The decentering effect of the x ray grid is the extra absorption of the x ray grid lead bar to the X-ray primary signal with the information signal.
Decentering effect of x ray grid refers to the additional absorption of X-ray with information signal by lead bar of x ray grid.
There are 4 cases of decentering effect in x ray grid.
(1) Focusing grid inversion: the central line of the photo shows density and the rest is non density image.
(2) Lateral or lateral deviation from the focal length: two cases of lateral tilt focal length. One is that the photographic distance is the same as the grating focal length, but the X-ray tube focal length deviates from the focus line to one side; the other is that the photographic distance is the same as the grating focal length, while the grating plane is not vertical to the central line bundle of X-ray, and inclines to one side. At this time, the grid lead is cut equal to the original rays, resulting in a uniform density reduction image. Generally, it is difficult to identify from photos and images, and is mistaken for inadequate X-ray photography conditions.
(3) Upper and lower deviations from the grid focal length: When the X-ray tube focuses on the center of the grid, but it is located on or below the grid focal line, the cutting effect will also occur. When the X-ray tube focus is above the focus line (or point), the distance between the X-ray tube and the grating plane is called the far grating focus distance; when the X-ray tube focus is below the focus line (or point), the distance between the X-ray tube focus and the grating plane is called the near grating focus distance. If the deviation distance is the same, the loss rate of the original ray caused by the cutting effect of the near focal distance is greater than that of the far focal distance.
(4) Double deviation: lateral deviation and upper and lower deviation from grid focal length occur simultaneously, which is a common phenomenon in photography. Double deviations can cause uneven film exposure, while image density is high and low.
Author：X Ray Grids Maker
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Company: Weifang Newheek Electronic Tech Co., Ltd.
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