msmcdespot : looking at maps
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MSmcDESPOT : Looking at Maps. October 29, 2010. Motivation. Thus far we’ve been studying DV and DVF, which collapses all of our data into a single metric for each patient One of the key advantages of mcDESPOT is that it acquires whole brain maps - PowerPoint PPT PresentationTRANSCRIPT
MSmcDESPOT: Looking at Maps
October 29, 2010
Motivation
• Thus far we’ve been studying DV and DVF, which collapses all of our data into a single metric for each patient
• One of the key advantages of mcDESPOT is that it acquires whole brain maps
• We should start looking at our data as whole brain maps– Perhaps different subtypes of MS are associated
with different spatial distributions of MWF
Baseline: Mean MWF Normals
Baseline: Mean MWF CIS
Baseline: Mean MWF RRMS
Baseline: Mean MWF SPMS
Baseline: Mean MWF PPMS
Discussion
• There’s clearly a drop in overall MWF as we progress from CIS to RR to SP to PP
• Can’t really discern any favoring for locations of low MWF other than around the ventricles– DV maps would probably show this better than
anything, should generate a probabilistic DV map
Baseline: Std. Dev. MWF Normals
Baseline: Std. Dev. MWF CIS
Baseline: Std. Dev. MWF RRMS
Baseline: Std. Dev. MWF SPMS
Baseline: Std. Dev. MWF PPMS
Discussion• In normals, MWF has a much lower standard deviation in WM
areas• RR patients seem to have an overall lower standard deviation
than CIS– One interpretation might be that CIS patients are only starting to
lose myelin so there is a lot of variability among them• PP is by far the worst, the variance of MWF among the subjects
seems to be the same throughout the brain– This means that the amount and location of myelin lost among PP
patients varies wildly• Of course standard deviation is a group based measure, not
sure about the direct clinical application for one patient
1yr: Mean MWF CIS
1yr: Mean MWF RRMS
1yr: Mean MWF SPMS
1yr: Mean MWF PPMS
1yr: Std. Dev. MWF CIS
1yr : Std. Dev. MWF RRMS
1yr: Std. Dev. MWF SPMS
1yr: Std. Dev. MWF PPMS
Discussion
• The 1yr cross-section looks like the Baseline more or less
• Our previous observations still seem to hold
Difference Maps
• For each subject, the difference map was computed as MWF_1yr – MWF_baseline– Then the mean difference between patients was
computed for each subtype as well as the standard deviation of the differences
• The following maps may be hard to look at, they are highly non-traditional and probably it’s the first time anyone has ever seen such images
Difference: Mean CIS
Difference: Mean RRMS
Difference: Mean SPMS
Difference: Mean SPMS
Discussion
• There is a clear different between CIS and RR, with RR patients having much larger drops in MWF
• Actually, I feel like RR patients have the most actively changing MWF among all the subtypes looking at these images– Consistent with early stages being the most
active? Have to check the ages of our RR patients.
Difference: Std. Dev. CIS
Difference: Std. Dev. RRMS
Difference: Std. Dev. SPMS
Difference: Std. Dev. PPMS
Discussion
• Here again the RR seems to have lower variance than CIS– The interpretation is different though, this means
that the variation of the change in MWF is low– Perhaps RR patients are losing similar amounts of
myelin in the same areas of the brain?• Need to somehow show both mean MWF difference
and its standard deviation together
Ratio Maps
• For each subject, the ratio map was computed as MWF_1yr/MWF_baseline– Then the mean ratio between patients was computed for
each subtype as well as the standard deviation of the ratios• These maps are ugly, it is tough to tell what’s going on
– Ignore the white fringing around the brain, caused by regions of low MWF
– Inside the brain, they would indicate places where lesions with low MWF are• Maybe even they show lesions that have remyelinated a little as
(not as small MWF)/(really small MWF) = big number
Ratio: Mean CIS
Ratio: Mean RRMS
Ratio: Mean SPMS
Ratio: Mean PPMS
Discussion
• Hard to decipher these– CIS seems the most uniform, so the percent
change in MWF is perhaps low, which may not be clear based on just the mean difference maps
Ratio: Std. Dev. CIS
Ratio: Std. Dev. RRMS
Ratio: Std. Dev. SPMS
Ratio: Std. Dev. SPMS
Discussion
• CIS and RR seem about the same here• Clearly there’s higher variability for the change
in MWF among progressive patients as was also visible in the standard deviation difference maps
Thoughts
• This is more data than someone can humanly process, need to identify key regions
• Unsupervised exploratory data mining techniques could be worth pursuing, since our outcomes of EDSS and ΔEDSS are problematic– Goal here is to find patterns in the data rather
than trying to predict an outcome