iodinated contrast-induced thyrotoxicosis.iodinated contrast media adverse reactions.clinical applications of dual-energy CT.as low as reasonably achievable (ALARA).These were Eugene W Caldwell (1870-1918) 6, a radiologist and qualified engineer, who received a patent for an automated timing device to move the grid 4 and Hollis E Potter (1880-1964) 5, who was the first to present the development at a scientific event, namely the winter meeting of the Central Section of the American Roentgen Ray Society (ARRS) in February 1915 4. Two American radiologists independently of Bucky also came up with the idea of a moving grid. Not long after his original invention, Bucky introduced a moving grid to overcome the problems inherent with a static device. History and etymologyĪnti-scatter grids were developed by Gustav Bucky (1880-1963), a German-American radiologist who patented a stationary grid in 1913. However, this leads to increased x-ray tube loading and radiation exposure to the patient. Image contrast can be improved by increasing the grid ratio by increasing the height of the lead strips or reducing the interspace. The contrast improvement factor is the ratio between the contrast with a grid and without a grid. It indicates the increase in patient dose due to the use of a grid. The Bucky factor is the ratio of radiation on the grid to the transmitted radiation. Generally used where the anatomy is >10 cm:īarium studies (including lateral cervical)īreast ( mammography): uses 4:1 grid ratio Grids are commonly used in radiography, with grid ratios available in even numbers, such as 4:1, 6:1, 8:1, 10:1 or 12:1. Moving grids (also known as Potter-Bucky or reciprocating grids): eliminates the fine grid lines that may appear on the image when focused or parallel grids are used cannot be used for portable films Parallel grid: used for short fields or long distances Virtual grid: no actual grid is used latest innovation for scatter reduction by digitally reconstructing a radiographįocused grids (most grids): strips are slightly angled so that they focus in space so must be used at specified focal distances The strip line density (number of strips per cm) is 1/(D+d), where d is the thickness of the strip. A grid ratio of 8:1 is generally used for 70-90 kVp technique and 12:1 is used for >90 kVp technique. The working ability of a grid is described by the grid ratio, which is the ratio of the height of the lead strips (h) to the distance between two strips, i.e. the interspace (D). As scattered radiation is increased in "thicker" patients and at larger field sizes, grids are useful in such scenarios to improve image contrast. The strips can be oriented either linear or crossed in their longitudinal axis. They are made of parallel strips of high attenuating material such as lead with an interspace filled with low attenuating material such as carbon fiber or organic spacer. Grids are placed between the patient and the x-ray film to reduce the scattered radiation reaching the detector (produced mainly by the Compton effect) and thus improve image contrast.
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