MRI MIDTERM

within seconds of tissue being placed in a magnetic field the hydrogen protons will assume one of two possible spin states or energy levels 
A. high or low energy 
B. parallel or anti parallel 
C. aligned or opposed 
D. all of the above

while in the magnetic field hydrogen protons wobble this wobbling is known as

partial volume averaging is the result of large voxel imaging acquired 
A. large fov 
B. low image matrix 
C. thick slices 
D. all of the above

__________ is an example of a sampling artifact and occurs in both the phase and frequency direction where signal from outside the fov is superimposed 
A. aliasing 
B. fold over 
C. wrap around 
D. all

the 180 rf pulse that follows the initial 90 dg rf pulse in a spin echo sequence will produce an echo while correcting for 
A. all of the above 
B. magnetic susceptibility effects 
C. chemical shift 
D. magnetic field inhomegeneity

an inversion recovery sequence begins with ____

in a fast spin echo sequence the effective TE are the echos that are encoded 
A. with the first phase encoding steps
B. with a low amplitude phase encoding gradient 
C. in the outer edges of the k-space 
D. with a amplitude phase encoding gradient 

in a fast spin echo pulse sequence if the echo train length is increased by a factor of four:
A. the scan will be twice as fast 
B. the scan will be one time faster 
C. the scan will be four times as fast
D. the scan will be three times as fast 

a leak in the RF shielding can result in extraneous signals entering the scan room and manifesting themselves as ________ artifactt on images

hydrogen in fat and hydrogen in water precess at different frequencies; this shift in resonant frequency is referred to as _______

Truncation and gibbs artifact can minimized by ______ encoding steps 
A. increasing the phase 
B. increasing the right 
C. increasing the k-space
D. increasing the frequency 

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

magnetic susceptibility artifact appears as a ________ in the area of metal 
A. corduroy
B. zipper artifact
C. signal void 
D. herringbone 

if the slice thickness is increased from 3mm to 6mm the voxel colume will _______ and the SNR will increase by a factor of _________
A. quadruple
B. double/2 (double)
C. double/2 = 4 quadruple 
D. stay the same/zero

in a FSE acquisition the number of echoes produced in a single repitition is an operator selectable parameter known as the ____ (2 things)

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

when a long effective TE is selected it can be used in combination with a ______ however, when a short TE is used it should be used with a _____ to minimze image blurring

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/phase encoding 
B. phase direction/frequency encoding
C. phase direction/phase encoding 
D. frequency direction/frequency encoding 

a 2d acquisition selectively excites a ____ of tissue while a 3d acquisition excites a ______
A. slice/slab
B. proton/slab
C. slice/slice 
D. atom/molecule

A voxel that is isotropic is _____ in ______ dimensions and shaped like

as the frequency matrix increases scan time 
A. increases 
B. stays the same
C. decreases 

if a 256 frequency encoding is selected , the system will sample the echo ______ in the presence of the frequency encoding gradient

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 applies with a different amplitude/ polarity

increasing the matrix increases the number of phase and frequency steps and therefore 
A. decreases voxel size 
B. has no effect
C. increase voxel size 

increasing the number of phase and/ or frequency encodings _______
A. increases voxel volume and increases snr 
B. reduces voxel volume and SNR
C. increases voxel volume and increases snr 
D. reduces voxel volume and increases snr

increasing the number of phase encoding (samplings)
A. reduces samples and therefore reduces truncation
B. increases samples and there reduces truncation
C. increases samples and therefore increases truncation artifact 

the slice thickness is determined by 
A. amplitude of slice selection gradient 
B. transmitter bandwidth 
C. amplitude (slope) of the slice selection gradient and or transmitter bandwidth d.neither

in a 2d single slice selection scan time is determined by the ____ _____ ____

Increasing the NSA by a factor of four increases sampling time ______ and increases snr about ______
A. 2 and 2 
B. 4 and 2 
C. 4 and 4 
D. 2 and 4

the FOV controls the _____ in 2 dimensions
A. pixel size 
B. slice thickness
C. voxel thickness 

to reduce the FOV by 20% the voxel volume would decreases by

the only way the spatial resolution can be increases is 
A. increase voxel volume 
B. reduce voxel volume 
C. A&C
D. reduce the pixel size 

Increasing the FOV _____
A. reduces voxel volume and reduces snr
B. reduce voxel volume and increases snr 
C. increases voxel volume and reduces snr 
D. increases voxel volume and increases snr 

the matrix is the ______ chosen to make the image 
A. voxel size 
B. none
C. the fov and slice thickness 
D. number of phase and frequency encodings 

as the phase matrix increases scan time ____

conventional SE sequences can acquire T2 or PD contrast with _________ selections 
A. short tr 
B. long ti times
C. large flip angle 
D. long tr 

long tr sequences yield 
A. large flip angles 
B. long ti times
C. long scan times 
D. short scan times 

In a gradient echo sequence ______ is manipulated to maintain image contrast

As the flip angle is reduce ( assuming tr is constant) spins with longer t1 times exhibit greater longitudinal recovery and the image becomes 
A. more t1 weighted 
B. only t1 weighted 
C. less t1 weighted 
D. none

the flip angle that produces the maximum signal for a given tr is known as 
A. 90 deg flip angle 
B. fourier angle 
C. ernst angle 
D. 180 deg flip angle

Inversion recovery sequences were initially utilized to get images with very strong
A. t1 weighting 
B. PD weighting
C. t2 weighting 
D. t2* weighting 

Inversion sequences begin with 180 rf pulse to invert longitudinal magnetization. After the inversion there is a operator specified delay time known as the ______.
A. tr 
B. flip angle
C. ti
D. te 

FLAIR sequences are useful for demonstrating 
A. all
B. strokes
C. white matter disease 
D. infections 

at 1.5 T STIR sequences generally use TI times of

At 1.5 T FLAIR sequences generally use TI times of

Longer TE allows for _______ slices 
A. more
B. none
C. less
D. no change 

using a short effective te places the echoes in the train in _______ of k space 
A. bottom
B. anywhere
C. top 
D. center 

FSE image blurring increases as the effective TE 
A. stays the smae 
B. decreases 
C. increases 
D. doubles

In a spin echo sequence the time between the 90 rf pulse and 180 pulse is

Presaturation pulses usually occur 
prior to ______ pulse

An inversion recovery sequence, image contrast is controlled by:
A. tr te ti
B. ti 
C. ti and te 
D. TR and TE 

A narrow bandwidth 
A. decreases susceptibility artifact 
B. increases susceptibility artifact 
C. does not change susceptibility
D. decreases snr

the best pulse sequence to minimize susceptibility artifact is 
A. gradient 
B. FSE 
C. SE
D. EPI

the effective te or target te is the echo that is encoded in the _____ most portion of k space 
A. upper
B. central
C. lower 
D. outer

FSE images are obtained by filling ______ of k space at the same time in each TR period 
A. multiple lines 
B. no lines 
C. all lines
D. one line 

Selecting a long te (80 msec or higher) will produce an image with

Using a long TR does not make image _____ it makes it less ______

If PD weighting is desired a short TE is selected (20ms or less) to reduce the ______ and a long TR is then selected (2000ms) to reduce ___________

reducing the tr increases the _____ on the image
A. t1 weighting 
B. none
C. PD weighting 
D. t2 weighting 

as we increases TR scan time 
A. reduce by half
B. decrease 
C. increase 

As the tr increase the imaging time (within the sequence ) _____and therefore the number of slices allowed during the sequence _______