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). They slide onto the tube, directly below the window. Similar to aperture diaphragms, cones and cylinders are easy to use. The flange can also be made to telescope, increasing its total length ( Figure 5-6). The flange can vary in length and can be shaped as either a cone or a cylinder. A cone or cylinder is essentially an aperture diaphragm that has an extended flange attached to it. It should be noted that grids do nothing to prevent scatter production they merely reduce the amount of scatter reaching the IR.Ĭones and cylinders are shaped differently ( Figure 5-5), but they have many of the same attributes. 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. Beam-restricting devices decrease the x-ray beam field size and the amount of tissue irradiated, thereby reducing the amount of scatter radiation produced. The radiographer must act to minimize the amount of scatter radiation reaching the IR.īeam-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. 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. Additionally, scatter radiation decreases radiographic contrast for both film-screen and digital images. Scatter radiation is detrimental to radiographic quality because it adds unwanted exposure (fog) to the image without adding any patient information.ĭigital IRs are more sensitive to lower-energy levels of radiation such as scatter, which results in increased fog in the image. Explain the air gap technique and describe its use.Ĭontrolling the amount of scatter radiation produced in a patient and ultimately reaching the image receptor (IR) is essential in creating a good-quality image. Recognize how beam restriction and use of grids affect patient radiation exposure.ġ5. Identify the factors to be considered in using a grid.ġ4. Describe different types of grid cutoff that can occur and their radiographic appearance.ġ3. Demonstrate use of the grid conversion formula.ġ2. List the various types of stationary grids, and describe the function and purpose of a moving grid.ġ1.

Describe the construction of grids, including the different types of grid pattern, dimensions, and grid focus.ġ0. Describe the purpose of a radiographic grid.Ĩ. State the purpose of automatic collimators or positive beam-limiting devices.ħ. Describe each of the types of beam-restricting devices.Ħ. State the purpose of beam-restricting devices.ĥ. Explain how scatter radiation affects digital and film-screen images.Ĥ. State all the important relationships in this chapter.ģ. Define all the key terms in this chapter.Ģ. After completing this chapter, the reader will be able to perform the following:ġ.

Types of grids and flyrails