Diffusion weighted imaging sequences are now widely available on Magnetic Resonance Imaging (MRI) scanners. Diffusion Tensor Imaging (DTI) of the brain is able to show white matter tracts and is now commonly used in human medicine to study brain anatomy, tumors, structural pathways,. . . The purpose of this study was to show the interest of DTI to reveal the white matter fibers in the dogs' brain. DTI MR Images for this study were obtained with a 3 T system of 4 dogs euthanized for other reasons than neurological disorders. Combined fractional anisotropic (FA) and directional maps were obtained in the first 2 hours after death. The heads were amputated immediately after scanning and stored in 10% formalin until preparation for dissection. An experienced anatomist tracked white matter tracts with clinical relevance using the scanner software. The selected tracts were volume rendered and correlated with gross dissection. Using DTI we were able to track relevant neurological connections, such as the corticospinal tract, the optic and the cerebellar tract. The three dimensional anatomy is better presented using modern visualization techniques. DTI seems to be a valuable tool in order to present clinically relevant white matter tracts to neurological clinicians and researchers. Anat Rec, 296:340-349, 2013. V C 2013 Wiley Periodicals, Inc.Key words: brain; diffusion tensor imaging; dog; anatomy Since a few years, Magnetic Resonance Imaging is a reference technique for imaging the brain in different planes (sagittal, transversal, coronal) and the use of 1,5T to 7T MRI allows more and more accurate and detailed visualization of white matter localization than conventional CT-Scan and X-Ray (Van Thielen et al., 2010). However, an atlas of all the white matter tracts would be particularly useful for providing detailed anatomical data that is not available in studies based on conventional MRI data (Lawes et al., 2008). So we

28Although ultrasonography is widely used in equine orthopaedics, its use in the distal portion 29 of the digit is still limited. The purpose of this descriptive study was to document the normal 30 ultrasonographic appearance of the distal palmar digital area imaged at the distal pastern and 31 between the bulbs of the heels. Ultrasonographic images were obtained with a 7.5 MHz 32 microconvex transducer in 10 fresh equine cadaver forelimbs and 5 sound horses. Sagittal, 33 parasagittal and transverse images were obtained from the proximal aspect of the middle 34 phalanx to the distal sesamoid bone. Anatomical sections were obtained from 5 cadaver 35 specimens to correlate sonographic appearance with anatomical findings. The remaining 36 cadaver limbs were dissected to confirm normalcy. Ultrasonographic exams were possible on 37 all digits but distal images were more difficult to obtain in digits with long heels. Bony 38 structures (palmar surface of the middle phalanx and proximal border of the distal sesamoid 39 bone) and soft tissue structures (deep digital flexor tendon, digital tendon sheath, proximal 40 palmar recess of the distal interphalangeal joint, proximal recess of the podotrochlear bursa, 41 collateral sesamoidean ligaments) identified on the anatomical slices, were seen on the 42 matched ultrasonographic slices. Ultrasonography provides good anatomical details of the 43 palmar distal digit. The images of this study will serve as a reference for clinical studies on 44 ultrasonography of the palmar distal digit. 45 46

During preclinical stages of cattle orally infected with bovine spongiform encephalopathy (BSE), the responsible agent is confined to ileal Peyer's patches (IPP), namely in nerve fibers and in lymph follicles, before reaching the peripheral and central nervous systems. No infectivity has been reported in other bovine lymphoid organs, including jejunal Peyer's patches (JPP). To determine the potential sites for prion neuroinvasion in IPP, we analyzed the mucosal innervation and the interface between nerve fibers and follicular dendritic cells (FDC), two dramatic influences on neuroinvasion. Bovine IPP were studied at three ages, viz., newborn calves, calves less than 12 months old, and bovines older than 24 months, and the parameters obtained were compared with those of JPP. No differences in innervation patterns between IPP and JPP were found. The major difference observed was that, in calves of less than 12 months, IPP were the major mucosal-associated lymphoid organ that possessed a large number of follicles with extended FDC networks. Using a panel of antibodies, we showed that PP in 24-month-old bovines were highly innervated at various strategic sites assumed to be involved in the invasion and replication of the BSE pathogen: the suprafollicular dome, T cell area, and germinal centers. In PP in calves of less than 12 months old, no nerve fibers positive for the neurofilament markers NF-L (70 kDa) and NF-H (200 kDa) were observed in contact with FDC. Thus, in view of the proportion of these protein subunits present in neurofilaments, the innervation of the germinal centers can be said to be an age-dependent dynamic process. This variation in innervation might influence the path of neuroinvasion and, thus, the susceptibility of bovines to the BSE agent.

Recently, we published a first anatomical diffusion tensor imaging (DTI) atlas regarding white matter tracts in the canine brain. The purpose of this study was to show the significance of DTI in the revelation of the white matter fibres in the feline brain (i.e., to obtain an anatomical DTI atlas of images) and to descriptively compare these to previously obtained white matter fibre images of the canine brain. DTI MR Images of four cats euthanized for reasons other than neurological disorders were obtained with a 3 T system. Combined fractional anisotropic (FA) and directional maps were obtained within the hour after death. An experienced anatomist tracked white matter tracts of clinical relevance using the scanner software. After validation of these tracts, we compared relevant neurological connections between the cat and the dog. Comparison of cerebral structures between different species is easier when the three dimensional anatomy is visualized by using DTI. 3D rendered DTI images clearly show major differences in neurological architecture between cats and dogs for example, the more important space occupying role of the limbic system, and the less diffuse, less nodular, less pronounced and thinner fibre bundles in the feline brain compared to the canine brain (except for the cerebellum different parts connecting fibres passing through the brainstem which are pronouncedly developed). Anat Rec, 300:1270-1289, 2017. © 2017 Wiley Periodicals, Inc.

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