Ex vivo susceptibility-weighted imaging anatomy of canine brain-comparison of imaging and histological sections

Abstract

Now that access of large domestic mammals to high-field MRI becomes more common, techniques initially implemented for human patients can be used for the structural and functional study of the brain of these animals. Among them, susceptibility-weighted imaging (SWI) is a recent technique obtained from gradient echo (GE) imaging that allow for an excellent anatomical tissue contrast and a non-invasive assessment of brain iron content. The goal of this study was to design an optimal GE SWI imaging protocol to be used in dogs undergoing an MRI examination of the brain in a 3-Tesla scanner. This imaging protocol was applied to ex vivo brains from four dogs. The imaging protocol was validated by visual inspection of the SWI images that provided a high anatomical detail, as demonstrated by their comparison with corresponding microscopic sections. As resolvable brain structures were labeled, this study is the first to provide an anatomic description of SWI images of the canine brain. Once validated in living animals, this GE SWI imaging protocol could be easily included in routine neuroimaging protocols to improve the diagnosis of various intracranial diseases of dogs, or be used in future comparative studies aiming at evaluating brain iron content in animals.

Keywords: atlas; brain; canine; histology; susceptibility-weighted imaging.

Figure 1

Tranverse section of the telencephalon at the level of the corpus striatum. Susceptibility-weighted images of the canine brain (left) and corresponding histological slide, Weil myelin staining (right). TELENCEPHALON (1 – 23): 1, Cingulum; 2, Cingulate gyrus; 3, Marginal gyrus; 4, Marginal sulcus; 5, Middle suprasylvian gyrus; 6, Middle suprasylvian sulcus; 7, Middle ectosylvian gyrus; 8, Middle ectosylvian sulcus; 9, Rostral sylvian gyrus; 10, Rhinal fissure; 11, Corpus callosum; 12, Subcallosal bundle; 13, Fornix; 14, Rostral commissure; 15, Centrum semiovale; 16, Caudate nucleus; 17, Putamen; 18, Globus Pallidus; 19, Internal capsule; 20, External capsule; 21, Extreme capsule; 22, Claustrum; 23, Lateral ventricle. CRANIAL NERVES: 24, Optic chiasm.

Figure 2

Transverse section of the diencephalon at the level of the infundibulum. Susceptibility-weighted images of the canine brain (left) and corresponding histological slide, Weil myelin staining (right). TELENCEPHALON (1–23): 1, Cingulum; 2, Cingulate gyrus; 3, Marginal gyrus; 4, Marginal sulcus; 5, Middle suprasylvian gyrus; 6, Middle suprasylvian sulcus; 7, Middle ectosylvian gyrus; 8, Middle ectosylvian sulcus; 9, Rostral sylvian gyrus; 10, Caudal sylvian gyrus; 11, Pseudosylvian fissure; 12, Corpus callosum; 13, Subcallosal bundle; 14, Fornix; 15, Caudate nucleus; 16, Putamen; 17, Internal capsule; 18, External capsule; 19, Extreme capsule; 20, Claustrum; 21, Amygdaloid body; 22, Hippocampus; 23, Lateral ventricle. DIENCEPHALON (24–31): 24, Thalamic nuclei; 25, Interthalamic adhesion; 26, Reticular thalamic nucleus; 27, Optic tract; 28, Mamillothalamic tract; 29, Infundibulum; 30, Endopeduncular; 31, Third ventricle. MULTIPLE BRAIN REGIONS (32): 32, Corticopontine, corticobulbar, and corticospinal projection fibers.

Figure 3

Transverse section of the diencephalon at the level of the geniculate bodies. Susceptibility-weighted images of the canine brain (left) and corresponding histological slide, Weil myelin staining (right). TELENCEPHALON (1–20): 1, Cingulum; 2, Cingulate gyrus; 3, Splenial sulcus; 4, Splenial gyrus; 5, Suprasplenial sulcus; 6, Marginal gyrus; 7, Marginal sulcus; 8, Middle suprasylvian gyrus; 9, Middle suprasylvian sulcus; 10, Middle ectosylvian gyrus; 11, Caudal ectosylvian gyrus; 12, Middle ectosylvian sulcus; 13, Caudal ectosylvian sulcus; 14, Rhinal fissure; 15, Piriform cortex; 16, Corpus callosum; 17, Subcallosal bundle; 18, Caudal commissure; 19, Hippocampus; 20, Lateral ventricle. DIENCEPHALON (21–26): 21, Optic tract; 22, Lateral geniculate nucleus; 23, Medial geniculate nucleus; 24, Optic radiation; 25, Pulvinar; 26, Third ventricle. MESENCEPHALON (27–30): 27, Crus cerebri; 28, Red nucleus; 29, Substantia nigra; 30, Mesencephalic aqueduct. MULTIPLE BRAIN REGIONS (31–32): 31, Medial longitudinal fasciculus; 32, Spinothalamic tract.

Figure 4

Tranverse section of the mesencephalon. Susceptibility-weighted images of the canine brain (left) and corresponding histological slide, Weil myelin staining (right). TELENCEPHALON (1–12): 1, Cingulate gyrus; 2, Splenial sulcus; 3, Splenial gyrus; 4, Suprasplenial sulcus; 5, Marginal gyrus; 6, Marginal sulcus; 7, Ectomarginal gyrus; 8, Middle suprasylvian sulcus; 9, Caudal ectosylvian gyrus; 10, Caudal sylvian gyrus; 11, Hippocampus; 12, Lateral ventricle. MESENCEPHALON (13–18): 13, Crus cerebri; 14, Rostral colliculus; 15, Periaqueductal gray; 16, Brachium of the caudal colliculus; 17, Interpeduncular nucleus; 18, Mesencephalic aqueduct. RHOMBENCEPHALON (19–20): 19, Pontine nuclei; 20, Transverse fibers of pons. MULTIPLE BRAIN REGIONS (21–22): 21, Medial longitudinal fasciculus; 22, cerebellothalamic and cerebellorubral tracts.

Figure 5

Tranverse section of the metencephalon, at the level of the pons. Susceptibility-weighted images of the canine brain (left) and corresponding histological slide, Weil myelin staining (right). TELENCEPHALON (1–9): 1, Cingulate gyrus; 2, Splenial sulcus; 3, Suprasplenial sulcus; 4, Marginal sulcus; 5, Ectomarginal gyrus; 6, Ectomarginal sulcus; 7, Caudal suprasylvian gyrus; 8, Caudal ectosylvian gyrus; 9, Occipital gyrus. RHOMBENCEPHALON (10–21): 10, Rostral cerebellar peduncle; 11, Middle cerebellar peduncle; 12, Transverse fibers of pons; 13, Dorsal tegmental nucleus; 14, Vestibular Nuclei; 15, Pontine nucleus of the trigeminal nerve; 16, Superior central nucleus; 17, Locus coeruleus; 18, Ventral spinocerebellar tract; 19, Cerebellar vermis; 20, Paraflocculus; 21, Fourth ventricle. MULTIPLE BRAIN REGIONS (22–23): 22, Reticular formation; 23, Medial longitudinal fasciculus. CRANIAL NERVES: 24, Trigeminal nerve.

Figure 6

Tranverse section of the myelencephalon and cerebellum, at the level of the genu of the facial nerve. Susceptibility-weighted images of the canine brain (left) and corresponding histological slide, Weil myelin staining (right). TELENCEPHALON (1–7): 1, Splenial gyrus; 2, Suprasplenial sulcus; 3, Marginal sulcus; 4, Ectomarginal gyrus; 5, Ectomarginal sulcus; 6, Caudal suprasylvian gyrus; 7, Occipital gyrus. RHOMBENCEPHALON (8–19): 8, Caudal cerebellar peduncle; 9, Vestibular Nuclei; 10, Cerebellar vermis; 11, Lingula; 12, Flocculus; 13, Fastigial cerebellar nucleus; 14, Pyramidal tract; 15, Nucleus of the spinal tract of the trigeminal nerve; 16, Spinal tract of the trigeminal nerve; 17, Superior Olivary nucleus; 18, Trapezoid body; 19, Genu of facial nerve. MULTIPLE BRAIN REGIONS (20–21): 20, Reticular formation; 21, Medial lemniscus.

Figure 7

Tranverse section of the myelencephalon and cerebellum at the level of cerebellar nuclei. Susceptibility-weighted images of the canine brain (left) and corresponding histological slide, Weil myelin staining (right). RHOMBENCEPHALON (1–13): 1, Caudal cerebellar peduncle; 2, Vestibular Nuclei; 3, Cerebellar vermis; 4, Ansiform lobule; 5, Paraflocculus; 6, Fastigial cerebellar nucleus; 7, Interpositus cerebellar nucleus; 8, Dentate cerebellar nucleus; 9, Pyramidal tract; 10, Nucleus of the spinal tract of the trigeminal nerve; 11, Spinal tract of the trigeminal nerve; 12, facial motor nucleus; 13, Fourth ventricle. MULTIPLE BRAIN REGIONS: 14, Reticular formation.