In vivo study of cerebral white matter in the dog using diffusion tensor tractography

Abstract

Conventional magnetic resonance imaging (MRI) allows investigators and clinicians to observe the anatomy and injuries of the cerebral white matter (CWM) in dogs. However, dynamic images based on the diffusion tensor (DT) technique are required to assess fiber tract integrity of the CWM. Diffusion tensor tractography (DTT) produces a three-dimensional representation in which data are displayed on a colored map obtained from the anisotropy of water molecules in the CWM tracts. Fractional anisotropy (FA) is a value that measures changes in water diffusion, which can occur if the CWM tracts are displaced, disrupted, or infiltrated. The goal of this study was to determine the feasibility of DTT for in vivo examination of the normal appearance of CWM in dogs through visual and quantitative analysis of the most representative CWM tracts. Nine tractographies were performed on healthy dogs using a 3T MRI scanner. T1- and T2-weighted images and DTI were acquired at different planes. Using DTT, three-dimensional reconstructions were obtained. Fractional ansisotropy and apparent diffusion coefficient (ADC) values of the right and left corticospinal tracts, corpus callosum, cingulum, and right and left fronto-occipital fasciculus were determined. Tract reconstructions were similar in 8/9 healthy dogs. Values for FA and ADC were similar in all the dogs. In one dog, tract reconstructions were inhomogeneous; these were displaced because it had larger lateral ventricles. Findings indicated that DTT is a feasible technique for in vivo study of CWM in dogs and that it complements information from conventional MRI.

Keywords: cerebral white matter; diffusion tensor; dog; in vivo; tractography.

Fig 1

Images illustrating the corticospinal tract in a healthy dog. (A) Diffusion tensor tractography (DTT) image, side view. (B) T1-Weighted image and DTT image, sagittal view. (C) Diffusion tensor tractography (DTT) image on the colored map, transverse sectional view.

Fig 2

Images illustrating the corpus callosum in a healthy dog. (A) Diffusion tensor tractography (DTT) image, side view. (B) T1-weighted image and DTT image, dorsal view. (C) Diffusion tensor tractography image on the colored map, dorsal view.

Fig 3

Images illustrating the cingulum in a healthy dog. (A) Diffusion tensor tractography (DTT) image, dorsal view. (B) T1-weighted image and DTT image, dorsal view. (C) Diffusion tensor tractography image on the colored map, dorsal view.

Fig 4

Images illustrating the fronto-temporo-occipital tract in a healthy dog. (A) Diffusion tensor tractography (DTT), side view. (B) T1-weighted image and DTT image, sagittal view. (C) Diffusion tensor tractography image on the colored map, dorsal view.

Fig 5

Comparison between a healthy dog with large lateral ventricles and a healthy dog with normal ventricles. (A) Diffusion tensor tractography (DTT) image, corticospinal tract with altered topography and corpus callosum due to large lateral ventricles, dorsal view. (B) Diffusion tensor tractography image, corticospinal tract with normal downward topography of the fibers, dorsal view. (C) T1-weighted image and DTT image, corticospinal tract with anterior and lateral displacement of the fibers and of the corpus callosum due to large lateral ventricles, dorsal view. (D) T1-weighted image and DTT image, corticospinal tract with normal downward topography of the fibers, dorsal view. (E) Diffusion tensor tractography image of the corticospinal tract on the colored map with anterior and lateral displacement of the fibers and of the corpus callosum due to large lateral ventricles, dorsal view. (F) Diffusion tensor tractography image, corticospinal tract on the colored map with normal topography of the fibers, dorsal view.