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Figure 3. (a) Mean diffusion (D) and fractional anisotropy maps (FA) for a stroke patient at three time points: 37 h (left column), 1 week (central column) and 3 months (right column). FA is lower row and D is upper row. These maps demonstrate the regions of interest (ROIs) used in this study. The lesion ROIs are presented in orange and the control ROIs in green. Each of these ROIs consisted of 5 x 5 x 1 voxels. (b) This figure illustrates the p:q plane for the stroke patient, with lesion and control ROIs at (a) 37 h, (b) at 1 week and (c) at 3 months. The control ROIs are denoted in blue and the lesion ROIs in red. The arrows demonstrate the trajectory followed by the lesion in this patient and show schematically how, while the control ROIs remain in roughly the same region in the p:q plane, the ischaemic lesion demonstrates a trajectory composed of acute (reduction in p, reduction in q), subacute (normalization of p while q remains low) and chronic (increased p while q remains low) phases. The inset shows schematically the location of the lesion ROI with respect to the control ROI and a line of constant fractional anisotropy. As FA is function of the angle 
, the figure indicates that at 37 h the lesion has a higher FA than the control, while at 1 week it has a lower FA than the control.
