Day 6: Who Do I Look Like?
The MRI Answer
The correct answer is "b".
Here is an explanation from our imaging expert,
These images demonstrate intermittent corruption of
the data, typically by electrical problems. They have
been artificially generated by using viewit to modify
the raw data from the reference image before
transforming it. On the left, a few data points have
been modified, as might happen if an electrical
transient (such as a static discharge, sometimes
called an "arc") occured during the digitization of
one echo. Note the elevated background level. The
venetian blind pattern becomes a crosshatch with two
arcs, and with multiple arcs, may be indistinguishable
from random noise. A transmitter arc looks different,
since it affects the MR magnetization directly, and
does not occur during digitization.
On the right, some part of each of three rows of
the data has been set to zero, as might happen if a
computer problem caused loss of data, or a loose cable
momentarily (for a few milliseconds) prevented the
received signal from being digitized (sometimes called
"dropout"). Note the similarity (and differences) to
the motion/instability case. The width of the band at
the center is inversely proportional to the duration
of the dropouts. Look closely to see the droputs.
For more information on artifacts, click here to
visit the MRI
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