Hello,
I wouldn't mind jumping on this issue more broadly. Diffusion indices like FA, ADC, RD, and AD have more clear physiologic correlates. But what does the length of a tract, the volume of a tract, or the number of streamlines say about physiology? Tract length seems to be very dependent on head size. Or, for example, a person with a long corticospinal tract might simply be taller. At the very least these indices should be included with nuisance variables controlling for brain size. Length and volume measures seem to be very much affected by pulse sequence parameters, further calling into question their utility (see Wang et al., 2012; doi: 10.1016/j.neuroimage.2011.12.062). However, tract volume at least makes more intuitive sense (for example, quantifying Wallerian degeneration in T1 scans is essentially a volume measure). I thought Alan raised an important issue.
Anthony
On 5/25/16 10:34 AM, Alan Francis wrote:
Hi Imagers -
I am looking at the Uncinate fasciculus in a Cannabis use disorder (CUD). I found that CUD subjects have significantly shorter tract length and a significant group x side interaction in comparison with controls. Have you seen this before? What is the interpretation of this finding?
Thank you,
Alan
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