Morphological modeling via isosurfacing: the laryngeal skeleton of gekkonid lizards as a test case

A novel technique for modeling microscopic anatomical structures in three dimensions was developed as part of a survey of gekkonid laryngeal skeletal morphology (Reptilia: Gekkonidae). Excised larynges were transversely sectioned at 10 microns and stained using standard procedures. With a projection microscope, outline drawings of the sectioned laryngeal cartilages were made at regular intervals, depending on the rate and degree of structural change observed while sampling. The drawing set was digitized with a flatbed scanner, and aligned using 'NIH Image' for Macintosh computers. Physical connectivity between successive outlines was provided by inserting one or more artificial slices between those that had been digitized, and draping a skin of rendered contours over all of the interstitial spaces present in the template. The Application Visualization System, a general purpose visualization package for UNIX-based computer systems, was used to visualize and render the resulting 'isosurfaces', which appear as solid three-dimensional objects and can be viewed from any perspective. Since isosurfaced reconstructions can be based on as little as 20% of the cross-sections available, this procedure has the potential to be a valuable research tool for future morphological work at the microscopic level.