Confounds in Image Registration

Sune Darkner¹, Matthew George Liptrot¹, Jon Sporring¹

Many of the analysis methods applied to neuroimaging are dependent upon correct co-registration of datasets. The direction in which the registration is applied (image A registered to image B, or vice-versa) may vary depending upon the topic of interest without consideration of possible confounds this may involve. Here we show how even affine registration is subject to inverse inconsistency, where the co-registration result is different depending upon the direction chosen. A difference of 0.5 voxels is demonstrated for a pure translational, affine registration. Care must therefore be taken when performing co-registration in order to minimize subsequent directionality-based confounds.