A question I had about the gradient tables for Tracula - I recently came across this passage from Hui Zhang:

"To correct for any errors that you identify, you need to first modify the gradient table, then repeat the tensor reconstruction. The modification of the gradient table typically involves flipping the signs of the x or y component of all gradient vectors. To determine the correct flipping of the signs in a systematic way, it is necessary to understand why this happens. The reason is that the gradient directions are always defined with respect to some right-handed frame of reference, while the frame of reference of the acquired image data is typically NOT right-handed. This mismatch is the cause of the problem. The sign flipping intends to fix this mismatch and the key is to identify the difference between the two frames of reference in question. In our experience, if the data is acquired on SIEMENS scanners, the signs of x gradient components need to be flipped; for GE scanners, it is usually the y components." (from http://dti-tk.sourceforge.net/pmwiki/pmwiki.php?n=Documentation.VisualizationTool). 

Does this mean that the gradient tables i get from dcm2nii need to have the Y component flipped for my GE acquisitions or is this adjusted in the tracula processing?

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