The result is a tremendous increase in radiographic contrast. There are different types of grid depending on the way the lead strips are arranged and the number, thickness and height of the lead strips. Lead strips can be arranged in a focused, parallel, or crossed fashion. Most grids are focused . Grid artifacts are created on the radiographs when the focused grid is not in a correct position.
Artifacts produced by a malpositioned grid are easily identifiable.
Grid ratio Grid ratio is the ratio of the height of the lead strips divided by the distance between 2 lead strips. The higher the ratio, the more efficiently the grid stops scatter radiation. However, the grid stops a significant proportion of the primary beam as well , and high ratio grids require higher output x-ray unit. In addition, recall that scatter radiation contributes to the making of a radiograph and that reducing scatter therefore requires more x-rays to make the image. The number of lead strips per inch and the lead content are other factors to consider.