Visualizing Diffusion Tensor Volume Differences

We present a technique for visualizing the differences between two diffusion tensor MR (DT-MRI) volumes. Our technique registers two DT-MRI’s and then produces a 3D model that allows a user to simultaneously view structure in each volume. The geometric model is based on an earlier one developed to visually represent a single volume with a carefully chosen set of streamtubes [6,7]. In the new model, we choose corresponding tubes in both volumes and show how they differ as a way to display the differences between the volumes. Saturation is used to indicate the magnitude of the difference between corresponding points on streamtubes. Streamtubes follow the orientation of the principal eigenvector of the diffusion tensor at each point in the volume. The cross-section at each point of the streamtube is an ellipse determined by the second and third eigenvectors and eigenvalues of the diffusion tensor. We apply the method to four cases. In the first, we show how the choice of integration method can change the streamtubes by comparing streamtubes generated with different integration methods. In the second case, we show difference models for two volumes that are identical except for noise. In the third case we show differences between two volumes acquired from the same human subject but at different orientations.