Laser scanner digitizes fish skeletons
As part of a collaborative effort with the Gulf Coast Research Laboratory (Ocean Springs, MS), Robert Cromwell at Purdue University (West Lafayette, IN) is studying the feasibility of measuring fish skeletons using laser-scanning and rangefinding techniques. As a low-cost alternative to computed tomography (CT) or magnetic-resonance imaging (MRI), the results obtained are similar to a reconstructed CT image.
"Precise and detailed three-dimensional models of the development of a species provide a quantitative means of detecting abnormality and, thus, detect the effects of pollution," says Cromwell. After digitizing dorsal, lateral, and ventral views of a fish skull, a map can be created containing approximately 500 ¥ 200 points, each of which contains the (x,y,z) location of the corresponding point on the skull with a resolution of 0.2 ¥ 0.4 mm in each dimension.
In the photograph-like image, there is a one-to-one match between the pixels and the x,y,z values encoded in other images. This allows structures such as sutures between cranial bones to be located in three dimensions. Intensity maps of the digitized images show the local surface orientation, using a lighting model that simulates a point light source above the viewer`s left shoulder. Because range data from the sensor are encoded as hue, blue points indicate far distances and red points those indicate points nearer the sensor.
Robert Cromwell can be reached at firstname.lastname@example.org.