Diffusion imaging protocol effects on genetic associations

Laboratory of Neuro Imaging, Department of Neurology, UCLA School of Medicine, Los Angeles, CA.
Proceedings / IEEE International Symposium on Biomedical Imaging: from nano to macro. IEEE International Symposium on Biomedical Imaging 05/2012; DOI: 10.1109/ISBI.2012.6235712
Source: PubMed


Large multi-site image-analysis studies have successfully discovered genetic variants that affect brain structure in tens of thousands of subjects scanned worldwide. Candidate genes have also associated with brain integrity, measured using fractional anisotropy in diffusion tensor images (DTI). To evaluate the heritability and robustness of DTI measures as a target for genetic analysis, we compared 417 twins and siblings scanned on the same day on the same high field scanner (4-Tesla) with two protocols: (1) 94-directions; 2mm-thick slices, (2) 27-directions; 5mm-thickness. Using mean FA in white matter ROIs and FA 'skeletons' derived using FSL, we (1) examined differences in voxelwise means, variances, and correlations among the measures; and (2) assessed heritability with structural equation models, using the classical twin design. FA measures from the genu of the corpus callosum were highly heritable, regardless of protocol. Genome-wide analysis of the genu mean FA revealed differences across protocols in the top associations.

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    • "Similar results have also been reported in studies of young children (Brouwer et al, 2010) and in older individuals (eg, Pfefferbaum et al, 2001). Recently, it was also shown in the same Australian population as ours that the heritability of callosal FA, particularly in the genu, is high regardless of imaging protocol differences (Jahanshad et al, 2012b). Here, we show that predictions of microstructural measures may be made based on a few common polymorphisms. "
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