[Mristudio-users] Impact of white matter lesionson on accuracy of fiber tracking (FACT)

[Yakushev, Igor]

Dear Colleagues,



I wonder if there is any empirical evidence about impact of white matter lesions (WML) on accuracy of fiber tracking? The following questions are of specific interest:

1) what is the (at least expected) range of FA-values in a WML? Can FA-values within a WML (at least a proportion of voxels) be still within the range typical for "normal" WM?

2) To what extent can one exclude/minimize impact of WML on performance of FACT (in a specific brain region) by simply adjusting the FA-threshold?

3) In other words, if one tracts a specific fiber bundle within the brain with a pronounced vascular encephalopathy (VE) at a common FA-threshold of 0.2, and the resulting track looks fine, i.e. not worse as in a subject without any VE, can one conclude that there was just no WML over the course of this particular track and tracking is likely to be not biased by VE in this subject?

4) Let's lower the FA-threshold down to 0.05, repeat the above analysis and consider two possible outcomes: a) fiber tracking in the VE+ subject produced considerably less fibers than in the VE- subject; b) fiber tracking produced the same results in both subject. Can one now conclude that tracking of this particular bundle is a) biased b) not biased by VE, respectively?



Thanks.

Igor





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Igor Yakushev, MD

Department of Psychiatry

University Medical Center Mainz

Mainz, Germany