Paleoradiology

Paleoradiology (ancient radiology) is the study of archaeological remains through the use of radiographic techniques, such as X-ray, CT (computer tomography) and micro-CT scans. It is predominately used by archaeologists and anthropologists to examine mummified remains due to its non-invasive nature. Paleoradiologists can discover post-mortem damage to the body, or any artefacts buried with them, while still keeping the remains intact. Radiological images can also contribute evidence about the person's life, such as their age and cause of death. The first recorded use of paleoradiology (although not by that name) was in 1896, just a year after the Rōntgen radiograph was first produced. Although this method of viewing ancient remains is advantageous due to its non-invasive manner, many radiologists lack expertise in archeology and very few radiologists can identify ancient diseases which may be present.
Techniques.
CT.
CT scans are most commonly used in paleoradiological studies because they can create images of soft tissue, organs and body cavities of mummified remains without performing an invasive and damaging autopsy. This enables archaeologists and anthropologists to digitally unwrap the remains and reveal what they contain. CT scanners create these images by taking multiple radiographic planes (or cuts) of the body at different angles which records the layers of different structures in the remains. This differs from typical radiographic scans (X-rays) where all the structural layers are documented in one image, which can create shadows and therefore limit their accuracy.
There are several main viewing techniques used in CT imaging.
After these different views of the remains have been obtained, it is possible to create a three-dimensional reconstruction of the body. This brings into focus details which may have been missed on the axial imagining. Algorithm manipulation is used to create the rotational 3D images. In paleoradiology, the 3D images provide a greater understanding of the remains themselves. For example, in 2002, a study of nine Egyptian mummies found that by using the 3D reconstructions they could see the preservation of soft tissues, such as the penis on one male body and braided hair on female remains. The 3D modelling also illustrated discrepancies between the remains, as some had their internal organs removed while others had not.
Due to their ability to take multiple planes of the remains, CT scans are able to virtually 'fly through' the body to assess internal composition and cavities. These techniques are commonly used for diagnostic scans such as colonoscopy and bronchoscopy, and the same method is applied to ancient remains. This enables researchers to digitally look through the remains from the top down, as though they were watching a short video of footage from the interior of the body. The technique presents observable data from the hollow cavities in the chest and abdomen regions. It can demonstrate whether there are internal organs present or if, in the case of Egyptian mummies, linen has been packed to maintain the body shape of the remains.
Micro-CT.
Micro-CT is a specialised form of CT scan used to create images with pixels in micrometres. These images are frequently used for bone density examinations and produce greater detail for images of bony structures. This radiology technique is often used to examine the teeth from mummified remains.
Early use (1895–1970).
Radiographs, or X-rays, have been used to study and observe ancient remains since their invention by Wilhelm Röntgen in 1895. This early form of X-ray, sometimes known as Röntgenograms, was immediately used by physicists, anthropologists, anatomists and archaeologists as shown below.
Current use in archaeology.
CT scans are the most common radiological technique used in modern archaeology due to their ability to provide more detailed information about ancient remains (such as soft tissue and blood vessels) and to produce 3D images by taking layers of different angled pictures. Archaeologists are able to collect data such as age, sex, the cause of death, socioeconomic status, mummification and burial practices by analysing the CT images. The images can also reveal whether the remains were subject to ancient diseases or post-mortem damage. Although paleoradiology practices are used on preserved remains such as European bog bodies and frozen bodies from the High Andes, they are more frequently documented in the analysis of Egyptian mummified remains.
Egyptology.
CT scans are used in Egyptology to gain insight into mummified bodies without risking damage to the integrity of the remains. Hoffman's recent study of nine Egyptian remains discovered new information regarding the mummification practices of Egyptians. The typical process of mummification, as written by Herodotus, involves the removal of the four major internal organs (liver, intestines, lungs and stomach) and placement of them in four canopic jars. The heart is removed, embalmed and placed back into the body as it is an important feature in the journey to the Egyptian afterlife. However, Hoffman discovered that this was not the case in all mummies. Through analysis of CT-produced 3D images, the "fly-through" technique and a combination of axial and coronal images, it was discovered that four of the remains had not had their internal organs removed and in another four the heart could not be identified. Hoffman suggests this may be due to socioeconomic differences between the mummies during the time they were alive. CT scans were further used in Hoffman's study to potentially identify one of the remains as Ramesses I, a Pharaoh during New Kingdom Egypt. It was found that the mummification practices of this particular body were in conjunction with those typically used during the New Kingdom period, as images showed rolled linen placed inside the body in order to preserve its shape. The mummy's arms were also found to be placed across the chest as a symbol of nobility.
Imaging done by Rethy Chhem, in 2004, was able to correct a diagnosis of Ramesses II from X-rays done in 1976. The incorrect diagnosis had been of ankylosing spondylitis, a form of arthritis. However, Chhem perceived that the pharaoh actually had diffuse idiopathic skeletal hyperostosis, a calcification of the joints causing ligaments to attach to the spine. The CT images provided a clearer and more detailed image of the spine when compared with the early X-rays. This enabled the researchers to provide a greater insight into diseases found in ancient remains and achieve a more accurate diagnosis.
A recent CT scan of Tutankhamun in 2006 was able to provide evidence against the 'homicide theory'. A depression fracture noted on the skull from X-rays taken 30 years previously was found to be a post-mortem injury rather than a cause of death. The hole in the head had been created in order to continue the embalming process of mummification. This CT investigation was also able to confirm Tutankhamun's age of death as nineteen and disprove the idea that the young pharaoh had suffered from scoliosis; rather the bend in his spine was from additional post-mortem damage to the body.
Disadvantages.
Although the information and evidence gathered by radiological imaging of ancient remains have been largely beneficial to the fields of archaeology and anthropology, not all of the information can be considered accurate due to the lack of radiologists who specialise in paleopathology. Instead, to obtain the most information from CT or X-ray images a team must meet to discuss the findings (e.g. for a skeletal study of the remains, an orthopaedic surgeon, bone pathologist and musculoskeletal radiologist would meet). Another disadvantage to this technique is the low contrast resolution. The researcher may be unable to determine a difference between soft tissue and artefacts left from the embalming process. Due to the decomposed state of some of the mummified remains, it can also be difficult to distinguish internal organs due to shrinkage and a lack of preservation. Post-mortem injuries and damage to the body can also hinder the ability of radiological scans to provide accurate information for researchers. For example, in frozen remains, there can difficulty when differentiating whether a CT suggests the body has air-inflated lung tissue or if there is frozen fluid in the lungs.
Paleoradiology is informative in its ability to assist in determining the age of death of the remains, however, this is not always completely accurate or available information. In a sample of bog bodies, 35% were not able to be identified with any age group and 30% could not be sex determined. A radiological study of an iceman was only able to produce an estimate of 40–50 years at age of death. In order to achieve a more accurate time frame, the body would have to be subject to an autopsy or similar physical assessment which would cause irreversible damage to the remains.
Another disadvantage of paleoradiology is the difficulty in transporting the equipment or the artefact/remains to spaces where the images can be taken. For example, in 2005 the mummy of Tutankhamun was imaged using a CT-scanner which had to be brought from the Cairo Museum to tomb KV62 in the Valley of the Kings. This was due to the fragile state of the remains which were unable to be removed from the climate-controlled tomb. In this study, funding came from a five-year grant from the Supreme Council of Antiquities, which was aided by the donation of a Siemens CT-scanner by the National Geographic Society, however typically funding for research can be problematic as equipment is costly and there may not be sufficient interest to prompt donations.