MRI MIDTERM pt 2

reducing the TR will increase the saturation and therefore will result in ____________ the SNR

TE is the time  _______
A. between initial rf excitation pulse and collection of an echo 
B. between initializing 180 and 90 pulses 
C. between 90 rf pulse 
D. time between 90deg and 180 pulse

For FSE imaging scan time for a 2D acquisition can be calculated as what formula:

for a 2D volume scan time can be calculated how

For an EPI acquisiton scan time is calculated by

TR is the time between successive 
A. none
B. 180 rf pulse 
C. 360 pulse 
D. 90 rf pulse 

TR is generally chosen by the amount of _______ desired on the image 
A. t2 contrast 
B. t1 contrast 
C. t2 and t1

for T1 information in the brain at 1.5T TR times of ______ are usually desired

Pixel size is determined by _____ & ______

to determine the pixel size 
A. fov divided by slice thicknes 
B. thickness divided by FOV
C. FOV is divided by amtrix along one side by FOV divided by MAtrix along the other 
D. matrix divided by matrix 

For the area of the pixel 
A. multiply one side by the other 
B. add one side by other
C. divide one side by other

for the voxel volume 
A. multiply one side by other side then mutliply that answer by slice thickness 
B. divide one side by the other side by thickness 
C. add one side to the other side + thhickenss 
D. subtract one side from the other side -- thickness

For an isotropic voxel

In most cases to demonstrate pathology, high contrast _)_______ are selected 
A. gradient echo
B. t2 weighted images 
C. inversion recovery 
D. t1 weighted images 

the image contrast is determined by the pulse sequence selected and its associated extrinsic paramters (4 things)

when the SNR is adequate the image quality is generally good however when SNR is bad 
A. all
B. blurry
C. grainy
D. streaky

generally the resolution is determined by the 
A. TR & TE 
B. NSA & BW 
C. voxel Size 
D. all of the above

voxel size is determined by 
A. all
B. fov & slice thickness 
C. FOV & matrix 
D. imaging matrix (phase & frequency encoding steps)

during MR image acquisition unwanted signals is known as 
A. radar
B. debris 
C. waste
D. noise 

the acronym snr refers to ratio

Noise is random and originated from multiples sources including 
A. system elctronics 
B. the patient 
C. all
D. the environment 

when metal is present within the body the magnetic field around such object is 
A. artifactual 
B. normal
C. greatly distorted 
D. homogenous 

one direction in k space represents phase information while other represents 
A. snr 
B. frequency
C. resolution
D. amplitude 

high amplitude phase encoding steps (edge of k-space) are weighted more to
A. image contrast 
B. spatial resolution 
C. snr 
D. A&C

Low amplitude phase encoding steps (center of k - space) are weighted more to ______
A. snr
B. A&C
C. image contrast 
D. spatial resolution 

as slice thickness is increased 
A. spatial resolution doubles 
B. there is no change in the spatial resolution
C. spatial resolution is reduced 
D. spatial resolution is increased 

the first gradient to be applied is the ______ gradient 
A. oblique
B. phase encoding
C. frequency encoding 
D. slice selection

in a spin echo sequence the frequency encoding gradient is applied during the

In a spin echo sequence the phase encoding gradient is applied 
A. during the production of the echo
B. after frequency encoding 
C. before slice selection 
D. after slice selection 

With each repetition, the phase encoding gradient will be applied with a different
A. bandwidth 
B. radiofrequency 
C. amplitude/polarity 
D. sampling point

spatial resloution maybe increased by acquiring a greater 
A. FOV
B. number of slices 
C. number of phase encoding steps 
D. number of rf pulses 

Increasing the number of phase encoding steps causes the scan time to 
A. reduce by half
B. decrease 
C. increase 
D. stays the same

the magnetic susceptiibility can be defined as the

the nucleus of the hydrogen atom is

iron is an example of a ______ substance

a diamagnetic substances exhibit ______ when placed in an externally applied magnetic field 
A. very slight positive or attractive effect
B. a very slight negative repelling effect 
C. a high positive or attractive effect 
D. high negative or repelling effect

exposing magnetized tissue to an rf field at the Larmor frequency first causes the hydrogen spins to _________
A. precess out of phase 
B. all of the spins in the low energy state absorb energy from the rf and move to the high energy
C. precess in phase 
D. some of the spins in the low energy state absorb energy from the RF field and move to the high energy state 

the combination of t2 spin spin, inhomogeneities and chemical shift result in a rapid loss of transverse magnetization known as __________
A. t1
B. t2*
C. PD
D. t2

the tz* image susceptibility artifacts are more prominent on 
A. inversion recovery images 
B. fast spin echo images
C. spine echoes 
D. gradient echo images 

the longitudinal magnetization regrows along the z-axis as spins in the high energy state lose energy during a process known as ___
A. t1 recovery 
B. t2 decay 
C. transverse decay
D. spin spin decay 

what is the gyromagnetic ratio for hydrogen at 1.5 Tesla

a insulator can be characterized by which of the following:
A. facilitates the flow of electrons 
B. resistant to the flow of electrons 
C. is not useful in mri imaging
D. allows electrons to flow in one direction only 

magnets are said to have 
A. eminent domain
B. well defined boarders 
C. well organized magnetic domains 
D. a large well organized group of echoes 

gradient echo sequences are more sensitive to field inhomogeneities than spin echo based sequences because they lack
A. a 180 deg refocusing pulse 
B. sufficient time to recover
C. a full 90 deg initial pulse 
D. sufficient rf to attain thermal equilibrium

a inversion recovery sequence with a short ti(STIR) can suppress signal from
A. gadolinium enhancement
B. fat
C. water
D. a&b

In a multi echo conventional spin echo sequence each of the echoes will have a different 

A. te
B. tr
C. spatial resolution
D. ti

the gradient that is on during the production of the echo is the 
A. slice select 
B. phase
C. frequency 
D. 2 or more if oblique

the condition that exists in a gradient echo sequence when the TR is shorter than the t2/t1 of the tissue is called

what give the most chemical shift artifact

chemical shift artifact can be characterized by a bright and dark band on opposite sides of certain anatomy. Which direction would we see this artifact on MRI images 
A. frequency direction 
B. outer edges of k space
C. center of k space 
D. phase direction