What Is An X-Ray Grid?

An X-ray grid is the part of an X-ray machine that filters out randomly deflected radiation that can obscure or blur an image produced by the machine. It was invented in 1913.

An X-ray grid is a filtering device that ensures the clarity of the image on X-ray film. When an X-ray machine sends radiation through an object, specifically a body, the object absorbs or deflects most of the rays. Only about 1 percent of the X-rays pass through the body on a straight line and burn an image onto the film. The deflected X-rays can hit the film at random angles, obscuring the image. The grid filters out these random X-rays.

An X-ray grid in its most basic form is a grate with a series of narrow strips of metal that stop X-rays–usually lead, nickel or aluminum. The grid resembles a set of horizontal window blinds that is partially open. X-rays that create the true image on the film travel in a straight line, so they will pass right through the grid. Deflected X-rays that would add noise to the image hit the grid strips at an angle and will not hit the film.

To ensure that enough of the X-rays that are traveling on a straight line pass through the grid, the strips of metal on the grid must be extremely thin. Competing grid manufacturers often tout their ability to produce the thinnest grid strips.

Dr. Gustav Bucky invented the X-ray grid in 1913. He described it as a honey-combed lead grid. His design was imperfect, with lead strips thick enough to appear as lines on the X-ray image. He attempted to remove these lines by moving the grid during X-ray exposure.

Dr. Bucky lent his name to an important measurement of the X-ray grid. The "Bucky factor" refers to the ratio of X-rays that hit the grid vs. those that actually pass through the grid. This measurement includes both the radiation that creates the image and the scattered "noise" radiation. This ratio is important because it informs the X-ray technician how high the radiation setting on the X-ray machine has to be in order to produce a clear image.