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X-ray Vision: Diagnostic X-rays and CT Scans
Published in Suzanne Amador Kane, Boris A. Gelman, Introduction to Physics in Modern Medicine, 2020
Suzanne Amador Kane, Boris A. Gelman
One way of getting around the similarities in x-ray absorption of many tissues is to utilize contrast media – radiopaque materials introduced into the soft tissues of the body. This is necessary, for example, in imaging the heart and the digestive tract, where the very similar densities and effective Z values of water, blood, and muscle make distinguishing any differences in x-ray absorption particularly difficult. Barium (Z = 56) and iodine (Z = 53) are the two elements most commonly incorporated into contrast media. The high Z of these elements makes them absorb x-rays much more strongly by the photoelectric effect than soft body tissues (Figure 5.10). In addition, the compounds into which these elements are incorporated for imaging are denser than water. Barium and iodine in particular are chosen because their main x-ray absorption edges (the K-edge; see Section 5.4 for the discussion of absorption edges) fall at 37.4 and 33.2 keV, respectively, in a range corresponding to typical diagnostic x-ray energies. As Figure 5.10 illustrates, the mass attenuation coefficients of iodine and barium rise abruptly just above their K-edge energies, resulting in significantly enhanced x-ray absorption by the contrast medium if x-rays with this energy range are used. The contrast agent's greater radiopaqueness creates large contrasts in absorption with surrounding soft tissues, making their presence easily discernible on a radiograph. This means that if the contrast agent is introduced into a specific region of the body, then the anatomy of that region can be easily visualized in turn.
Reduction and Fixation of Sacroiliac joint Dislocation by the Combined Use of S1 Pedicle Screws and an Iliac Rod
Published in Kai-Uwe Lewandrowski, Donald L. Wise, Debra J. Trantolo, Michael J. Yaszemski, Augustus A. White, Advances in Spinal Fusion, 2003
Kai-Uwe Lewandrowski, Donald L. Wise, Debra J. Trantolo, Michael J. Yaszemski, Augustus A. White
For successful vertebral augmentation, the practitioner must first be confident that the osteoporotic VCF(s) is the source of the pain. Other causes of back pain, such as sacral insufficiency fractures, must be ruled out by a complete history and physical examination. Once this has been established, the next challenge is determining the symptomatic level. By percussing the midline of the spine, the most tender level is determined. This can then be marked by a radiopaque marker, such as paper clip, prior to obtaining radiographs. Also, the examiner can attempt to identify the number of the spinous process. Plain radiographs are useful in assessing overall spinal balance. Cobb angles can be measured to better quantitate the degree of deformity. Vertebral compression can be measured by comparing respective anterior and posterior VB heights to the closest adjacent normal levels. While the presence and morphology of a VCF can be well appreciated on plain films, the acuity of the fracture cannot be determined. If the symptomatic level is unclear by physical examination, advanced imaging modalities should be pursued. The authors routinely obtain an MRI prior to performing kyphoplasty (Figure 1). Acute fractures demonstrate increased signal intensity on T2 images [28,29]. STIR images are particularly helpful in differentiating fracture from malignancy. For patients in whom MRI cannot be performed, a computerized tomogram (CT) is another option. These images give better bony detail and are
Production and anodising of highly porous Ti–Ta–Zr–Co alloy for biomedical implant applications
Published in Corrosion Engineering, Science and Technology, 2019
Muhammet Recep Soran, Ilven Mutlu
X-ray digital radiography was used for radiographic investigation of the imaging properties (radiopaque or radiolucent behaviour) of the samples. X-ray control panel (Balteau NDT) was employed in order to control the test parameters. The samples were exposed to X-rays at 90 kV, 14.3 mA, for 10 s at standard mode (small focus). Film focus distance (FFD) was 70 cm. HD phosphor detector was employed. Phosphor imaging plate (IP) with 14 × 17 inch dimensions (Flex HR digital imaging plate, Carestream, Industrex) was used. VMI 5100MS computed radiography (CR) scanner was used. Starrview 8.0 image processing software was employed for the image processing.