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ARTIFACTS & QUALITY CONTROL
WEEK SIX

Objective
?Identify various types of artifacts
?Be able to identify artifact from
other imaging issues
?Learn how to correct artifact
issues

? ��Wrapping�� of anatomy outside
the FOV back into the image.
? Can occur along the frequency
or phase encoding axis
?Compensation
Techniques
? Increasing FOV as far as the coil
will allow
? Use oversampling in the phase
direction
? Spatial pre saturation pulses
can be placed over the
anatomy

? You have patients who
have hip replacements,
etc. and have hardware
in place. This will
cause an artifact to
your image.
?Compensation
Techniques
? Increasing bandwidth

? The ability or how well a
property can be magnetized.
? Results in signal loss and
dephasing in that structures
boundaries.
? Mostly affected because of
metal in the area.
? Be sure to remove all metal
from patient, use SE or FSE
sequences, decrease TE to
allow for more.

? ��ringing�� artifact at high
and low signals.
? Best seen in cervical
spine and brain
? Occurs when an over
and under estimation of
signal is produced at
high contrast levels.
? Increase the number of
phase encoding steps
to minimize this artifact.

? Appears as black or white
band at fat and water
interfaces occurring in the
frequency direction.
? It is impossible to get rid
of this artifact but you can
reduce it.
? Reducing field strength
? Keep FOV lowest as possible
? Reduce the bandwidth on high
field units

? Occurs when RF
enters the room
during a scan
? Occurs either
frequency or phase
direction
? To correct this issue
call the engineer.

? Respiration, cardiac, blood flow,
CSF fluid, swallowing, peristalsis,
body movements
? ��ghosting��
? Corrective measures can include:
? Changing your phase and frequency
directions
? Using pre-saturation bands over that
area
? Incorporate the use of respiratory gating
or asking the patient to hold their
breath.
? Cardiac gating with ECG leads that will

? The machine
averages a portion
of tissue in one
slice.
? Results in poor
spatial resolution
and signal intensity
? Use thinner slices

? Our image experiences an
increase in T1 weight and
decrease in SNR.
? ��slice overlap artifact��
? When your acquisition slices
overlap onto another and more
protons get saturated
? Decreased signal and contrast
? One way to correct this is by
decreasing the angle of the slices

?RF pulse meant for a
neighboring slice is
pre excited and
results in loss of
signal in a slice.
?Leave a gap of 1/3
slice thickness
?Alternate the slices
by using interleaving

? It can be like
looking through
two window
screens
? Aliasing of one
side the body to
the other
? Make use of the
SE sequence
? Patient keeps
their arms in
FOV

?Experience the
same artifacts as
routine MR
imaging such as
noise, ghosting
and motion
artifacts

? Breath holds by patient or Respiratory
Gating/Triggering
? Suppression imaging techniques
? Cardiac gating
? Increase FOV
? Change direction to or from phase or frequency
? Contact engineer for RF leaks
? Use SE or FSE sequences instead

Objective
?Learn basic quality control (QA)
measures to correct problems
?Learn the importance of regular
quality control in MR
?Learn how to care for coils, door
seals, coil cables

? Test checks the
accuracy with which
a slice of specified
thickness is reached.
?Can affect the image
contrast
?Can cause a low
signal to noise ratio.

? Test of the scanner��s ability to
correct small objects when the
contrast-to-noise ratio is very high so
that it does not play a role in
completing it��s job.
? Technologist will visually inspect if
the white dots are clear

? The
technologist
will visually
inspect how
many dots they
can count to
complete this
test.

? ROI denotes areas
where technologist
will test for noise
inside the phantom
around the
phantom.
? A calculation and
comparison with
previous values is
made.

? Identify is the magnet
is drifting or RF
instability
? Scanner is
automatically tuned
to water for the
correct slice position
and fat saturation.
? Phantom is scanned
to acquire a reading
for CF

? This denotes the
power needed for an
RF pulse
? Must remain
constant
? Available pre and
post scan

?making length
measurements on the
images from one point
to the other end point.

? Always handle coil and cables gently
? Don��t drop coils or slam them
? Don��t�� allow cables to hit the floor
? Some cables have prongs, so be careful when
plugging them in as they can break
? Check door seals for RF shielding compromise
? Inspect coil cables for any separations and
cracks

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Artifacts and Quality Control

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