![]() Grid efficiency: The ability of a grid to absorb non–image-forming radiation in the production of a quality radiograph. Grid cutoff: A progressive decrease in transmitted x-ray intensity caused by absorption of primary x-rays by the grid lines. Grid: A device made of lead strips embedded in a spacing material, placed between the patient and the film, designed to absorb non–image-forming radiation. Geometric unsharpness: Loss of detail due to geometric distortion. Geometric distortion: Variation in normal size and shape of anatomic structures due to their position in relation to the x-ray source and film. Also called crisscross grid.Įlongation: Distortion of anatomic structures so that the image appears longer than actual size, owing to the x-ray beam not being directed perpendicular to the film surface.įocused grid: A grid with a parallel center lead strip and inclined strips on either side that radiate at progressively greater angles.įoreshortening: Distortion of anatomic structures when the image appears shorter than actual size due to the plane of interest not being parallel to the film surface. Radiation that is reflected from behind the image plane back to the image.Ĭontrast: The measurable difference between two adjacent densities.Ĭrossed grid: Two parallel or two focused grids that are set at right angles. Backscatter: Process of scattering or reflecting radiation in the opposite direction from that intended.
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