Unique Technical Challenges

Field imaging by its very nature is conducted in poorly controlled conditions under unpredictable circumstances. The paleoimaging team needs to be aware of and anticipate many unique challenges in order to accomplish the objectives of a given imaging study. Efforts need to be made to be efficient and creative in an attempt to conserve resources and collect the best possible images. Experience-based challenges to field imaging research with problem resolutions are presented below.

Figure 2.38A An AP pelvis radiograph of George/Fred with the left hand superimposed over the ilium, sacrum and coccyx.

Multiple Images on One Film Since x-ray film is a precious commodity in the field, as much of the film surface as possible should be utilized. An example of this situation is apparent when the objects to be imaged are smaller than the x-ray film, such as individual bones from a disarticulated skeleton. Although disarticulated skeletal components present less complex imaging challenges than experienced in the examination of mummified remains, careful planning is still necessary. In order to optimize film use, several objects of similar density can be placed on the surface of a cassette film holder, and a single exposure can be taken to produce an image of multiple components.

Figure 2.38B A nonscreen Polaroid image of the left hand.

Figure 2.39 a skull being stabilized with commercially available radiolucent positioning devices.

If multiple projections of a singular skeletal component, such as a skull, or images of multiple objects that vary in density are desired on a single sheet of film, each object may be exposed individually. The procedure is achieved by dividing the film into sections, such as halves or quadrants, with the unexposed sections being partitioned by lead shielding. In order to minimize the weight of the equipment that is transported to the field site, local shielding materials, such as rocks or concrete blocks found at the study site, can be substituted for the lead shielding. After the first exposure, the exposed area is covered, and the next section of the film to be used is uncovered. The procedure is repeated until the entire

Figure 2.40 Foam purchased locally in southern Peru used to position this chiribaya mummy.

Figure 2.41A The cervical, thoracic, and lumber vertebrae were positioned for a superior-inferior (SI) projection. Small pieces of foam (A) were employed to stabilize certain vertebra and ensure that the vertebral bodies were parallel to the film plane. Note that the number of the specimen (B) in lead numerals was placed on the cassette along with a marker (C) to indicate the right side.

Figure 2.41A The cervical, thoracic, and lumber vertebrae were positioned for a superior-inferior (SI) projection. Small pieces of foam (A) were employed to stabilize certain vertebra and ensure that the vertebral bodies were parallel to the film plane. Note that the number of the specimen (B) in lead numerals was placed on the cassette along with a marker (C) to indicate the right side.

surface of the film has been utilized (Figures 2.47A and 2.47B). A simple grid system using tape can be designed on the surface of the film cassette to ensure there will be little or no double exposure situations.

Low-Density Objects: Too a in Taphonomic conditions, such as an acidic peat bog, will decalcify remains, rendering the skeletal system nearly radiolucent. This decalcification reduces the density and renders any residual bony structures virtually invisible to x-rays when using standard exposure settings. A pair of bog mummies, found in 1904 near the town of Weerdinge and now in the collection at the Drents Museum in Assen, the Netherlands, was the focus of a field radiographic examination (Death in a Bog 2002). The minimum factors that could be set on the 1952 vintage Picker Field Army x-ray unit used

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