Using SIENA for atrophy measurements in MS, I am wondering, whether the
PBVC is influenced by acute black holes.
In the following example an acute black hole showed up in m04 over four
The render image showed a big change in the area of the acute black hole
from m04 to m06 (see attachment).
To evaluate the impact of this acute black hole I manually edited the
flow images (m04-m06) and calculated the number of non-zero Pixels and
the mean (avwstats -V -m) (see below).
Although through editing only a small portion of the overall number of
Px changed, the mean has changed dramatically (38,7%).
As I understand, the mean is one factor in the calculation of the
overall change, so this acute black hole may influence the result and is
taken as atrophy.
How would you interpret the change in the mean flow, does it
significantly impact the overall PBVC?
Are there other factors accounting for these kinds of errors?
Is there a possibility to mask such areas?
Should such images be excluded from analysis?
image # non-zero Px mean of non-zero Px
m04-m06-flow 152475 0,000354
m06-m04-flow 148526 -0,000528
after editing flow images and erasing change detected in the area of the
acute black hole
m04-m06-flow-mod 151872 0,000217
m06-m04-flow-mod 148382 -0,000490
difference between normal and edited images
# Px m04-m06: 603 = 0,395%
# Px m06-m04: 144 = 0,097%
mean of non-zero Px m04-m06: 0,000137 = 38,7%
mean of non-zero Px m06-m04: 0,000038 = 7,2%
Dr. Martin Hardmeier
Department of Neurology
University Hospital Basel
Tel: 0041-61-2652525; pager -2913