Manufacture of Three-Dimensional Image and Virtual Dissection Program of the Rat Brain Stem

Abstract

Three-dimensional (3D) structures of nuclei and tracts in the rat brain stem are too complex to be understood by books describing primarily two-dimensional (2D) pictures. The purpose of this study was to prepare a new educational tool for understanding 3D structures of the rat brain stem. We attempted to manufacture a virtual dissection program on which 3D images of the rat brain stem could be sectioned or rotated. A brain stem, extracted from a Sprague-Dawley rat, was serially sectioned into 135 specimens using a Cryocut. Each specimen was stained with osmium, printed using an enlarger, and inputted to a computer using a scanner. 2D images of rat brain stem were aligned on the alignment program. In all 2D images, 33 nuclei and tracts of the rat brain stem were manually drawn: 3D images of the brain stem were reconstructed through a volume-based rendering of the 2D images. Using the 3D images of the rat brain stem as the main feature, a virtual dissection program was manufactured. Dissection functions such as sectioning 3D images of the rat brain stem to show its plane and rotating 3D images of the selected nuclei and tracts were established. Examples of understanding 3D structures of the rat brain stem using the virtual dissection program were as follows. 1) Gracile nucleus looked like sperm, whose head faced cranially; and tail faced caudally. Cuneate nucleus looked like spoon, and the sperm head seemed to be put in the spoon. 2) Dorsal motor nucleus of vagus nerve was intervened between solitary nucleus and hypoglossal nucleus. These three structures of the bilateral sides surrounded the central canal. 3) Lateral lemniscus was flat as if pressed by the bilateral sides. The cranial part of lateral lemniscus was narrow and faced dorsally; the caudal part of lateral lemniscus was surrounded by a horseshoe-shaped middle cerebellar peduncle. The virtual dissection program of the rat brain stem was helpful in understanding 3D structures of nuclei and tracts in the rat brain stem. Next plan of this series of studies is to manufacture a virtual dissection program of the human brain stem.