Thousands of years ago in ancient Egypt, a cat, a bird, and a snake met ceremonious yet unfortunate ends. Sacrificed for the benefit of humans venturing into the afterlife, the animals were preserved and wrapped, forever logged into the historical record as mummies. And now, scientists are peering through their delicate bandages—the snake wrapped up in an oval, the cat having snapped at the neck at some point in the past few millennia, the bird still taking a fairly birdlike shape—to show the animals in stunning detail.
Writing today in the journal Scientific Reports, a multidisciplinary team of researchers in the UK describe how they used microCT technology—think of it like the computerized tomography (aka CT) scan you’d get in a hospital, only with a way higher resolution—to uncover new details about how the critters lived and died. Spoiler alert: You do not want to be a sacrificial animal.
When you lie down in a CT scanner, an x-ray emitter rotates around you, shooting beams through your body. A collector opposite the emitter gathers these x-rays, creating a 2D snapshot of your body with each rotation. After many rotations, the technician combines these 2D images all together to create a 3D representation of your insides. “But then there’s a resolution limit to that technology,” says Swansea University materials scientist Rich Johnston, lead author on the new paper.
Because we’re working in 3D here, resolution is measured as a three-dimensional voxel, the counterpart to the two-dimensional pixel. Medical scanners go down to around a 100-micron (a millionth of a meter) voxel size, and that works just fine for humans—our morphology is much bigger than a cat’s or snake’s or bird’s. But to get a good look inside these tiny mummies, Johnston and his colleagues needed to bump up the resolution. “You can’t really make out features, you can’t do accurate measurements” at human-scale resolution, Johnston says. “You just won’t see the types of things that we were able to determine—causes of death, or what the last stages of an animal’s life might have been like, how it was kept.”
The solution was microCT, which allowed these researchers to get down to around 20 microns. Unlike a human CT scan, this device doesn’t rotate around a stationary subject—it’s got a fixed x-ray emitter and detector, and the technician can move the object around within the device. “The main difference is we can move the sample closer to the source of the x-rays, which increases the resolution,” says Johnston.