focused grid


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Related to focused grid: linear grid, parallel grid

grid

 [grid]
1. a grating.
2. in radiology, a device consisting essentially of a series of narrow lead strips closely spaced on their edges and separated by spacers of low density material; used to reduce the amount of scattered radiation reaching the x-ray film.
3. a chart with horizontal and perpendicular lines for plotting curves.
Amsler grid see Amsler charts.
baby grid a direct-reading chart on infant growth.
cross-hatched grid two linear grids that are superimposed at right angles to each other, used for maximal scatter cleanup.
Cross-hatched grids are fabricated by sandwiching two linear grids together so that their grid strips are perpendicular. From Bushong, 2001.
grid cutoff differences in radiographic intensity that are caused by improper focusing of the lead lines of a grid.
focused grid a linear grid in which all of the lead strips are aligned in a tilted fashion toward a centering point.
linear grid a grid designed to permit the passage of the primary beam by having lead lines aligned in the same direction separated by radiolucent interspacing material. There are two types, parallel and focused.
Wetzel grid a direct-reading chart for evaluating physical fitness in terms of body build, developmental level, and basal metabolism.

fo·cus·ed grid

a grid (2) in which the divergent beam of x-rays from a particular distance range will be parallel to the lead strips.

focused grid

an x-ray grid that has lead foils placed at an angle so that they all point to a focus at a specific distance.

fo·cused grid

(fōkŭst grid)
A term used in radiography; a grid type in which angled lead foils point toward a focus.

grid

1. a grating; in radiology, a device consisting essentially of a series of narrow lead strips closely spaced on their edges and separated by spacers of low density material; used to reduce the amount of scattered radiation reaching the x-ray film.
2. a chart with horizontal and perpendicular lines for plotting curves.

grid cassette
a radiographic cassette with a grid permanently installed in it.
grid cutoff
excessive loss of radiation beam because of incorrect angulation between the tube and the lead strips.
grid diaphragm
a grid interposed between the film and the x-ray beam. See also (1) above.
grid factor
because of the filtering out of rays by the lead strips there is a loss of penetrating effect of the beam so that exposure time must be increased.
focused grid
the lead strips in the grid are sloped slightly inwards at the top so that the apertures more closely approximate the angle taken by the rays in a diverging beam.
linear grid
a cassette grid in which the radiopaque strips are parallel to each other.
grid map
a map marked by a grid of numbered intersecting parallel lines making it possible to identify particular locations numerically.
movable grid
one that moves during the exposure of the film to the x-ray beam: a Potter-Bucky grid.
nonfocused grid
see parallel grid (below).
parallel grid
the lead strips in the grid are parallel to each other and vertical to the plane of the film. This has the disadvantage that more diverging rays are absorbed by the grid at the edges of the film than at the center with a lowering of exposure there.
Potter-Bucky grid
a focused grid moved mechanically across the x-ray beam. Suited only to large installations. Called also Bucky and Potter-Bucky diaphragm.
pseudo-focused grid
something of the same effect as a focused grid is obtained by gradually lowering the height of the strips in the grid as they approach the edge of the grid.
grid ratio
the ratio between the height of the strips to the distance separating them. The greater the ratio the more rays will be filtered out.
reciprocating grid
one that moves during the exposure of the subject to the beam of radiation.
rotating grid
one that moves while x-rays are being generated.
stationary grid
one that is stationary while the film is being exposed so that there is a pattern of grid lines on the radiograph.
grid tube
a special tube designed to take cineradiographic x-rays.
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