128 times b. 192 times c. 256 times d. 512 times
c
If one was to reduce the FOV by 20%, the voxel volume would decrease by __________. a. 20 % b. 30 % c. 40 % d. 50 %
c
In general, inversion sequences begin with a 180 degree RF pulse to invert Mz. After the inversion there is an operator specified delay time known as the __________. a. TR b. TE c. TI d. Flip angle
c
Increasing the TE increases the amount of transverse magnetization decay between the excitation pulse and the sampling of the echo and therefore will result in (a/an) __________ in SNR. a. increase b. doubling c. reduction d. no change
c
MR image characteristics are generally selected on the basis of: __________. a. suspected pathology and anatomy to be imaged b. patient tolerance and acquisition time c. a & b
c
Pixel size is determined by __________. a. FOV & slice thickness b. imaging matrix (#phase & # frequency encoding steps) c. FOV & Matrix d. all of the above
c
Selecting a long TE (80 msec or higher) will then produce an image with __________. a. More T1 contrast b. Less T1 contrast c. More T2 contrast d. Less T2 contrast
c
Signal-to-noise is affected by __________ parameter(s) that is manipulated (and those that are generally not manipulated) in MRI. a. certain b. some c. every d. there is no effect on SNR
c
The ability to visualize the effect of adequate image contrast and SNR collection is known as __________. a. Signal- to-noise b. Resolution-to-noise c. Contrast-to-noise d. all of the above
c
The contrast parameters that effect SNR includes: __________. a. TR & TE b. TR, TE & flip angle c. TR, TE, TI and flip angle d. These parameters do not affect SNR
c
The flip angle that produces the maximum signal for a given tissue at a given TR is known as the __________. a. 90' flip angle b. 180' flip angle c. Ernst angle d. Fourier angle
c
The hardware that affects SNR includes: __________. a. the static magnetic field (Bo) b. the radiofrequency field (B1) c. a & b d. none of the above
c
The image contrast is determined by the pulse sequence selected and it's associated extrinsic parameters __________. a. TR & TE b. TR, TE & flip angle c. TR, TE, TI and flip angle d. These parameters do not affect SNR
c
The slice thickness is determined by the __________. a. amplitude (slope) of the slice selection gradient b. the transmitter bandwidth c. amplitude (slope) of the slice selection gradient and/or the transmitter bandwidth d. neither amplitude (slope) of the slice selection gradient nor the transmitter bandwidth
c
The term SNR refers to a ratio of __________. a. Sonar nuclear radar b. Sound-not-noise c. Signal-to-noise d. Sensory noise radio
c
When acquiring axial images of the neck and hypointense signal in blood vessels is desired, presaturation pulses can be prescribed __________ to the slices. a. superior b. inferior c. superior and inferior d. anterior
c
128. Fat saturation is a __________ suppression technique. a. chemical shift selective b. spectral c. spatial d. a &
d
131. Calculate the available imaging time for the following cardiac gated acquisition, if the heart-rate is 60 BPM and the trigger delay is 50 ms and the trigger window is 10%. a. 1000 ms b. 800 ms c. 100 ms d. 850 ms
d
133. __________ is an example of a sampling artifact and occurs in both the phase and frequency directions where signal from outside the FOV is superimposed in the FOV. a. "fold-over" b. "wrap-around" c. " aliasing" d. all of the above
d
135. Examples of reconstruction artifacts include the so-called __________ artifacts. a. "fold-over" b. "zipper artifact" c. "chemical shift" d. "herringbone
d
141. Partial volume averaging is the result of large voxel imaging acquired with __________. a. large FOV b. thick slices c. small matrix d. all of the above
d
An MR image can be thought of as having basic characteristic(s) including: . a. image contrast b. signal-to-noise c. spatial resolution d. all of the above
d
Echoes generated following higher amplitude phase encoding gradients are encoded for the __________ "lines" of k-space and echoes generated following lower amplitude phase encoding gradients are encoded for the __________ "lines" of k-space. a. Outer / outer b. Central / inner c. Inner / outer d. Outer / inner
d
FLAIR sequences are generally used to suppress the signal from __________. a. fat b. water c. gray matter d. CSF
d
FLAIR sequences are useful for demonstrating __________. a. strokes b. infections c. white matter disease d. all of the above
d
For an EPI acquisition, scan time can be calculated by: a. TR x Ny x NSA b. TR x Ny x NSA x # slices (partitions) c. TR x Ny x NSA/ ETL d. TR x NSA x #shots
d
If the slice thickness doubles, the SNR __________. a. increases b. decreases c. stays the same d. doubles
d
If the voxel volume doubles, the SNR __________. a. increases b. decreases c. stays the same d. doubles
d
In order to acquire T2 contrast with short scan times, the __________. a. TR can be reduced (to increase scan time) and the flip angle can be reduced (to maintain image contrast) b. TR can be reduced (to reduce scan time) and the flip angle can be increased (to maintain image contrast) c. TR can be increased (to reduce scan time) and the flip angle can be reduced (to maintain image contrast) d. TR can be reduced (to reduce scan time) and the flip angle can be reduced (to maintain image contrast)
d
Magnetic susceptibility artifact is proportional to __________. a. field strength, voxel volume, and TE b. size of metal and type of metal c. type of imaging sequence d. all of the above
d
Noise is random and originates from multiple sources including __________. a. the environment b. the patient c. system electronics d. all of the above
d
The "Effective TE", or "Target TE" is the echo that is encoded for the __________ most portion of k-space. a. outer b. lower c. upper d. central
d
The acquisition time is determined by several imaging parameters including: __________. a. TE, TI & flip angle b. TR, TE, FOV c. slice thickness and gap d. TR, Matrix, NSA and in some cases # slices and ETL
d
The image contrast is determined by the pulse sequence selected and it's associated extrinsic parameters as well as the intrinsic parameters __________. a. T1 b. T2 and T2* c. tissue's proton density d. all of the abov
d
The only way the spatial resolution can be increased is to __________. a. reduce the voxel volume b. increase the voxel volume c. reduce the pixel size d. a & c
d
The term "sampling parameters" refers to parameters that control the amount of time spent sampling the MR signal including: __________. a. NSA, NEX, Acquisitions, etc. b. phase encodings or in the 3D acquisition the # slices (partitions) c. receiver bandwidth d. all of the above
d
Voxel size is determined by __________. a. FOV & slice thickness b. imaging matrix (#phase & # frequency encoding steps) c. FOV & Matrix d. all of the above
d
Voxel volume is determined by __________. a. FOV b. thickness c. matrix d. all of the above
d
When a long effective TE is used, it should be used in combination with a __________ and when a short TE is used, it should be used in combination with a __________. a. long ETL / long ETL b. short ETL / short ETL c. short ETL / long ETL d. long ETL / short ETL
d
With sampling parameters, SNR increases __________ with the change. a. directly b. inversely c. as the quadratic d. as the square root
d