Figure 2.
A, Single-subject horizontal images of FA, parallel diffusivity (λ‖), and perpendicular diffusivity (λ⊥) showing lesion in the dorsal column at 3 d (left) and 30 d (right) after dorsal root axotomy. The locations of the lesion in the dorsal column are indicated by yellow arrows. The unit of the color bars for the parallel and perpendicular diffusivity images is 10−5 cm2/s. B, Serial axial parallel diffusivity images at four different levels along the spinal cords at 3 d (left) and 30 d (right) after axotomy with streamlines generated by fiber tracking (FT) in the ipsilateral and contralateral dorsal column. Tracking of the ipsilateral streamlines started from seed pixels within the lesion at L2, whereas tracking of the contralateral streamlines started from seed pixels in the contralateral dorsal column at L2. These streamlines are color coded by the local FA, λ‖, and λ⊥ values [FT(FA), FT(λ‖), and FT(λ⊥), respectively] along each streamline. The unit of the color bars for the parallel and perpendicular diffusivity images is 10−5 cm2/s. The axial locations of these selected images are indicated by the dashed lines in the images in A. The locations of the lesions are indicated by yellow arrows. In the ipsilateral dorsal column, the streamlines generated by fiber tracking starting at the lesion at L2 closely follow the lesion at other levels. C, Renderings of diffusion tensors as three-dimensional ellipsoids in the dorsal columns at 3 d (left) and 30 d (right) after axotomy. The yellow arrows indicate the locations of the lesions. For each tensor, the lengths of the three axes of each tensor are proportional to the three eigenvalues, and the color reflects the FA value. The two insets in the middle show magnified views of individual diffusion tensors as three-dimensional ellipsoids in the lesion and contralateral dorsal column at 30 d after axotomy.