Paleoimaging: Field Applications for Cultural Remains and Artifacts PDF

Preface

Background and Rationale

Medical and industrial imaging methods have the potential to be powerful tools in both the documentation and data collection procedures found in many nontraditional settings. Each technology described in this text has been applied to alternate settings, such as mummified human remains, soon after its historical development. In addition to providing useful data for analysis, these powerful tools have the added benefit of being nondestructive, thereby preserving the remains or artifacts for future analysis with yet to be developed technologies. The authors began this work to provide a basis for understanding the field application of various imaging modalities in bio-anthropological settings. However, these imaging modalities have also been applied in studies of non-biological specimens. Section III, Artifact Analysis, has been included to present the broader application potential of these imaging methods.

An array of imaging methods has been employed in anthropological and archaeological research. When applied individually, certain information can be obtained. When applied in a complementary manner, not only can additional data be collected, but also the relationships among those data may often enhance our understanding of the meaning of their associations.

In the recent past, literature referred to the use of a single imaging method or modality, such as x-ray, endoscopy, or computed tomography (CT) scans. More recently, scientific papers and presentations have adopted the term multimodal imaging. Since each modality has advantages and disadvantages, most researchers support the construct that no single modality can obtain all the data possible from a given subject. Therefore, multiple imaging methods need to be applied in an attempt to maximize data collected and to enhance the interpretability of those data.

Conventional, or standard x-rays (radiographs), yield a two-dimensional image of three-dimensional objects. In addition, the images have the associated problems of superimposition of shadows, an inability to differentiate structures of similar densities, magnification, and distortion. Without creative application technique a standard x-ray cannot provide data describing the true spatial relationship of an object or organic feature within the broader context of the body as a whole. Conventional radiography does, however, have the potential to be highly portable and can yield much information that would be otherwise unobtainable. Radiography is ideally suited for the field research environment.

Endoscopy can complement the radiograph, providing an image with shape, contour, color, and location of what was only a shadow on the x-ray. Additionally, the endoscope can be used to guide instruments for retrieval of tissues or artifacts from within a closed environment, such as a body cavity, coffin, or tomb. The instrumentation is portable and well suited for field imaging studies.

If the subject of the study can be moved, computed tomography (CT) could be employed to better reveal the spatial relationships within the subject. The CT scan can also guide biopsy or artifact retrieval procedures. Although "portable" CT scanners exist, their size and the logistics of terrain often result in limited availability in remote field settings. In addition, the hardware and software of these units place limitations on the type of data obtainable. The data collected by the more recently introduced multidetector CT (MDCT) scanner, once stored, can be reformatted to view the study object from multiple planes and generate 3-D representations of those data. The 3-D image can be of the object as a whole or feature a single organ, structure, or artifact associated with the subject. The data may also be animated to rotate the object for multi-directional viewing and analysis.

Computed radiography (CR) and direct digital radiography (DR) have the advantage of being filmless systems that allow manipulation of the displayed image to improve the image exposure, possibly revealing otherwise "invisible" structures. Since CR and DR generate 2-D images, superimposition of shadows and many of the other disadvantages associated with conventional radiography are still problematic.

Magnetic resonance imaging (MR) has also found its way into the anthropological arena and adds data otherwise unobtainable by the other mentioned modalities. Unlike the other modalities described, x-rays are not involved in the production of MR images. High intensity magnetic fields are manipulated to, most commonly, measure the "mobile" hydrogen content of the object under investigation. Like the CT instrumentation, MR imaging requires the study subject to be brought to an imaging or research facility.

Photographic documentation and analysis is another mode applied in the paleoimaging setting. Standard and filtered photographs allow for continued indirect visual analysis once the researcher has departed the original research site. Newer photographic methods can produce 3-D representations of surface characteristics allowing the researcher to view surface features from various angles.

Each of the tools in the multimodal-imaging arsenal comes with its unique application limitations. For example, CT scanners are quite large and weighty, making them difficult to apply in field or remote settings. Additionally, CT scans have the potential to produce tremendous numbers of images, many of which contribute little to the study. Endoscopy requires an access route. Conventional or computed radiography, while portable, produces 2-D images.

The use of the term multimodal therefore indicates the natural evolution of imaging in anthropological and archaeological research, moving from specific single modality imaging studies to those that incorporate several imaging methods. Collectively, multimodal imaging, when applied to anthropological and archaeological research, has come to be known as "paleoimaging." The term paleo refers to studies involving ancient, prehistoric, primitive, or early structures or cultures. However, the term paleoimaging has been generalized to a broader context to include not only prehistoric subjects but also the analysis of historic human or animal remains, associated artifacts, and in archaeological applications. The data collected through paleoimaging methods have been applied using both the medical approach, where the study subjects are transported to an imaging facility and, in contrast, the anthropological approach, where the subjects are examined in or very near the original context.

In anthropological and archaeological research context is critical. The burial location, relationship and position of objects, and burial goods are all critical data requiring analysis within or as close to the original context as possible. Once an object, such as mummified human remains, is moved, the context is altered. Not only the relationship among related objects, buildings, and tombs, but what is held within a mummy bundle or within the mummy itself, too, can be disturbed, further altering the internal context. Whenever possible, researchers would do well to employ in context field imaging methodology for initial data collection.

In context field imaging demonstrates the nondestructive nature of the described modalities and is the main focus of this book. Once the object is moved from its original context, the nondestructive nature of a study is jeopardized. The actual act of moving the object may in fact be destructive. If the use of advanced imaging, such as a CT scan, is warranted, the decision to transport the subject to an imaging facility needs to be based upon the safety of the study subject and what additional data the advanced imaging may add to the case at hand. If on-site field imaging is conducted, those data can contribute to the risk/ benefit decision of whether or not to move the object for more advanced imaging.

Standards: Methods and Procedures

Another critical issue surrounding paleoimaging research is that of methodological and procedural standards. Many reports in the literature often omit specific details regarding technical factors, such as radiographic exposure settings, data recording media, specific instrumentation, or endoscopic lenses used as related to the imaging data collected. Another issue is that many who are new to the paleoimaging arena may be experienced at gathering data and interpreting images produced from living subjects but not from mummified remains. Mummies, for the most part, are completely desiccated. The desiccation process, as well as many artificial preparation procedures creating that mummy, alters the manner in which imaging data can be attained for maximal interpretability. Collecting images that call for a new exposure setting or positioning approach may not be considered due to a lack of experience in operating the equipment in archaeological or anthropological contexts. Interpretation, too, can be challenging to the untrained eye. The morphologic changes seen in organ systems among the varied mummification processes, for example, may lead to misinterpretation of the significance of structures by someone who is accustomed to interpreting images from hydrated, living patients.

In Paleoimaging: Field Applications for Cultural Remains and Artifacts, Section II, Paleoimaging Standards, the authors offer application standards for the varied imaging modalities as applied to this specific line of research. The methodological and procedural standards offered in this text are intended to assist researchers in obtaining the desired data in an accurate, efficient, and reproducible manner.

Artifact Imaging

The paleoimaging techniques described in this text have a natural application in the imaging of non-biological cultural artifacts. Section III, Artifact Analysis, of Paleoimaging: Field Applications for Cultural Remains and Artifacts demonstrates how multimodal imaging can assist nondestructive data collection in an archaeological context. Imaging applications to help discover such variables as ceramic construction and technology complexity, orientation and composition of grave goods, temporal context based on artifact analysis, differentiation between authentic and fraudulent artifacts, and imaging works of art for conservation purposes are described.

Safety in Field Paleoimaging Projects

Radiation safety and field safety concerns presented in Section IV, Safety Concerns in the Field, describe the application and situational variables that will allow safe data collection in challenging field settings. The radiation safety and field safety discussions are intended to provide those involved in field imaging projects with the basic understanding of the safety issues at hand as well as practical means of preparing for and conducting paleoimaging studies in a safe and responsible manner.

The Paleoimaging Team-A Brief Discourse

Bioanthropological and bioarchaeological research naturally calls upon the skills of various scientists from many disciplines. Among those disciplines are those individuals skilled in paleoimaging. When considering the data attainable from the varied imaging studies applied to the anthropological and archaeological setting, several variables need to be considered: the data collection or paleoimaging process, recalibration of those processes for additional data collection, and the interpretation of these data. It would seem logical then that to conduct such research one would need someone to collect the data, a paleoimager, and someone to interpret the data. While this may seem straightforward, it is the opinion of the authors that the researchers filling these roles should have special qualifications.

Paleoimagers (Data Collectors)

Paleoimagers need to be experienced in the examination of naturally and intentionally mummified animal and human remains, and various types of artifacts. Collecting the data requires skills related to radiographic exposure settings, positioning, familiarity with morphologic variations seen associated with varied mummification methods, recording media, and data collection manipulation skills. These skills should also include an understanding of what data need to be collected given the research objectives and with careful consideration of the context. For example, setting the exposure variables and selecting the type of film and film holder to image the bony skeleton within a mummy bundle would likely not visualize desiccated organ remnants inside the mummy. Exposure variables set to pick up features of the integument would also reveal features of the wrappings. Knowing when and how to use imaging modalities to best acquire the desired images requires creativity and skillful application of the many exposure and positioning variables.

Additionally, the individual must possess the skills and knowledge necessary to override preset protocols built into the software of sophisticated instrumentation designed to image living hydrated patients in medical settings. It is, therefore, a combination of skills required that are associated with the practice of radiography, coupled with knowledge of anthropological variations and the significance of nuances in the data collected. A paleoimager, as it relates to radiographic data collection, should be a radiologic technologist who has been mentored by a seasoned field paleoimager and bioanthropologist as there are no current preparation programs for this growing field. The individual needs to be trained in multiple modalities, the medical and industrial applications of those modalities, and well versed in the limitations of each modality. Further, the individual needs to be an expert in cross-sectional anatomy and be familiar with pathological conditions and the signs those conditions may leave behind in mummified tissue. Another required attribute is that the individual be technically adept and creative as much of the research is conducted in remote areas without reliable electricity sources or water, thus requiring instrument modification adapting to the given situation. Critical thinking is paramount.

Endoscopic data collection needs to be conducted by an individual familiar with the many technical variables associated with these procedures. The individual needs to have a working knowledge of the instrumentation possibilities including both medical and industrial tools. Media archiving skills are also important. Biopsy techniques and artifact retrieval skills are necessary as these techniques are often specific to the research objectives. An understanding of anatomy and physiology is critical as is the understanding of pathological changes in organs and tissues. Further, an understanding of the varied morphologic changes seen among various mummification practices is vital. This paleoimager, too, must be creative and adaptive to the varied research environments. In addition to the knowledge and skill base described, a seasoned field endoscopist and a bioanthropologist should mentor the individual in order to maximize the application of this modality.

The importance of photographic documentation of paleoimaging research cannot be understated. The photographer need not only be an expert in photographic methods but also be well aware of what is critical information to document. Typically, the photographer is under the direction of the project coordinator, usually an anthropologist or bioarchaeologist. However, the ideal photographer would know what to photograph and when to photograph and blend in naturally with the workflow. The photographic documentation required includes, but is not limited to, contextual documentation, procedural documentation, scientific documentation, and an artful representation of the remains or artifacts under investigation.

Paleoimaging Interpreters

Initially, it would seem that since much of the data collected is radiographic, a radiologist would be the logical individual to make the interpretations. While this may be true, there are very few true paleoradiologists available. In fact, there are no specialized training programs in this area of expertise. Too often a radiologist becomes a paleoradiologist as soon as she/he interprets her/his first mummy x-ray. Sadly, this oversimplifies the challenges faced in the interpretation of images produced from mummified human remains. The radiologist does possess the skills necessary for interpretation when the subjects are living hydrated patients. However, the morphologic changes seen among the varied mummification practices require the radiologist to be well versed in the processes of mummification and their effects on the human body. While the radiologist's skills involving differential diagnosis are critical to the interpretation of data, the analyses should include consultation with a physical anthropologist, bioanthropologist, or bioarchaeologist as well as a paleopathologist. It is only with this expert input regarding such variables as cultural practices surrounding the mummification method, dietary habits of the culture, and knowledge of varied environmental impacts on human tissue over time, that differential diagnoses can more accurately be determined. The paleoimaging interpreters, then, should include the radiologist (mentored by bioanthropology, bioarchaeology, physical anthropology, and paleopathology), along with a bioanthropologist, physical anthropologist and/or a bioarchaeologist, and a paleopathologist who is well versed in imaging modalities.

In summary, the ideal paleoimaging team would include a photographer, a radiographer, an endoscopist, a radiologist, a bioanthropologist or bioarchaeologist, a physical anthropologist, and a paleopathologist, all of whom would have specialty training and experience in the process of human mummification and its morphologic and taphonomic impact on the remains. Additional medical experts such as trauma physicians, orthopedists, pulmonary specialists, and dentists, as well as many others, should be available to enhance the interpretation of those data related to their area of expertise.

Summary

Paleoimaging: Field Applications for Cultural Remains and Artifacts is a work intended to describe the strengths and limitations of imaging applications in varied nontraditional field settings. The text offers methodological and procedural standards for the application of these modalities as well as standards for interpretation of the collected data. The authors hope that this text will contribute to those researchers who desire to employ paleoimaging in their research projects. The text intends to contribute to the growing field of mummy science studies. The potential contribution of this work rests in the concept that the interpretation and understanding of ancient cultures can only be as good as the data collected.