1 Paleoradiology: History and New Developments - Academia.dk

Chapter 2
Paleoradiologic Techniques
George Saab, Rethy K. Chhem, and Richard N. Bohay
2.1
X-ray Imaging For Bioarcheology
X-ray imaging is used in three main types of human
bioarcheological investigations. The first deals with
the identification of anatomical structures that allow
the determination of the stature, age at death,
and gender. The second is to identify diseases in ancient
skeletal remains and mummies. The last is the
study of hominid fossils embedded in a burial matrix
(Chhem and Ruhli 2004). In order to achieve these
goals, bioarcheologists may need to undertake several
steps. Bioarcheological materials can be submitted
first to an x-ray investigation, and high-quality images
can be obtained. The images are stored either on
the traditional x-ray films or, more recently, on digital
data supports. The ideal image analysis will be performed
by radiologists with not only a qualification
in musculoskeletal pathologies, but also equipped
with an adequate and working knowledge of ancient
bioarcheological materials. Alternatively, there can be
collaboration between bioarcheologist and radiologist.
These steps underline the need for adequate xray
equipment and appropriate qualification in paleoradiology
(Chhem 2006). X-ray studies have also been
used to evaluate cultural material from archeological
settings (Lang and Middleton 1997).
This chapter provides a general description of
conventional and advanced imaging techniques suitable
for bioarcheological applications. These include
analogue and digital radiography, imaging physics,
digital archiving, recent developments in computed
tomography (CT), novel imaging methods, and threedimensional
specimen reconstruction techniques. A
section on dental radiography has also been included.
The imaging physics principles contained herein are
not meant to be comprehensive, but rather to elucidate
simple radiographic production factors that produce
the best possible images. These factors exploit two
important distinctions between bioarcheological and
medical imaging applications: (1) the specimens do
not move and (2) the total x-ray dose is less of a concern
than it would be with a living subject. Emphasis
is given to those technical factors that can be cont-
rolled without costly upgrades. Care has been taken
to avoid the use of physics and mathematical jargon
in order to make this chapter accessible to readers without
a background in radiology and physics.
X-ray equipment is available either in a hospital
radiology department or in an anthropology department.
In the former, one faces a few challenges,
including the lack of specialized staff for taking radiographs
of bioarcheological materials, but also the
competition with clinical services. However, this
is where one can have access to more advanced and
costly imaging procedures such as CT scanning. Hospital
x-ray equipments have also been used successfully
to image 1-million-year-old slate fossils from the
Devonian era (Hohenstein 2004). These plates of slate
measure around 35 mm in thickness and contain a
large variety of fossilized specimens including sponges,
jellyfish, coral, mollusks, worms, and arthropods.
The role of x-ray was to identify the fossilized animals,
and to guide their exposure and preparation for paleontological
study. Conversely, some x-ray equipment
already available in an anthropology department may
have a few limitations. Some types of x-ray equipment
designed to study small specimens may not allow the
study of an entire mummy or a large bone such as the
femur or pelvis. In either department, mastering key
concepts in x-ray imaging will help bioarcheologists
to obtain the highest-quality image from their specimens.
Beyond hospital facilities, a research imaging
center offers the most cutting-edge technology (micro-CT
scan and others) for the radiological assessment
of bioarcheological materials. From this short
review, bioarcheologists are facing technical, scientific,
medical, and financial issues. Access to x-ray
facilities, especially advanced imaging tests, represents
the first challenge. Finding the expert to read
and interpret the findings is also a major challenge.
Diagnostic errors are common in paleopathology not
only when x-rays are read by a radiologist with no
specialized qualification in musculoskeletal pathologies,
but also when the reader has no knowledge of the
taphonomic processes that have altered the physical
characteristics of skeletal specimens relative to those
of the live clinical model. This stresses the value of a
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