By examining altered x-rays, scientists can create "phase contrasts" in which the fossils stand out clearly against the amber.
Once the fossils' positions are known, they are again exposed to a synchrotron beam—but this time while being rotated.
The team then "virtually extracted" 356 exquisitely detailed fossil organisms, which included microscopic mites, larger wasps, flies, spiders, and plant remains.
The digital images can also be scaled up or printed to create physical models.
David Grimaldi is an amber expert at the American Museum of Natural History in New York City, who helped pioneer the use of imaging technology to study insect fossils.
Grimaldi, who was not involved in the new work, said it was an improvement over past techniques, which relied on CT scanners similar to those used in hospitals.
With synchrotron imaging, fossils that were previously inaccessible can now be studied, Grimaldi said.
"Most of the amber that comes from the Cretaceous deposits in France is opaque," he said.
"A dense suspension of organic particles [makes] it difficult to see more than a few millimeters into the piece."
Other researchers, such as Uwe Bergmann, a senior scientist at the Stanford Linear Accelerator Center in California, are employing related synchrotron-based x-ray techniques to create "elemental maps" that highlight specific chemical elements in fossils.
"If you create an image of calcium, you bring out [the bones] much clearer," Bergmann said.
By focusing on other elements, scientists could one day reconstruct the skin and soft tissues of ancient animals.
"In the fossilization process, the skin and everything turns into stone, but some of the chemical elements of the original skin are still trapped in there," he said.
(Related news: 'Dinosaur Mummy' Found; Has Intact Skin, Tissue" [December 3, 2007].)
"What we would love to do is recreate the soft tissue or stomach contents of something that has not lived for millions of years."
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