Four cutting effects of the grid?

Everyone knows that the grid can make the image clearer and can absorb scattered rays, mainly used on the chest frame and X-ray machine. Let’s take a look at the four cutting effects of the grid.
 (1) Upside-down grid: The center line of the photo shows density, while the rest has no density image.

 (2) Off-level grid or off-center grid: There are two cases of lateral tilt grid focal length. First, the photographic distance is consistent with the focal length of the grid, but the X-ray tube focus deviates from the focus line (or focus point) to one side; second, the photographic distance is consistent with the grating focal length, and the grid plane is not perpendicular to the X-ray center beam, to one side Tilted at a certain angle. At this time, the grid lead strip cuts the same amount of original rays, thereby producing an image with a uniformly reduced density. It is generally difficult to identify from photo images, which is mistaken for X-ray photography conditions.

 (3) Off-focus grid: When the X-ray tube is in focus at the center of the grid, but it is located on the grid focus line or below, it also produces a cutting effect. When the X-ray tube focus is above the focus line (or point), its distance from the grid plane is called the far-gate focal length; when the X-ray tube focus is below the focus line (or point), its distance from the grid plane , called the near grid focal length. If the deviation distance is the same, the loss rate of the original ray caused by the cutting effect of the near-gate focal length is greater than the far-gate focal length.

 (4) Double deviation: lateral deviation and upper and lower off-grid focal lengths occur simultaneously, which is a situation often encountered in photography. Double deviation can cause uneven film exposure, and the density of the photo image is high on one side and low on the side.

Author：Alina