Canine Hippocampal Formation Composited into Three-Dimensional Structure Using MPRAGE

Abstract

ABSTRACT. This study was performed to anatomically illustrate the living canine hippocampal formation in three-dimensions (3D), and to evaluate its relationship to surrounding brain structures. Three normal beagle dogs were scanned on a MR scanner with inversion recovery segmented 3D gradient echo sequence (known as MP-RAGE: Magnetization Prepared Rapid Gradient Echo). The MRI data was manually segmented and reconstructed into a 3D model using the 3D slicer software tool. From the 3D model, the spatial relationships between hippocampal formation and surrounding structures were evaluated. With the increased spatial resolution and contrast of the MPRAGE, the canine hippocampal formation was easily depicted. The reconstructed 3D image allows easy understanding of the hippocampal contour and demonstrates the structural relationship of the hippocampal formation to surrounding structures in vivo.KEY WORDS: 3D, canine, hippocampal formation, MPRAGE.J. Vet. Med. Sci. 72 (7): [853][854][855][856][857][858][859][860] 2010 The hippocampal formation is located in the medial surface of the temporal lobe, along the floor and medial wall of the temporal horn of the lateral ventricle [1,2]. The hippocampal formation is shaped like a C [19]. It extends in a curve, starting from the amygdala ventrally in each piriform lobe and progressing caudodorsally and then cranially over the diencephalon [8,21]. The caudal end of the hippocampal formation tapers under the splenium of the corpus callosum [22]. Dorsal to the caudal thalamus, the hippocampal formation of each cerebral hemisphere meets at the medial plane, and the fornix, the hippocampal commissure, is formed at this region [2,8]. The hippocampal formation can be divided into three parts: a cranial part, or head, a middle part, or body and a caudal part, or tail [8]. It is again divided into 3 main transverse zones: the dentate gyrus; the hippocampal proper, also called the cornus ammonis (CA); and the subiculum [1,2,24].Abnormalities of the hippocampal contour and volume play important roles in several functions such as spatial response in dogs [12] [5,17]. These have been resulted in increased importance of the precise understanding of the hippocampal anatomy. These also have made three-dimensional (3D) hippocampal structure importance in medical image.MRI has been the principal method for studying structural brain change in vivo [11]. Normal MR images of canine brain has been described in previous studies [13,14]. They have only depicted the normal canine brain using a low field strength MRI scanner. In those images, description of the hippocampal formation and the perihippocampal structures were not available. It was because of their small size and ambiguity with the perihippocampal structures and low field strength having decreased signal to noise ratio [11]. There haven't been MRI studies that focused on the hippocampal formation itself. In addition, it is not easy to comprehend 3D relationship among the brain structures on MRI. Currently, the 3D canine hippocampal imag...

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