Three-dimensional reconstruction of median eminence microvascular modules.

To test the hypothesis that the median eminence microvasculature has a direct regulatory role in the hormonal communication between the brain and the pituitary gland, it is necessary to determine whether the physical means for such control (e.g. smooth muscle sphincters strategically located in the capillary plexus) actually exists. Our approach is to search for such structures in transmission electron micrographs of thin serial sections of the median eminence. The complexity of these images and the anticipated need to include large numbers of them in the study led us to consider computer reconstruction for this problem. We report here the successful three-dimensional reconstruction of capillary modules using digital image processing techniques for capillary feature detection/extraction, for construction of montages (mosaics) of overlapping images of the same section, and for automatic image registration by two independent methods without the use of fiducial marks. These tasks have been performed manually in nearly all the published neurobiological reconstructions; here they are performed by programs using only the mathematical properties of the images. Methods like those described here provide the only practical means for executing large scale reconstructions and gaining significant new information about the regulation of blood flow in this region of the brain.