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5A. CAT scans (right) confirm that the inner object is indeed bone with a medullary cavity. It has been beveled to a point and the cross-section scans show grooves around the point which appear to be cut marks (sharpening marks?). The inner bone is 4.5 cm. long. |
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5B. To study these grooves, contact prints were made of the cross-section scans on sensitized paper 1 mm. thick (the scans were 1 mm. apart). The rounded outline of the outer cortex of the inner bone was dissected carefully under magnification and the discs were stacked to allow 3D construction of the point and its grooves. This model (right) illustrates V-shaped cut marks, some parallel and others merging or intersecting, a pattern not seen with rodent or larger carnivore grooves. |
5C. Stereolithography*
Non-Invasive production of a plastic model from the new 1 mm. spiral sections
of a CAT scan. In this case, a nearly transparent model of the outer horse
bone contrasts with the dark area (red) plastic of the denser bone tool point, the
red color reflects its greater density.
Accuracy is about one tenth of a mm. Note the grooves near the tip and
the taphonomy around the snap break at the base. This technique avoids
the need to break open the bone, with inevitable damage to the inner bone.
It has been used successfully to image unwrapped mummies and for diagnostic
and therapeutic medical and dental simulations.
Hjalgrim, H. et al., 1995. Stereolithography, American Journal of Physical
Anthropology, 97:329-333.
Blair, J., S. Mraz (Ed.), 1947. European Effort Refines Medical Prototyping,
Machine Design, Feb. 6, 36-38.
*For more information on advanced modeling techniques, call or write Marc
McAllister,
INOVA, 8505 Greenville Avenue, Suite 114, Richardson, TX 75081. Telephone
(972) 761-0491.
