- New propagation-based phase-contrast imaging can capture soft tissues of ancient remains in details.
- It generates a 3D high-spatial cellular and subcellular resolution.
- The technology can help better understand lifestyle, diseases, and death of ancient times.
X-ray radiography and computed tomography (CT) are some of the most used techniques for nondestructive analysis of animal and human mummies. These X-ray methodologies depend on absorption contrast, and they have been extremely useful in fields like paleopathology and archaeology.
Absorption contrast works great when examining bone and other dense material, but it can’t provide enough details when it comes to soft tissues. That’s why researchers at KTH Royal Institute of Technology in Sweden instead proposed a propagation-based phase-contrast imaging.
This new method is capable of imaging soft tissues of mummies and other ancient remains up to a microscopic level. The primary goal of the study is to provide an effective alternative to traditional CT for examining ancient soft tissue.
In this study, researchers have examined an Egyptian mummified human right hand from the Museum of Mediterranean. The hand belonged a male and dated back to around 400 BCE.
Resolution of Output Images
Schematic of experimental setup | Courtesy of researchers
While traditional CT depends on the X-ray absorption in the sample, propagation-based phase-contrast CT examines the induced phase shift of X-rays. Since the phase shift in soft tissues is nearly 3 orders of magnitude bigger than X-ray absorption energies, it outputs superior quality with details (at cellular resolution), allowing researchers to better distinguish between different types of tissues.
More specifically, it generates a 3D high-spatial cellular and subcellular resolution that enhances the discovery of soft tissues and makes it easier to differentiate between healthy and pathologic tissue.
CT of mummified hand showing soft tissue (right) | courtesy of researchers
The existing 2D techniques limit the viewing capability to a single direction, risking missed features. Phase-contrast CT, on the other hand, provides an option to search through reconstructed pictures in arbitrary areas or rendered as a total volume. This could be very useful for extracting samples for genetic or biochemical examination.
The resolutions of final pictures were between 6 and 9 micrometers. Thus, researchers were able to observe the remains of nerves, blood vessels, and adipose cells. In fact, they successfully detected blood vessels in the nail bed and distinguished multiple skin layers.
The study points out the advantage of traditional CT over old techniques used in soft tissue paleopathology that require harsh tissue-extraction and chemical processing, which are harmful to ancient, fragile specimens. Just like CT has become a standard method for investigating ancient remains, researchers believe that propagation-based phase-contrast imaging will soon replace the existing method.
This new technology will help archaeologists extract detailed data from soft tissue and better understand lifestyle, diseases, and death of ancient times. Overall, it opens up new possibilities of virtual histology, further decreasing the requirement of old invasive methods. Eventually, this will lead to useful discoveries in medical research and paleopathology.