A a fx e e e s

Figure 2.41B The resulting radiograph of the vertebrae positioned for the SI (superior-inferior) projection.

Figure 2.42 A wastebasket (A) can serve as a satisfactorily cassette (B) support for a cross-table radiograph where the x-ray (C) is directed horizontally.

in this study were 45 kVp, 10 mA, and 1/2 s. Even at the lowest settings, the exposure was too much to demonstrate the low-density structures resulting in an image that showed no evidence of skeletal structures (Figure 2.48).

There are two conventional approaches to reducing the x-ray output or the mAs. The first is to directly decrease the mAs. However, since the mA was already at the lowest setting, exposure time was the only other factor that could have been reduced. Unfortunately, because the timing device was a spring-loaded mechanism similar to a common egg timer, there was no way to reliably lower the time setting with any accuracy. A second approach to decreasing the exposure is to increase the distance. If the distance could be doubled from 40 in. (101 cm) to 80 in. (203 cm), the quantity of radiation reaching the image receptor would be quartered (see inverse square law). However, there was not sufficient tubing material to raise the x-ray source up to 80 in. (203 cm) (Figure 2.49). After noticing a black

Figure 2.43A A cardboard box cut to form a tunnel to pass the mummy through.

aluminum material that was used for lighting, it was decided to create a filter using the aluminum. Several layers of the material were taped over the x-ray tube aperture (Figure 2.50), which effectively absorbed about 50% of the lower energy portion of the x-ray beam before it reached the mummy (Figure 2.51). This resulted in a satisfactory exposure, adding valuable data to the imaging study.

Cannot Get Two Views, or When Two Views Just Are Not Enough As previously stated, radiographs are two-dimensional images of three-dimensional objects, and at least two projections or views are necessary to provide an idea of the spatial orientation of structures within a body. However, even with a second projection at 90°, superimposition can still make it difficult to determine the relative position of objects. Photographs have always

Figure 2.44 PVc pipe was used to produce the angulated frame to support an x-ray cassette (A) held in place with duct tape. the x-ray tube (B) was resting on the table in order to achieve the necessary angulation of the x-ray beam.
Figure 2.45 Two 1 x 3 in. (2.5 x 7.5 cm) pine boards (A) provide the space required to form a "tunnel" beneath the mummified remains to accommodate the cassette (B).

had a similar problem in separating objects from the background, middle ground, or foreground. In 1843, Sir David Brewster invented the lenticular or refracting stereoscope, which was adapted into the hand stereoscope used in photography (Eisenberg 1992c). Since over 50 years had elapsed before Roentgen's announcement of his discovery, it wasn't long before the popular illusionary photographic method would be applied to x-ray imaging. In March

Figure 2.46 A tape sling used to support the Polaroid cassette above the chest of a mummy in Guanajuato, Mexico.

1896, Elihu Thomson suggested using the stereoscopy in radiology (Eisenberg 1992d), and it was quickly adapted for complex anatomical regions such as the skull, chest, and pelvic areas (Files 1962a). Prior to the advent of other modalities, particularly computed tomography, stereoradiography was routinely taught to student radiographers.

As with many radiographic procedures, there are several approaches to obtaining ste-reoradiographs. The first, and most common, requires a linear shift of the x-ray source at a ratio of 1:10 (Files 1962b; Cahoon 1965a). If the SID is 40 in. (101 cm), then the total tube shift should be a total of 4 in. (10 cm), 2 in. (5 cm) in either direction from center. For optimal results, the direction of shift was specified to be at right angles to the predominating lines of the part being radiographed. The "predominating lines" in the thorax are the

Figure 2.47B A radiograph of two cervical vertebrae where rocks were used to permit three positions on a single film.

Figure 2.47B A radiograph of two cervical vertebrae where rocks were used to permit three positions on a single film.

Figure 2.48 the overpenetrated and overexposed initial Polaroid image of the left arm of the Weerdinge mummy.
Figure 2.49 the set-up for the Weerdinge mummy study. the x-ray tube was at the maximum distance from the mummified remains.
Figure 2.50 several layers of the black aluminum (arrows) were taped over the window of the x-ray tube.
Figure 2.51 the resulting radiograph after the beam had been filtered. the radius and ulna were clearly visible.
Figure 2.52 A Stanford x-ray stereoscope. One of the pair of images was placed on each view box (A) and aligned while looking through the viewer (B).

ribs, so the direction of the shift should be longitudinally, along the vertebral column. For stereo images of the long bones, the shift would be transversely across the bones. Since the skull is a complex structure with bony components along several planes, it is the exception, and the shift may be in either direction depending on which structures are to be visualized (Cahoon 1965b).

Stereoradiography was routinely employed in chest radiography prior to the advent of computed tomography. This was a common procedure, particularly during the period when tuberculosis was epidemic in the United States. Stereo viewing devices were constructed specifically for viewing the image that provided a "suggestion" of depth of field (Figure 2.52).

There are two important considerations in acquiring satisfactory stereo projections. The first requirement is that the object under examination must not be moved between exposures. To achieve this goal, the object must be elevated to create a space to accommodate the film. If there is an x-ray table available, the tray under the table would provide more satisfactory results. However, if the x-ray table approach is selected, there is an additional consideration. In medical imaging, the tray under the table is employed when body parts are thicker than about 4 in. (10 cm). Since higher kV is required to penetrate the thicker body parts, more scatter radiation will be produced. In order to minimize the scatter reaching the film, a device termed a grid is built into the top of the tray mechanism. The grid is composed of parallel lead strips. In some x-ray tables, the grids will move back and forth in a transverse direction or reciprocate during the exposure. More commonly called

Figure 2.53A George/Fred was placed on the x-ray table transversely. the long axis of the table is in the direction of the yardstick. the center ray of the x-ray beam would be directed to the center of the chest (A). For the first exposure, the center ray was shifted 2 in. (5 cm) to the right (B). A total 4 in. (10 cm) shift to the left (c) was the center for the second exposure.

Figure 2.53B the resulting cR image of the first exposure processed on a Konica medical cR system. Note the relative position of the calcified hilar lymph nodes (A) and the radiopaque artifact (B).
Figure 2.53C Because the radiopaque object is more distant from the liver, there is a greater shift of the object on the second image. since the relative position of the calcified nodes are closer to the spine, the shift in position is not as great.

a Bucky, after one of the individuals who developed the device, the motion of the device eliminates any shadow of the lead strips from appearing on the image and is more efficient at capturing the scatter radiation. In other tables, the grid is fixed in position above the tray, and close inspection of the resulting image will reveal the linear shadows of the lead strips. In either case, the central ray of the x-ray beam must be centered on the midlongitu-dinal axis of the x-ray table. Moving the central ray transversely across the table will result in a portion of the beam being absorbed by the grid; this is termed grid cut-off. Therefore, the second requirement, if the tray under the table is going to be employed, is that the shift must be along the center line of the table. The transverse x-ray tube shift technique was employed to get a perspective of the calcified hilar lymph nodes on a mummy known as George/Fred. In order to employ the transverse shift, the mummy had to be placed transversely across the x-ray table. In that position, his chest was over the center of the table and the Bucky tray beneath it (Figures 2.53A, 2.53B, and 2.53C).

The second approach to stereoradiography is based on angular rather than a linear shift. Either the body or object can be rotated between 6° and 8° (Carlton and Adler 1992) or the

Figure 2.54 The cobra coffin from the Rosicrucian Museum in san Jose, california.

x-ray source can be angled a total of 5°. The latter method was employed on a small Egyptian cobra coffin at the Rosicrucian Museum in San Jose, California (Mummy Menagerie 2003). The imaging challenge was to identify the contents of the small wooden coffin that had the approximate dimensions of 4 x 4 x 7 in. (10 x 10 x 18 cm). The coffin also had a snakelike carving mounted on its lid (Figure 2.54). The museum curator wanted to know what was in the coffin but did not want to risk opening the fragile artifact. A Polaroid image quickly demonstrated the skeletonized remains of at least one but possibly two snakes. Because the remains were on the bottom of the box, a lateral projection would only show superimposed skeletal elements. Since the remains were fragile, the box couldn't be tilted for an oblique projection. Although an oblique view could have been obtained by keeping the coffin flat and angling the film and x-ray source, the edges of the box were so close that they would end up superimposed over the skeletal remains. A stereoradiograph could provide the information necessary. The coffin was built up on foam with a space to place the film behind it. On the first exposure, the x-ray tube was directed horizontally with the center of the x-ray beam directed to the center of the small box. The film was changed and the second exposure was taken with the x-ray tube angled 5°, but the central ray was still directed through the center of the coffin (Figure 2.55). When viewed stereoscopically, two snake skulls were noted, demonstrating the value of this stereoradiographic technique (Figure 2.56).

Positioning Challenge: Going for the Long Shot In field imaging, it is often the case that the "subject" cannot be moved. In addition, the x-ray tube and/or image receptor may not be able to be placed in an optimal position to collect the desired data. In these cases... go long! The approach is straightforward and follows the aforementioned direct square law: as the SID increases, the mAs, particularly the exposure time, must be increased. In order to determine the proper exposure values when using a "long shot," an acceptable

Figure 2.55 The setup for one of the two stereoradiographs of the cobra coffin.

exposure for a shorter distance can be inserted into the inverse-square formula (mAsnew = mAs0ld[Distance0ld/Distancenewl2).

While working in Lima, Peru, on the collection of mummy bundles from the site known as Purachuco, a lateral projection of the skull of a mummy was required (House of Bundles 2002). The mummy was in a supine position on an examination table. The head was turned to the right, but due to the fragile state of the remains, the mummy couldn't be rotated. The only location to place the x-ray tube that matched the angle of the head was on the edge of a loft above the mummy (Figures 2.57A and 2.57B). Acceptable images of other areas of the body were obtained using 10 mAs at 48 in. or 4 ft (122 cm). The new SID was

Figure 2.56 Stereoradiographs of the cobra coffin.
Figure 2.57A The relative position of the x-ray tube (a) and the mummy (B) looking up at the loft.

approximately 16 ft (488 cm). The following calculation was employed: (new distance/old distance)2; (16/4)2 (10 mAs) = (4)2 (10 mAs) = 16 (10 mAs) = 160 mAs.

It is important to recall that the longer the exposure time, or when using multiple short exposures, the greater is the risk of overheating the x-ray tube. Cooling-off periods between multiple exposures must be employed and, when indicated, external cooling of the tube may be required. Therefore, four exposures, each at 40 mAs, were taken with a 30 s pause between exposures. The result was a usable lateral skull x-ray completing the data set for that mummy (Figure 2.58).

Will Not Fit on the Film: Too Big The largest-size medical x-ray cassette is 14 x 36 in. (35.6 x 91 cm), which could accommodate the entire spine on a single image for scoliosis studies. It would seem logical to take two separate standard 14 x 17 in. (35.6 x 43.2 cm) cassettes and then, once processed, simply put the images together. Unfortunately, it's not that simple. Why? The answer has to do with a basic property of the x-ray beam: it diverges from the source. The only portion of the x-ray beam that is vertical is at the center of the cone of divergence. If two views were taken, let's say of an entire leg, on the smaller cassettes the first would be centered over midfemur and second, over midtibia and fibula. The knees on the two processed images wouldn't match up.

Many instances arise in field research situations when the object is larger than the largest image receptor available. To avoid the issue of beam divergence and to acquire a single image of a large object can be problematic. This problem can be resolved by using multiple, slightly overlapped sheets of film to form a single, large image receptor. In addition, it should be noted that the SID must be sufficient to cover the entire film surface.

Figure 2.57B The relative position of the x-ray tube (A) and the mummy (B) looking down from the loft.

Finally, using the direct square law, an exposure time can be calculated. If the desired results require a nonscreened image, along with the increased SID, additional increases in the exposure time will be necessary. Imaging the object in this manner, once processed, the individual images can be "stitched together" with commercially available photography processing programs such as Photoshop®, creating a seamless, single, complete image of the oversized object. Polaroid film worked well for this application. Since the Polaroid film was already in a light-tight flexible envelope, the film packets were easily fixed in place to a surface with masking tape in order to create a "single" large image receptor. An example demonstrating the use of multiple Polaroid film envelopes to produce a single image of a baboon mummy will be presented in Chapter 9.

The procedure can be done with a number of cassettes; however, with multiple overlapping cassettes the metal edge of each cassette would be superimposed on the adjacent film, creating an artifact on the developed image. If instant film, such as Polaroid, is not available and if cassettes are to be used as the image receptors, the subject must be supported by a sheet of Plexiglas or some other radiolucent material. The support would permit cassettes to be put into place or removed, one after the other, from under the Plexiglas. In this way, the imaging can be conducted without moving the subject. A lateral radiograph of the Soap Lady mummy at the College of Physicians Mütter Museum in Philadelphia, Pennsylvania, will provide an example of "merging" multiple images. As part of a proposed new display, a complete AP and lateral radiograph of the entire mummy was needed. To acquire the lateral projection, a 14 x 36 in. (35.6 x 91 cm) was selected and a track was constructed (Figure 2.59) to support the cassette over the entire length of the mummy. In order to

Figure 2.58 The nearly lateral radiograph of the mummy's skull. Although the humerus (arrow) partially obscured the maxilla and mandible, it was possible to determine that the mummy was edentulous.

Figure 2.59 A lateral projection cassette support system was constructed with a 32 x 12 x 3/4 in. (81.2 x 30.5 x 1.9 cm) plywood base (A). A 36 in. (91.4 cm) long, 7/8 x 1/2 in. (2.2 x 1.29 cm) aluminum track (B) that held the cassette was mounted on a 28 in. (71 cm) long, 1% x 1% in. (3.8 x 3.8 cm) pine board (C). Once the support system was in place, counterweights, such as sand bags, were placed on the plywood to stabilize it.

Figure 2.59 A lateral projection cassette support system was constructed with a 32 x 12 x 3/4 in. (81.2 x 30.5 x 1.9 cm) plywood base (A). A 36 in. (91.4 cm) long, 7/8 x 1/2 in. (2.2 x 1.29 cm) aluminum track (B) that held the cassette was mounted on a 28 in. (71 cm) long, 1% x 1% in. (3.8 x 3.8 cm) pine board (C). Once the support system was in place, counterweights, such as sand bags, were placed on the plywood to stabilize it.

Figure 2.60 Without moving the x-ray tube, multiple lateral images of the soap Lady were taken, processed, scanned with a flatbed scanner with transparency adapter, and assembled to produce a single lateral image.

Figure 2.60 Without moving the x-ray tube, multiple lateral images of the soap Lady were taken, processed, scanned with a flatbed scanner with transparency adapter, and assembled to produce a single lateral image.

cover the entire mummy, the x-ray tube was placed at a 140 in. (356 cm) SID. A total of four exposures were taken, digitized on a flatbed scanner with a transparence adapter and "assembled" to create a single image (Figure 2.60).

A nonscreen approach is by far the easiest and provides the greatest flexibility. A film support can be constructed using a sheet of Foamcore cut to the desired size. In the darkroom, conventional radiographic film is placed onto the support and held in place using thumbtacks. There should be at least 1/2 in. (1.25 cm) of overlap as each additional sheet of film is fixed to the surface of the support. Once the films are all in place, six layers of black gardening plastic or a single layer of black pool liner are used to make the "film holder" light tight. Duct tape should be used to secure the covering material. Using this nonscreened method, an image receptor of virtually any size can be constructed.

We used this nonscreened Foamcore film holder approach on an articulated 84 in. (213 cm) skeleton also at the Mütter Museum in Philadelphia. The individual, who suffered from gigantism during life, was mounted in a cabinet with two other mounted skeletons. The giant's skeleton could not be removed from the case for a radiographic study. There was insufficient space to get the required distance to cover a film holder over 90 in. (229 cm) tall (Figure 2.61). Therefore, two Foamcore support film holders were constructed. As previously described, the images were scanned in and "stitched" together (Figure 2.62). Among the imaging findings was a lack of organized trabecular pattern within the proximal femurs, suggesting the bones had not been subjected to weight-bearing stresses for several months prior to the individual's death.

Several factors should be taken into consideration before this procedure is undertaken. Since long distances are required between the image receptor and x-ray source, long exposure times will be needed. In addition, if film will be exposed directly without the amplifying effect of intensifying screens, the exposure times could require a total of minutes. Therefore, if many specimens are going to be imaged using this method, the high heat loading of the x-ray tube will reduce the tube "life."

Cannot Come out of the Cave: Redefining Portable Whenever possible, radiography should be conducted in situ or as close to the recovery site as possible. This approach preserves the context and allows assessment of the mummified remains or artifacts to be made prior to moving or transport. Many field situations arise in which the subject cannot be moved due to its fragility or because of local cultural customs. In these situations, the term portable takes on greater meaning. In one example, we were to radiograph and conduct endoscopy on the mummified ancestral remains of the Ibaloi people that had been placed in caves deep in the Kabayan Jungle on the island of Luzon in the Philippines (Cave Mummies of the Philippines 2002). Local customs would only permit the remains to be moved around within a cave, and they could not be removed from the caves for study. The

Figure 2.61 The setup employed to radiograph the Mütter Giant. The x-ray tube (A) was positioned to take an AP projection of the lower portion of the legs. The nonscreen black plastic film holder (B) was resting against the sheet of Foamcore (C).

challenge was to establish an imaging facility at the mouth of these remote caves. A gasoline generator was required to provide power for the radiographic and endoscopic instruments. The generator was strapped to a long pole and carried to the caves by two members of the Philippine Army who also served as a security team. The x-ray unit was a compact 1952 vintage U.S. Army field unit stripped down to its bare necessities and the image receptor was 8 x 10 in. (20.3 x 25.4 cm) Polaroid' Type 803 film. The "higher-speed" or "faster" Polaroid film was selected in order to reduce the exposure time by a factor of eight. The x-ray tube and image receptor support devices were fashioned with whatever was available in or around the cave. The tube was often balanced on rocks in the cave, with the film being supported by an ancient coffin or small stones (Figure 2.63). The images provided information related to the age at the time of death and remnants of soft tissue (Figure 2.64), substantiating the villager's claims of embalming procedures. The quality of the radiographs demonstrated that imaging studies can be conducted in extreme settings.

Cannot Get the Cassette under/behind Subject Superimposition has been mentioned several times as a disadvantage of conventional radiography. The problem is compounded by mummified remains, whether they are in a flexed or extended position, due to the

Figure 2.62 The assembled AP and lateral radiographs of the Mütter Giant. (Images courtesy of andrew Nelson, PhD.)

immobile position of their extremities. Not only might an arm or a hand obscure a clear view of, for example the spine, but it may also make it difficult to make an assessment of the extremity itself. Since there may not be enough space for a cassette with intensifying screens to fit between the anatomical parts of interest, a flexible nonscreen film holder might provide a solution.

An example of this flexible nonscreened film holder approach was demonstrated in the study of a sideshow mummy. Sideshow mummies were uniquely American phenomena. Unclaimed bodies, embalmed with either arsenic or formalin, were procured by entrepreneurs and incorporated into the traveling entertainment circuits that were popular in the late 19th and early 20th centuries. In order to attract paying costumers, sideshow promoters would create an incredible story surrounding the individual's life and subsequent demise and our example, Hazel Farris, was no exception (An Unwanted Mummy 2001). Her legend stated that she was the wife of a man in Louisville, Kentucky. They both had a history of drinking and domestic disputes. One night, Hazel told her husband that she wanted to buy a hat, he said no, and so she shot him dead. Three sheriff's deputies came to investigate, and she shot and killed all of them. The sheriff came in and entered into a scuffle with Hazel during which her ring finger was shot off. Hazel then bested the sheriff

Figure 2.63 The setup employed to radiograph the Ibaloi mummy within the cave.

and shot him dead as well. Hazel fled back to her home in Bessemer, Alabama, where she became a "lady of the night." Hazel confessed her crime to a lover, who decided to turn her in for a $500 reward that was placed on Hazel. Hazel didn't want to go to jail, so she committed suicide by drinking arsenic in whiskey. Or so the story goes.

The missing ring finger became important to the study to determine whether it was a pre- or perimortem event. Unfortunately, the hand was crossed over the body and, even with angled projections, an unobstructed view, free of superimposition, wasn't possible (Figure 2.65A). However, there was sufficient space to slide a Polaroid film packet between the hand and the lower abdomen (Figure 2.65B). The result was an image of her hand free of superimposition and the finger in question appeared to have been amputated well before the time suggested by the story that brought people into the tent to view her remains (Figure 2.65C).

In another field imaging case, there was inadequate space beneath or on the side of the mummy to accommodate a cassette. The mummy, known as Princess Anna, was at rest in Kastle, Germany (Princess Baby 2002). The legend states that Anna was the daughter of King Ludwig IV and died while in the Kastle region. The distraught king ordered that she be preserved for eternity. Friars mummified Anna, and she is currently interred in a wooden case at the church in Kastle. Due to her fragile state, the remains couldn't be lifted high enough to permit the rigid cassette to be placed underneath the body. In addition, her left shoulder was so close to the side of the case that it precluded the use of a

Figure 2.64 The excellent state of preservation is demonstrated by the presence of tracheal rings (arrows) seen on this lateral chest radiograph of an Ibaloi mummy.
Figure 2.65A The Polaroid image of Hazel Farris' hand superimposed over her abdomen, making it impossible to assess the condition of her fourth finger (arrow).
Figure 2.65B The Polaroid film packet (arrow) placed between the right hand and the abdomen.

cassette for lateral projection. The nonscreen approach provided a solution for both problems. The flexible nature of the Polaroid film package allowed it to be smoothly positioned behind the mummy with minimal manipulation (Figure 2.66). The packet had sufficient stiffness to be slid between the shoulder and side of the case without curling onto the body (Figure 2.67).

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