Final Review Flashcards
Spatially locating along a short axis of the anatomy is called ________ encoding
a. phase
b. frequency
c. slice
d. gradient
a. phase
In gradient echo pulse sequences, the slice select gradient is switched on during the excitation pulse only
a. true
b. false
a. true
As long as at least _________ of the lines of k-space that have been selected are filled during acquisition, then an image may be produced
a. one third
b. one fourth
c. one fifth
d. half
d. half
In a fast echo sequence with an echo train of 14, how many RF pulses are applied for a given slice during one TR period?
a. 1
b. 15
c. 14
d. 2
b. 15
Which of the following RF flip angles would result in the largest transverse component, assuming the net magnetization is initially in the longitudinal direction?
a. 30 degrees
b. 45 degrees
c. 60 degrees
d. 75 degrees
d. 75 degrees
In which of the following pulse sequences would you expect to find the shortest TR?
a. gradient echo
b. fast spin echo
c. inversion recovery
a. gradient echo
Optimization of image quality in MRI generally represents a compromise between:
a. image contrast, SNR and acquisition time
b. height, width and depth of voxel
c. patinet age and time of day
d. none of the above
a. image contrast, SNR and acquisition time
In most instances, when spacial resolution is increased, signal to noise is?
a. increased
b. decreased
c. unchanged
d. doubles
b. decreased
The ________ controls the amount of data stored in each line of k-space
a. NMV
b. NTC
c. NEX
d. SNR
c. NEX
Voxel volume is determined by
a. FOV
b. slice thickness
c. matrix
d. all of the above
d. all of the above
As the voxel size increases the SNR __________
a. Increases
b. Decreases
c. Stays the same
d. Doubles
a. Increases
In most cases, to demonstrate anatomy, high SNR ____ are selected
a. TI weighted images
b. T2 weighted images
c. Inversion recovery
d. Gradient echo
a. TI weighted images
Only increasing the TE allows for _______ slices
a. More
b. Less
c. No change
d. None of the above
b. Less
If the slice thickness doubles, SNR ___________
a. Increases
b. Decreases
c. Stays the same
d. Doubles
d. Doubles
An inversion sequence that utilizes a short T1 is often referred to as________
a. STIR
b. FLAIR
c. FSE
a. STIR
The force that can cause a ferromagnetic object such as an O2 tank to become a projectile in the fringe field is called:
a. GMF
b. Torque
c. RF
d. Translational attraction
d. Translational attraction
The mechanism of T2 contrast enhancements agents is to:
a. Increase T2 relaxation time, therefore producing low signal
b. decrease T2 relaxation time, therefore producing low signal
c. increase T2 relaxation time, therefore producing high signal
d. decrease T2 relaxation time, therefore producing high signal
b. decrease T2 relaxation time, therefore producing low signal
To double the SNR we need to increase the NEX and the scan time by a factor of:
a. three
b. four
c. two
d. five
b. four
In large voxels, individual signal intensities are averaged together and not represented as distinct within the voxel. This results in:
a. partial voluming
b. black space
c. white space
d. no image detail
a. partial voluming
To obtain good resolution, achieving thin slices requires the slice select gradient slope to be:
a. horizontal
b. gradual
c. steep
d. vertical
c. steep
A gradient is employed exposing the patient’s body to a series of increasing or decreasing mag. field strengths for slice selection. In what relation to the slice is this gradient applied?
a. anti-parallel
b. perpendicular
c. parallel
d. oblique
b. perpendicular
Faraday’s law of induction states that if a loop of wire is moved through a mag. field _______ will be created in the wire
a. a mag. wave
b. a voltage
c. torque
d. resonance
b. a voltage
Protons that are aligned with the mag. field (B0) are refered to as all of the following EXCEPT:
a. spin up
b. parallel
c. low energy spins
d. high energy spins
d. high energy spins
Frequency can be defined as the:
a. rate of phase change per unit time
b. phase/s
c. Fourier equation
d. amplitude of the signal
a. rate of phase change per unit time
T2 decay:
a. the time it takes 63% of NMV to recover and realign with B0
b. spin-spin relaxation loss of coherence. The time is takes 63% of transverse mag. to be lost
c. Time between RF excitation pulses
d. the time from the application of RF pulse to peak of resonant signal we recieve; controls T2 relaxation
b. spin-spin relaxation loss of coherence. The time is takes 63% of transverse mag. to be lost
Repetition time (TR):
a. the time it takes 63% of NMV to recover and realign with B0
b. spin-spin relaxation loss of coherence. The time is takes 63% of transverse mag. to be lost
c. Time between RF excitation pulses
d. the time from the application of RF pulse to peak of resonant signal we recieve; controls T2 relaxation
c. Time between RF excitation pulses
Echo time (TE):
a. the time it takes 63% of NMV to recover and realign with B0
b. spin-spin relaxation loss of coherence. The time is takes 63% of transverse mag. to be lost
c. Time between RF excitation pulses
d. the time from the application of RF pulse to peak of resonant signal we recieve; controls T2 relaxation
d. the time from the application of RF pulse to peak of resonant signal we recieve; controls T2 relaxation
T1 recovery:
a. the time it takes 63% of NMV to recover and realign with B0
b. spin-spin relaxation loss of coherence. The time is takes 63% of transverse mag. to be lost
c. Time between RF excitation pulses
d. the time from the application of RF pulse to peak of resonant signal we recieve; controls T2 relaxation
a. the time it takes 63% of NMV to recover and realign with B0
Excitation:
a. the application of an RF pulse at exactly the Larmor frequency of hydrogen that causes resonance
b. spin-spin relaxation loss of coherence. The time is takes 63% of transverse mag. to be lost
c. Time between RF excitation pulses
d. the time from the application of RF pulse to peak of resonant signal we recieve; controls T2 relaxation
a. the application of an RF pulse at exactly the Larmor frequency of hydrogen that causes resonance
Any two 90 degree RF pulses produce a _________ echo
a. an FID
b. no signal
c. a Hahn echo
d. none of the above
c. a Hahn echo
Parameters in a T2 gradient echo:
a. long TR, long TE, small flip angle
b. long TR, short TE, small flip angle
c. long TR, short TE, large flip angle
d. short TR, short TE, large flip angle
a. long TR, long TE, small flip angle
Logically each line of phase encoding data is combined to allow the FT to determine position along the Y axis, the # of phase encoding steps determines: a. the # of voxels along the Y axis b. the # of pixels along the X axis c, the # of voxels along the X axis d. the # of pixels along the Y axis
d. the # of pixels along the Y axis
To produce high signal:
a. there must be a small component of coherent mag in the transverse plane
b. there must be a large component of coherent mag in the longitudinal plane
c. there must be a large component of coherent mag in the transverse plane
d. c. there must be a small component of coherent mag in the longitudinal plane
c. there must be a large component of coherent mag in the transverse plane
The middle of the axis of the gradients remain at the same field strenght as the main mag. field due to:
a. polarity
b. magnetic isocenter
c. gradient echo
d. mag. field gradient
b. magnetic isocenter
Which of the following parameters control the amount of T1 weighting?
a. TR
b. TE
c. RELAXATION
d. FAT
a. TR
