X-rays have been used as a method by which to see inside bodies since they were discovered by Wilhelm Rontgen in 1895. Some of the first ‘patients’ to be studied in this way were Egyptian animal mummies which were not able to be damaged by the somewhat unknown effects of radiation. Since this time, radiography has become increasingly invaluable in clinical practice on living humans and animals, but it has become one of the primary research techniques to investigate the contents of wrapped mummy bundles, preventing the need to unwrap, and ultimately destroy them.
Radiography has been widely used at the University of Manchester since the 1970s to study the mummy collections. From these early stages when plain film X-rays were the main method, the technology involved in radiography has developed quickly and we are now able to use much more advanced technologies to gain a better understanding of mummies and how they were made. Although CT scans have been around since 1979, their routine use on mummies has really occurred since 2000. Advances made since 2005 with the introduction of fully digitised methods have reduced the complexity of the X-ray and CT process and have made it much easier to share results with fellow researchers around the world.
As part of the Ancient Egyptian Bio Bank project, over 300 animal mummies have been studied through a collaborative partnership with the Central Manchester NHS Trust. The Trust have allowed access to radiography facilities and experienced staff outside of clinic hours to enable this work to take place. In fact, the mummies always attract a lot of attention when they go to the hospital with patients and staff alike taking a keen interest in the rather unusual patients! We tend to study mummies in groups of around 20 mummies at a time, simply because it is logistically difficult to deal with more than this in one session. We always have experienced conservators and curators on hand to ensure that the mummies are kept safe during the process. Most mummies do not need to be handled at the hospital at all as they can be scanned in their protective boxes which minimises the dangers of handling and keeps movement to a minimum.
During their visit to the hospital, all mummies are given a full investigation using X-rays and they also receive a full body CT scan. X-rays are taken in two opposing angles to ensure that we obtain the maximum amount of information about each specimen. In some cases, the contents are lying at an unusual angle within the bundle which means that further images are required taken at oblique angles to capture any missing information. X-rays have the advantage of giving excellent spatial resolution of the contents, but they do suffer from magnification and superimposition of structures which can make interpretation difficult. The advantage of a CT scan is that images are obtained from multiple directions which eliminates these issues and allows for direct measurement of bones and increases our chances of identifying anomalies. The data obtained through the CT process to 3D print anomalies from inside mummies, giving the ability to handle them directly and compare them to skeletal collections. CT has proved successful in identifying non-skeletal material within mummy bundles such as egg-shell, feather and reeds which often don’t show well on X-ray.
Clinical radiography is limited by the radiation doses allowed by the equipment. For mummies which reveal interesting anomalies, it is sometimes possible to use industrial CT (micro-CT) where higher radiation is used to obtain better resolution. Some mummies which have appeared ‘empty’ when scanned at the hospital, have revealed skeletal contents when scanned using this technique. This battery of radiographic techniques provides the best available method to see inside mummies non-invasively.
Find out more in the exhibition (including an interactive micro-CT scanner!), Gifts for the Gods: Animal Mummies Revealed, at Manchester Museum from 8th October 2015..