Chapter 5 Chapter Outline Controlling the amount of scatter radiation produced in a patient and ultimately reaching the image receptor (IR) is essential in creating a good-quality image. Scatter radiation is detrimental to radiographic quality because it adds
unwanted exposure (fog) to the image without adding any patient information. Digital IRs are more sensitive to lower-energy levels of radiation such as scatter, which results in increased fog in the image. Additionally, scatter radiation decreases radiographic contrast for both film-screen and digital images. Increased scatter radiation, either produced within the patient or higher-energy scatter exiting the patient, affects the exposure to the patient and anyone within
close proximity. The radiographer must act to minimize the amount of scatter radiation reaching the IR. Beam-restricting devices and radiographic grids are tools the radiographer can use to limit the amount of scatter radiation that affects the radiographic image and exposure to the patient or personnel. Beam-restricting devices decrease the x-ray beam field size and the amount of tissue irradiated, thereby reducing the amount of scatter radiation produced. Radiographic
grids are used to improve radiographic image quality by absorbing scatter radiation that exits the patient, reducing the amount of scatter reaching the IR. It should be noted that grids do nothing to prevent scatter production; they merely reduce the amount of scatter reaching the IR. Several types of beam-restricting devices, which differ in sophistication
and utility, are available. All beam-restricting devices are made of metal or a combination of metals that readily absorb x-rays. Cones and cylinders are shaped differently (Figure 5-5), but they have many of the same attributes. A cone or cylinder is essentially an aperture diaphragm that
has an extended flange attached to it. The flange can vary in length and can be shaped as either a cone or a cylinder. The flange can also be made to telescope, increasing its total length (Figure 5-6). Similar to aperture diaphragms, cones and cylinders are easy to use. They slide onto the tube, directly below the window. Cones and cylinders limit unsharpness surrounding the radiographic image more than aperture
diaphragms do, with cylinders accomplishing this task slightly better than cones (Figure 5-7). However, they are limited in terms of available sizes, and they are not interchangeable among tube housings. Cones have a particular disadvantage compared with cylinders. If the angle of the flange of the cone is greater than the angle of divergence of the primary beam, the base plate or aperture diaphragm of the cone is
the only metal actually restricting the primary beam. Therefore, cylinders generally are more useful than cones. Cones and cylinders are almost always made to produce a circular projected field, and they can be used to advantage for particular radiographic procedures (Figure 5-8). Recommended textbook solutions
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Which of the following will help to reduce scattered radiation?Time: Minimizing the time of radiation exposure will reduce the radiation dose. Distance: Increasing the distance between the patient and the radiation source will reduce exposure by the distance squared.
Which of the following processes is most responsible for the production of scatter radiation?x-posure/scatter/scatter. Which of the following is not a way to reduce the production of scatter radiation?Scatter Control. |
What is the most effective method to reduce the production of scatter radiation
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