For what are grids used on an X
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In medical imaging, an anti-scatter grid (also known as a Bucky-Potter grid) is a device for limiting the amount of scattered radiation reaching the detector, thereby improving the quantity of diagnostic medical x-ray images. The grid is positioned on the opposite side of the patient from the x-ray source, and between the patient and the X-ray detector or film. Reducing the amount of scattered x-rays increases the image's contrast resolution, and consequently the visibility of soft tissues. Show History[edit]The device was first invented by German radiologist Gustav Peter Bucky, who showed in 1913 that a grid can be used to 'reject' scattered x-rays before they reach the detector. It was later improved by American radiologist Hollis E. Potter by introducing moving grid. The Bucky-Potter grid facilitated the transition from small glass photographic plates to film in a variety of sizes. Operation[edit]Scattered x-rays do not travel in parallel to rays that pass directly through the patient. The quantity of scattering depends on several factors including: x-ray beam area, x-ray photon energies (determined by tube voltage setting), thickness of the tissue, and the composition of the tissue. By 'rejecting' scattered x-rays before they reach the detector, the Bucky-Potter grid improves recorded contrast. The grid is constructed of a series of alternating parallel strips of lead and a radiolucent substance such as a plastic, carbon fibre, aluminium, even paper. The grid is placed between the patient and the detector during the exposure. Radiation which has travelled straight through the patient from the x-ray source moves directly through the radiolucent potions of the grid and strikes the detector. Radiation which has been scattered while travelling through the patient strikes the lead strips at an angle, and is either attenuated or further scattered. As a result, only radiation which has travelled directly through the patient is imaged on the detector, increasing contrast. The single most important parameter that influences the performance of an anti-scatter grid is the grid ratio. The grid ratio is the ratio of the height to the width of the interspaces (not the grid bars) in the grid. Grid ratios of 8:1, 10:1, and 12:1 are most. A 5:1 grid is most common for mammography. The grid is essentially a one-dimensional Collimator and increasing the grid ratio increases the degree of collimation. Higher grid ratios provide better scatter cleanup, but they also result in greater radiation doses to the patient. In addition, though higher ratios are possible, they require greater radiation intensity increases when used, require more precise positioning, and are more expensive to produce. Drawbacks[edit]Grids are used particularly in examinations where a large quantity of scatter is created, i.e., those involving a large volume of tissue being irradiated and those requiring low energy i.e. voltage. The scatter would otherwise degrade the image by reducing the contrast and resolution. Use of a grid, however, requires a greater radiation exposure to the patient as a good deal of primary beam is also attenuated by the lead slats, and for this reason grids are not used for all examinations, particularly in pediatric practice. One drawback of a fixed radiographic grid is that it creates grid lines on the image. Hollis Potter (1880-1964) showed in 1920 that these grid lines could be eliminated by moving the grid at right angles to the grid lines during the exposure. If the range and speed of motion is sufficient, the grid lines will be blurred out. The motion may be oscillating, vibrating, or reciprocating and must be continuous and smooth. The motion must also begin before exposure and continue until after exposure. Grids from Archana Koshy Ant-scatter grids: They are designed specifically to reduce scatter. An increase in the grid ratio will make the grid more effective at reducing scatter, but will also require higher x-ray tube technique.An X-ray grid is the part of an X-ray machine that filters out randomly deflected radiation that can obscure or blur an image produced by the machine. It was invented in 1913. PurposeAn X-ray grid is a filtering device that ensures the clarity of the image on X-ray film. When an X-ray machine sends radiation through an object, specifically a body, the object absorbs or deflects most of the rays. Only about 1 percent of the X-rays pass through the body on a straight line and burn an image onto the film. The deflected X-rays can hit the film at random angles, obscuring the image. The grid filters out these random X-rays. DesignAn X-ray grid in its most basic form is a grate with a series of narrow strips of metal that stop X-rays--usually lead, nickel or aluminum. The grid resembles a set of horizontal window blinds that is partially open. X-rays that create the true image on the film travel in a straight line, so they will pass right through the grid. Deflected X-rays that would add noise to the image hit the grid strips at an angle and will not hit the film. PrecisionTo ensure that enough of the X-rays that are traveling on a straight line pass through the grid, the strips of metal on the grid must be extremely thin. Competing grid manufacturers often tout their ability to produce the thinnest grid strips. InventionDr. Gustav Bucky invented the X-ray grid in 1913. He described it as a honey-combed lead grid. His design was imperfect, with lead strips thick enough to appear as lines on the X-ray image. He attempted to remove these lines by moving the grid during X-ray exposure. Bucky FactorDr. Bucky lent his name to an important measurement of the X-ray grid. The "Bucky factor" refers to the ratio of X-rays that hit the grid vs. those that actually pass through the grid. This measurement includes both the radiation that creates the image and the scattered "noise" radiation. This ratio is important because it informs the X-ray technician how high the radiation setting on the X-ray machine has to be in order to produce a clear image. 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About the Author James McGill is an award-winning, Boston-base journalist and media professional with 13 years of experience in the academic book publishing, magazine, newspaper and web industry. His expertise extends from politics to information technology. What is the purpose of a grid on an XThe antiscatter grid plays an important role for enhancing image quality in projection radiography by transmitting a majority of primary radiation and selectively rejecting scattered radiation.
For what are grids used on an XFunction of a grid is to absorb scatter radiation before it can reach the film, thereby improving contrast of the radiographic image. The higher the grid ratio, the moreeffective scatter radiation cleanup.
What is the use of a grid?A grid is a collection of horizontal and vertical lines creating a pattern against which we can line up our design elements. They help us to create layouts in which our elements won't jump around or change width as we move from page to page, providing greater consistency on our websites.
Where is the grid located in XThe grid is positioned on the opposite side of the patient from the x-ray source, and between the patient and the X-ray detector or film. Reducing the amount of scattered x-rays increases the image's contrast resolution, and consequently the visibility of soft tissues.
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