Transcript RT 4912 Review - Weber State University

RT 4912 Review (A)
Rex T. Christensen MHA RT (R) (MR) (CT) (ARRT) CIIP
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Websites:
http://www.fonar.com/glossary.htm
http://www.mr-tip.com/serv1.php?type=welcome
http://www.imaios.com/en/e-Courses/e-MRI
6 Key Imaging Goals
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Optimize Contrast
Optimize Coverage and Slice Thickness
Optimize Resolution
Minimize Artifacts
Maximize Patient Throughput
Optimize Signal to Noise (SNR)
Scenario 1
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Radiologist asks for a MRCP to visualize the
biliary system.
Scenario 2
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Radiologist wants a sagittal T2 FSE fatsat knee
with better signal and better resolution.
Scenario 3
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A coronal T1 wrist is too grainy
Scenario 4
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A FSE T2 fatsat brachial plexus does not get
good fat saturation.
Scenario 5
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FSE T2 IACs have low spatial resolution
Build a Protocol/Optimize It!
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Brain w/wo contrast
Routine knee
Routine L-spine
Advantages/Disadvantages
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Changing FOV
Changing Slice Thickness
Changing ETL
Changing NSA/NEX
Changing TE
Changing Bandwidth
Changing TR
If this…..then this…..
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P. 136 and P.137
MRI in Practice
I have a question?
Student Questions
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a.
b.
c.
d.
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1. Higher magnetic field strength is generally
associated with which item listed?
decreased T2
higher SNR
less scan time d. increased spatial resolution
all of the above
correct answer B
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a.
b.
c.
d.
e.
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2. What is the advantage of using partial flip
angles in gradient echo pulse sequence?
A "steady state" is established in which most of
the tissue magnetization remains longitudinal.
It increase MR signal intensity.
Very short TR's can be used
both a and c
none of the above
correct answer is D
Steady State
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Shorter TR than a T1 or T2 sequence. There is
no time for transverse magnetization to decay
before the next pulse sequence. Flip angles of
30 to 45 degrees and a TR less than 50 ms.
Gradient Echo
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T1 gradient echo – T1 times of tissues
maximized and T2 times of tissues minimized
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larger flip angle to avoid longitudinal recovery of fat
and water.
T2 gradient echo – smaller flip angle to – T2
times of tissues maximized and T1 times of
tissues minimized
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Smaller flip angle allows longitudinal recovery
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a.
b.
c.
d.
e.
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3. Which of the following results from an
increase in the number of averages of an MRI
scan?
decreased scan time
increased SNR
increased artifact
increase spatial resolution
decreased spatial resolution
correct answer is B
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a.
b.
c.
d.
e.
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4. T2-weighted images are perfomed with:
short TE and short TR
short TE and long TR
long TE and long TR
TE equals TR
none of the above
correct answer is C
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a.
b.
c.
d.
e.
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5. If the technologist decreases the field of view
it will:
results in an image that depicts more area
improves spatial resolution
increase Signal to noise ratio
increases T1 weighting
both B and D
correct answer is B
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a.
b.
c.
d.
e.
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6. On single slice gradient echo images, rapidly
flowing blood appears:
dark
bright
dark or bright
depends on the vessel
both dark and bright
correct answer is B
Nursing mothers should suspend breast feeding
for up to ___ hours after an MRI exam with
contrast.
a. 12
b. 24
c. 24-30
d. 36-48
 answer: d
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The distance that the 5 Gauss line stands from
the isocenter of the magnet is:
a. 5ft
b. dependent upon the field strength of the magnet
c. dependent upon the field strength, geometry, and type
of shielding of the magnet.
d. dependent only upon the magnet and shielding
 answer: c
The Unit of measure for RF absorption is:
a. Volts per pound
b. amps per liter
c. watts per kilogram
d. volts per Tesla
 Answer: C
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Contraindications for an MRI exam include:
1. Cardiac pacemaker
2. ferromagnetic aneurysm clips
3. renal failure
a. 1 only
b. 2 only
c. 1 and 2
d. 1 and 3
 answer c
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A joint effusion of the left knee would appear as
what on a T2 weighted scan?
Dark area around the joint
b. Unremarkable
c. Bright area around the joint
d. Similar signal with the surrounding soft tissue
Answer: C
a.
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Inversion recovery sequences are primarily used
to identify
Pathology
b. Anatomy
c. Multiple sclerosis plaques
d. Fluid
Answer: C
a.
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Gadolinium contrast shortens which imaging
sequence
T2
b. IR
c. T1
d. FLAIR
Answer: C
a.
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What scanning sequence is used to evaluate for
strokes?
T2*
b. FLAIR
c. Diffusion Weighted Imaging
d. T1
Answer: C
a.
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What plane would be used to see the corpus
callosum in profile?
Transverse
b. Coronal
c. Sagittal
d. Oblique
Answer: C
a.
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How will freely diffusing water appear on a
DWI scan?
a.
b.
c.
Isointense
Bright
Dark
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ADC – Apparent Diffusion Coefficient
Restricted diffusion = low ADC (dark)
 Unrestricted diffusion = high ADC (same as trace
image)
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Trace image
Restricted diffusion = bright
 Unrestricted diffusion = no change
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What is the fringe field distance of 1.5 T
magnet?
2 Gauss
b. 5 Gauss
c. 7 Gauss
d. 1.5 Gauss
Answer: B
a.
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On a FLAIR or T2 weighted sequence a
subdural hematoma will appear
a.
b.
c.
Hypointense
Isointense
Hyperintense
References:
Westbrook, Catherine and Kaut, Carolyn (1998). MRI In Practice, 3rd Edition,
Malden, MA: Blackwell Science, Inc.