Computer Graphics World

July 2009 39 Digital Imaging ■ ■ ■ ■ pixel value with a higher dose of radiation, and it's all digital," says Mango. Once the image appeared on the computer screen, the experts used cutting-edge image-pro- cessing techniques for a clearer picture of what lied within the dense rock that is, es- sentially, what's left of Leonardo. Once again, the group had to apply knowledge they had garnered from in- dustrial-engineering applications (looking for buried conduits and pipes in concrete structures, for instance) to paleontology. "In some respects, it wasn't so diff erent— we were looking inside a structure for hid- den features," says Mango, "but it just wasn't something I or Steve had experience with. So we were learning as we went along," in terms of getting the optimal source dose and exposure time for this unique subject. As Mango points out, the exposure time was as long as two-and-a-half hours for the most challenging shots. Mango does not believe anyone has X-rayed a dinosaur before, and what made this project so challenging was Leonardo's thickness, which required a great deal of energy to penetrate. While the Iridium and Cobalt are high-energy sources and can achieve the desired penetration, the trade-off is they produce lower-quality im- agery in terms of detail and sharpness than a typical X-ray with a less-potent source. Another hindrance was the steel frame sup- porting Leonardo. A welder was able to re- move some of the braces, but some still had to remain, as did the plaster matrix used to prep and protect the specimen. " e matrix was an irregular shape, and it was in the way. We had some diffi culty discerning what is really the dinosaur fos- sil versus the surrounding rock matrix and plaster," says Mango. " at is where the expertise of the imaging experts, such as Andersen, comes in. ey are able to work around obstacles like that." While the scientifi c team was hoping to see certain organs, such as the heart and the chambers of the heart (" eir expec- tations were sky-high," says Mango), the jury is still out as to whether those organs are present. Mango and the others agree that there appears to be some evidence of organs as well as artifacts in the digestive track. "Eventually we might have been able to perfect the techniques a little more, but I am not sure we would ever have been able to get a better view given the limitations of the specimen and how radiography works, how the rocks scatter the X-ray beam and such," Mango notes. Nevertheless, the team was indeed happy with the results, which showed great prom- ise, thus whetting their appetites for more information. Some time after the initial forensic examination and seven years after Leonardo was discovered, he was trans- ported to the NASA Ellington Field non- destructive testing lab for further X-rays that once again used a Cobalt-60 source. ere, some of the steel structure was removed and heavy wooden supports were added to the perimeter, as to not block the X-rays. While looking at the X-rays in Houston, the group encountered a prehistoric mys- tery: ey had noticed, for the fi rst time, that some of Leonardo's ribs were miss- ing, but they couldn't fi gure out why. Per- plexed, Andersen examined the outside of the dinosaur more closely. "We hadn't noticed that Leonardo had been bitten. You should be able to look at him and realize there is a bite mark on his side, but no one ever did," says Andersen. In fact, upon further examination, Ander- sen noticed that the ribs were not missing, but hung from a big fl ap of skin and fl esh that was now on the dinosaur's belly side. "You can see the rib bones there and part of the stomach," he describes. "At fi rst, they thought, 'No, it can't be,' and when they looked at him some more, they said, 'You're right. He was bitten,' " Andersen further recalls. is led the sci- entists to hypothesize that the dinosaur had been attacked and mortally wounded prior to death. It's Elemental In addition to the X-ray and digital scanning processes, the scientists conduct- ed an elemental scan on Leonardo's forearm that had broken off. Paleon tologist Pete Larson and chemist Bob Morton took the arm to Stanford University, where researchers used a linear accelerator to produce an X-ray fl uorescent image, or elemental scan, of the fossil piece. The machine scans the surface of the object, and a camera registers and records the results as a 2D image based on the heavier elements present—cal- cium, phosphorous, potassium, iron, cobalt, and so forth. The scientists rotated the arm seven degrees and did another scan, resulting in a 3D false-color im- age. According to Larson, the polarizing light for the 3D image of the elemental scan enables the group to see the topography of the specimen, along with the chemicals present. Thus, the image on the computer screen will show a mixture of these colors, one for each element found, and in the corresponding concentrations. "The idea is that you can see a pattern on Leonardo, and you get a good idea of what color his skin was, since certain elements give off specifi c colors," says imaging expert Art Andersen. For example, copper sulfate results in a blue hue. "This is brand-new science," Andersen points out. While the outcome of the arm didn't reveal all that much, the group believes that another body part, such as the chest, could show far more.

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